$1 to $1.75 per gallon of gasoline equivalent).1,2 But the real cost of hydrogen to automotive consumers can be 2 1/2 to 3 times as much. The high retail cost of hydrogen inhibits the development of a hydrogen economy.3 The large difference between the retail and wholesale costs of hydrogen arises in large part because the volumetric energy density of hydrogen is low (with gaseous hydrogen at 350 bar, one-tenth that of gasoline). The only commercially viable strategy for hydrogen storage in a vehicle at the present time is compressed gaseous storage (350 to 700 bar), which is costly not only for the storage canisters onboard vehicles but also for the compressors and electricity required for compression at refueling stations. Refueling time and safe hydrogen storage and handling facilities at retail stations are also factors that have a negative impact on the development of a hydrogen economy for transportation.

A low-cost hydrogen storage technology offering high volumetric storage densities with modest pressurization requirements could lead to a major reduction of the retail-wholesale gap for hydrogen. A mid-sized car with a hydrogen fuel cell could have a fuel consumption of 1 kg of hydrogen per 80 miles (80 miles per gallon of gasoline equivalent). If the desired range is 350 miles, a storage system with 4 percent hydrogen by weight translates to less than 120 kg of total weight. This weight penalty can be offset by reductions in the weight of other auto body parts.

Some present hydrogen storage sorbents have capacities below the target indicated, other sorbents suffer deterioration in use, and still others require complex systems to handle the energy requirements during sorption and desorption.

However, the range of materials investigated until now has been limited (metal hydrides, carbon). The theoretical design of sorbents (liquids or solids) with unique compositions and structure coupled with favorable physical and chemical interactions with hydrogen molecules is a good starting point for further research.

1  

Williams R.H. Decarbonized Fossil Energy Carriers and Their Technological Competitors. Prepared for the International Panel on Climate Change Workshop on Carbon Capture and Storage, Regina, Saskatchewan, Canada, 18–21 November 2002.

2  

Simbeck D.R. and Chang E. Hydrogen Supply: Cost Estimate for Hydrogen Pathways—Scoping Analysis. NREL/SR-540–32525. July, 2002. Golden, CO: National Renewable Energy Lab.

3  

The hydrogen economy has been envisioned as the large-scale use of hydrogen as an energy carrier generated from any of a variety of fuels or feedstocks, to be used in the transportation, industrial, and building sectors, and requiring an infrastructure for its transmission and delivery.



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