technology for distributed manufacture may reduce production costs through efficiency improvements and possibly by enabling reduced capital requirements for ancillary storage and filling equipment.
Recommendation 4-1. Increased research and development investment in support of breakthrough approaches should be made in small-scale reformer and electrolyzer development with the aim of increasing efficiency and reducing capital costs. A related goal should be to increase the safety and reduce the capital intensity of local hydrogen storage and delivery systems, perhaps by incorporating part or all of these capabilities in the hydrogen-generating technologies.
Finding 4-2. It is clear that the vast majority of current private and governmental investments in the manufacture of hydrogen for fuel cell vehicles are aimed at the direct use of molecular hydrogen. Because of the inherent difficulties in the transportation, distribution, and storage of molecular hydrogen, it is apparent that other approaches for hydrogen generation may have advantages for transportation and for on- and off-board storage. The latter include compounds that, on reaction with water or some other reactant, generate hydrogen, and solid-state carriers that contain high concentrations of adsorbed or absorbed hydrogen that liberate the stored hydrogen through the application of heat. Many possibilities exist in these categories, but few have received significant research support. Solid-state hydrogen carriers will probably not be useful for the transportation and distribution of hydrogen, but may be valuable for local and/or on-board vehicle storage. The committee strongly supports the requested Department of Energy budget increases in the vital area of hydrogen storage. The committee believes, however, that major shifts in emphasis should be made immediately in order to make sure that the many new ideas currently available are properly examined—because without relatively near-term confidence by industry and government leaders, interest in continuing the pursuit of fuel cell vehicle transportation uses is likely to wane over time.
Recommendation 4-2. The Department of Energy should halt efforts on high-pressure tanks and cryogenic liquid storage for use on board the vehicle. These technologies are in a pre-commercial development phase, and in the committee’s view they have little promise of long-term practicality for light-duty vehicles. The DOE should apply most if not all of its budgets to the new areas described in Finding 4-2 with the objective of identifying as quickly as possible a relatively few, promising technologies. Where relevant, efficient waste-recycling studies for the chemically bound approaches should be part of these studies. Even during this winnowing process the DOE should continue to elicit new concepts and ideas, because success in overcoming the major stumbling block of on-board storage is critical for the future of transportation use of fuel cells.
Finding 4-3. The evolution of the transportation and delivery and storage systems for hydrogen will transition several times as hydrogen demand increases over many decades. This would of necessity mean continuous and overlapping shifts from small-scale delivery and storage, to distributed manufacture and storage, to centralized production with extensive pipeline, distribution, and storage networks. Such a complex evolution would likely benefit from systems analysis to help guide the optimum research and technology investment strategies for any given stage of the evolution and thus enable the most effective progress toward the long-term end states.
Recommendation 4-3. Systems modeling for the hydrogen supply evolution should be started immediately, with the objective of helping guide research investments and priorities for the transportation, distribution, and storage of molecular hydrogen. In addition, parallel analysis of the many alternatives for other means of supplying hydrogen to fuel-cell-powered facilities and vehicles should be performed; such analysis is needed to prevent wasteful expenditures and to help focus attention on viable technology that would potentially compete with the direct supply and delivery of molecular hydrogen and that might be useful for all or portions of the future hydrogen economy.
Finding 4-4. Hydrogen is particularly difficult to ship from a manufacturing site to filling facilities for vehicle servicing. In fact, the cost to ship and store can easily equal the costs of production. These costs are directly related to molecular hydrogen’s thermodynamic properties, low molecular weight, and consequently high diffusion capabilities, and to its great flammability and ability to form explosive mixtures over a wide range of concentrations. Particular concerns relate to the energy losses during compression and liquefaction and to the tendency of hydrogen to embrittle some current pipeline materials.
Recommendation 4-4. Research and technology development should be carried out in support of novel concepts that promise major improvements in the cost and efficiency of compressors for molecular hydrogen and reductions in the cost of pipeline materials, valves, and other leak-prone components of its distribution system. Initial research should focus on those components that are directly related to distributed hydrogen production. In later years, research should shift to components for large, centralized production plants with extensive pipeline and storage facilities. The committee believes that current Department of Energy plans call for research that relates primarily to centralized molecular hydrogen manufacture—a need that is many decades in the future—and consequently may shortchange other, more immediate needs.