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- Can we calculate the efficiency of a natural photosynthesis process?
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- Is it possible to collect energy from a moving roller coaster?
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Can traditional gasoline-powered cars be converted to run on hydrogen fuel cells?
Yes — but it probably makes more sense to start with buses and long-haul trucks than passenger cars…By Jennifer Sutton
First of all, says John Heywood, professor of mechanical engineering, and director of the Sloan Automotive Research Laboratory, let’s define the word “convert.” A traditional vehicle can be retrofitted with a new hydrogen fuel-cell engine, he says, but it is far too challenging and costly to be worth the effort. “The only cases where a retrofit might make sense is in large diesel vehicles like buses or long-haul trucks,” Heywood says.
But the prospect of changing our gasoline-engine technology so that more and more cars run on hydrogen fuel cells, he says, is more attainable. However, don’t look for them on the road anytime soon.
Hydrogen fuel-cell vehicles, effectively run on batteries powered by hydrogen instead of the electric power grid. The fuel cell converts the hydrogen and oxygen in the air into water, and in the process it produces electricity. As long as hydrogen and oxygen keep flowing into the fuel cell, it never goes dead. Hydrogen fuel cells have the potential for reducing harmful emissions (depending on how the hydrogen is produced) and will decrease the U.S.’s dependence on foreign petroleum. The disadvantage: in order to put hydrogen-powered cars on the road, Heywood says, we must change not only our vehicle technology, but also our entire fuel supply and fuel distribution system.
Hydrogen fuel cell technology has been around for years but has yet to take root in the marketplace. “A decade ago, hydrogen was getting all the attention, and electricity was barely on the list,” Heywood says. The recent introduction of hybrids and battery-powered cars has proven more successful, he says, largely because the change they represent can happen incrementally, without having to build an entirely new system for storing and delivering fuel. “Hydrogen’s not dead,” he says. “It’s just difficult to think about such a major change.”
There are two ways to make hydrogen fuel, one clean, one not so clean. Electrolyzing water — splitting the hydrogen from the oxygen — produces no direct emissions, but the process requires more energy than it produces. Hydrogen also comes from partly burning methane gas and reacting it with steam, which separates the resulting gas into oxygen and hydrogen. In other words, in order to produce “clean” hydrogen fuel you need to start with fossil fuels (coal or natural gas), which come with the same old climate-compromising problems.
“The critical question is how can we produce hydrogen in efficient ways that also produce low emissions?” he says. “We’ve got a lot of fossil fuels around — more than we think. So we can keep being bad boys and girls, which doesn’t motivate us to make changes.”
Thanks to John Dugdale of Atlanta, GA, for this question.
Posted: March 2, 2010