Capture/Low-Carbon Energy Group

1. Al-Housseiny, Talal, Peichun Tsai, Zhong Zheng, and Howard Stone, 2011: The effect of permeability gradients on immiscible displacement in Hele-Shaw flows. American Physical Society,
   [ Abstract ]

   In heterogeneous media, it is well known that when a fluid of high viscosity displaces a less viscous fluid, the interface can still be unstable and exhibit finger-like patterns due to capillary fingering. Motivated by porous media flows in natural geological formations, we consider homogeneous displacement in a Hele-Shaw cell subjected to a permeability gradient. The permeability gradient is introduced by linearly varying the Hele-Shaw cell depth. We study how capillary forces can affect interfacial stability in the presence of the gradient via linear stability analysis. Depending on the system, we find that surface tension can either have a stabilizing or a destabilizing role. We report the emergence of an important dimensionless parameter--the ratio of the permeability gradient to the capillary number--that determines the stability of the interface along with the well-studied viscosity ratio. Experiments testing the theoretical findings will also be presented.

2. Guo, Xiangbo, Guangjian Liu, and Eric Larson, 2011: High Octane Gasoline Production by Upgrading Low-Temperature Fischer-Tropsch Syncrude. Industrial & Engineering Chemistry Research, American Chemical Society, 50, doi:10.1021/ie200041m 9743-9747
   [ Abstract ]

   Technology selection for refining the lighter fractions of syncrude produced by low-temperature Fischer-Tropsch (LTFT) synthesis into high octane motor-gasoline with no decrease in distillate production has been investigated. It was found that an upgrading scheme based on Pt/L-zeolite reforming, non-hydrogen aromatization and olefin oligomerization can produce high quality motor gasoline which can meet current gasoline specifications (Euro-4). A second scheme, which we call "full aromatization", is also evaluated on the basis of liquid yield and octane number. The full aromatization process appears to be the least complex refining scheme that provides a sufficiently high octane number, but the gasoline produced from this process may require additives to meet current motor gasoline specifications.

3. Larson, Eric, et al., September 2011: Life Cycle Greenhouse Gas Analysis of Advanced Jet Propulsion Fuels: Fischer-Tropsch Based SPK-1 Case Study (AFRL-RZ-WP-TR-2011-2138) In http://www.dtic.mil,
   [ Abstract ]

   The purpose of this report is to provide a framework and guidance for estimating the life cycle greenhouse gas emissions for transportation fuels, specifically aviation fuels. The focus on aviation fuels was driven by the patterns of fuel use by the federal government. Policies such as those outlined in Section 526 of EISA 2007 cause federal agencies to institute enforceable guidelines for procuring low-carbon alternative fuels. Federal consumption of fuels is dominated by the Department of Defense and the Air Force consumes more fuel than any of the other military services or federal agencies (Defense Science Board 2008). Thus, aviation applications may become early adopters of low-carbon transportation fuels. The US Air Force convened a working group of individuals from government agencies, universities, and companies actively engaged in assessing greenhouse gas emissions from transportation fuels, and requested that this group develop guidance on procedures for estimating greenhouse gas emissions in aviation applications, using currently available data and tools.

4. Liu, Guangjian, Eric Larson, Robert H. Williams, Thomas Kreutz, and Xiangbo Guo, 2011: Making Fischer-Tropsch Fuels and Electricity from Coal and Biomass: Performance and Cost Analysis. Energy Fuels, Published on Web 12/06/2010, (25), doi:10.1021/ef101184e 415-437
   [ Abstract ]

   Major challenges posed by crude-oil-derived transportation fuels are high current and prospective oil prices, insecurity of liquid fuel supplies, and climate change risks from the accumulation of fossil fuel CO₂ and other greenhouse gases in the atmosphere. One option for addressing these challenges simultaneously involves producing ultraclean synthetic fuels from coal and lignocellulosic biomass with CO₂ capture and storage. Detailed process simulations, lifecycle greenhouse gas emissions analyses, and cost analyses carried out in a comprehensive analytical framework are presented for 16 alternative system configurations that involve gasification-based coproduction of Fischer-Tropsch liquid (FTL) fuels and electricity from coal and/or biomass, with and without capture and storage of byproduct CO₂. Systematic comparisons are made to cellulosic ethanol as an alternative low GHG-emitting liquid fuel and to alternative options for decarbonizing stand-alone fossil-fuel power plants. The analysis indicates that FTL fuels are typically less costly to produce when electricity is generated as a major coproduct than when producing mainly liquid fuel. Coproduction systems that utilize a cofeed of biomass and coal and incorporate CO₂ capture and storage in the design offer attractive opportunities for decarbonizing liquid fuels and power generation simultaneously. Such coproduction systems considered as power generators can provide decarbonized electricity at lower costs than is feasible with stand-alone fossil-fuel power plant options under a wide range of conditions. At a plausible GHG emissions price under a future U.S. carbon mitigation policy ($50/t CO_2eq), such a coproduction system built at a scale suitable for competing as a power generator would be able to provide low-GHG-emitting synthetic fuels at the same estimated unit cost as for coal synfuels characterized by ten times the GHG gas emission rate that are produced in a plant with CO₂ capture and storage that does not provide electricity as a major coproduct having three times the synfuel output capacity and requiring twice the total capital investment. Moreover, the low GHG-emitting synfuels produced by such systems would be less costly to produce than cellulosic ethanol and require only half as much lignocellulosic biomass.

5. Martelli, E., Thomas Kreutz, Michiel Carbo, S. Consonni, and D. Jansen, 2011: Shell coal IGCCS with carbon capture: Conventional gas quench vs. innovative configurations. Applied Energy, Elsevier, 88, doi:10.1016/j.apenergy.2011.04.046
   [ Abstract ]

   The Shell coal integrated gasification combined cycle (IGCC) based on the gas quench system is one of the most fuel flexible and energy efficient gasification processes because is dry feed and employs high temperature syngas coolers capable of rising high pressure steam. Indeed the efficiency of a Shell IGCC with the best available technologies is calculated to be 47-48%. However the system looses many percentage points of efficiency (up to 10) when introducing carbon capture. To overcome this penalty, two approaches have been proposed. In the first, the expensive syngas coolers are replaced by a "partial water quench" where the raw syngas stream is cooled and humidified via direct injection of hot water. This design is less costly, but also less efficient. The second approach retains syngas coolers but instead employs novel water-gas shift (WGS) configurations that requires substantially less steam to obtain the same degree of CO conversion to CO₂, and thus increases the overall plant efficiency. We simulate and optimize these novel configurations, provide a detailed thermodynamic and economic analysis and investigate how these innovations alter the plant's efficiency, cost and complexity.

6. Palter, J. B., M. Susan Lozier, Jorge Sarmiento, and Robert H. Williams, 2011: The supply of excess phosphate across the Gulf Stream and the maintenance of subtropical nitrogen fixation. Global Biogeochemical Cycles, American Geophysical Union, 25(GB4007), doi:10.1029/2010GB003955
   [ Abstract ]

   The subtropical North Atlantic is considered a hot spot for biological nitrogen fixation, with estimated rates between 1 and 20 x 10¹¹ mol nitrogen fixed annually. However, the region's nutrient reservoir beneath the euphotic zone is so enriched in nitrate relative to phosphate that it is perplexing how fixation might be sustained there. Here, we investigate whether the physical transport of excess phosphate into the subtropical gyre is sufficient to sustain nitrogen fixation in the gyre. Specifically, we assess the Ekman advection and isopycnal mixing of excess phosphate to the subtropical North Atlantic, using detailed hydrographic and nutrient sections occupied across the Gulf Stream combined with satellite wind data. Ekman advection and along-isopycnal mixing provide a source of approximately 2 x 10¹⁰ mol yr of excess phosphate in the northwestern subtropics, a physical mechanism that has the potential to support more than 3 x 10¹¹ mol yr^-1 of biological nitrogen fixation, after accounting for alternative sinks of excess phosphate. This excess phosphate supply across the gyre's northern boundary and high nitrogen fixation there offers a mechanism that can explain both the maintenance of subtropical North Atlantic nitrogen fixation in a phosphate-poor environment and help account for the weak gradients in the proxies of fixation observed along interior circulation pathways of the gyre.

7. Peabody, Christina, and Craig Arnold, 2011: The role of mechanically induced separator creep in lithium-ion battery capacity fade. Journal of Power Sources, Elsevier, 196, doi:10.1016/j.jpowsour.2011.05.023 8147-8153
   [ Abstract ]

   Lithium-ion batteries are well-known to be plagued by a gradual loss of capacity and power which occur regardless of use and can be limiting factors in the development of emerging energy technologies. Here we show that separator deformation in response to mechanical stimuli that arise under normal operation and storage conditions, such as external stresses on the battery stack or electrode expansion associated with lithium insertion/deinsertion, leads to increased internal resistance and significant capacity fade. We find this mechanically induced capacity fade to be a result of viscoelastic creep in the electrochemically inactive separator which reduces ion transport via a pore closure mechanism. By applying compressive stress on the battery structure we are able to accelerate aging studies and identify this unexpected, but important and fundamental link between mechanical properties and electrochemical performance. Furthermore, by making simple modifications to the electrode structure or separator properties, these effects can be mitigated, providing a pathway for improved battery performance.

8. Williams, Robert H., Guangjian Liu, Thomas Kreutz, and Eric Larson, 2011: Coal and Biomass to Fuels and Power. Annual Review of Chemical and Biomolecular Engineering, 2, doi:10.1146/annurev-chembioeng-061010-114126 529-553
   [ Abstract ]

   Systems with CO₂ capture and storage (CCS) that coproduce transportation fuels and electricity from coal plus biomass can address simultaneously challenges of climate change from fossil energy and dependence on imported oil. Under a strong carbon policy, such systems can provide competitively clean low-carbon energy from secure domestic feedstocks by exploiting the negative emissions benefit of underground storage of biomass-derived CO₂, the low cost of coal, the scale economies of coal energy conversion, the inherently low cost of CO₂ capture, the thermodynamic advantages of coproduction, and expected high oil prices. Such systems requiremuch less biomass to make low-carbon fuels than do biofuels processes. The economics are especially attractive when these coproduction systems are deployed as alternatives to CCS for stand-alone fossil fuel power plants. If CCS proves to be viable as a major carbon mitigation option, the main obstacles to deployment of coproduction systems as power generators would be institutional.

9. Azar, C., K. Lindgren, M. Obersteiner, K. Riahi, D. van Vuuren, K. Michel G. J. den Elzen, Kenneth Möllersten, and Eric Larson, 2010: The feasibility of low CO₂ concentration targets. Climatic Change, Springer Science+Business Media B.V. 2010, (100), doi:10.1007/s10584-010-9832-7 195-202
   [ Abstract PDF ]

   The United Nations Framework Convention on Climate Change (UN FCCC 1992) calls for stabilization of atmospheric greenhouse gas (GHG) concentrations at a level that would prevent dangerous anthropogenic interference with the climate system. We use three global energy system models to investigate the technological and economic attainability of meeting CO₂ concentration targets below current levels. Our scenario studies reveal that while energy portfolios from a broad range of energy technologies are needed to attain low concentrations, negative emission technologies—e.g., biomass energy with carbon capture and storage (BECCS)— significantly enhances the possibility to meet low concentration targets (at around 350 ppm CO₂).

10. Kreutz, Thomas, 2010: Prospects for producing low carbon transportation fuels from captured CO₂ in a climate constrained world. ScienceDirect, http://www.princeton.edu/pei/energy/publications/texts/Kreutz-GHGT10-final-%2810-29-10%29.pdf
    [ Abstract ]

    The climate implications of technologies that capture CO₂ to produce transportation fuels (CCTF) are investigated by study-ing two examples: biodiesel from microalgae and Sandia National Laboratory’s S2P process. Simple performance and economic models for each technology are examined in the context of a bifurcated – “pre-CCS” vs. “post-CCS” – climate regime in which CCTF uses CO₂ that is, respectively, captured from power plant flue gases or taken from CCS pipelines. CCTF promises to im-prove domestic energy security by converting sunlight and waste CO₂ into transportation fuels; in addition, these fuels are roughly climate neutral when CO₂ is captured from either flue gases or directly from the atmosphere. However, after the power sector becomes largely decarbonized under a stringent climate policy, large point sources of concentrated CO₂ are likely to be relatively rare, and unfortunately, fuels made from pipeline CO₂ destined for storage do not have markedly reduced net GHG emissions. Thus, absent the development of economical CO₂ capture from air, it’s difficult to see how CCTF can play a signifi-cant long term role in decarbonizing the US transportation sector (and thus reaching US climate goals).

11. Larson, Eric, G. Fiorese, Guangjian Liu, and Robert H. Williams, et al., 2010: Co-production of decarbonized synfuels and electricity from coal + biomass. Energy and Environmental Science, 3, doi:10.1039/b911529c 28-42
    [ Abstract ]

    Energy, carbon, and economic performances are estimated for facilities co-producing Fischer–Tropsch Liquid (FTL) fuels and electricity from a co-feed of biomass and coal in Illinois, with capture and storage of by-product CO₂. The estimates include detailed modeling of supply systems for corn stover or mixed prairie grasses (MPG) and of feedstock conversion facilities. Biomass feedstock costs in Illinois (delivered at a rate of one million tonnes per year, dry basis) are $ 3.8/GJ_HHV for corn stover and $ 7.2/GJ_HHV for MPG. Under a strong carbon mitigation policy, the economics of co-producing lowcarbon fuels and electricity from a co-feed of biomass and coal in Illinois are promising. An extrapolation to the United States of the results for Illinois suggests that nationally significant amounts of low-carbon fuels and electricity could be produced this way.

12. Li, T.X., D. L. Zhu, N. Akafuah, K. Saito, and Chung K Law, 2010: Synthesis, droplet combustion, and sooting characteristics of biodiesel produced from waste vegetable oils (In Press). Proceedings of the Combustion Institute, 1-22
    [ Abstract ]

    In light of the potential of fatty acid methyl ester (FAME, i.e. biodiesel) as a renewable energy source, an innovative acid catalyzed process was developed for the synthesis of biodiesel from waste vegetable oils. The synthesized biodiesels were analytically characterized for their major components, molar fraction and molecular weight of each component, the average molecular weight, and the heat of combustion. Their droplet combustion characteristics in terms of the burning rate, flame size, and sooting tendency were subsequently determined in a hightemperature, freely-falling droplet apparatus. Results show that the biodiesel droplet has higher burning rate, and that biodiesel in general has a lower propensity to soot because its molecular oxygen content promotes the oxidation of the soot precursors.

13. Liu, W., A.P. Kelley, and Chung K Law, 2010: Nonpremixed ignition, laminar flame propagation, and mechanism reduction of n-butanol, iso-butanol, and methyl butanoate (In Press). Proceedings of the Combustion Institute, 1-24
    [ Abstract ]

    The nonpremixed ignition temperature of n-butanol (CH3CH2CH2CH2OH), isobutanol ((CH3)2CHCH2OH) and methyl butanoate (CH3CH2CH2COOCH3) was measured in a liquid pool assembly by heated oxidizer in a stagnation flow for system pressures of 1 and 3 atmospheres. In addition, the stretch-corrected laminar flame speeds of mixtures of air- n-butanol / iso-butanol/ methyl butanoate were determined from the outwardly propagating spherical flame at initial pressures of up to 2 atmospheres, for an extensive range of equivalence ratio. The ignition temperature and laminar flame speeds of n-butanol and methyl butanoate were computationally simulated with three recently developed kinetic mechanisms in the literature. Dominant reaction pathways to ignition and flame propagation were identified and discussed through a Chemical Explosive Mode Analysis (CEMA) and sensitivity analysis. The detailed models were further reduced through a series of systematic strategies. The reduced mechanisms provided excellent agreement in both homogeneous and diffusive combustion environments and greatly improved the computation efficiency.

14. Liu, Guangjian, Robert H. Williams, Eric Larson, and Thomas Kreutz, 2010: Design Economics of Low-Carbon Power Generation from Natural Gas and Biomass with Synthetic Fuels Co-Production. International Conference on Greenhouse Gas Technologies (GHGT 10), Elsevier/Energy Procedia,
    [ Abstract ]

    There is growing optimism about the prospects for large natural gas reserves in shale formations. This paper explores the feasibility vis-à-vis coal power generation of a new approach for decarbonized natural gas power generation. Key features of process designs examined here are coproduction of synthetic transportation fuels with electricity and co-feeding of some biomass with natural gas in such co-production systems. Key questions addressed in the analysis of these systems are: 1) can the competitiveness of natural gas in economic dispatch be improved vis-à-vis a natural gas combined cycle, and 2) can the GHG emissions price needed to induce CCS for natural gas power generation be reduced from that required to induce CCS for NGCC. We find that gas/biomass co-production systems with CCS will be able to defend high capacity factors in economic dispatch at projected oil prices with only modest GHG emission prices. We also find that the breakeven GHG emission price needed to induce CCS for natural gas power generation is reduced considerably vis-à-vis NGCC-CCS.

15. Williams, Robert H., Guangjian Liu, Thomas Kreutz, and Eric Larson, 2010: Alternatives for Decarbonizing Existing USA Coal Power Plant Sites. International Conference on Greenhouse Gas Technologies (GHGT 10), Elsevier/Energy Procedia,
    [ Abstract ]

    A CO₂ capture and storage (CCS) retrofit strategy is compared to several repowering strategies for decarbonising existing coal power plant sites. The more promising repowering approaches analyzed seem to be a shift to natural gas via natural gas combined cycles and deployment of systems that coproduce synthetic liquid fuels plus electricity from coal and biomass with CCS. Under a wide range of plausible conditions, the latter option seems to the most promising approach for decarbonising these plant sites—exploiting simultaneously the carbon mitigation benefit of coprocessing biomass in CCS energy systems and the more general benefits offered by coproduction systems with CCS of: (i) a low CO₂ capture cost, (ii) a high efficiency of power generation, and (iii) large credit for the sale of the synfuel coproducts at current or higher oil prices.

16. Zheng, Zhong, Eric Larson, Z. Li, Guangjian Liu, and Robert H. Williams, 2010: Near-term mega-scale CO₂ capture and storage demonstration opportunities in China. Energy and Environmental Science, The Royal Society of Chemistry, 3(9), doi:10.1039/B924243K 1153-1169
    [ Abstract ]

    China is unique in the large number (nearly 400) of existing and planned projects for making ammonia, methanol, and other fuels and chemicals from coal. A natural by-product of these processes is a nearly pure CO₂ stream. Collectively, these facilities will emit (once all are operating) some 270 million tonnes of CO₂ per year. Taking advantage of the relatively low cost of capturing these CO₂ streams (as compared with capturing CO₂ from power plant flue gases), some of the 20 large-scale CO₂ capture and storage (CCS) demonstration projects called for by the leaders from the G8 to be deployed during the next decade might be expeditiously located in China. Our analysis identifies 18 coal-chemicals/fuels facilities, each emitting one million tonnes/year or more of CO₂, that are within 10 km of prospective deep saline aquifer CO₂ storage sites and an additional 8 facilities within 100 km. The potential CO₂ storage basins are identified based on work by others. We adapted two published cost models for CO₂ compression and transport to develop preliminary estimates of prospective costs for potential CCS projects in China. Our "N^th plant" cost estimates for the 18 projects where the CO₂ source is within 10 km of a sink, are between $9 and $13/tonne of CO₂. (The highest cost estimate among all evaluated projects was less than $21/tonne of CO₂.) The 10-year net-present value cost for projects ranged from $89 million to $1.15 billion, with more than 75% of the projects having net present value costs of $200 million or less. These relatively modest CCS costs suggest that there would be mutual value in international cooperation to support CCS demonstrations in China.

17. Consonni, S., R. E. Katofsky, and Eric Larson, September 2009: A Gasification-Based Biorefinery for the Pulp and Paper Industry. Chemical Engineering Research and Design, 87(9), doi:10.1016/j.cherd.2009.07.017 1293-1317
    [ Abstract ]

    This paper is drawn from a 2-year study of integrated pulpmill biorefineries based on black liquor (the lignin-rich byproduct of fiber extraction from wood) and wood residue gasification at a large kraft mill representative of those in the Southeast United States. The study included detailed mass-energy balance simulations, financial analyses, and energy and environmental benefits estimates for seven pulpmill biorefinery process configurations. All seven configurations include an oxygen-blown, high-temperature black liquor gasifier, syngas cooling, clean-up by a Rectisol (methanol) system, and a catalytic gas-to-liquid process; six of them also include a fluidized-bed, oxygen-blown biomass gasifier and a gas turbine combined cycle fully integrated with the gasification and syngas cooling section. Three biofuels were examined: dimethyl ether (DME), Fischer–Tropsch liquids, and ethanol-rich mixed-alcohols. For the integrated biorefineries analyzed here, the ratio of useful energy outputs (steam, electricity and fuels) to total energy inputs (black liquor, wood residuals and fuel oil) ranges from 66 to 74%; these values compare with about 57% for conventional systems based on Tomlinson boilers and 65% for gasification combined cycles that produce only electricity. Because of the integration of the biorefinery with the pulp and paper mill, the adjusted liquid fuel yield per unit of biomass – a measure of the effectiveness of biomass conversion to liquids – is far higher than for “standalone” gasification-based biorefineries or for ethanol production via biochemical conversion (based on enzymatic hydrolysis). Besides better energy performance, the integration between the biorefinery and the pulp mill effectively limits the specific capital investment associated with liquid fuels production to a surprisingly modest $60,000–150,000 per barrel of diesel equivalent per day—specific capital costs comparable to those for much larger coal-to-liquids facilities. Gasification-based pulp mill biorefinery technologies, once fully commercialized, offer the potential for attractive investment returns and, if implemented widely, significant energy and environmental benefits to the United States.

18. Dryer, F. L., Robert H. Williams, and Eric Larson, August 2009: How Aviation Can Clean up its Act. BBC News, http://news.bbc.co.uk/2/hi/sci/tech/8193125.stm,
19. Jin, H., Eric Larson, and F. E. Celik, 2009: Performance and Cost Analysis of Future, Commercially-Mature Gasification-Based Electric Power Generation from Switchgrass. Biofuels, Bioproducts, Biorefining, 3(2), doi:10.1002/bbb.138 142-173
    [ Abstract ]

    Detailed process designs and mass/energy balances are developed using a consistent modeling framework and input parameter assumptions for biomass-based power generation at large scale (4536 dry metric tonnes per day switchgrass input), assuming future commercially mature component equipment performance levels. The simulated systems include two gasifi cation-based gas turbine combined cycles (B-IGCC) designed around different gasifi er technologies, one gasifi cation-based solid oxide fuel cell cycle (B-IGSOFC), and a steam-Rankine cycle. The simulated design-point effi ciency of the B-IGSOFC is the highest among all systems (51.8%, LHV basis), with modestly lower effi ciencies for the B-IGCC design using a pressurized, oxygen-blown gasifi er (49.5% LHV) and for the B-IGCC design using a low-pressure indirectly heated gasifi er (48.6%, LHV). The steam-Rankine system has a simulated effi ciency of 33.0% (LHV). Detailed capital costs are estimated assuming commercially mature (‘N^th plant’) technologies for the two B-IGCC and the steam-Rankine systems. B-IGCC systems are more capital-intensive than the steam-Rankine system, but discounted cash fl ow rate of return calculations highlight the total cost advantage of the B-IGCC systems when biomass prices are higher. Uncertainties regarding prospective mature-technology costs for solid oxide fuel cells and hot gas sulfur clean-up technologies assumed for the B-IGSOFC performance analysis make it diffi cult to evaluate the prospective electricity generating costs for B-IGSOFC relative to B-IGCC. The rough analysis here suggests that B-IGSOFC will not show improved economics relative to B-IGCC at the large scale considered here.

20. Larson, Eric, G. Fiorese, Guangjian Liu, Robert H. Williams, Thomas Kreutz, and S. Consonni, 2009: Co-production of decarbonized synfuels and electricity from coal + biomass with CO₂ capture and storage: an Illinois case study. Energy and Environmental Science,
    [ Abstract ]

    Energy, carbon, and economic performance are estimated for facilities co-producing Fischer- Tropsch Liquid (FTL) fuels and electricity from a co-feed of biomass and coal in Illinois, with capture and storage of by-product CO₂. The estimates include detailed models of supply systems for corn stover or mixed prairie grasses (MPG) and of feedstock conversion facilities. Biomass feedstock costs in Illinois (delivered at a rate of one million tonnes per year, dry basis) are $3.8 GJ_HHV for corn stover and $7.2/GJ_HHV for MPG. Using a strong carbon mitigation policy, the economics of co-producing low-carbon fuels and electricity from a co-feed of biomass and coal in Illinois are promising. An exploration to the United States of the results for Illinois suggests that nationally significant amounts of low-carbon fuels and electricity could be produced this way.

21. Larson, Eric, H. Jin, and F. E. Celik, 2009: Large-Scale Gasification-Based Co-Production of Fuels and Electricity from Switchgrass. Biofuels, Bioproducts, Biorefining, 3(2), doi:10.1002/bbb.137 174-194
    [ Abstract ]

    Large-scale gasifi cation-based systems for producing Fischer-Tropsch (F-T) fuels (diesel and gasoline blendstocks), dimethyl ether (DME), or hydrogen from switchgrass – with electricity as a coproduct in each case – are assessed using a self-consistent design, simulation, and cost analysis framework. We provide an overview of alternative process designs for coproducing these fuels and power assuming commercially mature technology performance and discuss the commercial status of key component technologies. Overall effi ciencies (lower-heatingvalue basis) of producing fuels plus electricity in these designs ranges from 57% for F-T fuels, 55–61% for DME, and 58–64% for hydrogen. Detailed capital cost estimates for each design are developed, on the basis of which prospective commercial economics of future large-scale facilities that coproduce fuels and power are evaluated.

22. Larson, Eric, S. Consonni, R. E. Katofsky, K. Iisa, and W. J. Frederick, Jr., January 2009: An Assessment of Gasification-Based Biorefining at Kraft Pulp and Paper Mills in the United States, Part B: Results. TAPPI Journal, 7(12), 4-12
    [ Abstract ]

    Commercialization of black liquor and biomass gasification technologies is anticipated in the 2010–2015 timeframe, and synthesis gas from gasifiers can be converted into liquid fuels using catalytic synthesis technologies that are already commercially established today in the gas-to-liquids or coal-toliquids industries. This set of two papers describes key results from a major assessment of the prospective energy, environmental, and financial performance of commercial gasification-based biorefineries integrated with kraft pulp and paper mills. Seven detailed biorefinery designs were developed for a reference mill in the southeastern United States, together with the associated mass/energy balances, air emissions estimates, and capital investment requirements. The biorefineries provide chemical recovery services and co-produce process steam for the mill, some electricity, and one of three liquid fuels: a Fischer-Tropsch synthetic crude oil (which could be refined to vehicle fuels at an existing petroleum refinery), dimethyl ether (a diesel engine fuel or propane substitute), or an ethanol-rich mixed-alcohol product. Compared with installing new Tomlinson power/recovery systems, biorefineries would require more capital investment and greater purchases of woody residues for energy use. However, because biorefineries would be more efficient, have lower air emissions, and produce a more diverse product slate, for nearly all cases examined, the internal rate of return (IRR) on the incremental capital investment lies between 14% and 18%, assuming a $50/bbl world oil price. The IRRs would more than double if plausible federal and state financial incentives were captured. Industry-wide adoption of such biorefining in the United States would provide significant energy and environmental benefits to the country.

23. Larson, Eric, S. Consonni, R. E. Katofsky, K. Iisa, and W. J. Frederick, Jr., 2009: An Assessment of Gasification-Based Biorefining at Kraft Pulp and Paper Mills in the United States, Part A: Background and Assumptions. TAPPI Journal, 7(11), 8-14
    [ Abstract ]

    Commercialization of black liquor and biomass gasification technologies is anticipated in the 2010–2015 time frame, and synthesis gas from gasifiers can be converted into liquid fuels using catalytic synthesis technologies that are already commercially established in the gastoliquids or coal to liquids industries. This set of two papers describes key results from a major assessment of the prospective energy, environmental, and financial performance of commercial gasification based biorefineries integrated with kraft pulp and paper mills [1]. Seven detailed biorefinery designs were developed for a reference mill in the southeastern United States, together with the associated mass/energy balances, air emissions estimates, and capital investment requirements. The biorefineries provide chemical recovery services and coproduce process steam for the mill, some electricity, and one of three liquid fuels: a FischerTropsch synthetic crude oil (which could be refined to vehicle fuels at an existing petroleum refinery), dimethyl ether (a diesel engine fuel or propane substitute), or an ethanol rich mixed alcohol product. This paper describes the key assumptions that underlie the biorefinery designs. Part B will present analytical results.

24. Laser, M., Eric Larson, B. Dale, M. Wang, N. Greene, and L. R. Lynd, March 2009: Comparative Analysis of Efficiency, Environmental Impact, and Process Economics for Mature Biomass Refining Scenarios. Biofuels, Bioproducts, Biorefining, 3(2), doi:10.1002/bbb.136 247-270
    [ Abstract ]

    Fourteen mature technology biomass refining scenarios – involving both biological and thermochemical processing with production of fuels, power, and/or animal feed protein – are compared with respect to process efficiency, environmental impact – including petroleum use, greenhouse gas (GHG) emissions, and water use–and economic profitability. The emissions analysis does not account for carbon sinks (e.g., soil carbon sequestration) or sources (e.g., forest conversion) resulting from land-use considerations. Sensitivity of the scenarios to fuel and electricity price, feedstock cost, and capital structure is also evaluated. The thermochemical scenario producing only power achieves a process efficiency of 49% (energy out as power as a percentage of feedstock energy in), 1359 kg CO₂ equivalent avoided GHG emissions per Mg feedstock (current power mix basis) and a cost of $0.0575/kWh ($16/GJ), at a scale of 4535 dry Mg feedstock/day, 12% internal rate of return, 35% debt fraction, and 7% loan rate. Thermochemical scenarios producing fuels and power realize efficiencies between 55 and 64%, avoided GHG emissions between 1000 and 1179 kg/dry Mg, and costs between $0.36 and $0.57 per liter gasoline equivalent ($1.37 – $2.16 per gallon) at the same scale and financial structure. Scenarios involving biological production of ethanol with thermochemical production of fuels and/or power result in efficiencies ranging from 61 to 80%, avoided GHG emissions from 965 to 1,258 kg/dry Mg, and costs from $0.25 to $0.33 per liter gasoline equivalent ($0.96 to $1.24/gallon). Most of the biofuel scenarios offer comparable, if not lower, costs and much reduced GHG emissions (>90%) compared to petroleum-derived fuels. Scenarios producing biofuels result in GHG displacements that are comparable to those dedicated to power production (e.g., >825 kg CO₂ equivalent/dry Mg biomass), especially when a future power mix less dependent upon fossil fuel is assumed. Scenarios integrating biological and thermochemical processing enable waste heat from the thermochemical process to power the biological process, resulting in higher overall process efficiencies than would otherwise be realized – efficiencies on par with petroleum-based fuels in several cases.

25. Lynd, L. R., Eric Larson, N. Greene, M. Laser, J. Sheehan, B. Dale, S. Mc Laughlin, and M. Wang, March 2009: The Role of Biomass in America's Energy Future: Framing the Analysis. Biofuels, Bioproducts, Biorefining, 3(2), doi:10.1002/bbb.134 113-123
    [ Abstract ]

    The Role of Biomass in America’s Energy Future (RBAEF) project, initiated during the first half of 2003, has sought to identify and evaluate paths by which biomass can make a large contribution to energy services and determine means to accelerate biomass energy use. In addressing these issues, the study has focused on future, mature, technologies rather than today’s technology. This perspective – the first of eight papers that comprise this issue – introduces the project, providing an operative definition of and method for estimating mature technology, a rationale for choosing the model feedstock, a list of the conversion technologies considered, and as a point of reference, a brief overview of the energy flows through a typical petroleum refinery. The subsequent papers are introduced as well.

26. Martelli, E., Thomas Kreutz, and S. Consonni, 2009: Comparison of coal IGCC with and without CO₂ capture and storage: Shell gasification with standard vs. partial water. Energy Procedia, Washington, DC, 1(1), doi:10.1016/j.egypro.2009.01.080 607-614
    [ Abstract ]

    This work provides a techno-economic assessment of Shell coal gasification -based IGCC, with and without CO₂ capture and storage (CCS), focusing on the comparison between the standard Shell configuration with dry gas quench and syngas coolers versus partial water quench cooling.

27. Seshadri, K., T. F. Lu, O. Herbinet, S. Humer, U. Niemann, W. J. Pitz, R. Seiser, and Chung K Law, 2009: Experimental and kinetic modeling study of extinction and ignition of methyl decanoate in laminar nonpremixed flows. Proceedings of the Combustion Institute, 3(1), doi:10.1016/j.proci.2008.06.215 1067-1074
    [ Abstract ]

    Methyl decanoate is a large methyl ester that can be used as a surrogate for biodiesel. In this experimental and computational study, the combustion of methyl decanoate was investigated in non-premixed, nonuniform flows. Experiments were performed employing the counterflow configuration with a fuel stream made up of vaporized methyl decanoate and nitrogen, and an oxidizer stream of air. The mass fraction of fuel in the fuel stream was measured as a function of the strain rate at extinction, and critical conditions of ignition were measured in terms of the temperature of the oxidizer stream as a function of the strain rate. A detailed mechanism of 8555 elementary reactions and 3036 species has been developed previously to describe combustion of methyl decanoate. Since it is not possible to use this detailed mechanism to simulate the counterflow flames because the number of species and reactions is too large to employ with current flame codes and computer resources, a skeletal mechanism was deduced from this detailed mechanism using the "directed relation graph" method. This skeletal mechanism has only 713 elementary reactions and 125 species. Critical conditions of extinction and critical conditions of ignition were calculated using this skeletal mechanism and they were found to agree well with experimental data. In general, the methyl decanoate mechanism provides a realistic kinetic tool for simulation of biodiesel fuels.

28. Tilman, D., Robert H. Socolow, J. A. Foley, J. Hill, Eric Larson, L. R. Lynd, Stephen W. Pacala, J. Reilly, Timothy Searchinger, C. Sommerville, and Robert H. Williams, July 2009: Beneficial Biofuels - The Food, Energy, and Environment Trilemma. Science, Washington, D.C., American Association for the Advancement of Science, 325(5938), doi:10.1126/science.1177970 270-271
    [ Abstract ]

    Exploiting multiple feedstocks, under new policies and accounting rules, to balance biofuel production, food security, and greenhouse-gas reduction.
    Dramatic improvements in policy and technology are needed to meet global demand for both food and biofuel feedstocks.

29. Williams, Robert H., Eric Larson, Guangjian Liu, and Thomas Kreutz, 2009: Fischer-Tropsch Fuels from Coal and Biomass: Strategic Advantages of Once-Through (‘Polygeneration’) Configurations. Energy Procedia, 1(1), doi:10.1016/j.egypro.2009.02.252 4379-4386
    [ Abstract ]

    Systems that produce synthetic liquid fuels and electricity from coal and biomass with carbon capture and storage offer an attractive cost-competitive approach for decarbonising liquid fuels and electricity simultaneously.

30. Williams, Robert H., November 2009: Strategy Already Exists to Address CO₂ Emissions. Grand Forks Herald, http://www.gpisd.net/vertical/Sites/%7B1510F0B9-E3E3-419,
31. Xu, Y., Robert H. Williams, and Robert H. Socolow, 2009: China’s rapid deployment of SO₂ scrubbers. Energy and Environmental Science, 2, doi:10.1039/B901357C 459-465
    [ Abstract ]

    Details are gradually emerging regarding China’s extraordinary commitment to environmental technology that began in 2006. With the help of Chinese written references and some field verification, we tell here the story of the rapid deployment of sulfur dioxide scrubbers at coal power plants in 2006 and 2007. Scrubbers were installed in each of these years at plants with more than 100 000 megawatts of total generating capacity, overtaking the rate of construction of new coal power plants. Scrubber installation in each year equaled the entire scrubber capacity in the U.S. We also describe novel policies enacted by China in 2007 to increase the likelihood that installed scrubbers actually operate.

32. De Lorenzo, L., Thomas Kreutz, P. Chiesa, and Robert H. Williams, 2008: Carbon-free Hydrogen and Electricity from Coal: Options for Syngas Cooling in Systems Using a Hydrogen Separation Membrane Reactor. Proceedings of ASME Turbo Expo 2005, Reno, NV, June 6-9, 2005, 130(3), doi:10.1115/1.2795763
    [ Abstract ]

    Conversion of coal to carbon-free energy carriers, H₂ and electricity, with CO₂ capture and storage may have the potential to satisfy at a comparatively low cost much of the energy requirements in a carbon-constrained world. In a set of recent studies, we have assessed the thermodynamic and economic performance of numerous coal-to-H₂ plants that employ O₂-blown, entrained-flow gasification and sour water-gas shift (WGS) reactors, examining the effects of system pressure, syngas cooling via quench versus heat exchangers, “conventional” H₂ separation via pressure swing adsorption versus novel membrane-based approaches, and various gas turbine technologies for generating coproduct electricity. This study focuses on the synergy between H₂ separation membrane reactors (HSMRs) and syngas cooling with radiant and convective heat exchangers; such “syngas coolers” invariably boost system efficiency over that obtained with quenchcooled gasification. Conventional H₂ separation requires a relatively high steam-tocarbon ratio (S/C) to achieve a high level of H₂ production, and thus is well matched to relatively inefficient quench cooling. In contrast, HSMRs shift the WGS equilibrium by continuously extracting reaction product H₂, thereby allowing a much lower S/C ratio and consequently a higher degree of heat recovery and (potentially) system efficiency. We first present a parametric analysis illuminating the interaction between the syngas coolers, high temperature WGS reactor, and HSMR. We then compare the performance and cost of six different plant configurations, highlighting (1) the relative merits of the two syngas cooling methods in membrane-based systems, and (2) the comparative performance of conventional versus HSMR-based H₂ separation in plants with syngas coolers.

33. Jomaas, G., and Chung K Law, 2008: An Experimental Study on the Self-Acceleration of Cellular Spherical Flames. 46th Aerospace Sciences Meeting, Reno, NV, http://pcl.princeton.edu/Publications/Conference/AIAA-2008-1414-908.pdf,
    [ Abstract ]

    The time-resolved images and accelerating propagation speeds of spark-ignited, expanding spherical flames exhibiting both flame-front hydrodynamic and diffusionalthermal cellular instabilities were experimentally acquired in a constant and high pressure environment. From these data the acceleration exponent α defined through R(t)=C+At^α, where A and C are constants, was determined for the near-equidiffusive flames of ethylene and acetylene and non-equidiffusive flames of propane and hydrogen, recognizing that the former is subjected only to hydrodynamic instability while the latter to the diffusional thermal instability as well. Results show that the acceleration exponent seems to be bounded by the value of 1.34, which is approached for fast-propagating flames of small thicknesses, regardless of the nature of the cells. The characteristic cell sizes were also measured and were found to agree well, for the hydrodynamic cells, with the linear stability theory of Bechtold and Matalon. The possible attainment of a self-similar mode of propagation is suggested.

34. Kreutz, Thomas, Eric Larson, Guangjian Liu, and Robert H. Williams, 2008: Fischer-Tropsch Fuels from Coal and Biomass. Proceedings of the 25th Annual International Pittsburgh Coal Conference,
    [ Abstract ]

    The prospect of sustained high oil prices, the heavy dependence of the US on imports for meeting its oil needs, and Middle East turmoil have together catalyzed intense interest in secure domestic alternatives to oil for satisfying US transportation energy needs. Also, it is now highly likely that the US will soon put into place a serious carbon mitigation policy—in which the transportation sector, accounting for 1/3 of US GHG emissions from fossil fuel burning, is likely to get focused attention. The two most significant domestic supplies that might be mobilized to address these challenges are biomass and coal.
    Spurred by farm policy, biomass has long been a focus of development efforts that have focused on using food crops for making biofuels (primarily corn-based ethanol but also biodiesel derived from soybeans and canola). However, concerns about food price impacts [1] and indirect land use impacts of growing biomass for energy on croplands [2,3] have led to growing recognition that emphasis should be shifted instead to exploiting for energy mainly lignocellulosic feedstocks that don’t require use of food biomass for providing energy—such as various crop and forest residues and energy crops that can be grown on degraded lands. These options include cellulosic ethanol produced biochemically and synthetic fuels derived thermochemically via biomass gasification—so-called biomass to liquids (BTL) technologies. Renewable lignocellulosic biomass provided using modest fossil fuel inputs can be considered a nearly “carbon neutral” feedstock, since CO₂ released to the atmosphere is recycled via photosynthesis.
    Among BTL options the production of Fischer-Tropsch liquids (FTL) from biomass has been given considerable attention [4,5,6,7,8]. FTL offers as advantages over cellulosic ethanol the prospects that: (i) no significant transportation fuel infrastructure changes would be required for widespread use, (ii) the technology could plausibly come into widespread use more quickly than cellulosic ethanol, which needs considerably more development before it can be widely deployed, (iii) it can probably accommodate more easily the wide range of biomass feedstocks that are likely to characterize the lignocellulosic biomass supply - because gasification-based processes tend to more tolerant of feedstock heterogeneity than biochemical processes.
    Recent oil price increases have led to considerable interest in making synthetic fuels from coal—so called coal-to-liquid (CTL) fuels—in light of coal’s relatively low prices and the abundance of coal both in the US and in other world regions that are not politically volatile. Much of this attention has been focused on FTL [9,10,11,12]. Coal can do much to improve energy security if it is used to make FTL. Moreover, the synfuels provided would be cleaner than the crude oil products displaced (having essentially zero sulfur and other contaminants and ultralow aromatic content). Also, for FTL production via modern entrained flow gasifiers, the air pollutant emissions from the plant are extremely low. But synthetic fuels made from coal without capture and storage of by-product CO₂ result in net GHG emissions about double those from petroleum fuels. And even with CO₂ capture and storage (CCS), the net GHG emission rate would be no less than for the crude oil products displaced. This would not be an auspicious feature of CTL with CCS technology if society decides to pursue an energy future that avoids dangerous anthropogenic interference with climate—as is required by the UN Framework Convention on Climate Change; there is now near scientific consensus that this will require by mid-century deep reductions in GHG emissions worldwide relative to the current global GHG emission rate [13].
    One approach to this challenge is to identify negative GHG emissions opportunities that might offset the CTL emissions and emissions from other difficult-to-decarbonize energy sources. Among these are opportunities to provide FTL from biomass at strong negative GHG emission rates. A striking feature of FTL technology is that a natural part of the process is the production of a stream of pure CO₂, accounting for about ½ of the carbon in the feedstock. If this CO₂ were captured and stored via CCS for FTL derived from biomass, the biofuels produced would be characterized by strong negative GHG emissions, because of the geological storage of photosynthetic CO₂ [14]. However, sustainably-recovered biomass is expensive, and the size of the BTL facilities will be limited by the quantities of biomass that can be gathered in a single location—which implies high specific capital costs ($ per barrel/day).
    These challenges posed by the BTL-with-CCS option could be mitigated by co-processing biomass with coal in the same facility. The economies of scale inherent in coal conversion could thereby be exploited, the average feedstock cost would be lower than for a pure BTL plant, and if CCS were carried out at the facility, the negative CO₂ emissions associated with the biomass could offset the unavoidable positive emissions with coal, leading to FTLs with low, zero, or negative net emissions [15]. Since this CBTL-with-CCS idea was first introduced, there has been much government and industrial interest in the concept: (i) in 2007 an Air Force/National Energy Technology Laboratory study was released exploring the prospects that its 2016 goal for 16 alternative jet fuel supplies1 might be met via CBTL with CCS to the extent of reducing the GHG emission rate for the FTL so produced to 0.8 times the rate for the crude oil products displaced [17]; (ii) the CBTL with CCS concept got focused attention in a recent Western Governors’ Association Report on future transportation fuels [18]; (iii) the National Energy Technology Laboratory is carrying out a major study comparing a wide range of CTL, BTL, and CBTL options with and without CCS [19], and (iv) some synfuel project developers are pursing plans to incorporate biomass as a feedstock along with coal in future FTL projects—including an FTL plant with CCS being planned by Baard Energy on the Ohio River at Wellsville, Ohio, that would eventually produce 50,000 barrels per day of FTL with up to up to 30% biomass by weight [20].
    Despite the growing interest in using CCS and biomass along with coal in addressing simultaneously the energy insecurity and climate change challenges posed by fuels for transportation, there is not yet available a comprehensive analytical framework for deciding the most promising ways forward—including a systematic way of assessing: (i) BTL vs CBTL vs CTL options, (ii) the amounts of biomass that might be accommodated in CBTL systems, (iii) the appropriate scales for BTL and CBTL systems, (iv) the extent to which CO₂ capture might plausibly be pursued for all FTL systems derived from coal and/or biomass, and (v) prospective carbon policy impacts on FTL projects.
    This paper can be considered a first step toward addressing these issues. We present here a comprehensive analytical framework suitable for addressing these challenges and early results of applying this framework by making comparisons in a self-consistent manner of designs for 16 alternative CTL, BTL, and CBTL plants, with and without CCS, with regard to mass/energy/carbon balances and economics.

35. Larson, Eric, et al., 2008: Biofuel Production Technologies: Status, Prospects, and Implications for Trade and Development. United Nations Conference on Trade and Development, New York and Geneva, http://www.unctad.org/en/docs/ditcted200710_en.pdf,
    [ Abstract ]

    There is growing interest in biofuels in many developing countries as a means of “modernizing” biomass use and providing greater access to clean liquid fuels while helping to address energy costs, energy security and global warming concerns associated with petroleum fuels. This publication provides information about biofuels for use in helping to understand technology-related implications of biofuels development. It seeks to provide some context for (a) understanding the limitations of “first-generation” biofuels (made today from grains, seeds and sugar crops); (b) providing meaningful descriptions accessible to non-experts of “second-generation” biofuels (made from “lignocellulosic” biomass such as crop residues or purpose-grown grasses or woody crops); (c) presenting salient energy, carbon and economic comparisons among biofuels; and (d) speculating on the implications for trade and development of future expansion in global production and use of biofuels. Second-generation biofuels are not being produced commercially anywhere today. They are made from non-edible feedstocks, which limit the direct food vs. fuel competition associated with most first generation biofuels. Such feedstocks can be bred specifically for energy purposes, thereby enabling higher production per unit land area, and more of the above-ground plant material can be converted to biofuel, thereby further increasing land-use efficiency compared to first-generation biofuels. These basic characteristics of the feedstocks hold promise for lower feedstock costs and substantial energy and environmental benefits for most second-generation biofuels compared to most first-generation biofuels. On the other hand, second-generation biofuel systems require more sophisticated processing equipment, more investment per unit of production, and larger-scale facilities (to capture capital-cost scale economies) than first-generation biofuels. In addition, to achieve the commercial energy and (unsubsidized) economic potential of second-generation biofuels, further research, development and demonstration work is needed on feedstock production and conversion. Second-generation biofuels can be classified in terms of the processes used to convert the biomass to fuel: biochemical or thermochemical. Second-generation ethanol or butanol would be made via biochemical processing. Second-generation thermochemical biofuels may be less familiar to readers, but many are fuels that are already being made commercially from fossil fuels today using processing steps that in some cases are identical to those that would be used for biofuel production. These fuels include Fischer-Tropsch liquids (FTL), methanol, and dimethyl ether (DME). Many efforts are ongoing worldwide to commercialize second-generation biofuels. In the case of biochemical fuels, breakthroughs are needed in research and engineering of microorganisms designed to process specific feedstocks, followed by large-scale demonstrations to show commercial viability. Some 10 to 20 years are probably required before commercial production could begin on a substantial basis. In the case of thermochemical fuels, since many of the equipment components needed for biofuel production are already commercially established for applications in fossil fuel conversion, and processing is relatively indifferent to the specific input feedstock, less development and demonstration efforts are needed. Commercial production of thermochemical biofuels could begin in five to 10 years. Metrics for understanding and evaluating biofuel systems include land use efficiency, net lifecycle energy balance, net lifecycle greenhouse gas balance and economics. Among all biofuels, starch based first-generation fuels exhibit the lowest land use efficiency (measured in km/year of vehicle travel achievable with the biofuel produced from one hectare). Sugar-based first-generation fuels provide about double the land-use efficiency, and second-generation fuels provide an additional improvement of 50 per cent or more. In terms of net energy balances, corn ethanol in the United States today requires about 0.7 units of fossil energy to produce one unit of biofuel, Untied States soy biodiesel requires about 0.3 units of fossil energy, and Brazilian sugar cane ethanol requires only about 0.1 units of fossil energy per unit of ethanol. Most second-generation biofuels will have energy balances as positive as for Brazilian ethanol. Lifecycle greenhouse gas (GHG) emission reductions associated with a biofuel replacing a petroleum fuel vary with the biofuel and production process, which itself typically generates some GHG emissions. In general, higher GHG savings with biofuels are more likely when sustainable biomass yields are high and fossil fuel inputs to achieve these are low, when biomass is converted to fuel efficiently, and when the resulting biofuel is used efficiently in displacing fossil fuel. First-generation grain- and seed-based biofuels provide only modest GHG mitigation benefits. Sugar cane ethanol provides greater GHG emissions mitigation, and second-generation biofuels have still larger mitigation potential. Economics are a key driver for use of biofuels. With the exception of ethanol from sugar cane in Brazil, production costs of essentially all first-generation biofuels in all countries are inherently high due to the use of high-cost feedstocks. Even the most efficient producers of ethanol (outside Brazil) are not able to compete without subsidy unless oil prices are above the $50 to $70 per barrel price range. The Brazilian ethanol industry has evolved since its inception in the 1970s to be able to produce competitive ethanol with oil prices of around $30 per barrel. Second-generation biofuels would be made from lowercost feedstocks and so have the potential for more favourable economics than most first-generation fuels. The technologies described in this paper imply a number of issues for the development of biofuels industries in developing countries. Key limitations of first-generation biofuels – relating to direct food vs. fuel conflict, cost competitiveness, and greenhouse gas emissions reductions – are not likely to be substantially different in developing countries than in industrialized countries. On the other hand, for second-generation fuels, many developing countries have the potential to produce biomass at lower cost than in industrialized countries due to better growing climates and lower labour costs, and so may be able to gain some comparative advantage. The fact that second-generation biofuel technologies are primarily being developed in industrialized countries raises the question of technology relevance for developing countries. Technologies developed for industrialized country applications will typically be capital-intensive, labourminimizing, and designed for large-scale installations to achieve best economics. Biomass feedstocks may also be quite different from feedstocks appropriate to developing country applications. Developing countries will need to be able to adapt such technologies for their own conditions, which raises issues of technology transfer. For successful technology adoption and adaptation, it will be essential to have in place a technology innovation system in a country. This includes the collective set of people and institutions able to generate fundamental knowledge, to assimilate knowledge from the global community, to form effective joint ventures with foreign companies, to formulate government policies supportive of the required research and technology adaptation needs, to implement technology-informed public policies, etc. The innovation system in Brazil is a key reason for the success of its ethanol program. There are important roles for Government in fostering the development of biofuels industries in developing countries. The development of competitive second-generation industries will be facilitated by establishing regulatory mandates for biofuels use. Direct financial incentives could also be considered, with clear “sunset” provisions and/or subsidy caps built in from the start. Policies supportive of international joint ventures would help provide access for domestic companies to intellectual property owned by international companies. With a natural endowment of favourable climate for biomass production, developing country partners in such joint ventures might contribute host sites for demonstrations and first commercial plants, as well as avenues for entering local biofuels markets. Finally, for there to be sustainable domestic biofuels industries, there is a need for a strong international biofuel and/or biofuel feedstock trading system, since countries relying on domestic production alone would be subject to weather- and market-related vagaries of agriculture. In the context of global trade, sustainability certification may be instrumental to ensuring that widespread biofuel production and use will be conducive to the achievement of social and environmental goals, without, however, creating unnecessary barriers to international trade.

36. Succar, Samir, and Robert H. Williams, April 2008: Compressed Air Energy Storage: Theory, Resources, and Applications For Wind Power. Energy Systems Analysis Group, Princeton Environmental Institute, Princeton, NJ, http://www.princeton.edu/~cmi/research/Capture/Papers/SuccarWilliams_PEI_CAES_2008April8.pdf,
    [ Abstract ]

    This report reviews the literature on compressed air energy storage (CAES) and synthesizes the information in the context of electricity production for a carbon constrained world.
    
    CAES has historically been used for grid management applications such as load shifting and regulation control. Although this continues to be the dominant near-term market opportunity for CAES, future climate policies may present a new application: the production of baseload electricity from wind turbine arrays coupled to CAES.
    
    Previous studies on the combination of wind and CAES have focused on economics and emissions [1-10]. This report highlights these aspects of baseload wind/CAES systems, but focuses on the technical and geologic requirements for widespread deployment of CAES, with special attention to relevant geologies in wind-rich regions of North America.
    
    Large penetrations of wind/CAES could make substantial contributions in providing electricity with near-zero GHG emissions if several issues can be adequately addressed. Drawing on the results of previous field tests and feasibility studies as well as the existing literature on energy storage and CAES, this report outlines these issues and frames the need for further studies to provide the basis for estimating the true potential of wind/CAES.

37. Succar, Samir, September 2008: Baseload Power Production from Wind Turbine Arrays Coupled to Compressed Air Energy Storage. Ph.D. Thesis, Department of Electrical Engineering, Princeton University, http://proquest.umi.com/pqdlink?Ver=1&Exp=10-04-2014&FMT=7&DID=1594486331&RQT=309&attempt=1&,
    [ Abstract ]

    An analysis is presented of compressed air energy storage (CAES) and its potential for mitigating the intermittency of wind power, facilitating access to remote wind resources and transforming wind into baseload power. Although CAES has traditionally served other grid support applications, it is also well suited for wind balancing applications due its ability to provide long duration storage, its fast ramp rates and its high part load efficiencies. In addition, geologies potentially suitable for CAES appear to be abundant in regions with high- quality wind resources. This is especially true of porous rock formations, which have the potential to be the least costly air storage option for CAES. The characteristics of formations suitable for CAES storage and the challenges associated with using air as a storage fluid are discussed. An optimization framework is developed for analyzing the cost of baseload plants comprised of wind turbine arrays backed by natural gas-fired generating capacity and/or CAES. The optimization model analyzes changes to key aspects of the system configuration such as the wind turbine rating, the relative capacities of the system components, the size of the CAES storage reservoir and the wind turbine spacing. The response of the optimal system configuration to changes in natural gas price, greenhouse gas (GHG) emissions price, capital cost, and wind resource is also considered. Wind turbine rating is given focused attention because of its substantial impact on system configuration and output behavior. The generation cost of baseload wind is compared to that of other baseload options. To highlight the carbon-mitigation potential of baseload wind, the competition with coal power (with and without CO₂ capture and storage, CCS) is given prominent attention. The ability of alternative options to compete under dispatch competition is explored thereby clarifying the extent to which baseload wind can defend high capacity factors in the market. This analysis indicates that CAES might be well suited for balancing wind power output and enabling wind to achieve deep reductions in GHG emissions from power generation globally.

38. WGA Coal to Liquids Working Group, G. Parker, P. Bollinger, G. Schaefer, and D. Sheppard, 2008: Coal to Liquids. ,
    [ Abstract ]

    High oil prices and our country’s growing reliance on imported petroleum have created major opportunities ― as well as challenges ― to providing alternative transportation fuels using the West’s abundance of coal, oil shale, and oil sands. The majority of these resources are located on federal lands, and it is the goal of the Western Governors’ Association to find ways to maximize the benefits of developing these unconventional fuels, while balancing national, state and local interests.
    The WGA coal-to-liquids (CTL) Working Group has proposed a framework for establishing the energy policies, programs and initiatives that would be necessary to accomplish this objective. Of primary interest in the drafting of this report to the Western Governors are the processes for providing liquid transportation fuels from coal, because they offer the greatest opportunity for developing alternatives to imported petroleum in the near term-term (5 to 10 years).
    There is considerable public debate about the desirability of going forward with CTL technology because of climate-change concerns. The debate stems in large part from the growing recognition that deep reductions in total global CO₂ emissions may be needed by mid-century, especially in industrialized regions. Such a goal within that time frame implies that total greenhouse gas emissions for transportation fuels must be reduced to a small fraction of what they are now. Such goals for transportation fuels are problematic because fuel-cycle-wide greenhouse gas (GHG) emission rates for CTL are roughly double the rate for crude oil-derived products if the CO₂ is not captured and stored (CCS), and comparable to the rate with CCS. Clearly the ability to capture and store CO₂ is critical the future acceptance of CTL technology and its success in the market.

39. Boyd, P. W., T. Jickells, Chung K Law, S. Blain, E. A. Boyle, K. O. Buesseler, K. H. Coale, J. J. Culle, H. J. W. de Baar, M. Follows, M. Harvey, and C. Lancelot, et al., 2007: Mesoscale iron enrichment experiments 1993-2005: Synthesis and future directions. Science, 315, doi:10.1126/science.1131669 612-617
    [ Abstract ]

    Since the mid-1980s, our understanding of nutrient limitation of oceanic primary production has radically changed. Mesoscale iron addition experiments (FeAXs) have unequivocally shown that iron supply limits production in one-third of the world ocean, where surface macronutrient concentrations are perennially high. The findings of these 12 FeAXs also reveal that iron supply exerts controls on the dynamics of plankton blooms, which in turn affect the biogeochemical cycles of carbon, nitrogen, silicon, and sulfur and ultimately influence the Earth climate system. However, extrapolation of the key results of FeAXs to regional and seasonal scales in some cases is limited because of differing modes of iron supply in FeAXs and in the modern and paleo-oceans. New research directions include quantification of the coupling of oceanic iron and carbon biogeochemistry.

40. Chiesa, P., Thomas Kreutz, and G. G. Lozza, 2007: CO₂ Sequestration from IGCC Power Plants by Means of Metallic Membranes. Journal of Engineering for Gas Turbines and Power, 129, doi:10.1115/1.2181184 123-134
    [ Abstract ]

    This paper investigates novel IGCC plants that employ hydrogen separation membranes in order to capture carbon dioxide for long-term storage. The thermodynamic performance of these membrane-based plants are compared with similar IGCCs that capture CO₂ using conventional (i.e., solvent absorption) technology. The basic plant configuration employs an entrained-flow, oxygen-blown coal gasifier with quench cooling, followed by an adiabatic water gas shift (WGS) reactor that converts most of CO contained in the syngas into CO₂ and H₂. The syngas then enters a WGS membrane reactor where the syngas undergoes further shifting; simultaneously, H₂ in the syngas permeates through the hydrogen-selective, dense metal membrane into a counter-current nitrogen “sweep” flow. The permeated H₂, diluted by N₂, constitutes a decarbonized fuel for the combined cycle power plant whose exhaust is CO₂ free. Exiting the membrane reactor is a hot, high pressure “raffinate” stream composed primarily of CO₂ and steam, but also containing “fuel species” such as H₂S, unconverted CO, and unpermeated H₂. Two different schemes (oxygen catalytic combustion and cryogenic separation) have been investigated to both exploit the heating value of the fuel species and produce a CO₂-rich stream for long term storage. Our calculations indicate that, when 85 vol % of the H₂+CO in the original syngas is extracted as H2 by the membrane reactor, the membrane-based IGCC systems are more efficient by ~1.7 percentage points than the reference IGCC with CO₂ capture based on commercially ready technology.

41. Chu, S., J. Goldenberg, S. Arungu Olende, M. El-Ashry, G. Davis, T. B. Johansson, D. W. Keith, J. Li, N. Nakicenovic, R. Pachauri, M. Shafie-Pour, E. Shpilrain, Robert H. Socolow, K. Yamaji, and L. Yan, October 2007: Lighting the way - Toward a sustainable energy future. A Report to the InterAcademy Council, http://royalsociety.org/downloaddoc.asp?id=4695,
    [ Abstract ]

    Making the transition to a sustainable energy future is one of the central challenges humankind faces in this century. The concept of energy sustainability encompasses not only the imperative of securing adequate energy to meet future needs, but doing so in a way that (a) is compatible with preserving the underlying integrity of essential natural systems, including averting dangerous climate change; (b) extends basic energy services to the more than 2 billion people worldwide who currently lack access to modern forms of energy; and (c) reduces the security risks and potential for geopolitical conflict that could otherwise arise from an escalating competition for unevenly distributed energy resources.

42. Greenblatt, J. B., Samir Succar, D. C. Denkenberger, Robert H. Williams, and Robert H. Socolow, 2007: Baseload wind energy: Modeling the competition between gas turbines and compressed air energy storage for supplemental generation. Energy Policy, 35(3), doi:10.1016/j.enpol.2006.03.023 1474-1492
    [ Abstract ]

    The economic viability of producing baseload wind energy was explored using a cost-optimization model to simulate two competing systems: wind energy supplemented by simple- and combined cycle natural gas turbines (‘‘wind+gas’’), and wind energy supplemented by compressed air energy storage (‘‘wind+CAES’’). Pure combined cycle natural gas turbines (‘‘gas’’) were used as a proxy for conventional baseload generation. Long-distance electric transmission was integral to the analysis. Given the future uncertainty in both natural gas price and greenhouse gas (GHG) emissions price, we introduced an effective fuel price, p_NGeff, being the sum of the real natural gas price and the GHG price. Under the assumption of p_NGeff = $5/GJ (lower heating value), 650W/m² wind resource, 750km transmission line, and a fixed 90% capacity factor, wind+CAES was the most expensive system at ¢6.0/kWh, and did not break even with the next most expensive wind+gas system until p_NGeff = $9.0/GJ. However, under real market conditions, the system with the least dispatch cost (short-run marginal cost) is dispatched first, attaining the highest capacity factor and diminishing the capacity factors of competitors, raising their total cost. We estimate that the wind+CAES system, with a greenhouse gas (GHG) emission rate that is onefourth of that for natural gas combined cycle plants and about one-tenth of that for pulverized coal plants, has the lowest dispatch cost of the alternatives considered (lower even than for coal power plants) above a GHG emissions price of $35/tC_equiv., with good prospects for realizing a higher capacity factor and a lower total cost of energy than all the competing technologies over a wide range of effective fuel costs. This ability to compete in economic dispatch greatly boosts the market penetration potential of wind energy and suggests a substantial growth opportunity for natural gas in providing baseload power via wind+CAES, even at high natural gas prices.

43. Jomaas, G., Chung K Law, and J. K. Bechtold, 2007: On transition to cellularity in expanding spherical flames. Journal of Fluid Mechanics, 583, doi:10.1017/S0022112007005885 1-26
    [ Abstract ]

    The instant of transition to cellularity of centrally ignited, outwardly propagating spherical flames in a reactive environment of fuel–oxidizer mixture, at atmospheric and elevated pressures, was experimentally determined using high-speed schlieren imaging and subsequently interpreted on the basis of hydrodynamic and diffusional–thermal instabilities. Experimental results show that the transition Péclet number, Pe_c =R_c/l_L, assumes an almost constant value for the near-equidiffusive acetylene flames with wide ranges in the mixture stoichiometry, oxygen concentration and pressure, where R_c is the flame radius at transition and l_L the laminar flame thickness. However, for the non-equidiffusive hydrogen and propane flames, Pe_c respectively increases and decreases somewhat linearly with the mixture equivalence ratio. Evaluation of Pe_c using previous theory shows complete qualitative agreement and satisfactory quantitative agreement, demonstrating the insensitivity of Pe_c to all system parameters for equidiffusive mixtures, and the dominance of the Markstein number, Ze(Le - 1), in destabilization for non-equidiffusive mixtures, where Ze is the Zel’dovich number and Le the Lewis number. The importance of using locally evaluated values of l_L, Ze and Le, extracted from either computationally simulated one-dimensional flame structure with detailed chemistry and transport, or experimentally determined response of stretched flames, in the evaluation of Pe_c is emphasized.

44. Jomaas, G., J. K. Bechtold, and Chung K Law, 2007: Spiral waves in expanding hydrogen-air flames: experiment and theory. Proceedings of the Combustion Institute, 31(1), doi:10.1016/j.proci.2006.08.100 1039-1046
    [ Abstract ]

    We report herein the first experimental observation of spiral waves over propagating flame surfaces in rich hydrogen–air mixtures at elevated pressures up to 40 atm, conducted in a specially designed, optically accessible, constant-pressure combustion chamber. The observed spiral waves are a manifestation of the large Lewis number instability, exhibiting behaviors such as clockwise/counterclockwise rotation, meandering, and fast radial wave speeds that are similar to patterns often observed in other excitable media, for example the Belousov–Zhabotinsky reaction. In addition, these spiral waves also exhibit features that seem to be characteristic of combustion systems, such as the transition criterion for diffusional-thermal pulsating instability, and their confinement within the hydrodynamic cells that also develop over such high-pressure flames of much reduced flame thicknesses. A diffusional-thermal theory was developed that successfully describes the observed spiral patterns.

45. Larson, Eric, S. Consonni, R. E. Katofsky, K. Iisa, and W. J. Frederick, Jr., 2007: Gasification Based Biorefining at Kraft Pulp and Paper Mills in the United States. Proceedings of the 2007 International Chemical Recovery Conference, Quebec City, Canada, http://www.princeton.edu/pei/energy/publications/texts/Larson-etal-ICRC07-FINAL-,
    [ Abstract ]

    Commercialization of black liquor and biomass gasification technologies is anticipated in the 2010-2015 timeframe, and synthesis gas from gasifiers can be converted into liquid fuels using catalytic synthesis technologies that are already commercially established today in the gas-to-liquids or coal-to-liquids industries. This paper describes key results from a major assessment of the prospective energy, environmental, and financial performance of commercial gasification-based biorefineries integrated with kraft pulp and paper mills. Seven detailed biorefinery designs were developed for a reference mill in the Southeastern U.S., together with the associated mass/energy balances, air emissions estimates, and capital investment requirements. The biorefineries provide chemical recovery services and coproduce process steam for the mill, some electricity, and one of three liquid fuels: a Fischer-Tropsch synthetic crude oil (which would be refined to vehicle fuels at existing petroleum refineries), dimethyl ether (a diesel engine fuel or propane substitute), or an ethanol-rich mixed-alcohol product. Compared to installing new Tomlinson power/recovery systems, biorefineries would require more capital investment and greater purchases of woody residues for energy use. However, because biorefineries would be more efficient, have lower air emissions, and produce a more diverse product slate, for nearly all cases examined, the internal rate of return (IRR) on the incremental capital investment lies between 14% and 18%, assuming a $50/bbl world oil price. The IRRs would more than double if plausible federal and state financial incentives are captured. Industry-wide adoption of such biorefining in the United States would provide significant energy and environmental benefits to the country.

46. Meng, K., Robert H. Williams, and Michael Celia, 2007: Opportunities for low-cost CO₂ storage demonstration projects in China. Energy Policy, 35(4), doi:10.1016/j.enpol.2006.08.016 2368-2378
    [ Abstract ]

    Several CO₂ storage demonstration projects are needed in a variety of geological formations worldwide to prove the viability of CO₂ capture and storage as a major option for climate change mitigation. China has several low-cost CO₂ sources at sites that produce NH₃ from coal via gasification. At these plants, CO₂ generated in excess of the amount needed for other purposes (e.g., urea synthesis) is vented as a relatively pure stream. These CO₂ sources would potentially be economically interesting candidates for storage demonstration projects if there are suitable storage sites nearby. In this study a survey was conducted to estimate CO₂ availability at modern Chinese coal-fed ammonia plants. Results indicate that annual quantities of available, relatively pure CO₂ per site range from 0.6 to 1.1 million tonnes. The CO₂ source assessment was complemented by analysis of possible nearby opportunities for CO₂ storage. CO₂ sources were mapped in relation to China’s petroliferous sedimentary basins where prospective CO₂ storage reservoirs possibly exist. Four promising pairs of sources and sinks were identified. Project costs for storage in deep saline aquifers were estimated for each pairing ranging from $15–21/t of CO₂. Potential enhanced oil recovery and enhanced coal bed methane recovery opportunities near each prospective source were also considered.

47. Radulescu, M. I., and Chung K Law, 2007: The transient start of supersonic jets. Journal of Fluid Mechanics, 578, doi:10.1017/S0022112007004715 331-369
    [ Abstract ]

    This study investigates the initial transient hydrodynamic evolution of highly underexpanded slit and round jets. A closed-form analytic similarity solution is derived for the temporal evolution of temperature, pressure and density at the jet head for vanishing diffusive fluxes, generalizing a previous model of Chekmarev using Chernyi’s boundary-layer method for hypersonic flows. Two-dimensional numerical simulations were also performed to investigate the flow field during the initial stages over distances of ∼1000 orifice radii. The parameters used in the simulations correspond to the release of pressurized hydrogen gas into ambient air, with pressure ratios varying between approximately 100 and 1000. The simulations confirm the similarity laws derived theoretically and indicate that the head of the jet is laminar at early stages, while complex acoustic instabilities are established at the sides of the jet, involving shock interactions within the vortex rings, in good agreement with previous experimental findings. Very good agreement is found between the present model, the numerical simulations and previous experimental results obtained for both slit and round jets during the transient establishment of the jet. Criteria for Rayleigh–Taylor instability of the decelerating density gradients at the jet head are also derived, as well as the formulation of a model addressing the ignition of unsteady expanding diffusive layers formed during the sudden release of reactive gases.

48. Radulescu, M. I., G. J. Sharpe, Chung K Law, and J.H.S. Lee, 2007: The hydrodynamic structure of unstable cellular detonations. Journal of Fluid Mechanics, 580, doi:10.1017/S0022112007005046 31-81
    [ Abstract ]

    The study analyses the cellular reaction zone structure of unstable methane–oxygen detonations, which are characterized by large hydrodynamic fluctuations and unreacted pockets with a fine structure. Complementary series of experiments and numerical simulations are presented, which illustrate the important role of hydrodynamic instabilities and diffusive phenomena in dictating the global reaction rate in detonations. The quantitative comparison between experiment and numerics also permits identification of the current limitations of numerical simulations in capturing these effects. Simulations are also performed for parameters corresponding to weakly unstable cellular detonations, which are used for comparison and validation. The numerical and experimental results are used to guide the formulation of a stochastic steady one-dimensional representation for such detonation waves. The numerically obtained flow fields were Favre-averaged in time and space. The resulting onedimensional profiles for the mean values and fluctuations reveal the two important length scales, the first being associated with the chemical exothermicity and the second (the ‘hydrodynamic thickness’) with the slower dissipation of the hydrodynamic fluctuations, which govern the location of the average sonic surface. This second length scale is found to be much longer than that predicted by one-dimensional reaction zone calculations.

49. Sun, H., S. H. Yang, G. Jomaas, and Chung K Law, 2007: High-Pressure Laminar Flame Speeds and Kinetic Modeling of Carbon Monoxide/ Hydrogen Combustion. Proceedings of the Combustion Institute, 31(1), doi:10.1016/j.proci.2006.07.193 439-446
    [ Abstract ]

    Laminar flame speeds were accurately measured for CO/H₂/air and CO/H₂/O₂/helium mixtures at different equivalence ratios and mixing ratios by the constant-pressure spherical flame technique for pressures up to 40 atmospheres. A kinetic mechanism based on recently published reaction rate constants is presented to model these measured laminar flame speeds as well as a limited set of other experimental data. The reaction rate constant of CO + HO₂ fi CO₂ + OH was determined to be k = 1.15 · 10⁵T^2.278 exp(-17.55 kcal/RT) cm³ mol^-1 s^-1 at 300–2500 K by ab initio calculations. The kinetic model accurately predicts our measured flame speeds and the non-premixed counterflow ignition temperatures determined in our previous study, as well as homogeneous system data from literature, such as concentration profiles from flow reactor and ignition delay time from shock tube experiments.

50. Yuan, J., Y. Ju, and Chung K Law, 2007: On flamefront instability at elevated pressures. Proceedings of the Combustion Institute, 31(1), doi:10.1016/j.proci.2006.07.180 1267-1274
    [ Abstract ]

    Effects of pressure up to 3 atm on flame-front instability were numerically investigated for both linear and nonlinear growth stages at sub-unity and unity Lewis numbers. A sixth-order compact scheme and non-reflecting boundary conditions were used to capture the evolution of the flame front. Results show that in the linear instability growth stage, elevated pressure can extend the unstable range of flame-fronts and generate the fine flame cell structure. This effect can be qualitatively predicted by the theories when Le = 1.0; however the theories diverge at sub-unity Lewis numbers (e.g. Le = 0.7). In the nonlinear growth stage, the critical wave number (k_c) from the linear dispersion relation can be used as a reference length scale for the evolution of the flame cell structure. Since elevated pressure increases the critical wave number, small flame cells appear over large flame cells (deep folds) at high ambient pressures. Furthermore, flame-front hydrodynamic instability is excited when the lateral domain is enlarged.

51. Azar, C., K. Lindgren, Eric Larson, and K. Möllerstern, 2006: Carbon capture and storage from fossil fuels and biomass – Costs and potential role in stabilizing the atmosphere. Climatic Change, 74(1-3), doi:10.1007/S10584-005-3484-7 47-79
    [ Abstract ]

    The capture and storage of CO₂ from combustion of fossil fuels is gaining attraction as a means to deal with climate change. CO₂ emissions from biomass conversion processes can also be captured. If that is done, biomass energy with CO₂ capture and storage (BECS) would become a technology that removes CO₂ from the atmosphere and at the same time deliver CO₂-neutral energy carriers (heat, electricity or hydrogen) to society. Here we present estimates of the costs and conversion efficiency of electricity, hydrogen and heat generation from fossil fuels and biomass with CO₂ capture and storage. We then insert these technology characteristics into a global energy and transportation model (GET 5.0), and calculate costs of stabilizing atmospheric CO₂ concentration at 350 and 450 ppm. We find that carbon capture and storage technologies applied to fossil fuels have the potential to reduce the cost of meeting the 350 ppm stabilisation targets by 50% compared to a case where these technologies are not available and by 80% when BECS is allowed. For the 450 ppm scenario, the reduction in costs is 40 and 42%, respectively. Thus, the difference in costs between cases where BECS technologies are allowed and where they are not is marginal for the 450 ppm stabilization target. It is for very low stabilization targets that negative emissions become warranted, and this makes BECS more valuable than in cases with higher stabilization targets. Systematic and stochastic sensitivity analysis is performed. Finally, BECS opens up the possibility to remove CO₂ from the atmosphere. But this option should not be seen as an argument in favour of doing nothing about the climate problem now and then switching on this technology if climate change turns out to be a significant problem. It is not likely that BECS can be initiated sufficiently rapidly at a sufficient scale to follow this path to avoiding abrupt and serious climate changes if that would happen.

52. Hawkins, D. G., D. A. Lashof, and Robert H. Williams, 2006: What to do about coal. , http://www.scientificamerican.com/article.cfm?id=what-to-do-about-coal-2006, 295(3), 68-75
    [ Abstract ]

    1. Coal is widely burned for power but produces large quantities of climate changing carbon dioxide.
    2. Compared with conventional power plants, new gasification facilities can more effectively and affordably extract CO₂ so it can be safely stored underground.
    3. The world must begin implementing carbon capture and storage soon to stave off global warming.

53. Larson, Eric, A. Shanker, and T. B. Johansson, et al., 2006: Energy for Sustainable Development. Energy for Sustainable Development, 10(2), doi:10.1016/S0973-0826(08)60527-X
    [ Abstract ]

    The papers in this issue evolved from the Workshop on Liquid Biofuels for the Transport Sector in Developing Countries organized by the Scientific and Technical Advisory Panel (STAP) of the Global Environment Facility (GEF) and held August 29-September 2, 2005, in New Delhi. The workshop was motivated by the growing interest in renewable biofuels as substitutes for petroleum-derived products, evidenced by an increasing number of proposals to the GEF for biofuel projects. To help with decision-making regarding such projects, the GEF requested guidance from the STAP concerning the potential impact of biofuels on greenhouse gas emissions, biodiversity, land degradation, water consumption, food production, job creation and other socio-economic factors. Toward that end, the STAP brought together a range of biofuel experts and members of STAP, GEF, and its implementing agencies for the workshop. Presentations of national biofuel programs were made, as well as of biofuel technologies, land availability issues, socioeconomic factors, greenhouse gas emissions of alternative biofuels, and other issues. Presentations and background papers from the workshop are available for download at http://www.unep.org/stapgef/documents/ Wshop_docs/liquid_biofuels_2005/WorkshopDoc.htm. This issue of ESD begins with an overview article summarizing the findings of the workshop. Subsequent articles assess existing (Brazil) and prospective (South Africa and Argentina) national biofuel programs. A World Bank perspective on the Brazilian program and prospects for similar programs to be launched in other developing countries follows next. The subsequent two articles focus on biomass availability issues, one (Rattan Lal) from the standpoint of the implications of current agricultural practices and land fertility impacts for future biomass availability for biofuel and a second (Fallot et al.) presenting a high-level methodology for identifying countries with the best long-term potentials for dedicated biomass energy plantations, considering likely future land needs for food and fodder production. Next, Girard and Fallot provide a primer on different biofuels and biofuel production technologies, with particular emphasis on “first generation” biofuels (biodiesel and bioethanol). Larson reviews a vast literature relating to estimates of the life-cycle greenhouse gas emissions of different biofuels. Finally, an independent contribution from McCormick et al. describes recent political developments in Sweden that are likely to lead to much greater use of biofuels there in the near future. These papers provide important food for thought and action toward sustainable biofuel programs throughout the world. The articles as a whole highlight the multiplicity of technology, agriculture, economy, social, policy, environmental, and other issues involved with biofuels, and the corresponding challenges of introducing biofuels on significant enough scales to substantially impact rural development, energy security, petroleum substitution, and other issues of concern. The Brazilian experience illustrates that the challenges can be overcome, but the diversity intrinsic in biofuels calls for careful context-specific analysis, planning, policy formulation and implementation to maximize the chance of success. While this issue of ESD had its genesis in the GEF-STAP workshop, interest in biofuels extends far beyond the GEF, particularly with world oil prices approaching near-record high levels in 2006, making this an especially timely issue of ESD. In this regard, we, its guest co-editors, are especially grateful to the GEF and its Scientific and Technical Advisory Panel for their support, which is enabling a wide range of stakeholders beyond the GEF to benefit from the knowledge generated at the workshop.

54. Larson, Eric, 2006: A Review of Life Cycle Analysis Studies on Liquid Biofuel Systems for the Transport Sector. Energy for Sustainable Development, http://www.princeton.edu/pei/energy/publications/texts/Larson-biofuel-LCA-ESD-June-2006.pdf, X(2), 109-126
    [ Abstract ]

    Given current oil prices and the heavy dependence of many countries on imported oil, the potential for producing or importing liquid transportation fuels made from biomass is attracting keen interest in many developing and industrialized countries. There is also some interest in biofuels for climate change mitigation. This article reviews the rich literature of published life-cycle analyses (LCAs) of liquid biofuels, with a focus on elucidating the impacts that production and use of such biofuels might have on emissions of greenhouse gases. Reviews of LCAs for “conventional” liquid biofuels (biodiesel and sugar/starch bioethanol) and potential “future” liquid biofuels (Fischer-Tropsch fuels, dimethyl ether, and cellulosic bioethanol) are included. Striking features of the LCAs reviewed include almost exclusive contextual focus on Europe or North America, wide ranges in net energy balance results and GHG impacts among different biofuels and even for the same biofuel, and a lack of focus on evaluating GHG impacts per unit of land area. The wide range of reported LCA GHG results is due in part to the wide range of plausible values for key input parameters, among which the four most significant parameters exhibiting the greatest variability and/or uncertainty are (1) the climate-active species included in the calculation, (2) assumptions around N2O emissions, (3) the allocation method used for co-product credits, and (4) soil carbon dynamics. Finally, from a comparison of GHG impacts of biomass used for transportation fuels against those for stationary applications one concludes that under some conditions biofuels will provide greater GHG mitigation benefits, but under other conditions, biopower will be favored. It is difficult to make broad and unequivocal statements on this point. Case-specific analysis is required.

55. Larson, Eric, Robert H. Williams, and H. Jin, June 2006: Fuels and electricity from biomass with CO₂ capture and storage. Proceedings of the 8th International Conference on Greenhouse Gas Control Technologies (GHGT-8), Trondheim, Norway, http://www.princeton.edu/pei/energy/publications/texts/IK-Larson-et-al-GHGT8-FI,
    [ Abstract ]

    Mass/energy balances and financial analysis are presented for (1) plants co-producing Fischer- Tropsch diesel and gasoline blendstocks plus electricity from biomass and (2) biomass integrated gasification combined cycle power plants. Plant designs with and without carbon capture and storage are analyzed. The feedstock is switchgrass. For plants with CO₂ capture, we assume that the CO₂ is stored in deep saline aquifers or used for enhanced oil recovery.

56. Larson, Eric, S. Consonni, R. E. Katofsky, K. Iisa, and W. J. Frederick, Jr., December 2006: A Cost-Benefit Assessment of Gasification-Based Biorefining in the Kraft Pulp and Paper Industry, Volume 1: Main Report. US DOE and American Forest and Paper Assoc under DOE #DE-FC26-04NT42260, PEI (final), http://www.princeton.edu/pei/energy/publications/texts/Princeton-Biorefinery-Study-,
    [ Abstract ]

    Production of liquid fuels and chemicals via gasification of kraft black liquor and woody residues (“biorefining”) has the potential to provide significant economic returns for kraft pulp and paper mills replacing Tomlinson boilers beginning in the 2010-2015 timeframe. Commercialization of gasification technologies is anticipated in this period, and synthesis gas from gasifiers can be converted into liquid fuels using catalytic synthesis technologies that are in most cases already commercially established today in the “gas-to-liquids” industry.
    These conclusions are supported by detailed analysis carried out in a two-year project co-funded by the American Forest and Paper Association and the Biomass Program of the U.S. Department of Energy. This work assessed the energy, environment, and economic costs and benefits of biorefineries at kraft pulp and paper mills in the United States. Seven detailed biorefinery process designs were developed for a reference freesheet pulp/paper mill in the Southeastern U.S., together with the associated mass/energy balances, air emissions estimates, and capital investment requirements. Commercial (“Nth”) plant levels of technology performance and cost were assumed. The biorefineries provide chemical recovery services and co-produce process steam for the mill, some electricity, and one of three liquid fuels: a Fischer-Tropsch synthetic crude oil (which would be refined to vehicle fuels at existing petroleum refineries), dimethyl ether (a diesel engine fuel or LPG substitute), or an ethanol-rich mixed-alcohol product.
    Compared to installing a new Tomlinson power/recovery system, a biorefinery would require larger capital investment. However, because the biorefinery would have higher energy efficiencies, lower air emissions, and a more diverse product slate (including transportation fuel), the internal rates of return (IRR) on the incremental capital investments would be attractive under many circumstances. For nearly all of the cases examined in the study, the IRR lies between 14% and 18%, assuming a 25-year levelized world oil price of $50/bbl – the US Department of Energy’s 2006 reference oil price projection. The IRRs would rise to as high as 35% if positive incremental environmental benefits associated with biorefinery products are monetized (e.g., if an excise tax credit for the liquid fuel is available comparable to the one that exists for ethanol in the United States today). Moreover, if future crude oil prices are higher ($78/bbl levelized price, the US Department of Energy’s 2006 high oil price scenario projection, representing an extrapolation of mid-2006 price levels), the calculated IRR exceeds 45% in some cases when environmental attributes are also monetized.
    In addition to the economic benefits to kraft pulp/paper producers, biorefineries widely implemented at pulp mills in the U.S. would result in nationally-significant liquid fuel production levels, petroleum savings, greenhouse gas emissions reductions, and criteria-pollutant reductions. These are quantified in this study. A fully-developed pulpmill biorefinery industry could be double or more the size of the current corn-ethanol industry in the United States in terms of annual liquid fuel production. Forest biomass resources are sufficient in the United States to sustainably support such a scale of forest biorefining in addition to the projected growth in pulp and paper production.

57. Larson, Eric, S. Consonni, S. Napoletano, R. E. Katofsky, K. Iisa, and W. J. Frederick, Jr., December 2006: A Cost-Benefit Assessment of Gasification-Based Biorefining in the Kraft Pulp and Paper Industry, Volume 2: Detailed Biorefinery Design and Performance Simulation. Workshop Perspectives on Dangerous Climate Change, Tyndall Centre, Norwich, UK, http://www.princeton.edu/pei/energy/publications/texts/Princeton-Biorefinery-Proj,
    [ Abstract ]

    This volume illustrates the technologies, the assumptions and the modelization adopted to estimate the heat and mass balances of the biorefinery systems considered in this study.
    Accurately calculating the mass/heat balances is crucial not only to verify the feasibility of a conceptual design and the applicability of a technological option, but also to estimate economic returns and environmental impacts. The modelization presented in this volume allows calculating all the parameters needed to appraise the overall plant performances:
    - operating conditions of the most important components;
    - extra-biomass input required to satisfy the mill steam demand;
    - auxiliary power consumption;
    - steam and cold duties;
    - net power production;
    - net fuel production.
    These data are the basis to estimate capital and operating costs, and thus economic returns. The plant scheme and the operating conditions considered for each case are the outcome of significant screening work, which included the test of a considerable number of alternatives and sensitivity analyses. The basic feature that characterizes a plant scheme is the liquid fuel generated in the Fuel Synthesis Island (FSI), for which we’ve considered three cases:
    - DME
    - raw Fischer-Tropsch
    - Mixed Alcohol
    The type of fuel however does not fully characterize our plant configurations. The other basic options specified are:
    - the arrangement of the Fuel Synthesis Island (with or without syngas recycle);
    - the type of gas turbine (if any);
    - the type of biomass gasifier (if any).
    The combination of these options generates a relatively large number of alternative configurations. In this study we’ve focused on a total of seven cases which appear particularly meaningful and interesting: three for DME, three for Fischer-Tropsch and one for Mixed Alcohol. Although these seven cases do not exhaust the range of possible options, they give clear indications on the potential and the implications of pulpmill biorefinery systems.
    Given the complexity of the systems to be modeled and the variety of the technologies involved, the modelization has been particularly challenging. A BLGF plant comprises subsystems that fall in the realm of combustion and process technology (gasifier, heat exchangers, burners, etc.), others typical of the chemical industry (gas clean-up system, reactors, distillation columns, etc. ) and others belonging to power plant technology (steam cycle, gas turbine, compressors and expanders, etc.). As a consequence, no single simulation tool is ideally suited for modeling the whole integrated biorefinery. In this study we’ve combined the use of two computer codes:
    – GS, a code developed for research purposes at Politecnico di Milano and Princeton University;
    – Aspen Plus, a code originally developed at MIT and now commercialized by AspenTech Inc.
    Despite some complexity, the calculation algorithm based on these two codes provides an accuracy similar (or higher) to that of the most detailed engineering studies that can be found in the literature.
    The technologies and the design parameters considered for each major sub-system are in between the state-of-the-art and the projections for the timeframe of the “Nth plant” biorefinery. The results summarized in the last chapter of this volume allow appraising the merits of each plant option. The variety of the plant configurations analyzed in the study gives a wide range of power and fuel productions, as well as of efficiencies.

58. Larson, Eric, S. Consonni, R. E. Katofsky, M. Campbell, K. Iisa, and W. J. Frederick, Jr., December 2006: A Cost-Benefit Assessment of Gasification-Based Biorefining in the Kraft Pulp and Paper Industry, Volume 3: Fuel Chain and National Cost-Benefit Analysis. US DOE and American Forest and Paper Assoc under DOE #DE-FC26-04NT42260, PEI (final), http://www.princeton.edu/pei/energy/publications/texts/Princeton-Biorefinery-Study-,
    [ Abstract ]

    This volume contains the detailed assumptions for the well-to-wheels (WTW) analysis and provides complete results of the national impacts analysis for all three market penetration scenarios. Figure 1 illustrates the components modeled in the WTW analysis. This volume is primarily a data volume. The reader is referred back to Volume 1 for a more complete discussion of the WTW approach and a description of the market penetration scenarios. Note that the analysis, based on the assumptions presented here, is not intended to serve as a complete lifecycle analysis of biorefinery emissions. Rather the estimates provide indicative results of the potential impacts of biorefinery options relative to “business as usual” in the pulp and paper industry.

59. Larson, Eric, S. Consonni, R. E. Katofsky, K. Iisa, W. J. Frederick, Jr., C. Courchene, F. Anand, and M. Reallf, December 2006: A Cost-Benefit Assessment of Gasification-Based Biorefining in the Kraft Pulp and Paper Industry, Volume 4: Preliminary Biorefinery Analysis with Low-Temperature Black Liquor Gasification In , http://www.princeton.edu/pei/energy/publications/texts/Biorefinery-Study-Final-Rpt-Vol4.pdf,
    [ Abstract ]

    A number of concepts for black liquor gasification have been proposed in the past [1]. Our previous assessment of black liquor gasification combined cycle (BLGCC) systems [2] included detailed analysis of two different black liquor gasifier (BLG) designs, one (Chemrec design) operating at high temperature and pressure with the condensed phase leaving the gasifier as a molten liquid and one (MTCI design) operating at lower temperature and pressure, with the condensed phase leaving the gasifier as a solid.
    A key objective in the current biorefinery assessment was to understand the relative costs/benefits of liquid fuels production vis-¨¤-vis BLGCC electricity production. Accordingly, considering the limited resources available for our project, we made a tentative decision early in the project to focus the biorefinery analysis around a single black liquor gasifier design rather than carrying out parallel designs with two gasifiers, as we did in our BLGCC work. The BLGCC work showed more favorable performance and economics for BLGCC systems designed around the high-temperature BLG (HTBLG) design, so this one was selected for the detailed kraft pulp mill biorefinery designs described in Volume 1.
    However, because there was still considerable interest in the low-temperature BLG (LTBLG) design at the Department of Energy and in the pulp and paper industry, we pursued a preliminary analysis to evaluate the LTBLG in a biorefinery application to determine whether the more favorable performance and cost for the HTBLG in the BLGCC analysis would persist in biorefinery applications. This preliminary analysis, which is described in Section 2 of this volume, confirmed that the HTBLG would likely give better results than the LTBLG in the biorefinery applications we were examining in our study.
    This finding prompted discussion among project participants about what types of applications at pulp/paper mills would allow the unique features of the LTBLG technology to be best exploited. The unique features include the high hydrogen content of the synthesis gas and the nearly complete segregation of sulfur (to the gas phase) and sodium (to the condensed phase) that occurs due to the intrinsic thermodynamics of the LTBLG process.
    One possibility is that applications involving the synthesis of products with a high hydrogen content, e.g., ammonia or pure hydrogen, might favor the LTBLG over the HTBLG because of the much higher H₂:CO ratio that characterizes LTBLG product gas (H₂:CO of 2.6 versus 1.1 on a molar basis in our BLGCC study [2]). There is some merit to this line of reasoning. However, relatively inexpensive commercial water-gas shift (WGS) reactors can be used to increase the H₂:CO ratio of a synthesis gas to arbitrarily high values via the nearly-autothermal1 WGS reaction, CO + H₂:O ¡û¡ú H₂: + CO₂. Thus, the cost and energy efficiency penalties of including a WGS system in a HTBLG application (to obtain a high hydrogen content syngas) are relatively minor, and there would appear to be little or no inherent advantage to be gained by the LTBLG technology because of its unique high-hydrogen content syngas production.
    In contrast, there may be unique opportunities at a pulp mill to take advantage of the nearly complete segregation of sulfur and sodium that characterizes the LTBLG. Interestingly, this feature was one of the major factors contributing to the relatively unfavorable financial performance we predicted for the LTBLG in the BLGCC application at a pulp/paper mill using the kraft pulping process. The chemical segregation leads to a requirement that considerable additional causticizing capacity be installed at a kraft mill to enable the regeneration of the pulping liquor. If the concept of direct causticizing proves to be commercially viable, whereby the necessary pulping chemicals are largely regenerated directly by hydrolysis of the gasifier condensed phase [3], this might allow this limitation to be overcome at a kraft pulp mill. However, work on direct causticizing is still at the stage of laboratory investigations, and the most recent results from the Georgia Institute of Technology [4] suggest that direct causticizing may not work at conditions of low-temperature gasification. This finding led us to assess alternative pulping strategies (non-kraft processes) that might be able to achieve higher pulp yields using different pulping chemistries that take advantage of having separate streams of sulfur and sodium in the chemical recovery area. Section 3 in this Volume identifies some alternative pulping options and describes analysis aimed at better understanding the commercial implications of implementing the most promising of these. First we discuss analysis of a biorefinery application with the LTBLG using the same polysulfide pulping strategy as used for our biorefinery analyses in Volume 1.

60. Law, Chung K., A. Makino, and T. F. Lu, 2006: On the off-stoichiometric peaking of adiabatic flame temperature. Combustion and Flame, 145(4), doi:10.1016/j.combustflame.2006.01.009 808-819
    [ Abstract ]

    The characteristic rich shifting of the maximum adiabatic flame temperature from the stoichiometric value for mixtures of hydrocarbon and air is demonstrated to be caused by product dissociation and hence reduced amount of heat release. Since the extent of dissociation is greater on the lean side as a result of the stoichiometry of dissociated products, the peaking occurs on the rich side. The specific heat per unit mass of the mixture is shown to increase monotonically with increasing fuel concentration, and as such tends to shift the peak toward the lean side. It is further shown that this is the cause for the lean shifting of the adiabatic flame temperature of oxidizerenriched mixtures of N_mH_n and F₂ and of NH₃ and O₂, with various amounts of inert dilution, even though their maximum heat release still peaks on the rich side.

61. Lu, T. F., and Chung K Law, 2006: Linear-Time Reduction of Large Kinetic Mechanisms with Directed Relation Graph: n-Heptane and iso-Octane. Combustion and Flame, 144(1-2), doi:10.1016/j.combustflame.2005.02.015 24-36
    [ Abstract ]

    The algorithm of directed relation graph recently developed for skeletal mechanism reduction was extended to overall linear time operation, thereby greatly facilitating the computational effort in mechanism reduction, particularly for those involving large mechanisms. Together with a two-stage reduction strategy and using the kinetic responses of autoignition and perfectly stirred reactor (PSR) with extensive parametric variations as the criteria in eliminating unimportant species, a detailed 561-species n-heptane mechanism and a detailed 857-species iso-octane mechanism were successfully reduced to skeletal mechanisms consisting of 188 and 233 species, respectively. These skeletal mechanisms were demonstrated to mimic well the performance of the detailed mechanisms, not only for the autoignition and PSR systems based on which the reduced mechanisms were developed but also for the independent system of jet-stirred reactor. It was further observed that the accuracy of calculated species concentrations was equivalently bounded by the user-specified error threshold value and that the reduction time for a single reaction state is only about 50 ms for the large iso-octane mechanism.

62. Patra, P. K., K. R. Gurney, A. S. Denning, S. T. Maksyutov, T. Nakazawa, D. Baker, P. Bousquet, L. Bruhwiler, Y.-H. Chen, P. Ciais, S. Fan, I. Y. Fung, and M. N. Gloor, et al., 2006: Sensitivity of inverse estimation of annual mean CO₂ sources and sinks to ocean-only sites versus allsites observational networks. Geophysical Research Letters, 33(L05814), doi:10.1029/2005GL025403
    [ Abstract ]

    Inverse estimation of carbon dioxide (CO₂) sources and sinks uses atmospheric CO₂ observations, mostly made near the Earth’s surface. However, transport models used in such studies lack perfect representation of atmospheric dynamics and thus often fail to produce unbiased forward simulations. The error is generally larger for observations over the land than those over the remote/marine locations. The range of this error is estimated by using multiple transport models (16 are used here). We have estimated the remaining differences in fluxes due to the use of ocean-only versus all-sites (i.e., over ocean and land) observations of CO₂ in a time-independent inverse modeling framework. The fluxes estimated using the ocean-only networks are more robust compared to those obtained using all-sites networks. This makes the global, hemispheric, and regional flux determination less dependent on the selection of transport model and observation network.

63. Succar, Samir, J. B. Greenblatt, D. C. Denkenberger, and Robert H. Williams, 2006: An Integrated Optimization Of Large-Scale Wind With Variable Rating Coupled To Compressed Air Energy Storage. Proceedings of the AWEA Windpower 2006, Pittsburgh, PA, http://www.princeton.edu/~ssuccar/recent/Succar_AWEAPaper_June06.pdf,
    [ Abstract ]

    A methodology is presented for jointly optimizing the wind turbine specific rating and the storage configuration for a large-scale wind farm coupled to compressed air energy storage (CAES). By allowing the wind-storage system to be optimized in an integrated, variable rating framework the overall cost of energy (COE) can be reduced substantially. These changes also enhance the capacity factor of the wind array, reduce the storage capacity requirements of the baseload plant and reduce the greenhouse gas emission rate of the overall system relative to a separately optimized wind farm couple to CAES. The results of this analysis could have important implications for th ecompetitiveness of large-scale remote wind and the applicability of energy storage as a baseload wind strategy in a carbon constrained world.

64. Succar, Samir, J. B. Greenblatt, and Robert H. Williams, May 2006: Comparing Coal IGCC with CCS and Wind-CAES Baseload Power Options in a Carbon-Constrained World. Proceedings of the Fifth Annual Conference on Carbon Capture & Sequestration, Alexandria, Virginia, http://www.princeton.edu/~ssuccar/recent/Succar_NETLPaper_May06.pdf,
    [ Abstract ]

    Coal integrated gasification combined cycle (IGCC) with carbon capture and storage (CCS) has emerged as a potentially cost-effective carbon mitigation strategy. However carbon policies that make energy systems such as IGCC with CCS competitive with conventional fossil power generators will also bring other low carbon technologies into play. In particular, two strategies for generating baseload power from wind are investigated: pairing wind with dedicated natural gas generation and coupling wind energy to compressed air energy storage (CAES). The costs and performance of these options are analyzed in comparison to coal IGCC with and without CCS. We find that wind with natural gas backup faces significant challenges in economic dispatch competition due to high fuel prices. However CAES, a commercially ready technology, makes it possible to transform wind power into a baseload power option with the low short-run marginal cost needed to compete in baseload markets. Moreover, geologies suitable for CAES seem to be reasonably well distributed in wind-rich regions of the United States (e.g., Great Plains) where much of the new capacity for coal power generation is being planned. An economic analysis indicates that costs and greenhouse gas emission levels of wind-CAES systems fired with natural gas will be comparable to those of coal IGCC with CCS, and could be strong competitors for coal IGCC with CCS in providing baseload electricity in a carbon-constrained world.

65. Succar, Samir, J. B. Greenblatt, and Robert H. Williams, April 2006: Arguing the case for storage. Windpower Monthly, 22(4), 8-10
    [ Abstract ]

    Whether or not storage is needed depends on the aspirations for wind power. Although there is a large potential for wind power expansion in serving non-base load markets, this should be regarded as a near term opportunity for expanding wind generation from its current very small base production level. If wind energy is to become a truly large player in electricity markets globally it must be able to compete with base load power, which accounts for most electricity generation. Notably, 70% of US electricity and 60% of global electricity are currently provided by coal and nuclear power, mostly via base load power plants.

66. Sutto, T. E., H. Ollinger, H. Kim, Craig Arnold, and A. Pique, 2006: Laser transferable polymer-ionic liquid separator/ electrolytes for solid-state rechargeable lithium-ion microbatteries. Electrochemical Solid State Letters, 9(2), doi:10.1149/1.2142158 A69-A71
    [ Abstract ]

    A laser-transferable polymer gel separator formulated from an imidazolium-based ionic liquid, poly(vinylidene fluoride) (PVDF) - HFP, and ceramic nanoparticles was prepared and electrochemically characterized by ac-impedance spectroscopy and in lithiumion microbatteries. Size and weight percent effects of the nanoparticulates added to the laser-transferred separator indicate that nanoparticulates under 100 nm in size and in the 10 wt % range exhibited the highest ionic conductivity (1–3 mS/cm). Li-ion microbatteries prepared using this separator, a LiCoO₂ cathode, and a carbon anode maintained an average discharge voltage of up to 4.2 V with a reversible specific energy of 330 mWh/g.

67. Williams, Robert H., Eric Larson, and H. Jin, May 2006: Comparing climate - change mitigating potentials of alternative synthetic liquid fuel technologies using biomass and coal. Proceedings of the 5th Annual Conference on Carbon Capture and Sequestration, http://www.netl.doe.gov/publications/proceedings/06/carbon-seq/Tech%20Session%20178.pdf,
    [ Abstract ]

    The climate-change mitigation potentials of alternative options for making synthetic liquid fuel from coal and biomass without and with CO₂ capture and storage are explored. The emphasis is on making Fischer-Tropsch liquids, with comparisons to cellulosic ethanol. Particular attention is given to exploitation of the negative CO₂ emissions potential of CO₂ capture and storage for bioenergy systems. One Fischer-Tropsch option involves coprocessing biomass and coal. All liquid fuel production options involve production of electricity as a net coproduct. Both CO₂ aquifer storage and CO₂ enhanced oil recovery options are analyzed. The metrics by which the alternatives are compared are: (i) the net greenhouse gas emission rate associated with liquid fuel production and use, (ii) the specific capital cost of liquid fuel production, (iii) the lifecycle cost calculated for a fixed capital charge rate, and (iv) the internal rate of return on equity as a function of both the crude oil price and the price of greenhouse gas emissions. In addition, for options that involve biomass, liquid fuel yields per tonne of biomass are compared. And for enhanced oil recovery applications of the captured CO₂, the relative profitability of using CO₂ from synfuel plants and integrated gasifier combined cycle power plants is explored.

68. Williams, Robert H., Eric Larson, and H. Jin, June 2006: Synthetic fuels in a world with high oil and carbon prices. Proceedings of the 8th International Conference on Greenhouse Gas Control Technologies (GHGT-8), http://www.futurecoalfuels.org/documents/032007_williams.pdf,
    [ Abstract ]

    Four carbon management options are investigated for making Fischer-Tropsch fuels plus electricity: three processing coal and one co-processing coal and biomass. Energy and carbon balances are estimated. Economic analyses are carried out for carbon prices of $0 and $100 per tonne of carbon. Both levelized costs and internal rates of return on equity are estimated with CO₂ vented, and with CO₂ captured and stored in saline aquifers, and with CO₂ captured and used for enhanced oil recovery. Comparisons are made with coal integrated gasifier combined cycle power plants. When the carbon price is $100 per tonne of carbon, the co-processing option is the most economically attractive option for making Fischer-Tropsch liquids. Even at zero carbon price enhanced oil recovery applications of captured CO₂ will often be economically attractive where such opportunities exist. Enhanced oil recovery is a sufficiently large and economically interesting niche in the USA (and perhaps elsewhere) that it could enable wide near-term experience with gasification-based energy and carbon capture and storage technologies.

69. Xue, Y., and Y. Ju, 2006: Studies on the Liftoff Properties of Dimethyl Ether Jet Diffusion Flames. Combustion Science and Technology, 178(12), doi:10.1080/00102200600626140 2219-2247
    [ Abstract ]

    The liftoff properties of the DME jet diffusion flame were investigated experimentally and analytically with Emphasis on the influences of flame stretch and fuel oxygen. The present experiments showed that the DME jet diffusion flame exhibited a distinct liftoff phenomenon that differed from other hydrocarbon fuels. This unique phenomenon was analyzed theoretically by taking into consideration the effects of flame stretch and the fuel oxygen. The results showed that the stretch effect had a significant impact on the critical liftoff Schmidt number and the flame liftoff height. Based on these observations, a new criterion for the lifted flame at the blowout limit was presented. The results also demonstrated that the appearance of fuel oxygen in DME increases the fuel mixture fraction at the stoichiometric condition and changes the flame liftoff phenomenon. The effect of fuel oxygen was further investigated by adding air into propane and n-butane diffusion flames. It was found that with the increase of oxygen addition, both propane and n-butane flames change from the direct liftoff regime to the direct blowout regime. The results well described the unique liftoff phenomenon of DME and also applicable to other oxygenated and air diluted hydrocarbon fuels.

70. Chiesa, P., S. Consonni, Thomas Kreutz, and Robert H. Williams, 2005: Co-production of Hydrogen, Electricity, and CO₂ from Coal with Commercially Ready Technology. Part A: Performance and Emissions. International Journal of Hydrogen Energy, 30(7), doi:10.1016/j.ijhydene.2004.08.002 747-767
    [ Abstract ]

    This two-part paper investigates performances, costs and prospects of using commercially ready technology to convert coal to H₂ and electricity, with CO₂ capture and storage. Part A focuses on plant configuration and the evaluation of performances and CO₂ emissions. Part B focuses on economics, establishing benchmarks for the assessment of novel technologies and guidelines for technological development. In the co-production plants considered in the paper, coal is gasified to synthesis gas in an entrained flow gasifier. The syngas is cooled, cleaned of particulate matter, and shifted (to primarily H₂ and CO₂ in sour water–gas shift reactors. After further cooling, H₂S is removed from the syngas using a physical solvent (Selexol); CO₂ is then removed from the syngas, again using Selexol; after being stripped from the solvent, the CO₂ is dried and compressed to 150 bar for pipeline transport and underground storage. High purity H₂ (99.999%) is extracted from the H₂-rich syngas via a pressure swing adsorption (PSA) unit and delivered at 60 bar. The PSA purge gas is compressed and burned in a conventional gas turbine combined cycle, generating co-product electricity. The H₂/electricity ratio can be varied by lowering the steam-to-carbon ratio in the syngas or by letting part of the de-carbonized syngas by-pass the PSA unit. Performances and emissions of H₂/electricity co-production with CO₂ capture are compared with those of a system that vents the CO₂. We examine different methods of syngas heat recovery (quench versus radiant cooling) and explore the effects of changing the electricity/H₂ ratio, gasifier pressure and hydrogen purity. Results show that state-of-the-art commercial technology allows transferring to de-carbonized hydrogen 57–58% of coal LHV, while exporting to the grid decarbonized electricity amounting to 2–6% of coal LHV. In contrast to decarbonizing coal IGCC electricity, which entails a loss of 6–8 percentage points of electricity conversion when capturing CO₂ as an alternative to venting it, CO₂ capture for H₂ production gives a minor energy penalty (∼ 2 percentage points of export electricity). For H2 production, the efficiency gain achievable by hot syngas cooling vs. quench is a modest 2 percentage point increase in electricity for export, compared to 2–4 percentage points in the electricity case. Reducing H2 purity or increasing gasification pressure has minor effects on performance.

71. Duke, R., Robert H. Williams, and A. Payne, 2005: Accelerating residential PV expansion: demand analysis for competitive electricity markets. Energy Policy, 33(15), doi:10.1016/j.enpol.2004.03.005 1910-1929
    [ Abstract ]

    This article quantifies the potential market for grid-connected, residential photovoltaic (PV) electricity integrated into new homes built in the US. It complements an earlier supply-side analysis by the authors that demonstrates the potential to reduce PV module prices below $1.5/W^p by scaling up existing thin-film technology in 100MW^p/yr manufacturing facilities. The present article demonstrates that, at that price, PV modules may be cost effective in 125,000 new home installations per year (0.5GW^p/yr). While this market is large enough to support multiple scaled up thin-film PV factories, inefficient energy pricing and demand-side market failures will inhibit prospective PV consumers without strong public policy support. Net metering rules, already implemented in many states to encourage PV market launch, represent a crude but reasonable surrogate for efficient electricity pricing mechanisms that may ultimately emerge to internalize the externality benefits of PV. These public benefits include reduced air pollution damages (estimated costs of damage to human health from fossil fuel power plants are presented in Appendix A), deferral of transmission and distribution capital expenditures, reduced exposure to fossil fuel price risks, and increased electricity system reliability for end users. Thus, net metering for PV ought to be implemented as broadly as possible and sustained until efficient pricing is in place. Complementary PV ‘‘buydowns’’ (e.g., a renewable portfolio standard with a specific PV requirement) are needed to jumpstart regional PV markets.

72. Fiore, A. M., L. W. Horowitz, D. W. Purves, H. Levy II, M. J. Evans, Y. Wang, Y. Li, and R. M. Yantosca, 2005: Evaluating the contribution of changes in isoprene emissions to surface ozone trends over the eastern United States. Journal of Geophysical Research, 110(D12303), doi:10.1029/2004JD005485
    [ Abstract ]

    Reducing surface ozone (O₃) to concentrations in compliance with the national air quality standard has proven to be challenging, despite tighter controls on O₃ precursor emissions over the past few decades. New evidence indicates that isoprene emissions changed considerably from the mid-1980s to the mid-1990s owing to land-use changes in the eastern United States (Purves et al., 2004). Over this period, U.S. anthropogenic VOC (AVOC) emissions decreased substantially. Here we apply two chemical transport models (GEOS-CHEM and MOZART-2) to test the hypothesis, put forth by Purves et al. (2004), that the absence of decreasing O₃ trends over much of the eastern United States may reflect a balance between increases in isoprene emissions and decreases in AVOC emissions. We find little evidence for this hypothesis; over most of the domain, mean July afternoon (1300–1700 local time) surface O₃ is more responsive (ranging from -9 to +7 ppbv) to the reported changes in anthropogenic NO_x emissions than to the concurrent isoprene (-2 to +2 ppbv) or AVOC (-2 to 0 ppbv) emission changes. The estimated magnitude of the O₃ response to anthropogenic NO_x emission changes, however, depends on the base isoprene emission inventory used in the model. The combined effect of the reported changes in eastern U.S. anthropogenic plus biogenic emissions is insufficient to explain observed changes in mean July afternoon surface O₃ concentrations, suggesting a possible role for decadal changes in meteorology, hemispheric background O₃, or subgrid-scale chemistry. We demonstrate that two major uncertainties, the base isoprene emission inventory and the fate of isoprene nitrates (which influence surface O₃ in the model by -15 to +4 and +4 to +12 ppbv, respectively), preclude a well-constrained quantification of the present-day contribution of biogenic or anthropogenic emissions to surface O₃ concentrations, particularly in the high-isopreneemitting southeastern United States. Better constraints on isoprene emissions and chemistry are needed to quantitatively address the role of isoprene in eastern U.S. air quality.

73. Gale, J., J. Bradshaw, Z. Chen, A. Garg, D. Gomez, H. H. Rogner, D. Simbeck, Robert H. Williams, F. Toth, and D. van Vuuren, 2005: Sources of CO₂, Chapter 2 in Carbon Dioxide Capture and Storage. Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, MA, http://www.ipcc.ch/pdf/special-reports/srccs/srccs_chapter2.pdf,
    [ Abstract ]

    Assessing CO₂ capture and storage calls for a comprehensive delineation of CO₂ sources. The attractiveness of a particular CO₂ source for capture depends on its volume, concentration and partial pressure, integrated system aspects, and its proximity to a suitable reservoir. Emissions of CO₂ arise from a number of sources, mainly fossil fuel combustion in the power generation, industrial, residential and transport sectors. In the power generation and industrial sectors, many sources have large emission volumes that make them amenable to the addition of CO₂ capture technology. Large numbers of small point sources and, in the case of transport, mobile sources characterize the other sectors, making them less amenable for capture at present. Technological changes in the production and nature of transport fuels, however, may eventually allow the capture of CO₂ from energy use in this sector.
    Over 7,500 large CO₂ emission sources (above 0.1 MtCO₂ yr-1) have been identified. These sources are distributed geographically around the world but four clusters of emissions can be observed: in North America (the Midwest and the eastern freeboard of the USA), North West Europe, South East Asia (eastern coast) and Southern Asia (the Indian sub-continent). Projections for the future (up to 2050) indicate that the number of emission sources from the power and industry sectors is likely to increase, predominantly in Southern and South East Asia, while the number of emission sources suitable for capture and storage in regions like Europe may decrease slightly.
    Comparing the geographical distribution of the emission sources with geological storage opportunities, it can be seen that there is a good match between sources and opportunities. A substantial proportion of the emission sources are either on top of, or within 300 km from, a site with potential for geological storage. Detailed studies are, however, needed to confirm the suitability of such sites for CO₂ storage. In the case of ocean storage, related research suggests that only a small proportion of large emission sources will be close to potential ocean storage sites.
    The majority of the emissions sources have concentrations of CO₂ that are typically lower than 15%. However, a small proportion (less than 2%) have concentrations that exceed 95%, making them more suitable for CO₂ capture. The high content sources open up the possibility of lower capture costs compared to low-content sources because only dehydration and compression are required. The future proportion of highand low-content CO₂ sources will largely depend on the rate of introduction of hydrogen, biofuels, and the gasification or liquefaction of fossil fuels, as well as future developments in plant sizes.
    Technological changes, such as the centralized production of liquid or gaseous energy carriers (e.g., methanol, ethanol or hydrogen) from fossil sources or the centralized production of those energy carriers or electricity from biomass, may allow for CO₂ capture and storage. Under these conditions, power generation and industrial emission sources would largely remain unaffected but CO₂ emissions from transport and distributed energy-supply systems would be replaced by additional point sources that would be amenable to capture. The CO₂ could then be stored either in geological formations or in the oceans. Given the scarcity of data, it is not possible to project the likely numbers of such additional point sources, or their geographical distribution, with confidence (estimates range from 0 to 1,400 GtCO₂ (0–380 GtC) for 2050).
    According to six illustrative SRES scenarios, global CO₂ emissions could range from 29.3 to 44.2 GtCO₂ (8–12 GtC) in 2020 and from 22.5 to 83.7 GtCO₂ (6–23 GtC) in 2050. The technical potential of CO₂ capture associated with these emission ranges has been estimated recently at 2.6–4.9 GtCO₂ for 2020 (0.7–1.3 GtC) and 4.9– 37.5 GtCO₂ for 2050 (1.3–10 GtC). These emission and capture ranges reflect the inherent uncertainties of scenario and modelling analyses. However, there is one trend common to all of the six illustrative SRES scenarios: the general increase of future CO₂ emissions in the developing countries relative to the industrialized countries.

74. Jomaas, G., June 2005: An Experimental Study on the Laminar Burning Velocities and Stability Boundaries of Outwardly Propagating Spherical Flames. M.S. Thesis, Princeton University, 3141-T,
    [ Abstract ]

    Laminar flame speeds, Markstein lengths, and critical radii for the onset of cellular instabilities were experimentally determined for outwardly propagating spherical flames using a dual-chamber design that allows near-contant experimental pressures up to 60 atmospheres. Specifically, experiments were conducted for a wide range of pressures and equivalence ratios to yield flame speed data for acetylene, ethylene, ethane, propane and dimethyl ether in air. The flame-front movement was monitored using schlieren cinematography and recorded with a high-speed digital camera. Experimental data were then reduced in order to account for stretch effects, yielding laminar, unstretched flame speeds and Markstein lengths. The results were compared to numerical predictions that include detailed chemistry and transport properties. Further experiments were conducted to study the parameters controlling the onset of cellular instabilities, both hydrodynamic and diffusional-thermal in nature. The stabilizing effect of propane dilution of hydrogen flames was also extensively investigated at various pressures and mixing ratios, and the onset of instability was reasonably well predicted with a recently developed linear stability model. Furthermore, instabilities were analyzed for acetylene and ethylene flames. It was shown that the effects of the Lewis number and activation energy for these near-unity Lewis number flames are only weak functions of equivalence ratio, and as a result the observed instabilities were almost purely hydrodynamic, rendering the flame thickness being the single most important parameter governing the onset of instabilities. In general, the flames become unstable at a smaller radius as pressure is increased due to the reduction in flame thickness with increased burning rate. Non-equidiffusive fuels were also studied, and the increased(decreased) propensity for the onset of instability for flames with Le < 1 (LE) was demonstrated experimentally and confirmed by theory. By analyzing the stretch rate at the onset of instabilities, preferential diffusion effects were observed experimentally for laminar flames. Finally, the boundary for the onset of instabilities was found to correlate well in terms of the Merkstein and Karlovitz numbers for all the test conditions and fuels in this study, indicating its potential significance in the fundamental characterization of flame-front instabilities.

75. Ju, Y., and Y. Xue, 2005: Extinction and flame bifurcations of stretched dimethyl-ether premixed flames. Proceedings of the Combustion Institute, 30(1), doi:10.1016/j.proci.2004.08.258 295-301
    [ Abstract ]

    Extinction limits and flame bifurcation of lean premixed dimethyl ether–air flames are numerically investigated using the counterflow flame with a reduced chemistry. Emphasis is paid to the combined effect of radiation and flame stretch on the extinction and flammability limits. A method based on the reaction front is presented to predict the Markstein length. The predicted positive Markstein length agrees well with the experimental data. The results show that flow stretch significantly reduces the flame speed and narrows the flammability limit of the stretched dimethyl ether–air flame. It is found that the combined effect of radiation and flow stretch results in a new flame bifurcation and multiple flame regimes. At an equivalence ratio slightly higher than the flammability limit of the planar flame, the distant flame regime appears at low stretch rates. With an increase in the equivalence ratio, in addition to the distant flame, a weak flame isola emerges at moderate stretch rates. With a further increase in the equivalence ratio, the distant flame and the weak flame branches merge together, resulting in the splitting of the weak flame branch into two weak flame branches, one at low stretch and the other at high stretch. Flame stability analysis demonstrates that the high stretch weak flame is also stable. Furthermore, a K-shaped flammability limit diagram showing various flame regimes and their extinction limits is obtained.

76. Kreutz, Thomas, May 2005: A Potential Role for “Slipstream” H₂ from Coal IGCC with CO₂ Capture and Storage in an Emerging H₂ Economy for Transportation. Proceedings of the Fourth Annual Conference on Carbon Sequestration, Alexandria, VA,
    [ Abstract ]

    Large capital-intensive energy conversion facilities generally require high load factors to achieve favorable economic performance; this typically implies high and relatively constant demand profiles. For this reason, large centralized H₂ production plants are not well matched to the decentralized and variable H₂ demand characteristic of a nascent “H₂ economy” in the transportation sector. It is widely believed that small scale distributed H₂ production technologies such as natural gas steam reforming (SMR), located at H₂ refueling terminals, will be the most economical method of providing H₂ to vehicles. Unfortunately, this model fails to satisfy two key drivers for the H₂2 economy: low CO₂ emissions and increased energy supply security. We describe an alternative model of H₂ production and distribution based on relatively large, centralized sources of decarbonized H₂ from slipstreams of synthesis gas generated in coal integrated gasification combined cycle (IGCC) power plants with CO₂ capture and storage (CCS). We have investigated the design and economics of integrated systems that include syngas production, H₂ purification, compression, buffer storage, compressed gas distribution (via pipeline or truck), and delivery at refueling stations. The delivered cost of “slipstream” H₂ is found to be quite competitive with that of H₂ from distributed SMR. Furthermore, the cost is fairly insensitive to the amount produced (when the fraction of extracted syngas is relatively small, <5-10%), making it a good match for an evolving H₂ demand. At ~10% syngas extraction, IGCC+CCS can provide enough H₂ to fuel most of the light duty vehicles in U.S. cities. The results suggest that, in a climate-constrained future that involves widespread deployment of IGCC+CCS near urban areas, the H₂ economy may be fueled by coal-based decarbonized “slipstream” H₂ rather than large dedicated H₂ plants or small scale distributed H₂ production technologies.

77. Kreutz, Thomas, Robert H. Williams, S. Consonni, and P. Chiesa, 2005: Co-production of Hydrogen, Electricity, and CO₂ from Coal with Commercially Ready Technology. Part B: Economic Analysis. International Journal of Hydrogen Energy, 30(7), doi:10.1016/j.ijhydene.2004.08.001 769-784
    [ Abstract ]

    This two-part paper investigates performances, costs and prospects of using commercially ready technology to convert coal to H₂ and electricity, with CO₂ capture and storage. Part A focuses on plant configuration, performance, and CO₂ emissions. Part B focuses on the cost of producing H₂ and electricity, with and without reduced CO₂ emissions. Our estimates show that the costs for ∼ 91% decarbonized energy (via quench gasification at 70 bar) are about 6.2 ¢/kWh for electricity and about $ 1.0/kg (8.5 $/GJ, LHV) for hydrogen; these are, respectively, 35% and 19% higher than the corresponding energy costs with CO₂ venting. Referenced to these analogous CO₂ venting plants, the costs of CO₂ emissions avoided are ∼ 24 $/tonne for electricity and 11 $/tonne for H₂.

78. Larson, Eric, H. Jin, and F. E. Celik, October 2005: Gasification-Based Fuels and Electricity Production from Biomass, without and with Carbon Capture and Storage. Princeton Environmental Institute, Princeton University, http://www.hydrogen.energy.gov/analysis_repository/project.cfm/PID=226,
    [ Abstract ]

    We report here on design, mass-and-energy-balance calculations, and production cost estimates for gasification-based thermochemical conversion of switchgrass into Fischer-Tropsch (F-T) fuels, dimethyl ether (DME), and hydrogen, in all cases with some level of co-production of electricity. Also, some process designs are developed and analyzed that include capture of byproduct CO₂ for underground storage. Additionally, we present results for stand-alone electricity production using integrated gasification combined-cycle technology, both with and without carbon capture and storage (CCS). The feedstock considered in all cases is switchgrass, and the reference production scale is an “as received” input of 5,670 metric tons per day (tpd) of switchgrass having a moisture content of 20%. This corresponds to a dry matter flow of 4,536 tpd (or 5000 dry short tons per day). The 20% moisture level is sufficiently low that active drying of the feed material is not necessary before gasification. This saves considerable capital cost by avoiding a dryer, while imposing little if any efficiency penalty relative to systems with active drying utilizing low-grade waste heat. The physical and chemical characteristics of the assumed switchgrass are given in Table 1. The energy flow corresponding to 5,670 tpd of 20% moisture switchgrass is 983 MW higher heating value or 893 MW lower heating value.

79. Law, Chung K., G. Jomaas, and J. K. Bechtold, 2005: Cellular Instabilities of Expanding Hydrogen/Propane Spherical Flames at Elevated Pressure: Theory and Experiment. Proceedings of the Combustion Institute, 30(1), doi:10.1016/j.proci.2004.08.266 159-167
    [ Abstract ]

    An experimental and theoretical investigation of the onset of cellular instabilities on spherically expanding flames in mixtures of hydrogen and propane in air at elevated pressures was conducted. Critical conditions for the onset of instability were measured and mapped out over a range of pressures and mixture compositions. An asymptotic theory of hydrodynamic and diffusional-thermal cell development on flames in mixtures comprised of two scarce fuels burning in air was also formulated. Predicted values of Peclet number, defined as the flame radius at the onset of instability normalized by the flame thickness, were shown to compare favorably with the experimentally measured values.

80. Lu, T. F., and Chung K Law, 2005: A Directed Relation Graph Method for Mechanism Reduction. Proceedings of the Combustion Institute, 30(1), doi:10.1016/j.proci.2004.08.145 1333-1341
    [ Abstract ]

    A systematic approach for mechanism reduction was developed and demonstrated. The approach consists of the generation of skeletal mechanisms from detailed mechanism using directed relation graph with specified accuracy requirement, and the subsequent generation of reduced mechanisms from the skeletal mechanisms using computational singular perturbation based on the assumption of quasi-steady-state species. Both stages of generation are guided by the performance of PSR for high-temperature chemistry and auto-ignition delay for low- to moderately high-temperature chemistry. The demonstration was performed for a detailed ethylene oxidation mechanism consisting of 70 species and 463 elementary reactions, resulting in a specific skeletal mechanism consisting of 33 species and 205 elementary reactions, and a specific reduced mechanism consisting of 20 species and 16 global reactions. Calculations for laminar flame speeds and nonpremixed counterflow ignition using either the skeletal mechanism or the reduced mechanism show very close agreement with those obtained by using the detailed mechanism over wide parametric ranges of pressure, temperature, and equivalence ratio.

81. Ming, Y., L. M. Russell, and David F. Bradford, 2005: Health and Climate Policy Impacts on Sulfur Emissions Control. Geophysical Review, 43(R6400), doi:10.1029/2004RG000167
    [ Abstract ]

    Sulfate aerosol from burning fossil fuels not only has strong cooling effects on the Earth’s climate but also imposes substantial costs on human health. To assess the impact of addressing air pollution on climate policy, we incorporate both the climate and health effects of sulfate aerosol into an integrated-assessment model of fossil fuel emission control. Our simulations show that a policy that adjusts fossil fuel and sulfur emissions to address both warming and health simultaneously will support more stringent fossil fuel and sulfur controls. The combination of both climate and health objectives leads to an acceleration of global warming in the 21st century as a result of the short-term climate response to the decreased cooling from the immediate removal of short-lived sulfate aerosol. In the long term (more than 100 years), reducing sulfate aerosol emissions requires that we decrease fossil fuel combustion in general, thereby removing some of the coemitted carbon emissions and leading to a reduction in global warming.

82. Qin, X., and Y. Ju, 2005: Measurements of burning velocities of dimethyl ether and air premixed flames at elevated pressures. Proceedings of the Combustion Institute, 30, doi:10.1016/j.proci.2004.08.251
    [ Abstract ]

    Laminar burning velocities of dimethyl ether (DME) and air premixed flames at elevated pressures up to 10 atm were measured by using a newly developed pressure-release type spherical bomb. The measurement system was validated using laminar burning velocities of methane–air flames. A comparison with the previous experimental data shows an excellent agreement and demonstrates the accuracy and reliability of the present experimental system. The measured flame speeds of DME–air flames were compared with the previous experimental data and the predictions using the full and reduced mechanisms. At atmospheric pressure, the measured laminar burning velocities of DME–air flames are in reasonable agreement with the previous data from spherical bomb method, but are much lower than both predictions and the experimental data of the PIV based counterflow flame measurements. The laminar burning velocities of DME–air flames at 2, 6, and 10 atm were also measured. It was found that flame speed decreases considerably with the increase of pressure. Moreover, the measured flame speeds are also lower than the predictions at high pressures. In addition, experiments showed that at high pressures the rich DME–air flames are strongly affected by the hydrodynamic and thermal-diffusive instabilities. Markstein lengths and the overall reaction order at different equivalence ratios were extracted from the flame speed data at elevated pressures. Sensitivity analysis showed that reactions involving methyl and formyl radicals play an important role in DME– air flame propagation and suggested that systematic modification of the reactions rates associated with methyl and formyl formations are necessary to reduce the discrepancies between predictions and measurements.

83. Radulescu, M. I., Chung K Law, and G. J. Sharpe, 2005: Structure of unstable gaseous detonations waves. Physics of Fluids, 17(091105), doi:10.1063/1.1942517
    [ Abstract ]

    Detonation waves are supersonic combustion waves. The figures illustrate their typical unstable structure and the hydrodynamic compressible turbulence generated via instabilities and self-sustained by the chemical energy release. The grayscale photographs are schlieren records of the vertical density gradients in a methane–oxygen detonation wave, illustrating the turbulent structure comprised primarily of transverse shocks, shear layers, and density interfaces separating light reacted gases and heavier unreacted gas. The detonation propagates to the right at an average Mach number of ˜ 6. The color figures illustrate the structure of the wave (pressure and temperature) obtained numerically. The front is organized in a characteristic cellular structure and substructure, consisting of interacting triple shock Mach intersections (frontal Mach stems, incident shocks, transversely propagating reflected shocks, and convected shear layers). The triple points are driven by the chemical exothermicity behind the strong Mach stems. Due to the exponential dependence of the reaction rates on local temperature, gases shocked by the weaker incident shocks have ignition delay times several orders of magnitude longer, hence accumulate as unreacted volumes behind the front. These unreacted gases react mainly through turbulent mixing with the hot reacted gases. Shear layers at the triple shock interactions are Kelvin–Helmholtz unstable and promote gas ignition by turbulent mixing of mass and heat. The transverse shocks, which sweep perpendicularly to the main front, further disrupt these density interfaces by the Richtmyer–Meshkov instability involving the baroclinic torque. Unstable detonations thus rely on compressible turbulence interactions to promote the local reaction rates of gases which escape ignition due to the unsteadiness of the leading front. The detonation wave structure thus provides an excellent setting to study exothermicity-driven compressible turbulence, manifested primarily by the interaction of shocks, density interfaces, and vortical flows.

84. Thambimuthu, K., M. Soltanieh, J. C. Abanades, R. Allam, O. Bolland, J. Davison, P. Feron, F. Goede, A. Herrera, M. Iijima, D. Jansen, I. Leites, P. Mathieu, E. Rubin, D. Simbeck, K. Warmuzinski, M. Wilkinson, and Robert H. Williams, et al., 2005: Capture of CO₂. Carbon Dioxide Capture and Storage - Chapter 3, a special report of the IPCC, Cambridge University Press, Cambridge, MA, http://www.ipcc.ch/pdf/special-reports/srccs/srccs_chapter3.pdf,
    [ Abstract ]

    The purpose of CO₂ capture is to produce a concentrated stream that can be readily transported to a CO₂ storage site. CO₂ capture and storage is most applicable to large, centralized sources like power plants and large industries. Capture technologies also open the way for large-scale production of low-carbon or carbon-free electricity and fuels for transportation, as well as for small-scale or distributed applications. The energy required to operate CO₂ capture systems reduces the overall efficiency of power generation or other processes, leading to increased fuel requirements, solid wastes and environmental impacts relative to the same type of base plant without capture. However, as more efficient plants with capture become available and replace many of the older less efficient plants now in service, the net impacts will be compatible with clean air emission goals for fossil fuel use. Minimization of energy requirements for capture, together with improvements in the efficiency of energy conversion processes will continue to be high priorities for future technology development in order to minimize overall environmental impacts and cost.
    At present, CO₂ is routinely separated at some large industrial plants such as natural gas processing and ammonia production facilities, although these plants remove CO₂ to meet process demands and not for storage. CO₂ capture also has been applied to several small power plants. However, there have been no applications at large-scale power plants of several hundred megawatts, the major source of current and projected CO₂ emissions. There are three main approaches to CO₂ capture, for industrial and power plant applications. Postcombustion systems separate CO₂ from the flue gases produced by combustion of a primary fuel (coal, natural gas, oil or biomass) in air. Oxy-fuel combustion uses oxygen instead of air for combustion, producing a flue gas that is mainly H₂O and CO₂ and which is readily captured. This is an option still under development. Pre-combustion systems process the primary fuel in a reactor to produce separate streams of CO₂ for storage and H₂ which is used as a fuel. Other industrial processes, including processes for the production of low-carbon or carbon-free fuels, employ one or more of these same basic capture methods. The monitoring, risk and legal aspects associated with CO₂ capture systems appear to present no new challenges, as they are all elements of long-standing health, safety and environmental control practice in industry.
    For all of the aforementioned applications, we reviewed recent studies of the performance and cost of commercial or near-commercial technologies, as well as that of newer CO2 capture concepts that are the subject of intense R&D efforts worldwide. For power plants, current commercial CO₂ capture systems can reduce CO₂ emissions by 80-90% kWh^-1 (85- 95% capture efficiency). Across all plant types the cost of electricity production (COE) increases by 12-36 US$ MWh^-1 (US$ 0.012-0.036 kWh-1) over a similar type of plant without capture, corresponding to a 40-85% increase for a supercritical pulverized coal (PC) plant, 35-70% for a natural gas combined cycle (NGCC) plant and 20-55% for an integrated gasification combined cycle (IGCC) plant using bituminous coal. Overall the COE for fossil fuel plants with capture, ranges from 43-86 US$ MWh^-1, with the cost per tonne of CO₂ ranging from 11- 57 US$/tCO₂ captured or 13-74 US$/tCO₂ avoided (depending on plant type, size, fuel type and a host of other factors). These costs include CO₂ compression but not additional transport and storage costs. NGCC systems typically have a lower COE than new PC and IGCC plants (with or without capture) for gas prices below about 4 US$ GJ^-1. Most studies indicate that IGCC plants are slightly more costly without capture and slightly less costly with capture than similarly sized PC plants, but the differences in cost for plants with CO₂ capture can vary with coal type and other local factors. The lowest CO₂ capture costs (averaging about 12 US$/t CO₂ captured or 15 US$/tCO₂ avoided) were found for industrial processes such as hydrogen production plants that produce concentrated CO₂ streams as part of the current production process; such industrial processes may represent some of the earliest opportunities for CO₂ Capture and Storage (CCS). In all cases, CO₂ capture costs are highly dependent upon technical, economic and financial factors related to the design and operation of the production process or power system of interest, as well as the design and operation of the CO₂ capture technology employed. Thus, comparisons of alternative technologies, or the use of CCS cost estimates, require a specific context to be meaningful.
    New or improved methods of CO₂ capture, combined with advanced power systems and industrial process designs, can significantly reduce CO₂ capture costs and associated energy requirements. While there is considerable uncertainty about the magnitude and timing of future cost reductions, this assessment suggests that improvements to commercial technologies can reduce CO₂ capture costs by at least 20-30% over approximately the next decade, while new technologies under development promise more substantial cost reductions. Realization of future cost reductions, however, will require deployment and adoption of commercial technologies in the marketplace as well as sustained R&D.

85. Wang, X., D. L. Mauzerall, Y. Hu, A. G. Russell, Eric Larson, J.-H. Wood, D. Streets, and A. Guenther, 2005: A High-Resolution Emission Inventory for Eastern China in 2000 and Three Scenarios for 2020. Atmospheric Environment, 39(32), doi:10.1016/j.atmosenv.2005.06.051 5917-5933
    [ Abstract ]

    We develop a source-specific high-resolution emission inventory for the Shandong region of eastern China for 2000 and 2020. Our emission estimates for year 2000 are higher than other studies for most pollutants, due to our inclusion of rural coal consumption, which is significant but often underestimated. Still, our inventory evaluation suggests that we likely underestimate actual emissions. We project that emissions will increase greatly from 2000 to 2020 if no additional emission controls are implemented. As a result, PM2.5 concentrations will increase; however O₃ concentrations will decrease in most areas due to increased NO_X emissions and VOC-limited O₃ chemistry. Taking Zaozhuang Municipality in this region as a case study, we examine possible changes in emissions in 2020 given projected growth in energy consumption with no additional controls utilized (BAU), with adoption of best available end-of-pipe controls (BACT), and with advanced, low-emission coal gasification technologies (ACGT) which are capable of gasifying the high-sulfur coal that is abundant in China. Emissions of NH₃ are projected to be 20% higher, NMVOC50% higher, and all other species 130–250% higher in 2020 BAU than in 2000. Both alternative 2020 emission scenarios would reduce emissions relative to BAU. Adoption of ACGT, which meets only 24% of energy service demand in Zaozhuang in 2020 would reduce emissions more than BACT with 100% penetration. In addition, coal gasification technologies create an opportunity to reduce greenhouse gas emissions by capturing and sequestering CO₂ emissions below ground.

86. Xue, Y., X. Qin, and Y. Ju, January 2005: Study of Liftoff Mechanism of Nonpremixed Jet Flame near Unity Schmidt Number. AIAA-2005-546, 43rd AIAA Aerospace Sciences Meeting and Exhibit, Reno, Nevada, http://pdf.aiaa.org/preview/CDReadyMASM05_666/PV2005_546.pdf,
    [ Abstract ]

    Nonpremixed jet flames of dimethyl ether (DME) were studied both experimentally and theoretically to investigate flame liftoff near unity Schmidt number. It was found experimentally that although the DME nonpremixed flames have a Schmidt number larger than unity it cannot be lifted directly by increasing the flow rate. Lifted flames can only be established by igniting the mixture in a narrow region downstream of the jet at low flow rates. The results also show that the liftoff flow rate is less than that of the blowout limit of the attached flame. Theoretically, the self-similar Landau-Squire solution for a round jet is revisited and the combined effects of stretch and flame curvature on triple flame propagation speed were considered. It was found that the critical Schmidt number for liftoff shifts around unity. The critical Schmidt number is less than unity for fuel Le numbers larger than 0.5 and larger than unity for Le numbers less than 0.5.

87. Yuan, J., Y. Ju, and Chung K Law, 2005: Coupled hydrodynamic and diffusional-thermal instabilities in flame propagation at large Lewis numbers. Physics of Fluids, 17(O74106), doi:10.1063/1.1964845
    [ Abstract ]

    The dynamics of flame cell evolution due to the coupling between hydrodynamic and diffusional-thermal instabilities in subunity Lewis number flames was simulated using a sixth-order central difference scheme and newly developed nonreflective boundary conditions. Results show that the interaction between these two modes of instabilities yields distinct evolutions of cell splitting, merging, growth, local extinction, and lateral motion, leading to fluctuations of the flow and species concentrations as well as substantial increase in the flame speed. The study also demonstrates that small computational domains cannot correctly predict cell merging and transverse motion.

88. Zheng, X. L., T. F. Lu, Chung K Law, C. K. Westbrook, and H. J. Curran, 2005: Experimental and Computational Study of Nonpremixed Ignition of Dimethyl Ether in Counterflow. Proceedings of the Combustion Institute, 30(1), doi:10.1016/j.proci.2004.08.241 1101-1109
    [ Abstract ]

    The ignition temperature of nitrogen-diluted dimethyl ether (DME) by heated air in counterflow was experimentally determined for DME concentration from 5.9% to 30%, system pressure from 1.5 to 3.0 atm, and pressure-weighted strain rate from 110 to 170 s^-1. These experimental data were compared with two mechanisms that were, respectively, available in 1998 and 2003, with the latter being a substantially updated version of the former. The comparison showed that while the 1998-mechanism uniformly over-predicted the ignition temperature, the 2003-mechanism yielded a surprisingly close agreement for all experimental data. Sensitivity analysis for the near-ignition state based on both mechanisms identified the deficiencies of the 1998-mechanism, in particular, the specifics of the low-temperature cool flame chemistry in effecting ignition at higher temperatures, as the fuel stream is being progressively heated from its cold boundary to the high-temperature ignition region around the hot-stream boundary. The 2003-mechanism, consisting of 79 species and 398 elementary reactions, was then systematically simplified by using the directed relation graph method to a skeletal mechanism of 49 species and 251 elementary reactions, which in turn was simplified further by using computational singular perturbation method and quasisteady- state species assumption to a reduced mechanism consisting of 33 species and 28 lumped reactions. It was demonstrated that both the skeletal and reduced mechanisms mimicked the performance of the detailed mechanism with high accuracy.

89. Celik, F. E., Eric Larson, and Robert H. Williams, September 2004: Transportation Fuels from Coal with Low CO₂ Emissions. Proceedings of the 7th International Conference on Greenhouse Gas Control Technologies, (GHGT-7), http://www.princeton.edu/~cmi/research/Vancouver04/Celik,Larson,Williams,%20GHGT7,%202004.pdf
    [ Abstract ]

    We present energy and carbon balances and cost estimates based on detailed Aspen Plus process simulations for five plant designs to co-produce dimethyl ether (DME) and electricity from coal. Four of the designs include capture of CO₂ for long-term underground storage. We also illustrate the potential DME offers for reducing emissions by facilitating a shift to more energy-efficient vehicles.

90. Consonni, S., Eric Larson, and R. E. Katofsky, 2004: An Assessment of Black Liquor Gasification Combined Cycles, Part A: Technological Issues And Performance Comparisons. Proceedings of the 2004 ASME International Gas Turbine and Aeroengine Congress, Vienna,
    [ Abstract ]

    Black liquor gasification (BLG) technologies are under active commercial development in the United States and Europe. BLG has been proposed as a future replacement for Tomlinson boilers to provide more efficient, safer, environmentally-friendlier, and more cost-competitive chemical and energy recovery at kraft pulp and paper mills. Also, some pulping process improvements are more readily implemented with BLG than with black liquor combustion. This is Part A of a two-part paper summarizing results of a large study supported by the US Department of Energy, the American Forest and Paper Association, the Southern Company, and the Tennessee Valley Authority to assess performances, emissions, costs and overall benefits of black liquor gasification combined cycle (BLGCC) technology for the U.S. kraft pulp and paper industry. Part A discusses the status of leading black liquor gasification technologies and presents detailed mass and energy balances for BLGCC integrated with a pulp and paper mill producing 1725 metric tons per day of uncoated freesheet paper. The corresponding nominal flow of black liquor solids is 6 million lbs/day (or 438 MW of contained energy). Mass and energy balances are also presented at a comparable level of detail for state-of-the-art and advanced Tomlinson systems. Tomlinson performances are compared with that for three BLGCC configurations: (i) low-temperature, indirectly-heated gasifier coupled with a medium-power output heavy-duty gas turbine; (ii) high-temperature, oxygen-blown gasifier coupled with a medium-power output gas turbine; (iii) same high-temperature gasifier coupled with a utility-scale gas turbine, where the extra fuel input required to fully load the gas turbine is supplied by natural gas. With state-of-the-art Tomlinson technology, the integrated mill must import approximately 36 MW from the electric grid, which can be reduced to 11.5 MW with an advanced Tomlinson design. Medium-scale BLGCC allows export of 15-20 MW to the gird. This increases to 125 MW when the gasifier is coupled to the utility-scale gas turbine. The superior thermodynamic features of BLGCC are evidenced by th e high ratio (0.5 - 0.9) of extra electricity generated by the BLGCC to extra fossil fuel purchased (higher heating value basis).

91. Goldenberg, J., T. B. Johansson, A.K.N. Reddy, and Robert H. Williams, 2004: A global clean cooking fuel initiative. Energy for Sustainable Development, VIII(3), doi:10.1016/S0973-0826(08)60462-7 5-12
    [ Abstract ]

    This article calls for engaging the public and private sectors of developing and industrialized countries in a global clean cooking fuel initiative (GCCFI) to bring about a worldwide shift to clean fluid fuels for cooking and heating in 10-15 years’ time -- with an emphasis on providing clean fuel to the poorest households. This initiative is crucial to implementation of the Millennium Development Goals and the Plan of Implementation of the World Summit on Sustainable Development. The article builds on (1) analyses in this special issue of Energy for Sustainable Development of challenges to sustainable development posed by use of solid fuels for cooking and water heating (and for space heating in temperate climates) and opportunities for addressing them by bringing about a shift to clean fluid fuels, and (2) an extensive and compelling literature on the problems posed by this reliance on solid fuels.

92. Goldenberg, J., and T. B. Johansson, 2004: World Energy Assessment: Overview. World Energy Assessment: Overview, 2004 Update, (ISBN: 92-1-126167-8),
    [ Abstract ]

    The World Energy Assessment provides analytical background and scientific information for decision makers at all levels. It describes energy’s fundamental relationship to sustainable development and analyses how energy can serve as an instrument to reach that goal. This overview synthesises the key findings of the report, which is divided into six parts. Part I outlines the institutional framework, particularly at the United Nations level at which sustainable energy development is discussed, updating previous information to include the important decisions taken in Johannesburg in 2002 at the World Summit on Sustainable Development. Part II provides the basic facts concerning production of energy carriers and distribution and use of energy, taking 2001 as the reference year.The facts illustrate the heterogeneity among regions in resources availability and energy use. Part III considers the linkages between the current energy system and major global issues, including poverty alleviation, health, environmental protection, energy security, and the improvement of women’s and children’s lives.To meet objectives in these areas, major changes in local, regional, and global energy systems are needed. Part IV examines the energy resources and technological options available to meet the challenges identified. It concludes that physical resources are plentiful enough to supply the world’s energy needs through the twenty-first century and beyond, but that their use may be constrained by environmental and other concerns. Options to address these concerns through greater energy efficiency, use of renewable energy sources, and next-generation technologies – are then analysed. The analysis indicates that the technical and economic potential of energy efficiency measures is under-realised, and that a larger contribution by renewables to world energy use is already economically viable.Over the longer term, a variety of new renewable and advanced energy technologies may be able to provide substantial amounts of energy safely, at affordable costs, and with near-zero emissions. Part V synthesises and integrates the material presented in the earlier parts by considering whether sustainable futures – which address the issues discussed in part III using the options identified in part IV – are possible. The analysis shows that development based on current trends does not meet several criteria of sustainability. However, combinations of resources and technologies exist that would be economically feasible and meet most, if not all, sustainability challenges at the same time. Special attention is given to the challenge of bringing affordable energy to the rural areas of developing countries. It presents approaches to widening access to liquid and gaseous fuels for cooking and heating and to electricity for meeting basic needs and stimulating income-generating activities. Finally, the special challenges in the transportation sector are analysed. Part VI analyses policy issues and options that could shift current unsustainable practices in the direction of sustainable development, using energy as an instrument to reach that goal. Creating energy systems that support sustainable development will require policies that take advantage of the market to promote greater energy efficiency, increased use of renewables, and the development and diffusion of cleaner, next-generation energy technologies. Given proper signals, market actors could deliver much of what is needed. However, market forces alone are unlikely to meet the energy needs of poor people, or to protect adequately the environment. Sustainable development demands frameworks (including consistent policy measures and transparent regulatory regimes) to address these issues.

93. Keith, D. W., J. F. De Carolis, D. C. Denkenberger, D. H. Lenschow, S. Malyshev, Stephen W. Pacala, and P. J. Rasch, 2004: The Influence of Large-scale Wind-power on Global Climate. Proceedings of the National Academy of Sciences of the United States of America, 101(46), doi:10.1073/pnas.0406930101 16115-16120
    [ Abstract ]

    Large-scale use of wind power can alter local and global climate by extracting kinetic energy and altering turbulent transport in the atmospheric boundary layer. We report climate-model simulations that address the possible climatic impacts of wind power at regional to global scales by using two general circulation models and several parameterizations of the interaction of wind turbines with the boundary layer. We find that very large amounts of wind power can produce nonnegligible climatic change at continental scales. Although large-scale effects are observed, wind power has a negligible effect on global-mean surface temperature, and it would deliver enormous global benefits by reducing emissions of CO₂ and air pollutants. Our results may enable a comparison between the climate impacts due to wind power and the reduction in climatic impacts achieved by the substitution of wind for fossil fuels.

94. Kreutz, Thomas, and Robert H. Williams, September 2004: Competition Between Coal and Natural Gas in Producing H₂ and Electricity under CO₂ Emission Constraints. Proceedings of the 7th International Conference on Greenhouse Gas Control Technologies, (GHGT-7), http://www.princeton.edu/~cmi/research/Vancouver04/Kreutz%20-%20Williams%20,
    [ Abstract ]

    This study explores the competition between coal and natural gas in the large scale production of electricity and H₂ in a world with severe constraints on greenhouse gas emissions. We examine the economic conditions that fa-vor: 1) CO₂ capture vs. CO₂ venting, and 2) coal versus natural gas as the primary energy source, by varying the magnitude of an assumed carbon tax, the price of natural gas, and capacity factor of natural gas combined cycle (NGCC) plants. Coal-based conversion focuses on gasification: electricity from integrated gasifier combined cycle (IGCC) plants, and H₂ + electricity from gasification-based plants; both pure CO₂ capture and storage (CCS) and (the potentially less costly) co-capture and co-storage of H₂S+CO₂ are considered. We also examine the effect of 3 Party Covenant financing, a public subsidy for encouraging the commercial adoption of IGCC. The natural gas (NG) systems considered are NGCC for electricity and steam methane reforming for H₂ production.

95. Larson, Eric, and H. Yang, 2004: Dimethyl ether (DME) from coal as a household cooking fuel in China. Energy for Sustainable Development, VIII(3), doi:10.1016/S0973-0826(08)60473-1 115-126
    [ Abstract ]

    Dimethyl ether (DME) has characteristics similar to liquefied petroleum gas (LPG) as a household cooking fuel. As such, DME is an attractive fuel for clean cooking. DME can be made from any carbonaceous feedstock, including natural gas, coal, or biomass, using established technologies. Given China’s rich coal resources, the production and use of coal-derived DME as a cooking fuel in China could be attractive. This article reviews characteristics of DME and technology for making DME from coal. Conditions under which coal-derived DME in China would be cost-competitive with imported LPG in different regions of China are analyzed.

96. Larson, Eric, and H. Jin, et al., 2004: Thermochemical Fuels Production from Switchgrass. , Princeton, NJ, Princeton Environmental Institute, Unpublished
97. Law, Chung K., and O, C. Kwon, 2004: Effects of Hydrocarbon Substitution on Atmospheric Hydrogen-Air Flame Propagation. International Journal of Hydrogen Energy, 29(8), doi:10.1016/j.ijhydene.2003.09.012 867-879
    [ Abstract ]

    In order to evaluate the potential of partial hydrocarbon substitution to improve the safety of hydrogen use in general and the performance of internal combustion engines in particular, the outward propagation and development of surface cellular instability of spark-ignited spherical premixed flames of mixtures of hydrogen, hydrocarbon, and air were experimentally studied at NTP condition in a constant-pressure combustion chamber. With methane, ethylene, and propane being the substituents, the laminar burning velocities, the Markstein lengths, and the propensity of cell formation were experimentally determined, while the laminar burning velocities and the associated flame thicknesses were computed using recent kinetic mechanisms. Results show substantial reduction of laminar burning velocities with hydrocarbon substitution, and support the potential of propane as a suppressant of both diffiusional–thermal and hydrodynamic cellular instabilities in hydrogen–air flames. Such a potential, however, was not found for methane and ethylene as substituents.

98. Ming, Y., 2004: Influence of health-based policy on climate. Ph.D. thesis for Civil and Environmental Engineering, Princeton University,
    [ Abstract ]

    Sulfate aerosol from burning sulfur-containing fuels comprises the single most significant contribution to the climate effects of aerosol emissions: as a surface-layer pollutant it also imposes health costs on humans. There is growing epidemiological evidence identifying substantial economic costs from health effects associated with air pollutions (Hall et al., 1992). To make a start on assessing the impact on climate policy of addressing air pollution, we incorporate sulfate aerosol, which has a cooling effect (Adams et al., 2001), to an integrated-assessment model of fossil fuel emissions control. The climate and health damages, and carbon-based fossil fuel and sulfur control costs, are discounted from the total economic output available for consumption and investment. By maximizing per capital utility given available policy instruments, the optimal paths of global mean temperature and carbon and sulfur emissions are calculated.

99. Ogden, J. M., Robert H. Williams, and Eric Larson, 2004: Societal Lifecycle Costs of Cars with Alternative Fuels/Engines. Energy Policy, 32(1), doi:10.1016/S0301-4215(02)00246-X 7-27
    [ Abstract ]

    Effectively addressing concerns about air pollution (especially health impacts of small-particle air pollution), climate change, and oil supply insecurity will probably require radical changes in automotive engine/fuel technologies in directions that offer both the potential for achieving near-zero emissions of air pollutants and greenhouse gases and a diversification of the transport fuel system away from its present exclusive dependence on petroleum. The basis for comparing alternative automotive engine/fuel options in evolving toward these goals in the present analysis is the ‘‘societal lifecycle cost’’ of transportation, including the vehicle first cost (assuming large-scale mass production), fuel costs (assuming a fully developed fuel infrastructure), externality costs for oil supply security, and damage costs for emissions of air pollutants and greenhouse gases calculated over the full fuel cycle. Several engine/fuel options are considered—including current gasoline internal combustion engines and a variety of advanced lightweight vehicles: internal combustion engine vehicles fueled with gasoline or hydrogen; internal combustion engine/hybrid electric vehicles fueled with gasoline, compressed natural gas, Diesel, Fischer–Tropsch liquids or hydrogen; and fuel cell vehicles fueled with gasoline, methanol or hydrogen (from natural gas, coal or wind power). To account for large uncertainties inherent in the analysis (for example in environmental damage costs, in oil supply security costs and in projected mass-produced costs of future vehicles), lifecycle costs are estimated for a range of possible future conditions. Under base-case conditions, several advanced options have roughly comparable lifecycle costs that are lower than for today’s conventional gasoline internal combustion engine cars, when environmental and oil supply insecurity externalities are counted - including advanced gasoline internal combustion engine cars, internal combustion engine/hybrid electric cars fueled with gasoline, Diesel, Fischer– Tropsch liquids or compressed natural gas, and hydrogen fuel cell cars. The hydrogen fuel cell car stands out as having the lowest externality costs of any option and, when mass produced and with high valuations of externalities, the least projected lifecycle cost. Particular attention is given to strategies that would enhance the prospects that the hydrogen fuel cell car would eventually become the Car of the Future, while pursuing innovations relating to options based on internal combustion engines that would both assist a transition to hydrogen fuel cell cars and provide significant reductions of externality costs in the near term.

100. Williams, Robert H., December 2004: IGCC: Next Steps on the Path to Gasification-Based Energy from Coal. Expanding Energy Supply, in The National Commission on Energy Policy, http://www.bipartisanpolicy.org/sites/default/files/TA_C4.pdf, (Chapter 2), 351-381
     [ Abstract ]

     The integrated gasifier combined cycle (IGCC) makes it feasible to provide coal electricity as cleanly as natural gas combined cycle (NGCC) plants and to deal with the climate challenge via CO₂ capture and storage (CCS) with much lower energy and cost penalties than with coal steam-electric technologies. Moreover, IGCC is a stepping stone to provision of clean, secure, and climate-friendly supplies of synthetic fuels manufactured via gasification of coal and biomass with capture and storage underground of CO₂—synthetic fuels that will often be provided in polygeneration plants that also make electricity, as well as chemicals and process steam. Although IGCC technology has evolved to the point where electricity generation costs based on use of bituminous coals are about the same as for steam-electric plants, there are three major institutional challenges that must be overcome. The first is that coal IGCC technology is not likely to be launched in the market without appropriate promotion by the public sector, because much of what the technology offers are public (rather than private) benefits not yet reflected in energy market prices. The second is that, although all components of current IGCC CO₂ capture (CC) systems are fully proven and commercially available, no IGCC systems with CC have been built. Early field experience with CC technologies is needed even before a climate mitigation policy is put into place. The third is that the concept of a major future for coal in a climate-constrained world hinges on the viability of CO₂ storage at “gigascale”—the determination of which requires, along with more R&D on CO₂ storage, the conduct of many “megacale” CO₂ storage demonstration projects during the next 10-15 years.

101. Williams, Robert H., December 2004: Toward Polygeneration of Fluid Fuels and Electricity via Gasification of Coal and Biomass. Expanding Energy Supply, in The National Commission on Energy Policy, http://www.bipartisanpolicy.org/sites/default/files/TA_C4.pdf, (Chapter 4), 497-520
     [ Abstract ]

     The major challenges posed by transportation fuels are oil supply insecurity, the prospect of sustained high oil prices, health effects of air pollution, and the climate change risks posed by the buildup in the atmosphere of CO₂ from fossil fuel burning. The oil issues are the most pressing, and the climate challenge is the most daunting. The problems cannot be solved without radical changes in our transportation energy system—and getting started as soon as possible. A strategy for dealing effectively with these challenges in this quarter century is described. The elements of the strategy are: (i) bringing about a shift to energy-efficient hybrid-electric vehicles, (ii) the production of ultra-clean “designer” synthetic fuel from coal and biomass via gasification, and (iii) capture and underground storage of the CO₂ byproduct of synthetic fuel manufacture. This strategy makes it feasible to provide substantial quantities of clean liquid fuels for transportation without using oil, with ultra-low greenhouse gas emissions, without having to shift to a hydrogen economy, and with far less land than is required with fluid fuels produced from biomass only.

102. Williams, Robert H., 2004: $1 a Gallon Synthetic Liquid Fuel with the GHG Emission Rate of Hydrogen. , Unpublished
103. Zheng, X. L., and Chung K Law, 2004: Ignition of Premixed Hydrogen/Air by Heated Counterflow under Reduced and Elevated Pressures. Combustion and Flame, 136(1-2), doi:10.1016/j.combustflame.2003.09.016 168-179
     [ Abstract ]

     The temperature of an inert jet required to ignite a counterflowing lean premixed hydrogen/air jet was experimentally determined over the pressure range of 0.6 to 7 atm and computationally simulated using detailed chemistry and transport. Results show that, compared to the homogeneous explosion limits, ignition takes place at higher temperatures and exhibits five limits over the pressure range investigated. The first and second ignition limits resemble the corresponding first and second homogeneous explosion limits, except they have steeper slopes in the pressure–temperature response, with the first limit being affected by the significant transport loss of the H radical and the second limit modified by the activation of the otherwise metastable HO₂ radicals by the diffusively enriched H₂. The third and fifth ignition limits are respectively manifestations of the lowand high-pressure responses of the third homogeneous explosion limit behavior, which is nevertheless punctuated by the fourth ignition limit characterized by the HO₂–H reactions. Furthermore, the fourth ignition limit runs fairly parallel to the crossover temperature, but is shifted to lower temperatures. An explicit expression, 2k₁ = {2k₁₀/(k₁₀ +k₁₁)}k₉[M], was derived and found to describe well this limit as well as the extended second limit observed in previous flow reactor studies. It is further shown that, since transport effects are inherently important for the present premixed system because of the diffusive loss of H to the hot, inert side of the counterflow, the ignition temperature increases substantially with increasing strain rate at all pressures and that such a sensitivity can be moderated by doping the inert flow with a small amount of oxygen.

104. Blouch, J. D., J. Y. Chen, and Chung K Law, 2003: A Joint Scalar PDF Study of Nonpremixed Hydrogen Ignition. Combustion and Flame, 135(3), doi:10.1016/S0010-2180(03)00160-3 209-225
     [ Abstract ]

     A two-step process was adopted to model turbulent ignition that takes advantage of the possibility of decoupling the mechanical flow from chemical reaction due to the small amount of heat release before ignition. In the first step, a Reynolds stress model is employed to calculate a chemically frozen, turbulent counterflow. The second step models the ignition event by solving a joint scalar PDF equation using a Monte Carlo technique. The frozen velocity field is used to initialize the PDF model and to govern its evolution. As observed in previous DNS calculations, ignition occurs at a “most reactive” mixture fraction. The present calculations indicated that turbulence intensity had little effect on ignition temperatures, which were about 30 K higher than, but parallel to, laminar ignition temperatures. Similar results were found for both the IEM and modified Curl’s mixing model. Turbulent ignition temperatures were similar to laminar ones when the mixing model was modified to account for preferential diffusion. These results are different from turbulent ignition experiments since the experiments did indicate a turbulent intensity effect on ignition of up to 35 K. These discrepancies were attributed to shortcomings in the molecular mixing models in the flows of interest where the turbulent Reynolds numbers are low. A potential source of this problem was identified as the representation of the scalar mixing frequency as a constant ratio of the scalar to flow time.

105. De Laquil, P., C. Wenying, and Eric Larson, 2003: Modeling China’s Energy Future. Energy for Sustainable Development, VII(4), doi:10.1016/S0973-0826(08)60378-6 40-56
     [ Abstract ]

     The analysis in this paper builds on a previous China MARKAL modeling effort to further explore alternative energy-technology strategies and assess the extent to which they could enable China to meet its social and economic development goals while ensuring national energy-supply security and promoting environmental protection and sustainable development. The present analysis is intended to help sharpen the focus on key strategic issues, policies, and programs for promoting an advanced energy-technology strategy in general and coal polygeneration technology in particular. The detailed assessment of coal polygeneration technology is warranted because of its potentially central role in providing clean synthetic transportation fuels as well as electricity. The paper explores the following set of specific issues: (1) the costs and benefits of advanced energy-technology strategies compared to strategies based on coal combustion for electricity generation and direct coal liquefaction to produce liquid fuels, (2) the impact that delays in the introduction of polygeneration technologies might have on overall energy system costs and on meeting environmental and energy security goals, (3) the impact of future, crisis-induced oil price shocks, (4) the impact of insufficiently aggressive end-use energy efficiency efforts, and (5) the relative costs of achieving reductions in air pollution and CO₂ emissions with different energy-technology strategies. The analysis indicates that an energy development strategy based on advanced technologies, including efficient end-use technologies, renewables, and coal gasification-based energy supply technologies, can enable China to meet economic development, clean air, energy security and greenhouse gas mitigation targets consistent with sustainable development. A ‘‘business-as-usual’’ strategy, even including direct coal liquids technology, cannot meet target caps on oil and gas imports. In addition, the analysis indicates that over the 55-year modeling period (1995 to 2050) an advanced technology strategy would involve only a small (1 %) increase in total energy-system cost compared with a ‘‘business-as-usual’’ strategy. The advanced technology strategy requires significantly higher capital investments in energy technologies, but these result in significantly lower fuel costs, especially from reduced fuel imports.

106. Gurney, K. R., R. M. Law, A. S. Denning, P. J. Rayner, D. Baker, P. Bousquet, L. Bruhwiler, Y.-H. Chen, P. Ciais, Y. Fan, I. Y. Fung, and M. N. Gloor, 2003: TransCom 3 CO₂ inversion intercomparison: 1. Annual mean control results and sensitivity to transport and prior flux information. Tellus, Series B, International Meteorological Institute in Stockholm, 55(2), doi:10.1034/j.1600-0889.2003.00049.x 555-579
     [ Abstract ]

     Spatial and temporal variations of atmospheric CO₂ concentrations contain information about surface sources and sinks, which can be quantitatively interpreted through tracer transport inversion. Previous CO₂ inversion calculations obtained differing results due to different data, methods and transport models used. To isolate the sources of uncertainty, we have conducted a set of annual mean inversion experiments in which 17 different transport models or model variants were used to calculate regional carbon sources and sinks from the same data with a standardized method. Simulated transport is a significant source of uncertainty in these calculations, particularly in the response to prescribed “background” fluxes due to fossil fuel combustion, a balanced terrestrial biosphere, and air–sea gas exchange. Individual model-estimated fluxes are often a direct reflection of their response to these background fluxes. Models that generate strong surface maxima near background exchange locations tend to require larger uptake near those locations. Models with weak surface maxima tend to have less uptake in those same regions but may infer small sources downwind. In some cases, individual model flux estimates cannot be analyzed through simple relationships to background flux responses but are likely due to local transport differences or particular responses at individual CO₂ observing locations. The response to the background biosphere exchange generates the greatest variation in the estimated fluxes, particularly over land in the Northern Hemisphere. More observational data in the tropical regions may help in both lowering the uncertain tropical land flux uncertainties and constraining the northern land estimates because of compensation between these two broad regions in the inversion. More optimistically, examination of the model-mean retrieved fluxes indicates a general insensitivity to the prior fluxes and the prior flux uncertainties. Less uptake in the Southern Ocean than implied by oceanographic observations, and an evenly distributed northern land sink, remain in spite of changes in this aspect of the inversion setup.

107. Katofsky, R. E., S. Consonni, and Eric Larson, October 2003: A Cost-Benefit Analysis of Black Liquor Gasification Combined Cycle Systems. Proceedings of the Fall Tech Conf, Tech Assoc of the Pulp and Paper Industry, Atlanta,
     [ Abstract ]

     Black liquor gasification (BLG) technologies are under active commercial development in the United States and Europe. BLG has been proposed as a future replacement for Tomlinson boilers to provide more efficient, safer, and environmentally-friendlier chemical and energy recovery. Also, some pulping process improvements are more readily implemented with BLG than with black liquor combustion. Because of potential efficiency and process benefits, BLG is viewed as an important technology for enhancing the competitiveness of the pulp and paper industry. Much of the focus on BLG development has been on the coupling of chemical recovery with electricity production via gas turbine combined cycle technology (BLGCC). A better understanding of the economics and potential regional and national benefits of BLGCC could help catalyze commercialization of these systems. To that end, this paper summarizes the main results of a detailed study sponsored by the US Department of Energy, the pulp & paper industry and two electric utilities to assess the costs and benefits of BLGCC technology at the mill, Southeast US regional, and US national level [0]. The status of leading black liquor gasification technologies is summarized. Detailed mass and energy balances and capital cost estimates are presented for different BLGCC configurations and compared to state-of-the-art and advanced Tomlinson-based recovery systems. These are used for milllevel financial comparisons and to assess regional and national environmental benefits and energy savings potential.

108. Larson, Eric, S. Consonni, and R. E. Katofsky, October 2003: A Cost-Benefit Assessment of Biomass Gasification Power Generation in the Pulp and Paper Industry, Final Report. Princeton Environmental Institute, Princeton University, http://www.princeton.edu/pei/energy/publications/texts/BLGCC_FINAL_REPORT_8_OCT_2003.pdf,
     [ Abstract ]

     The U.S. pulp and paper industry, with with its substantial capacity for producing and using renewable biomass energy - 1.6 quads in 2002 - has the potential to contribute significantly to addressing global warming and U.S. energy security concerns, while potentially also improving its own global competitiveness. A key requirement for substantially enhancing renewable energy use in this industry to achieve these goals is the commercialization of breakthrough technologies, especially gasification. Gasification of biomass produces a fuel gas ("syngas") consisting largely of hydrogen (H₂) and carbon monoxide (CO) that can be cleanly converted into electricity in a gas turbine combined cycle or, in the longer term, into transportation fuels such as Fischer-Tropsch liquids or hydrogen.
     The predominant form of biomass energy available at pulp mills today is black liquor, the lignin-rich byproduct of fiber extraction from wood. Black liquor contains about half the energy of the wood input to a kraft pulp mill, along with all of the spent pulping chemicals (Na₂S and NaOH) used in the kraft process, the predominant process for pulp production. At pulp mills today, black liquor is burned in so-called Tomlinson recovery boilers to generate steam and recover pulping chemicals for re-use. The steam is expanded through a turbine to make electricity that meets a portion of the process electricity needs. Some steam is extracted from the turbine to provide all of the process steam needs of the mill.
     The majority of Tomlinson boilers now operating int he United States will reach the end of their 30 - 40 years lifetimes over the next 10 to 20 years. Thus, there is intense interest in the pulp and paper industry in having improved black liquor processing technology commercially available in the 2010 time frame. At the same time, there are growing public interests in expanding the role of clean renewable energy to address environmental and energy security concerns. These private and public interest can potentially both be met by commercial implementation of black liquor gasification.
     This study examines in greater depth and breadth than previous studies the prospective costs and benefits of commercializing black liquor gasification combined cycle (BLGCC) cogeneration systems. The analysis was carried out with guidance from an industry-government Steering Committee, with review by a board of independent experts, and with inputs from many other individuals.
     The underlying basis for results obtained in this study are detailed engineering desings, capital costs, and operating costs for "N^th plant" BLGCC and Tomlinson cogeneration systems the authors developed in consultation with equipment developers, industrial design engineers, pulp and paper industry experts, and a variety of others. Prospective characteristics of two black liquor gasification technologies under commercial development (one high-temperature design and one low-temperature design) are used in the BLGCC designs.
     With these inputs, energy, environmental, financial, and economic evaluations of alternative cogeneration systems were made in the context of a reference mill having process characteristics representative of expected typical mills in the 2010 time frame in the Southeastern U.S., where 2/3; of kraft mill capacity is located. The reference mill produces uncoated freesheet paper from a mix of hardwood and softwood. The nominal scale of the mill is 6 million lbs/day of black liquor solids (BLS) - 1,495 million Btu/h or 438 MW_fuel - corresponding to 1,900 machine dry short tones per day of paper production (1,725 metric tonnes). Pulp mills processing more than 6 million lbs/day BLS account for about 1/3 of all U/S. capacity today, and this fraction will grow over time as mill consolidations continue.
     Three BLGCC designs were developed incorporating gasification technologies and design philosophies: two "mill-scale" cases (each with a different gasifier design), wherein the BLGCC system is sized to the flow of black liquor available at the reference mill, and one "utility-scale" case employing a larger gas turbine co-firing natural gas with black liquor syngas to achieve higher electricity output. Detailed mass and energy balances were calculated for each of the BLGCC design, along with a conventional Tomlinson design for comparison. Due to the inherently higher thermodynamic efficiency of gas turbine-based cogeneration compared to steam-turbine cogeneration (as reflected in a higher electricity-to-steam production capability), BLGCC systems are able to produce more electricity than needed by the mill, while meeting the same steam demand as a Tomlinson system. A consequence of this is that for the same process steam demand, a BLGCC requires additional fuel to be consumed (e.g., purchased wood residues and/or natural gas) to maximize electricity production.
     This study confirms results of earlier studies showing BLGCC systems offer the prospect for significant improvements in energy efficiency compared to Tomlinson systems. In particular, at the reference mill at Tomlinson system would need to import 36 MW_e to meet its onsite electricity needs - about 1/3 of the total process electricity demand. In contrast, the mill-scale and utility-scale BLGCC systems would have available for expoert 15 - 11 MW_e and 126 MW_e, respectively. Importantly, the efficiency with which purchased fuels are converted into electricity in teh BLGCC cases ranges from 50% to 96%, which compares favorably with the efficiency of making electricity form stand-alone power plants that might be displaced by the excess BLGCC power.
     Aside from efficiency benefits, a distinctive and intrinsic feature of BLGCC technology is the expected low relative emissions of most pollutants compared to a modern Tomlinson system employing sophisticated pollution controls. Per unit of black liquor processed, BLGCC systems would provide considerable improvements in air emissions, some improvements in water pollution, and a similar solid waste emissions profile as Tomlinson technology. When environmental emissions are considered on a per-unit-of-electricity-generated basis, BLGCC systems would exhibit improved environmental characteristics across the board relative to Tomlinson technology. Moreover, if the difference in the power generated between a BLGCC system and the Tomlinson system is assumed to displace power generation on the grid, there would be additional reductions in environmental impacts associated with the displaced grid emissions in most regions of the United States.
     Prospective internal rates of return (IRR) on incremental investments in BLGCCs in place of Tomlinson systems were calculated assuming commercially-mature cost levels for both systems. IRRs up to 20% were calculated without considering the value of any environmental or renewable energy benefits of BLGCC. If economic values for environmental and renewable energy benefits are factored into the analysis, e.g., considering values for renewable energy attributes similar to those that currently benefit wind power and closed loop biomass systems, IRRs of 35% are possible.
     Beyond the energy, environmental, and economic benefits at the mill level, widespread implementation of BLGCC systems would produce regional and national benefits. These were estimated for both the Southeast region and for the United States under different technology market penetration assumptions.
     In the Southeast, where total electricity demand is projected to double by 2030, BLGCC technology has the potential to contribute up to 4,000 MW (mill-scale configuration) to more than 11,000 MW (utility-scale configuration) of generating capacity beyond that needed to meet process demands at the mills. Moreover since BLGCC plants would be smaller than typical central station power plants, they would be more numerous and dispersed, which may allow capital investments in the transmission and distribution system to be deferred while improving overall grid reliability.
     At such levels of penetration, BLGCC systems would contribute importantly to meeting any future mandated renewable electricity requirements in the Southeast (Renewable portfolio standards - RPS - are already in place in 12 states across the nation, although not yet in the Southeast). Under a future scenario in which 5% of all new electricity supply in the Southeast region is mandated to be renewable, aggressive deployment of BLGCC systems could meet nearly half of the required renewable electricity supply in 2020.
     Nationally, BLGCC technology (particularly in "utility-scale" configurations) could provide a host of economic, environmental, and energy security benefits, including the potential to displace more that 360 billion Btu per year of fossil fuel use within 25 years of introduction, with a corresponding reduction of more than 35 million tons per year of CO₂ emissions. The following table summarized potential national benefits identified in this study.
     The attractive IRRs on Nth plant BLGCC investments, together with the substantial public benefits that could result from such investments, suggest a public-private partnership as an appropriate approach to addressing research, development, and demonstration (RD&D) issues (identified in this study) during the nest few years to bring BLGCC systems to commercial readiness. Delaying commercial deployment of BLGCC technology could carry with it an opportunity cost that is estimated here to be up to $9 billion.
     It may be noted that this study considered only electricity as the energy export from gasification-based systems. In this regard, commercializing BLGCC could be the first step in the evolution to future biorefineries that would take fuller advantage of the characteristics of gasification as a "breakthrough" technology platform. Conversion of black liquor to high-value chemicals and/or transportation fuels, e.g., F-T middle distillates or hydrogen, should be a focus of future analysis to better understand the possibilities. Moreover, such studies should also examine the potential for gasifying forest residues collected sustainably from the vicinity of the mills. Estimates suggest that the energy contained in potential supplies of such resifues could match the amount of energy in black liquor. In time, a gasification-based biorefinery industry might extend beyond the pulp and paper industry, whereby biomass crops would be grown for conversion to heat, electricity, fuels, chemicals, animal feed, and other commodity products.

109. Larson, Eric, and T. Ren, August 2003: Synthetic Fuel Production by Indirect Coal Liquefaction. Energy for Sustainable Development, VII(4), doi:10.1016/S0973-0826(08)60381-6 79-102
     [ Abstract ]

     This paper reports detailed process designs and cost assessments for production of clean liquid fuels (methanol and dimethyl ether) by indirect coal liquefaction (ICL). Gasification of coal produces a synthesis gas that can be converted to liquid fuel by synthesis over appropriate catalysts. Recycling of unconverted synthesis gas back to the synthesis reactor enables a larger fraction of the coal energy to be converted to liquid fuel. Passing synthesis gas once over the synthesis catalyst, with unconverted synthesis gas used to generate electricity in a gas turbine combined cycle, leads to less liquid fuel production, but provides for a significant second revenue stream from sale of electricity. Recently-developed liquid-phase synthesis reactors are especially attractive for ‘‘oncethrough’’ processing. Both ‘‘recycle’’ and ‘‘once-through’’ plant configurations are evaluated in this paper. Because synthesis catalysts are poisoned by sulfur, essentially all sulfur must be removed upstream. Upstream removal of CO₂ from the synthesis gas is also desirable to maximize synthesis productivity, and it provides an opportunity for partial decarbonization of the process, whereby the removed CO₂ can be captured for underground storage. The analysis here suggests that co-capture and co-storage of CO₂ and H₂S (if this is proven technically feasible) could have important favorable impacts in some cases on liquid fuel production costs. Furthermore, the lifecycle CO₂ emissions from production and use of fuels made by ICL would be lower than with production and use of petroleum-derived transportation fuels. If CO₂ is not captured at ICL facilities, lifecycle CO₂ emissions to the atmosphere would be considerably higher than lifecycle emissions with petroleum-derived fuels.

110. Larson, Eric, Z. Wu, P. De Laquil, C. Wenying, and P. Gao, 2003: Future Implications of China’s Energy-Technology Choices. Energy Policy, 31(12), doi:10.1016/S0301-4215(02)00171-4 1189-1204
     [ Abstract ]

     This paper summarizes an assessment of future energy-technology strategies for China that explored the prospects for China to continue its social and economic development while ensuring national energy-supply security and promoting environmental sustainability over the next 50 years. The Markal energy-system modeling tool was used to build a model of China’s energy system representing all sectors of the economy and including both energy conversion and end-use technologies. Different scenarios for the evolution of the energy system from 1995 to 2050 were explored, enabling insights to be gained into different energy development choices. The analysis indicates a business-as-usual strategy that relies on coal combustion technologies would not be able to meet all environmental and energy security goals. However, an advanced technology strategy emphasizing (1) coal gasification technologies co-producing electricity and clean liquid and gaseous energy carriers (polygeneration), with below-ground storage of some captured CO₂; (2) expanded use of renewable energy sources (especially wind and modern biomass); and (3) end-use efficiency would enable China to continue social and economic development through at least the next 50 years while ensuring security of energy supply and improved local and global environmental quality. Surprisingly, even when significant limitations on carbon emissions were stipulated, the model calculated that an advanced energy technology strategy using our technology-cost assumptions would not incur a higher cumulative (1995–2050) total discounted energy system cost than the business-as-usual strategy. To realize such an advanced technology strategy, China will need policies and programs that encourage the development, demonstration and commercialization of advanced clean energy conversion technologies and that support aggressive end-use energy efficiency improvements.

111. Law, R. M., Y.-H. Chen, K. R. Gurney, and 3 Transcom, 2003: TransCom 3 CO₂ inversion intercomparison: 2. Sensitivity of annual mean results to data choices. Tellus, [B], 55(2), 580-595
     [ Abstract ]

     TransCom 3 is an intercomparison project for CO₂ source inversions. Annual mean CO₂ concentration data are used to estimate CO₂ sources using 16 different atmospheric transport models. Here we test the sensitivity of the inversion to the concentration data. We examine data network choice, time period of data, baseline data selection and the choice of data uncertainty used.We find that in most cases regional source estimates lie within the source uncertainty range of the control inversion. This indicates that the estimated sources are relatively insensitive to the changes in data that were tested. In the data network tests, only the Australian region source estimates varied over a much larger range than that given by the control case uncertainty estimate. For the other regions, the sensitivity to data network was within or close to the uncertainty range. Most of the sensitivity was found to be associated with a small number of sites (e.g. Darwin, Easter Island). These sites are often identified by the inability of the inversion to fit the data at these locations. The model-mean inversion values are mostly insensitive to the time period of data used, with the exception of temperate North America and the tropical Indian ocean. Data selection has a small impact on source estimates for the mean across models, but individual model sensitivity can be large. The magnitude of data uncertainties controls the relative magnitude of the estimated source uncertainty and the spread in model source estimates. Smaller data uncertainties lead to larger differences in source estimates between models. Overall, the data sensitivity tests performed here support the robustness of the control inversion source estimates presented in Gurney et al. (2003. Tellus 55B, this issue). The test results also provide guidance in setting up and interpreting other inversions.

112. Maksyutov, S. T., T. Machida, H. Mukai, P. K. Patra, T. Nakazawa, G. Inoue, and 3 Transcom, 2003: Effect of recent observations on Asian CO₂ flux estimates with transport model inversions. Tellus, 55(2), 522-529
     [ Abstract ]

     We use an inverse model to evaluate the effects of the recent CO₂ observations over Asia on estimates of regional CO₂ sources and sinks. Global CO₂ flux distribution is evaluated using several atmospheric transport models, atmospheric CO₂ observations and a “time-independent” inversion procedure adopted in the basic synthesis inversion by the Transcom-3 inverse model intercomparison project. In our analysis we include airborne and tower observations in Siberia, continuous monitoring and airborne observations over Japan, and airborne monitoring on regular flights on Tokyo–Sydney route. The inclusion of the new data reduces the uncertainty of the estimated regional CO₂ fluxes for Boreal Asia (Siberia), Temperate Asia and South-East Asia. The largest effect is observed for the emission/sink estimate for the Boreal Asia region, where introducing the observations in Siberia reduces the source uncertainty by almost half. It also produces an uncertainty reduction for Boreal North America. Addition of the Siberian airborne observations leads to projecting extra sinks in Boreal Asia of 0.2 Pg C yr^-1, and a smaller change for Europe. The Tokyo–Sydney observations reduce and constrain the Southeast Asian source.

113. Patra, P. K., S. T. Maksyutov, and 3 Transcom, 2003: Sensitivity of optimal extension of CO₂ observation networks to the model transport. Tellus, 55(2), 498-511
     [ Abstract ]

     Optimal extensions of the surface CO₂ observation network have been determined using 15 global transport models and a time-independent inverse model. The regional average CO₂ flux estimate uncertainty is minimized based on theTransCom-3 (level 1) framework.Anensemble model calculation shows that the regional average CO₂ flux uncertainties could be reduced to about 0.36, 0.32, 0.28 or 0.26 Gt C yr^-1 per region, from about 0.53 Gt C yr^-1 per region corresponding to the basic network, after adding 5, 10, 15 or 20 optimally located stations, respectively. The additional station locations are mostly found in continental South America and Africa. The distribution of the efficiency in estimation of flux uncertainty reduction per station tends to become more uniform with the extension of the network. We show that the multimodel approach to network design converges if a large enough extension is considered; about 20 stations in this inverse model framework. The reduction in the flux uncertainty for the first few stations depends on the model of atmospheric transport, and is nearly proportional to the simulated signal from local emissions in the surface layer. In addition, it is seen that the simulated spatial and temporal variability of CO₂ concentration has significant influence on the distribution of the additional stations as well as determining the regional flux estimate uncertainty.

114. TFEST, Task Force on Energy Strategies and Technologies, 2003: Transforming Coal for Sustainability: a Strategy for China. Energy for Sustainable Development, VII(4), 21-30
     [ Abstract ]

     In October 2002 the 16^th Party Congress established the goal of expanding China’s economy fourfold by 2020 and defined the Three E’s strategy for Economic development, Energy security, and Environmental protection. In pursuing these goals, China’s energy system cannot continue to expand using the current approach. The risks are that:
     • China will become overly dependent on oil imports as a result of the rapidly growing demand for liquid fuels, especially in the transportation sector,
     • Severe additional public health and environmental damages will occur in China with very large economic consequences (projected to grow from over 7% of GDP to 13% of GDP in 2020), and
     • Climate change impacts will become significant, and China will not be able to make its contribution to mitigating greenhouse gas (GHG) emissions under the United Nations Framework Convention on Climate Change.

115. Williams, Robert H., 2003: Toward Zero Emissions for Transportation Using Fossil Fuels. Proceedings of the VIII Biennial Asilomar Conference on Transportation, Energy, and Env Policy, Washington, DC, Tranportation Research Board, (ISBN: 0309085713), 61-103
     [ Abstract ]

     The hydrogen (H²) fuel cell is receiving considerable attention as the fuel and engine option of choice for the automobile in the long term. The world's major automakers are racing to develop the technology - a quest bolstered in early 2002 by the Bush Administration's announcement of Freedom CAR (Cooperative Automotive Research), a collaboration between U.S. automakers and the U.S. government aimed at developing fuel cell cars and the associated H² fuel infrastructure. A transition to H² as a major energy carrier alternative to gasoline and diesel fuel and the fuel cell as an alternative to the internal combustion engine would be very costly and would require many decades. So these technologies must offer benefits that exceed the huge costs involved. Yet the societal costs of a business-as-usual future in which the automobile continues to be dominated by hydrocarbon-fueled internal combustion engine vehicles (ICEVs) are also arguably huge. Concerns about oil supply insecurity, air pollution damages, and climate change motivate serious consideration of introducing H² as a transport fuel.

116. Williams, Robert H., 2003: Decarbonized Fossil Energy Carriers and Their Energy Technological Competitors. Proceedings of the Workshop on Carbon Capture and Storage of the IPCC, Saskatchewan, Canada, Energy Research Center of the Netherlands, http://www.princeton.edu/pei/energy/publications/texts/Williams_02_Decarbonized_Fossil.PDF, 119-135
     [ Abstract ]

     Stabilizing atmospheric CO₂ in the range 450 - 550 ppmv requires deep reductions in CO₂ emissions for both electricity generation and markets that use fuels directly. Fossil fuel decarbonization/ CO₂ storage is an important option for reducing emissions from the power sector, but there are alternative non-carbon-based electricity options that will be strong competitors in terms of cost. Because of land-use constraints, use of carbon-neutral biofuels alone will be inadequate to solve the climate problem in markets that use fuels directly, so that it will probably also be necessary to introduce H₂ as an energy carrier. Costs for H₂ from fossil fuels with storage of the separated CO₂ are likely to be far less than costs of making H₂ from water using carbon-free (renewable or nuclear) electricity or heat sources. Although CO₂ capture and storage associated with making H₂ via gasification of coal and other carbonaceous feedstocks offers one of the least-costly approaches to a climate-friendly energy future, H₂ will not be widely used as an energy carrier for at least two decades. Nevertheless, thus making H₂ to serve industrial markets can provide low-cost CO₂ for CO₂ storage demonstration projects, thereby playing an important near-term role in understanding better the prospects for coping with climate change via decarbonizing fossil fuels and CO₂ storage.

117. Williams, Robert H., and Eric Larson, 2003: A Comparison of Direct and Indirect Liquefaction Technologies for Making Fluid Fuels from Coal. Energy for Sustainable Development, VII(4), doi:10.1016/S0973-0826(08)60382-8 103-129
     [ Abstract ]

     Direct and indirect liquefaction technologies for making synthetic liquid fuels from coal are compared. It is shown that although direct liquefaction conversion processes might be more energy efficient, overall system efficiencies for direct and indirect liquefaction are typically comparable if end-use as well as production efficiencies are taken into account. It is shown that some synfuels derived via indirect liquefaction can outperform fuels derived from crude oil with regard to both air-pollutant and greenhouse-gas emissions, but direct liquefaction-derived synfuels cannot. Deployment now of some indirect liquefaction technologies could put coal on a track consistent with later addressing severe climate and other environmental constraints without having to abandon coal for energy, but deploying direct liquefaction technologies cannot. And finally, there are much stronger supporting technological infrastructures for indirect than for direct liquefaction technologies. Prospective costs in China for some indirect liquefaction-derived fuels are developed but not costs for direct liquefaction-based synfuels, because experience with the latter is inadequate for making meaningful cost projections. Especially promising is the outlook for the indirect liquefaction product dimethyl ether, a versatile and clean fuel that could probably be produced in China at costs competitive with crude oil-derived liquid fuels. An important finding is the potential for realizing, in the case of dimethyl ether, significant reductions in greenhouse gas emissions relative to crude oil-derived hydrocarbon fuels, even in the absence of an explicit climate change mitigation policy, when this fuel is co-produced with electricity. But this finding depends on the viability of underground storage of H₂S and CO₂ as an acid gas management strategy for synfuel production. Many ‘‘megascale’’ demonstration projects for underground CO₂ storage and H₂S/CO₂ co-storage, along with appropriate monitoring, modeling, and scientific experiments, in alternative geological contexts, are needed to verify this prospect. It is very likely that China has some of the least-costly CO₂ sources in the world for possible use in such demonstrations. It would be worthwhile to explore whether there are interesting prospective demonstration sites near one or more of these sources and to see if other countries might work with China in exploiting demonstration opportunities at such sites.

118. Zheng, H,, Z. Li, W. Ni, Eric Larson, and T. Ren, 2003: Case Study of a Coal Gasification-Based Energy Supply System for China. Energy for Sustainable Development, VII(4), doi:10.1016/S0973-0826(08)60380-4 63-78
     [ Abstract ]

     ‘‘Syngas city’’ (SC) is a concept for a coal gasification-based energy supply system that deploys gasification-based polygeneration technologies to meet energy needs of coal-rich areas. This paper summarizes an assessment of the projected environmental impacts of implementing a SC strategy for Zaozhuang, Shandong Province, China. A SC scenario and a ‘‘business-as-usual’’ (BAU) scenario are developed for the Zaozhuang area considering the time-frame 2000 to 2020. A comparison of these scenarios is used to assess whether the SC concept for Zaozhuang could reduce air pollution and promote further economic development while meeting projected demand for energy services. On the basis of socio-economic assumptions, sectoral energy-demand projections are developed. Assumptions are made about expected rates of market penetration of dimethyl ether (DME) and methanol, two clean fuels derived via coal gasification. Emissions of air pollutants in the SC scenario are compared with those in the BAU scenario. Policies to promote the SC concept and technologies in China are proposed.

119. Duke, R., November 2002: Clean energy technology buydowns: economic theory, analytical tools, and the photovoltaics case. Ph.D. thesis for WWS, Princeton University, http://rael.berkeley.edu/old-site/PhD02-Duke.pdf,
     [ Abstract ]

     The conventional responses to the market failures that constrain energy innovation include market tuning (e.g. pollution taxes) as well as supply-push (i.e. public support for research, development, and demonstration). There is no similar consensus favoring demand-pull programs, but this dissertation develops an economic rationale for subsidies to pull emerging clean energy technologies down their respective experience curves. Even with optimal pollution taxes in place, such buydowns can improve welfare—primarily by correcting for learning-by-doing spillover that discourages firms from forward pricing (i.e. pricing below the short-term profit maximizing level to reduce costs through production experience). Learning spillover also occurs in other sectors, but the case for clean energy buydowns is unique. Governments wisely seek a broad supply-push portfolio, but only the most promising clean energy options merit demand-pull support because individual buydowns are costly and generate scant spin-offs absent successful commercialization of the targeted technology. Moreover, governments have more information about technologies at the deployment stage and failure to screen out poor prospects can yield entrenched corporate welfare programs (e.g. grain ethanol). The buydown selection criteria proposed herein favor support for photovoltaics (PV), and the recommended implementation strategy optimizes this support. Conventional analyses assume markets fully materialize as soon as the technology reaches financial breakeven, suggesting buydowns should be implemented as quickly as possible. The optimal path method introduced in this dissertation more accurately models demand and defines the welfare-maximizing subsidy/output schedule. An optimal PV buydown would triple current demand subsidies and sustain declining perunit support for over four decades. Such a buydown (initially targeting residential markets in industrialized countries) need never raise electricity rates by more than 0.5 percent while delivering roughly $50 billion in long-term net benefits (relative to a nosubsidy scenario) and allowing PV to provide over 5 percent of industrialized country electricity by 2030 (vs. less than 1 percent without subsidies). Finally, implementing buydowns at the regional level bypasses the international collective action problem and reduces the disruption from the failure of any single program. A decentralized approach also facilitates program innovation and reduces free rider subsidy costs—a crucial determinant of buydown economics.

120. Gurney, K. R., R. M. Law, A. S. Denning, P. J. Rayner, D. Baker, P. Bousquet, L. Bruhwiler, Y.-H. Chen, P. Ciais, S. Fan, I. Y. Fung, and M. N. Gloor, et al., 2002: Towards robust regional estimates of CO₂ sources and sinks using atmospheric transport models. Nature, 415, doi:10.1038/415626a 626-630
     [ Abstract ]

     Information about regional carbon sources and sinks can be derived from variations in observed atmospheric CO₂ concentrations via inverse modeling with atmospheric tracer transport models. A consensus has not yet been reached regarding the size and distribution of regional carbon fluxes obtained using this approach, partly owing to the use of several different atmospheric transport models. Here we report estimates of surface atmosphere CO₂ fluxes from an intercomparison of atmospheric CO₂ inversion models (the TransCom 3 project), which includes 16transportmodelsandmodelvariants. We find an uptake of CO₂ in the southern extra tropical ocean less than that estimated from ocean measurements, a result that is not sensitive to transport models or methodological approaches. We also find a northern land carbon sink that is distributed relatively evenly among the continents of the Northern Hemisphere, but these results show some sensitivity to transport differences among models, especially in how they respond to seasonal terrestrial exchange of CO₂. Overall, carbon fluxes integrated over latitudinal zones are strongly constrained by observations in the middle to high latitudes. Further significant constraints to our understanding of regional carbon fluxes will therefore require improvements in transport models and expansion of the CO₂ observation network within the tropics. We estimate annual average fluxes for the 1992-96 period using each transport model and a common inversion set-up (see Methods). Methodological choices for this 'control' inversion have been selected on the basis of knowledge gained from a wide range of sensitivity tests (to be reported elsewhere). Performing the inversion with multiple transport models gives mean estimated fluxes that are relatively insensitive to reasonable variations in the set-up-and estimated uncertainties that represent a more complete estimate of the true uncertainty. The maximum number of Southern 0cean fluxes had been noted a decade ago. 0ur sensitivity tests find that the near-uniformity of observed concentration in the Southern Hemisphere and the small uncertainty associated with those measurements make this result robust to the choice of observing network, prior flux estimates, global ocean constraint, and transport (see Fig 2 in Supplementary Information). The discrepancy also cannot be explained by a systematic bias in transport models, as the north-south transport has been investigated in a recent intercomparison where successful simulations of the observed meridional gradient in SF₆ suggested reasonable veracity in gross interhemispheric transport. 0ne possible reconciliation between the pCO₂ database and the inverse result presented here is suggested by recent ocean measurements taken during January and August 2000 in the Indian Ocean.

121. Kreutz, Thomas, Robert H. Williams, Robert H. Socolow, P. Chiesa, and G. G. Lozza, September 2002: Production of Hydrogen and Electricity from Coal with CO₂ Capture. Proceedings of the 6th International Conference on Greenhouse Gas Control Technologies (GHGT-6), http://www.princeton.edu/pei/energy/publications/texts/Kreutz_Kyoto_02.pdf,
     [ Abstract ]

     This paper summarizes a series of studies examining the prospective performance and cost of facilities that convert coal to H₂, co-product electricity and a stream of concentrated CO₂ (for sequestration). Synthe-sis gas is produced via oxygen-blown, entrained flow coal gasification, quench cooled and shifted to (pri-marily) H₂ and CO₂ via sulfur-tolerant water-gas shift (WGS) reactors. Our focus is on separating H₂ from the syngas and processing the carbon-bearing raffinate/purge gas to produce electricity and CO₂. We explore the use of novel inorganic membrane reactors for H₂ separation and compare their performance and cost with conventional gas separation technologies: CO₂ capture via solvent absorption followed by H₂ purification using pressure swing adsorption (PSA). This work highlights potential economic benefits of high system pressure, low H₂ purity, and co-sequestering CO₂ with sulfur-bearing waste gases, H₂S and SO₂.

122. Kwon, O, C., G. Rozenchan, and Chung K Law, 2002: Cellular Instabilities and Self-Acceleration of Outwardly Propagating Spherical Flames. Proceedings of the Combustion Institute, 29(2), doi:10.1016/S1540-7489(02)80215-2 1775-1784
     [ Abstract ]

     Using a recently developed constant and high-pressure combustion chamber, an experimental study was conducted on several aspects of cellular instabilities of outwardly propagating spherical premixed flames. Propane/air and hydrogen/oxygen/nitrogen flames of different concentrations and under elevated pressures were used to systematically identify the influences of thermal expansion ratio, flame thickness, global activation energy, mixture Lewis number, and global stretch rate on the generation of hydrodynamic and diffusional-thermal cells over the flame surface. In particular, it was demonstrated that hydrodynamic instability is greatly enhanced with increasing pressure and hence decreasing flame thickness, although the influence can also be moderated by the progressively important three-body termination reactions as the pressure increases. The onset of cellular instability was examined in light of the theory of Bechtold and Matalon, and satisfactory qualitative and acceptable quantitative comparisons were observed. The cellular flames were found to be self-accelerating, including those that are diffusionally unstable, with fractal dimensions between 2.20 and 2.25.

123. Larson, Eric, P. De Laquil, Z. Wu, W. Chen, and P. Gao, 2002: Exploring Implications To 2050 Of Energy-Technology Options For China. Proceedings of the 6th International Conference on Greenhouse Gas Control Technologies (GHGT-6), Elsevier Science, Oxford, UK, http://www.princeton.edu/pei/energy/publications/texts/Larson_Kyoto_-02.pdf, 881-887
     [ Abstract ]

     The MARKAL energy-system modeling tool was used to assess potential energy-technology strategies to 2050 for China that would enable continued economic development while ensuring energy-supply security and environmental sustainability. Our analysis suggests that continued reliance on domestic coal, which would help avoid high dependence on imported energy, is not inconsistent with achieving environmental objectives. However, a fundamental shift would be required from coal technologies based on combustion to those based on gasification, which enables the production of clean liquid fuels from coal and which facilitates CO₂ capture. Surprisingly, the total cumulative (1995-2050) discounted energy-system cost for an advanced-technology energy strategy that meets air pollution, energy security, and greenhouse gas emission goals would not be substantially higher than for a “business-as-usual” strategy that is unable to meet all these goals. To realize an advanced-technology future, China will need policies that i) encourage use of a wider variety of primary energy sources (especially biomass and wind) and clean synthetic fluid fuels from coal and biomass, ii) support the commercialization of radically new clean energy technologies, including those for CO₂ capture and below- ground storage, to ensure that they are available beginning in 10 to 20 years, and iii) support aggressive end-use energy efficiency improvements.

124. Larson, Eric, R. Hosier, and C. Page, 2002: Hydrogen Fuel- Cell Buses for Megacities of Developing Countries. Sustainable Development International, 99-104
     [ Abstract ]

     Diesel buses provide the most important motorized mode of transport in the megacities of developing countries today, but they are also major contributors to local air pollution and the accumulation of carbon dioxide in the atmosphere. Fuelcell buses (FCBs) – operating on hydrogen fuel – promise to reduce both local transportationrelated air pollution and greenhouse gas (GHG) emissions. This article reviews the rationale for FCBs, the status of FCB commercialization, and the UNDP/GEF FCB commercialization support programme.

125. Li, Y., 2002: International burden sharing of carbon control as the purchase of a global public good. Department of Energy, Environmental and Mineral Economics, Penn State - MS Thesis,
     [ Abstract ]

     This study estimates the burden-sharing of carbon control as the Purchase of a Global Public Good (PGPG). Under the PGPG system, an agency is responsible for buying emissions allowances, and every participating country can sell emissions allowances to the agency. The funds that the agency needs to buy the allowances are called "required payment" and are shared by the participating countries. According to allocation rules, the required payment of a country is determined as a function of (i) relative per capital GDP or (ii) relative per capital carbon emissions. These allocation rules are analyzed in two economic models, MiniCAM and MERGE. The cost allocation in 2010 by the PGPG system is also compared to the cost allocation implied by the Kyoto Protocol.

126. Williams, Robert H., 2002: Facilitating Widespread Deployment of Wind and Photovoltaic Technologies. 2001 Annual Report of the Energy Foundation, www.ef.org, http://www.ef.org/documents/WilliamsEssayFinal.pdf, 19-30
     [ Abstract ]

     At the global level, installed wind capacity has grown an average of 25 percent per year since 1990; by the end of 2000 it had reached 17.0 gigawatts of electrical capacity (GWe) and was generating about 0.24 percent of electricity worldwide. In the United States, average wind power prices (in 2000 dollars) fell from 47 cents per kilowatt-hour (kWh) in 1981 to 5.1 cents/kWh in 1995, as installed wind-power capacity expanded to about 1.5 GWe. For many large new wind farms in the United States, unsubsidized 30-year levelized life-cycle costs are currently about 5 cents/kWh-and less than 4 cents/kWh in areas of high average wind speeds. Wind-power costs are expected to decline further as the industry gains experience, learns to exploit economies of scale both by using turbines with larger unit capacities and by building larger wind farms (more turbines per farm), sees reductions in project financing costs as developers and financial institutions gain confidence in the technology and its market prospects, and makes technological improvements (e.g., higher hubs to exploit the stronger winds aloft, materials that lower maintenance costs).

127. Yuan, J., S. D. Tse, and Chung K Law, 2002: Dynamics of Flame Ball Formation from Localized Ignition: Effects of Elevated Pressure and Temperature. Proceedings of the Combustion Institute, 29(2), doi:10.1016/S1540-7489(02)80305-4 2501-2507
     [ Abstract ]

     A computational study was conducted on expanding spherical premixed flames to investigate the dynamics of flame-ball formation at elevated temperatures and pressures. Lean H₂/air mixtures were investigated using a time-dependent, spherically symmetric code with detailed chemistry, transport, and radiation submodels. Results show that, with increasing pressure, both the steady-state flame-ball radius and the H₂ consumption rate for a given mixture composition decrease monotonically up to 50 atm, varying approximately as p^-0.57. Furthermore, a window of pulsating flame behavior, near the upper dynamic flame-ball limit, was discovered and investigated. Within this window, an outwardly propagating flame begins to self-extinguish due to radiative losses but revives suddenly due to low-Lewis-number effects and evolves into a flame ball. More than one such cycle of behavior can occur for a given mixture concentration. Results further show that as the ambient mixture temperature is increased, the initial trend is a downward shift of the upper dynamic flame-ball limit. With reduced radiative loss, spherical flames continue to propagate outwardly for leaner mixture compositions without degenerating into flame balls, but at the same time, expand themselves into radiative extinction. Again, the role of radiative loss as both the requisite mechanism for and the limiting mechanism against the dynamic transformation of spherically propagating flames into flame balls is emphasized. Nonetheless, as the ambient temperature is increased to near 700 K (in an attempt to investigate the boundary defining the flameless combustion regime), steady flame balls are no longer attainable, with chemical reactions occurring at the boundary.

128. Zheng, X. L., J. D. Blouch, D. L. Zhu, Thomas Kreutz, and Chung K Law, 2002: Ignition of Premixed Hydrogen/Air in Heated Counterflow. Proceedings of the Combustion Institute, 29(2), doi:10.1016/S1540-7489(02)80201-2 1637-1644
     [ Abstract ]

     The inert temperature required to ignite a lean premixed hydrogen/air mixture in a counterflow was determined experimentally and numerically using detailed chemistry and transport. It was found that above Φ = 0.2, the ignition temperatures increased with increasing equivalence ratio. This effect is due to the fact that the ignition kernel is located on the hot, inert side of the flow and preferential diffusion of hydrogen makes the flow self-stratifying, resulting in a rich mixture in the ignition kernel even for a very lean freestream mixture. The dearth of O₂ in the kernel reduces the reaction rates to the point where diffusive loss becomes significant relative to the rates of kinetic production and consumption. In the presence of this significant transport loss mechanism, premixed ignition temperatures are much higher than non-premixed ignition temperatures and the influence of the strain rate is likewise increased. Adding a few percent of O₂ to the hot inert side of the flow lowers the kernel equivalence ratio and increases the reaction rates to the point where diffusive effects are no longer of the same order as kinetic effects. In these cases, the ignition temperatures drop significantly to values close to those of non-premixed ignition even though the free-stream flow is still predominantly premixed.

129. Goldenberg, J., T. B. Johansson, A.K.N. Reddy, and Robert H. Williams, 2001: Energy for the New Millenium. Ambio, 30(6), doi:10.1579/0044-7447-30.6.330 330-337
     [ Abstract ]

     The evolution of thinking about energy is discussed. When the authors began collaborating 20 years ago, energy was typically considered from a growth oriented, supply-side perspective, with a focus on consumption trends and how to expand supplies to meet rising demand. They were deeply troubled by the environmental, security and equity implications of that approach. For instance, about two billion people lack access to affordable modern energy, seriously limiting their opportunities for a better life. And energy is a significant contributor to environmental problems, including indoor air pollution, urban air pollution, acidification, and global warming. The authors saw the need to evolve a different perspective in which energy is provided in ways that help solve such serious problems. They argued that energy must become an instrument for advancing sustainable development—economically viable, need-oriented, self reliant and environmentally sound development—and that the focus should be on the end uses of energy and the services that energy provides. Energy technological options that can help meet sustainable development goals are discussed. The necessity of developing and employing innovative technological solutions is stressed. The possibilities of technological leapfrogging that could enable developing countries to avoid repeating the mistakes of the industrialized countries is illustrated with a discussion of ethanol in Brazil. The role foreign direct investment might play in bringing advanced technologies to developing countries is highlighted. Near-and long-term strategies for rural energy are discussed. Finally, policy issues are considered for evolving the energy system so that it will be consistent with and supportive of sustainable development.

130. Larson, Eric, and T. B. Johansson, 2001: Future Demands on Forests as a Source of Energy. Forests in a Full World, New Haven, CT, Yale University Press, Chapter 9, 111-160
     [ Abstract ]

     Most of the energy used in support of human activities is solar energy. It is solar energy that drives the weather, the seasons, the hydrologic cycle, agriculture, forests, the soccer game, the bicycles we ride, and the Americas cup races. Large supplementary amounts of energy for industrial and other uses are a recent phenomenon extending over a mere two centuries. Before the discovery and exploitation of fossil fuels, virtually all the energy used to support civilization for all of time had been solar energy, used more or less directly. The discovery of oil and coal made great reserves of solar energy as hydrocarbons over hundreds of millions of years suddenly available. The industrial system has been built into a solar-powered biophysical system that is the global environment. One might anticipate that an interest in preserving our own global environment would set limits on the scale and activities of the industrial system. The reality of the limits becomes even more clear and compelling when we realize that the purpose of technology is to enable a better and more comprehensive command of the resources of environment for human use. The free enterprise system that is the basis of democratic capitalism focuses on the profits to be made from applications of technology for industrial development and systematically overlooks the environmental consequences. Limits may not only be ignored but even denied as inappropriately inhibitory to economic growth. Fossil fuels have made wood fro fuel nearly obsolete in some parts of the world, yet wood remains a major reliance for heating and cooking among the approximately 4 billion poor of the world.

131. Larson, Eric, Robert H. Williams, M. Regis, and L. V. Leal, 2001: A Review of Biomass Integrated-Gasifier/Gas Turbine Combined Cycle Technology and its Application in Sugarcane Industries, with an Analysis for Cuba. Energy for Sustainable Development, V(1), doi:10.1016/S0973-0826(09)60021-1 54-76
     [ Abstract ]

     Biomass integrated-gasifier/gas turbine combined cycle (BIG/GTCC) systems will be capable of producing up to twice as much electricity per unit of biomass consumed and are expected to have lower capital investment requirements per kW of capacity than condensing-extraction steam turbine (CEST) systems, the present-day commercial technology for electricity production from biomass. The significant levels of biomass available as by-products of sugarcane-processing offer a potentially attractive application for BIG/GTCC systems. We review BIG/GTCC designs and ongoing demonstration and commercial projects and present estimates of the performance of two different BIG/GTCC plant configurations integrated into sugar or sugar-and-ethanol factories. Because of the importance of operating a cogeneration facility the year round in order to achieve attractive economics, we present estimates of the availability of and collection cost for sugarcane trash (tops and leaves) as a fuel supplementary to bagasse. We present estimated costs for electricity generated by commercially mature BIG/GTCC systems using sugarcane-biomass for fuel in a Southeast Brazilian context. The electricity costs are prospectively competitive with CEST-generated electricity, which motivates our analysis of how many BIG/GTCC units might need building (and at what cost) in order to reduce capital costs to competitive levels. We conclude with an assessment of the potential impacts on the Cuban energy sector of the introduction of BIG/GTCC cogeneration systems in that country’s sugarcane industry. Cuba’s high per-capita production of sugarcane and its heavy dependence on oil for energy provide attractive conditions for a large-scale energy-from-sugarcane program.

132. Li, J., X. Zhuang, P. De Laquil, and Eric Larson, 2001: Biomass Energy in China and its Potential. Energy for Sustainable Development, V(4), doi:10.1016/S0973-0826(08)60286-0 66-80
     [ Abstract ]

     Biomass is a significant source of energy in China today, particularly in rural areas. However, most current use of firewood and agricultural residues for cooking and heating brings with it detrimental effects of indoor air pollution and associated adverse health impacts. In addition, the time spent collecting biomass fuels creates a burden on women and children, which reduces their time available for more productive activities. The availability of clean, low-cost fuels for heat and power in rural areas based on modern biomass technologies could significantly increase living standards and would be helpful in promoting rural industrialization and the generation of employment in rural areas. In addition, since sustainable use of biomass leads to no net increase in CO₂ emissions, there would be global climate benefits arising from the widespread use of biomass. This article discusses the size of the biomass resource base in China, the current status of modernized biomass technology development, and near- and mid-term commercial targets for implementation of modern bioenergy systems in China. The article also describes some advanced biomass conversion systems that might play a role in China’s energy system in the longer term. Finally, it describes current barriers and constraints on increasing the penetration of modernized biomass energy in China, along with some policy suggestions for addressing these.

133. Liu, S., G. Wang, and P. De Laquil, 2001: Biomass Gasification for Combined Heat And Power in Jilin Province, People’s Republic of China. Energy for Sustainable Development, 5(1), 47-53
     [ Abstract ]

     This paper describes a project that is being co-funded by the Jilin Provincial Government and the United Nations Development Program to demonstrate the technical, economic and market viability of a modern biomass gasification system to provide cooking gas, heat and electricity to village communities in China. The paper summarizes the project background, organization and approach, and provides details of the preliminary design. The project is expected to be constructed and commissioned during 2001 and to undergo operation and evaluation in 2002 and 2003. A commercialization strategy and business plan will be developed to promote project replication.

134. Ogden, J. M., and Eric Larson, March 2001: Buying Down the Cost of Fuel Cells with Hydrogen Fueled Fleet Vehicles. Proceedings of the 12th Annual Meeting of the National Hydrogen Association, Washington, DC, 699-724
     [ Abstract ]

     Fuel cell vehicles are making rapid technical progress. However, the path toward commercialization is complicated by the issue of fuel choice. The design of the fuel cell vehicle is simpler with onboard hydrogen storage, and the vehicle is likely to be lower cost and more energy efficient that one using liquid fuels (such as gasoline or methanol) with an onboard fuel processor. But developing a refueling infrastructure is seen as more costly and challenging for hydrogen than for liquid fuels. For automobiles, availability of compact, low cost onboard hydrogen storage systems is also an issue. Recent studies suggest that the best long-term option for fuel cell vehicles is hydrogen in terms of vehicle costs, lifecycle costs and potential environmental benefits. However, it is often asserted that use of a liquid fuel such as gasoline or methanol will be required (at least initially) to get enough fuel cell vehicles on the road to buy down the cost via mass production to levels competitive with other low emission vehicles. Here we explore the possibility of going directly to hydrogen, buying down the cost of hydrogen fuel cell vehicles with centrally refueled fleet markets. Fleet vehicles are attractive initial markets for hydrogen fuel cells for several reasons: 1) often they are centrally refueled so that an extensive new refueling infrastructure is not required, 2) refueling and maintenance can be done by technically trained personnel in a controlled environment, 3) onboard storage constraints are less stringent for fleet operations than for private automobiles, and current compressed gas hydrogen storage would be adequate. Estimates of the size of centrally refueled fleet markets are made of cars, trucks and buses in the US and for buses globally. Mandated US markets for zero emission vehicles and alternative fueled fleet vehicles are discussed. We then assess whether fleet markets are large enough to buy down the cost fuel cell vehicles, and explore the issue of fuel choice during buy down. The projected cost of fuel cell vehicles as a function of cumulative mass production is calculated. The cumulative production and cost required for fuel cell vehicles to reach lifecycle cost competitiveness with advanced internal combustion engine hybrid vehicles is estimated. Buy down costs are compared for hydrogen, methanol and gasoline fuel cell vehicles. The potential impact of including the costs of environmental externalities (air pollutants and greenhouse gases) is explored. Hydrogen infrastructure development for fleet vehicles is discussed. Finally, a commercialization strategy for using centrally refueled fleets to buy down the cost of hydrogen fuel cells is sketched.

135. Schneider, L. C., A. P. Kinzig, Eric Larson, and L. A. Solarzano, 2001: Method for Spatially-Explicit Calculations of Potential Biomass Yields and Assessment of Land Availability for Biomass Energy Production in Northeastern Brazil. Agriculture, Ecosystems, and Environment, 84(3), doi:10.1016/S0167-8809(00)00242-5 207-226
     [ Abstract ]

     The Intergovernmental Panel on Climate Change (IPCC) has suggested that large-scale use of carbon-neutral or low-carbon biomass-derived energy will be essential in order to limit carbon emissions from the world’s energy sector in the future. The IPCC envisions as much as 400 million ha being devoted to biomass energy plantations by 2050. To realize production of biomass energy at such levels—in a manner that would be both biogeophysically sustainable and socially beneficial—will require planning and policy development at sub-national levels, taking into account biogeophysical, social, cultural, economic, institutional, and other factors. This paper presents amethod for spatially explicit calculations for estimating potential biomass yields over relatively large geographic regions. The calculations use geo-referenced data inputs that include rainfall, insolation, temperature, soil quality, and soil depth. The methodology is applied to the Northeast region of Brazil, which accounts for 10% of the area of South America. Northeast Brazil is an interesting site for illustrative purposes in part because it is biologically, geologically, and socio-economically diverse and in part because the main electric utility serving the region is exploring the development of biomass-based electricity generation to meet future increases in electricity demand. Results from a spatially explicit, biogeophysical model like that presented here could be combined with other spatially explicit information such as road layouts, existing land uses, population densities and growth rates, distributions of endangered species, archeologically significant areas, etc. to inform planning and policy development related to biomass energy at a regional or national level. One illustration of such an analysis is included here. For on-the-ground implementation of biomass production systems, finer-resolution analysis and intimate local participation is essential.

136. Williams, Robert H., 2001: Addressing Challenges to Sustainable Development with Innovative Energy Technologies in a Competitive Electric Industry. Energy for Sustainable Development, V(2), doi:10.1016/S0973-0826(08)60269-0 48-73
     [ Abstract ]

     Radical change in the energy system is essential in the decades immediately ahead in order to address effectively the multiple economic, social, environmental, and insecurity challenges posed by conventional energy. This can come about only through a concerted international effort to speed up the rate of technological innovation worldwide for technologies that offer promise in addressing sustainable development objectives – with particular attention given to developing countries, which account for much of the world’s energy demand growth and where problems posed by conventional energy are severe. The effort should be aimed at channeling some of the enormous private-sector financial and technological resources to the development and widespread deployment of such new energy technologies. In the industrialized countries, public policies supportive of innovation directed to the needs of the developing world as well as domestic needs are called for. Developing country governments should strive to make their countries favorable theaters for energy technological innovation that is supportive of their development needs. There is a need to complement such national policy measures with establishment at the multilateral level of a framework for channeling vast private-sector financial resources to this process, with emphasis on developing countries. Either new multilateral institutions should be created to carry out the needed activities or some existing institutions might be transformed to take on these new responsibilities. It is suggested that if the latter approach is taken, the Global Environment Facility might be given this responsibility. The ongoing process of reform to improve the economic efficiency of electricity markets can assist the needed transition to the needed new energy technologies – if reforms include measures to promote energy technological innovation in ways that would serve sustainable development objectives. The combination of rapid energy demand growth plus environmental and energy market reforms could potentially transform developing country energy markets into favorable theaters for energy technological innovation. Under these conditions, developing country governments would have considerable market power to direct the course of this innovation – including the power to induce the private sector to provide those new energy technologies that they believe are well-suited to their development needs. With large internal markets, large rapidly industrializing countries in particular have an opportunity to become market leaders for selected sustainable energy technologies, with eventual export capability. It is desirable to put the needed innovation policies in place soon. Fundamental policy changes such as those proposed are typically easier to introduce when institutions are in ferment, as is the case with ongoing power sector reforms. Once power sector reforms have been put into place the policy arena will become quiescent, and it will be more difficult to bring about fundamental change.

137. Williams, Robert H., 2001: Toward Zero Emissions from Coal in China. Energy for Sustainable Development, V(4), doi:10.1016/S0973-0826(08)60285-9 39-65
     [ Abstract ]

     China depends for most of its energy on coal – a situation that is likely to persist in the light of the abundance of its coal resources, the paucity of its oil and gas resources, and the reluctance of the government to allow China to become overly dependent on energy imports. The challenge is to find ways to use coal without the enormous air pollution damage caused by current conversion technologies and with greatly reduced carbon dioxide (CO₂) emissions. A coal energy system for China is proposed that could ultimately be characterized by near-zero emissions of both air pollutants and greenhouse gases. The key enabling technology is oxygen-blown (O₂–blown) gasification to generate synthesis gas from coal. This technology is used in commercially ready integrated gasification combined-cycle power plants that can provide electricity with air pollutant emissions as low as emission levels for natural gas combined-cycle plants. O₂-blown gasification is not yet used in China’s energy sector, although the technology is well-established in China’s chemical process industry. The key enabling strategy, which would often lead to attractive energy costs without further technological advances, is “polygeneration” – the co-production from synthesis gas of at least electricity and one or more clean synthetic fuels (e.g., dimethyl ether (DME), Fischer-Tropsch (F-T) liquids, hydrogen (H₂) and often also chemicals, town gas, and/or industrial process heat. The products of polygeneration could be used in the near term to serve a wide range of energy needs with extremely low levels of air pollutant emissions. In such polygeneration configurations CO₂ can often be produced in relatively pure streams as a co-product as a result of processing to increase the synthetic fuel’s hydrogen-to-carbon ratio. In the near term this CO₂ might be used profitably for enhanced oil recovery or enhanced recovery of methane from deep beds of unminable coal where resource recovery opportunities exist. For the longer term the potential exists for evolving the coal energy system to the co-production primarily of electricity and H₂ for serving urban areas, with most of the carbon in the coal ending up as CO₂ that is sequestered in geological reservoirs such as in depleted oil and natural gas fields and deep saline aquifers at low incremental cost – even where there are no opportunities for using the CO₂ for enhanced resource recovery. The H₂ so produced would be used for fueling zero-polluting fuel-cell vehicles, for distributed cogeneration (combined heat and power) applications in stationary fuel cells, and for cooking and heating applications as well. A third clean carbon-based synthetic fuel might also be needed for serving rural markets that would be difficult to serve with H₂, unless there are breakthroughs in H₂ storage technology. DME is a strong candidate for becoming the “third” clean energy carrier for China. Evolving a coal-based energy system that would be characterized ultimately by near-zero emissions of air pollutants and greenhouse gases would probably involve shifting the center of gravity for central-station power generation to the chemical process industries that would ultimately be co-producing as their major products electricity, H₂, and (perhaps) DME. Ongoing structural reforms in the electric power sector that encourage greater competition in power generation would facilitate the realization of this vision for coal.

138. Williams, Robert H., 2001: Nuclear and Alternative Energy Supply Options for an Environmentally Constrained World: a Long-Term Perspective. Nuclear Power and the Spread of Nuclear Weapons: Can We Have One Without the Other?, Brassey's, Washington, DC, http://www.princeton.edu/~cmi/research/Capture/Papers/nuclear.pdf, 85-122
     [ Abstract ]

     Nuclear power is commercial technology that offers the potential for providing electricity with zero emissions of air pollutants and greenhouse gases. Despite this promise, the nuclear power industry is stagnating. Most energy projections show that, although some new capacity will be added (primarily in Asia) there will be little or no net growth or even a decline in nuclear generating capacity worldwide over the next two decades (Williams, 2000). Nuclear power faces four serious challenges: costs that are typically higher than for alternatives; concerns about reactor safety; the lack of significant progress in dealing with radioactive waste disposal; and the the nuclear weapons connection to nuclear power. The recent World Energy Assessment (WEA, 2000) reached judgments that there are good prospects for addressing the reactor safety challenge satisfactorily, and that the waste disposal problem can probably be solved technically—though it will be difficult to convince publics that the problem is soluble. No judgment was reached on the cost challenge ("the proof is in the pudding"). And the WEA expressed skepticism regarding the prospects for coping effectively with the nuclear weapons connection to nuclear power. This skepticism is rooted in the formidable extent of the challenge of separating the peaceful atom from the military atom—especially at the high levels of nuclear power development needed to "make a dent" in climate change mitigation, as an alternative to continued reliance on fossil fuels over the longer term.

139. Wu, Z., P. De Laquil, Eric Larson, W. Chen, and P. Gao, 2001: Future Implications of China’s Energy-Technology Choices: Summary of a Report to the Working Group on Energy Strategies and Technologies. Energy for Sustainable Development, V(4), doi:10.1016/S0973-0826(08)60283-5 19-31
     [ Abstract ]

     This report summarizes results of an assessment of future energy-technology strategies for China built on analytical work carried out during the past several years by the Working Group on Energy Strategies and Technologies (WGEST) of the China Council for International Cooperation on Environment and Development (CCICED). The assessment identifies and highlights key implications of different advanced-energy technology strategies that could allow China to continue its social and economic development while ensuring national energy-supply security and promoting environmental sustainability. The MARKAL energy-system modeling tool was used to build a simplified model representing China’s energy system. Different scenarios for the evolution of energy supply and demand in China from 1995 to 2050 were explored with the model, enabling insights to be gained into different energy development choices that China might make. The overall conclusion from the analysis is that there are plausible energytechnology strategies that would enable China to continue social and economic development through at least the next 50 years while ensuring security of energy supply and improved local and global environmental quality. Remarkably, except for the case when very major reductions in carbon emissions are sought, the model predicts that such energy strategies would not involve significantly higher cumulative (1995-2050) discounted costs for the energy system than “business-as-usual” strategies. Furthermore, “business-as-usual” strategies, which were also modeled, will not enable China to meet all of its environmental and energy security goals. To meet these goals, an energy development strategy that relies on the introduction of advanced technologies is essential. To realize such strategies, policies are needed in China that will i) encourage utilization of a wider variety of primary energy sources (especially biomass and wind) and clean secondary energy carriers (especially synthetic fluid fuels from coal and biomass), ii) support the development, demonstration and commercialization of radically new clean energy conversion technologies to ensure that they are commercially available beginning in the next 10 to 20 years, and iii) support aggressive end-use energy efficiency improvement measures.

140. Ogden, J. M., Thomas Kreutz, and M. M. Steinbugler, 2000: Fuels For Fuel Cell Vehicles. Fuel Cells Bulletin, 3(16), doi:10.1016/S1464-2859(00)86613-4 5-13
     [ Abstract ]

     The issue of fuel choice impacts both fuel cell vehicle design and infrastructure development. In general, there is a trade-off between simpler vehicle design (hydrogen vehicles are inherently simpler than those with onboard fuel processors) and simpler infrastructure issues (liquid fuels such as gasoline or methanol are easier to store and handle, and are more compatible with the existing refueling infrastructure). In this article we compare fuel cell vehicle characteristics and infrastructure requirements for four possible fuel options: compressed hydrogen gas, methanol, gasoline and synthetic liquids derived from natural gas. The advantages and disadvantages of various fuels are discussed, and possible fuel strategies leading towards the commercialisation of fuel cell vehicles are explored.

141. Liu, Guangjian, Eric Larson, Robert H. Williams, and J. R. Katzer, in press: Gasoline from Coal and Biomass with CSS Performance and Cost Analysis. Proceedings of the 8th Annual Carbon Capture and Sequestration Conference, Pittsburgh, PA. 0/00.

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