One of the challenges facing fuel-cell cars is extending their range. The U.S. Department of Energy's National Renewable Energy Laboratory recently measured the ranges of 59 fuel-cell cars made by four industry teams (right). Even the best-performing team fell short of the 300-mile range needed for a commercial vehicle. Another challenge is lowering the price of hydrogen fuel. Making hydrogen from renewable energy sources such as wind, solar and biomass power is currently too expensive, but future technologies could make zero-emissions production more affordable (below).
Hydrogen Fuel-Cell Vehicle Range (miles)
Hydrogen Fuel-Cell Vehicle Range (miles)
fuel-cell cars, it would power about 150 million vehicles, or about 20 percent of the world's fleet. Although most hydrogen is produced and immediately used inside refineries or chemical plants, some 5 to 10 percent is delivered to distant locations by truck or pipeline. In the U.S. this delivery system carries enough energy to fuel several million cars, and it could serve as a springboard to a hydrogen economy.
Making hydrogen from fossil fuels, however, generates carbon dioxide as a by-product. If hydrogen were produced from natural gas, the most common method today, and used in an efficient fuel-cell car, the total greenhouse gas emissions would work out to be about 110 grams per kilometer driven. This amount is somewhat less than the total emissions from a gasoline hybrid vehicle (150 grams per kilometer) and significantly less than those from today's conventional gasoline cars (195 grams per kilometer).
The ultimate goal, though, is to produce hydrogen with little or no greenhouse gas emissions. One option is to capture the carbon dioxide emitted when extracting hydrogen from fossil fuels and inject it deep underground or into the ocean. This process could enable large-scale, clean production of hydrogen at relatively low cost, but establishing the technical feasibility and environmental safety of carbon sequestration will be crucial. Another idea is biomass gasification—heating organic materials such as wood and crop wastes so that they release hydrogen and carbon monoxide. (This technique does not add greenhouse gases to the atmosphere, because the carbon emissions are offset by the carbon dioxide absorbed by the plants when they were growing.) A third possibility is the electrolysis of water using power generated by renewable energy sources such as wind turbines or solar cells.
Although electrolysis and biomass gasification face no major technical hurdles, the current costs for producing hydrogen using these methods are high: $6 to $10 per kilogram. (A kilogram of hydrogen has about the same energy content as a gallon of gasoline, but it will propel a car several times as far because fuel cells are more efficient than conventional gasoline engines.) According to a recent assessment by the National Research Council and the National Academy of Engineering, however, future technologies and large-scale production and distribution could lower the price of hydrogen at the pump to $2 to $4 per kilogram [ see box on opposite page]. In this scenario, hydrogen in a fuel-cell car would cost less per kilometer than gasoline in a conventional car today.
Nuclear energy could also provide the power for electrolysis, although producing hydrogen this way would not be significantly cheaper than using renewable sources. In addition, nuclear plants could generate hydrogen without electrolysis: the intense heat of the reactors can split water in a thermochemical reaction. This process might produce hydrogen more cheaply, but its feasibility has not yet been proved. Moreover, any option involving nuclear power has the same drawbacks that have dogged the nuclear electric power industry for decades: the problems of radioactive waste, proliferation and public acceptance.
A New Energy Infrastructure because the u.s. has such rich resources of wind, solar and biomass energy, making large amounts of clean, inexpensive hydrogen will not be so difficult. The bigger problem is logistics: how to deliver hydrogen cheaply to many dispersed sites. The U.S. currently has only about 100 small refueling stations for hydrogen, set up for demonstration purposes. In contrast, the country has 170,000 gasoline stations. These stations cannot be easily converted to hydrogen; the gas is stored and handled differently than liquid fuels such as gasoline, requiring alternative technologies at the pump.
The need for a new infrastructure has created a "chicken and egg" problem for the incipient hydrogen economy. Consumers will not buy hydrogen vehicles unless fuel is widely available at a reasonable price, and fuel suppliers will not build hydrogen stations unless there are enough cars to use them. And although the National Research Council's study projects that hydrogen will become competitive with gasoline once a large distribution system is in place, hydrogen might cost much more during the early years of the transition.
One strategy for jump-starting the changeover is to first
JOAN OGDEN is professor of environmental science and policy at the University of California, Davis, and co-director of the Hydrogen Pathways Program at the campus's Institute of Transportation Studies. Her primary research interest is technical and economic assessment of new energy technologies, especially in the areas of alternative fuels, fuel cells, renewable energy and energy conservation. She received a Ph.D. in theoretical physics from the University of Maryland in 1977.
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