committee, December 2, 2002; Thomas, 2003) that it believes should be vigorously examined for their potential. Here again, narrowing the field as quickly as possible to focus on those few prospects with the most potential is a vital component of any research investment strategy.

All alternatives to molecular hydrogen relate to the manufacture of energetic metals or their hydrides, which, when reacted with water, emit hydrogen (Thomas, 2003). These materials would be shipped from centralized manufacturing sites by conventional truck, rail, or ship and distributed to consumer fuel cell vehicle filling facilities. Vehicles would be equipped with devices for reacting the compounds with water in order to generate fuel-cell-quality hydrogen and for storing the waste reactants. Waste would then need to be recycled or disposed of in an environmentally acceptable manner.

The principal game-changing features of these materials are the elimination of most safety and cost issues that high-pressure or cryogenically liquefied molecular hydrogen has, and the possibility of a major safety and range enhancement for on-board storage of hydrogen. Several small-vehicle demonstrations of the efficacy of this approach and its ability to provide acceptable driving range, hydrogen purity, and delivery rate and vehicle space efficiency have been successfully made (Bak, 2003). The use of 20 to 30 percent by weight of alkali-stabilized aqueous solution of sodium borohydride as fuel, which is pumped over a catalyst to generate hydrogen instantaneously, was demonstrated recently by DaimlerChrysler in its Chrysler Town and Country Natrium fuel cell minivan vehicle.7 This approach demonstrated the potential for meeting vehicle mileage, weight, and volume goals.8

The principal current shortcomings of these chemical methods for generating hydrogen are the high cost of manufacture of the chemicals and the not-yet-demonstrated technology for recycling or disposing of waste products effectively. Secondary issues include catalyst longevity over the vehicle life, fuel stability on board the vehicle, and the ability to meet automotive range and reliability requirements. However, all of these shortcomings, with the exception of the cost of recycling and initial manufacture, have had encouraging real-world demonstrations in full-sized passenger vehicles, as for example with the Natrium fuel cell vehicle.

The committee believes that this is an important area for further research and that it should be pursued vigorously to find the best chemicals for this use and to improve the economics of their manufacture and regeneration. The DOE should also continue to encourage other game-changing concepts because of the pivotal importance of this need to the future of fuel-cell-powered vehicles.

THE DEPARTMENT OF ENERGY’S HYDROGEN RESEARCH, DEVELOPMENT, AND DEMONSTRATION PLAN

The committee was pleased to be given an early draft of the DOE Office of Energy Efficiency and Renewable Energy’s “Hydrogen, Fuel Cells and Infrastructure Technologies Program: Multi-Year Research, Development and Demonstration Plan” (dated June 3, 2003) (DOE, 2003b). The following are the committee’s comments on this document regarding the areas of off-board storage, transportation, and distribution of hydrogen (see DOE [2003b], pp. 3-30 through 3-55).

Fundamentally, the committee agrees with the DOE’s assessment of the research needs in these important areas, especially those relative to pipeline costs and the need to improve the energetics of hydrogen compression and liquefaction. The committee differs with the DOE on near-term priorities. The committee believes that the requested increased funding in these areas should be prioritized to strongly favor solid or dense-phase storage of hydrogen, especially for on-board vehicle use, since on-board storage appears to be one of the primary obstacles to fuel cell vehicle practicality, along with the needed fuel cell cost reduction and reliability improvements.

FINDINGS AND RECOMMENDATIONS

The following findings and recommendations are based on the idea that some research and technology investments are at present more important than others in criticality and in time. This prioritization reflects the need to invest in overcoming the technology gaps that might be major stumbling blocks to immediate progress and to delay or reduce investment in those activities that, while very important, can wait for several years because they are not critical to near-term progress.

Finding 4-1. It seems likely that in the relatively near term (the next 10 to 30 years), distributed rather than centralized production of hydrogen will be a driver for the continued expansion of fuel-cell-powered private vehicles. Needs in the very early period are expected to be covered by shipment of pressurized or liquefied molecular hydrogen, but as volume requirements grow, such an approach may be deemed too expensive and/or too hazardous for continued widespread use. Distributed manufacture of molecular hydrogen seems most likely to be best done with small-scale natural gas reformers or by electrolysis of water. At present both technologies are capital-intensive and relatively energy-inefficient. Without such distributed manufacture, it seems likely that the very large centralized production and pipeline distribution investments will be difficult to justify and could slow conversion to hydrogen markedly. It seems possible that, in comparison with today’s state-of-the-art technology, the new

7  

The spent fuel cartridges would be regenerated at a central location.

8  

Additional information is available online at www.h2cars.biz/artman/publish/article_144.shtml. Accessed December 4, 2003.



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