□ Hydrogen fuel-cell cars could become commercially feasible if automakers succeed in developing safe, inexpensive, durable models that can travel long distances before refueling.
□ Energy companies could produce large amounts of hydrogen at prices competitive with gasoline, but building the infrastructure of distribution will be costly.
► Will motorists someday fill up their tanks with hydrogen? Many complex challenges must be overcome before a hydrogen-fueled future can become a reality.
Hopes for i
Using hydrogen to fuel cars may eventually slash oil consumption and carbon emissions, but it will take some time BY JOAN OGDEN
Developing cleaner power sources for transportation is perhaps the trickiest piece of the energy puzzle. The difficulty stems from two discouraging facts. First, the number of vehicles worldwide, now 750 million, is expected to triple by 2050, thanks largely to the expanding buying power of customers in China, India and other rapidly developing countries. And second, 97 percent of transportation fuel currently comes from crude oil.
In the near term, improving fuel economy is the best way to slow the rise in oil use and greenhouse gas emissions from cars and trucks. But even if automakers triple the efficiency of their fleets and governments support mass transit and smart-growth strategies that lessen the public's reliance on cars, the explosive growth in the number of vehicles around the world will severely limit any reductions in oil consumption and carbon dioxide emissions. To make deeper cuts, the transportation sector needs to switch to low-carbon, nonpetroleum fu els. Liquid fuels derived from woody plants or synthesized from tar sands or coal may play important roles. Over the long term, however, the most feasible ways to power vehicles with high efficiency and zero emissions are through connections to the electric grid or the use of hydrogen as a transportation fuel.
Unfortunately, the commercialization of electric vehicles has been stymied by a daunting obstacle: even large arrays of batteries cannot store enough charge to keep cars running for distances comparable to gasoline engines. For this reason, most auto companies have abandoned the technology. In contrast, fuel-cell vehicles—which combine hydrogen fuel and oxygen from the air to generate the power to run electric motors—face fewer technical hurdles and have the enthusiastic support of auto manufacturers, energy companies and policymakers. Fuel-cell vehicles are several times as efficient as today's conventional gasoline cars, and their only tailpipe emission is water vapor.
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