During the past year, we have deepened our understanding of not only membrane reactors for H2 manufacture from coal (the focus of our first year) but also alternative configurations of conventional technologies for making H2 from coal that involve use of physical solvents and pressure swing adsorption technologies for gaseous separation, instead of membranes. This extension resulted from our preliminary finding near the end of the previous year that the particular membrane reactor we had focused on did not seem to offer substantial economic benefits, relative to conventional H2 production technologies.
With researchers from the Department of Energetics of the Politecnico di Milano, we have been working on the decarbonization, via coal gasification, of electricity generation and H2 production. We have considerably expanded our data bases for modeling both the technical performance and engineering costs for components of energy conversion systems that are important to the achievement of low-cost fossil fuel decarbonization. We are now able to make performance and cost calculations for many alternative H2 and electricity production systems in relatively short times.
Our modeling activities have made it possible for us to reach some preliminary judgments:
- It is much more costly (in $/tC) to decarbonize electricity than H2 , which implies that the more quickly H2 fuel becomes competitive, the sooner a low-carbon low-carbon- energy future will emerge.
- It is more costly (in $/tC) to decarbonize natural gas than coal…but decarbonizing natural gas systems is not so urgent as decarbonizing coal systems.
- Even with a carbon valuation high enough to induce carbon capture and storage for the most promising coal electricity technology (IGCC), natural gas combined cycles with CO2 venting will provide less costly electricity, unless there are major coal technology breakthroughs.
- H2 manufacture offers the best prospects for coal, so that the coal industry should be interested in H2.
- Co-sequestration (storing carbon and sulfur together) and the production of fuel – grade H2 instead of pure H2, in combination, can reduce costs for H2 from coal ~ 20%, relative to pure H2 from coal with no co-sequestration.
- Carbon storage companies will seek the least costly CO2 sources—which will often be from facilities that make synthesis gas via gasification.
Markets for H2
During the past year we have carried out extensive lifecycle cost analysis of alternative fuel/engine combinations for cars. Our aim is to understand better the economic prospects for H2 fuel cell cars and the conventional ICE cars that are likely to be the main competitors to fuel cell cars at the time H2 fuel cell cars might be introduced. Because conventional technology is a moving target, if H2 fuel cell cars are motivated solely by climate concerns, we find that a carbon valuation of several hundred dollars per ton of carbon will be needed to justify, in terms of cost, a shift to mass produced H2 fuel cell cars – without major technological innovations. A case can be made that H2 fuel cell cars can compete with lower, more plausible carbon valuations, if health damage costs of air pollution (especially from small particles) and oil supply insecurity risks are also internalized – but valuations of these externalities are very uncertain.
This result suggests the importance of exploring other possible early markets where H2 might compete with conventional fuels in the presence of carbon valuations of less than $100/tC. Preliminary analysis suggests that the industrial fuel market is worth exploring for coal-derived H2 with carbon capture and storage. In that market, the high costs of small-scale compressed gaseous H2 storage can be avoided – costs which make automotive market development difficult.
Key inputs to our H2 fuel cell vehicle lifecycle cost assessment are estimates of the cost of H2 to consumers. These estimates, in turn, require estimates of H2 distribution infrastructure costs for vehicle applications. We have estimated, self -consistently, the costs of H2 production, pipeline distribution to filling stations, and use in vehicles. Not surprisingly, the cost of providing at refueling stations high pressure H2 for storage onboard vehicles represents a significant fraction of the total infrastructure cost. In contrast, it appears that the incremental costs for capturing/storing CO2 below ground are quite small, if storage costs are dominated by the costs of pipes and wells. Thus if H2 vehicles can be made competitive when the H2 is produced from fossil fuels with CO2 vented, these vehicles would probably also be competitive with the CO2 captured and stored.
Hydrogen Combustion and Safety
Experiments and computational simulation were conducted on the ignition of hydrogen/air mixtures by either a heated jet or a spark discharge. The flammability boundaries and the associated controlling chemistry were identified. It was further demonstrated that hydrogen flames are inherently unstable in their propagation, which could lead to flame wrinkling and transition to turbulence. The possibility of moderating the explosivity of hydrogen/air mixtures through hydrocarbon doping was also investigated.
Collaboration with Tsinghua University, Beijing
Collaboration between Princeton’s CMI and the new BP-sponsored carbon management program at Tsinghua University, Beijing, took several forms:
- a year-long visit to Princeton of a Tsinghua faculty member who, with Princeton collaborators, is modeling methanol and dimethyl ether production from syngas and identifying costs appropriate for U.S. and Chinese contexts;
- jointly producing energy scenarios for China, 1995-2050, to examine environmental, energy-security, energy cost, and energy resource implications of alternative energy technology paths;
- joint planning of a forthcoming Beijing workshop on “polygeneration,” the co – production of electricity, chemicals, fuels, and heat from fossil fuels;
- process design projects by Tsinghua graduate students, co -supervised by Princeton and Tsinghua;
- the week-long hosting by Tsinghua of Princeton graduate students investigating the future of coal in China, and traveling with Tsinghua graduate students to coal country in Shanxi province.
- The capacity for modeling clean and climate-friendly fossil energy systems is being extended in scope and intensity via this collaboration. The CMI modeling capability, which has focused on H2 and electricity production, is being extended to polygeneration systems. Much of the system component modeling already developed under CMI is directly relevant and is being transferred to analysis of these different energy systems.