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Clean machines

ASEE Prism, Sep 2003 by Grose, Thomas K

Hydrogen-powered cars may be one answer to the nation's pollution problems, but the technology is still more than a decade down the road > > By Thomas K. Grose

WILL "FREEDOM CARS" be zipping along America's highways in significant numbers in the next 10 years or so? That's a goal of the Bush administration. What President George W. Bush has dubbed Freedom Cars are fuel-cell vehicles powered by hydrogen- a clean, renewable resource - whose only emission is dribbles of water. In his State of the Union address last January, Bush announced plans to commit $1.7 billion over five years toward fuel-cell car research.

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Ultimately, the energy holy grail that oil companies, automakers, and environmentalists all say is attainable and desirable, is the so-called hydrogen economy. In that rosy scenario, hydrogen fuel cells would not only power vehicles but provide energy to heat and cool homes and offices. Then it would be goodbye to the "greenhouse gases" - particularly carbon dioxide - that some scientists claim contribute to global warming and are the noxious byproduct of the burning of fossil fuels. It also would free us from our dependency on nonrenewable fuels like petroleum. Fuel cells produce energy from the chemical reaction that occurs when hydrogen is mixed with oxygen. In a hydrogen economy, the hydrogen would be produced from water, using a process called electrolysis; the electricity for that method would come from other clean technologies, including solar and wind power.

That sounds great, right? And engineering academics familiar with fuel-cell technology certainly don't dispute the likelihood that a hydrogen economy is in our future. Eventually. They suspect that it may be a generation away. And they certainly don't expect to see mass production of hydrogen-powered cars within a decade or so. "To say we can have hydrogen cars in 12 years is nuts," says John B. Heywood, director of the Sloan Automotive Lab at the Massachusetts Institute of Technology. Yann G. Guezennec, a professor of mechanical engineering at Ohio State University's Center for Automotive Research, predicts that in 10 years' time, there will mainly be demonstration fuel-cell vehicles, a few bus fleets, and some limited production cars costing nearly $80,000. "But you are looking at 2020, at a minimum" before there is production of between 15,000 to 30,000 hydrogen cars a year.

Why so long? Well, certainly fuel-cell technology is not yet ready for prime time (more on that later). The biggest hurdle to overcome, however, is a lack of hydrogen distribution infrastructure and for that matter, hydrogen itself. As Guezennec points out: "Hydrogen is the most abundant element in the universe, but there are no hydrogen wells." Drivers today take for granted that they are rarely far from a gas station where they can "filler up" fairly economically. Our petroleum-based infrastructure that pumps oil from beneath the grounds or ocean beds of such far-flung locales as Saudi Arabia, Alaska, and Europe's North Sea and converts it to readily available gasoline is nearly a century old now. And it's efficient. To create a new hydrogen network from scratch will not only take time but plenty of money. Friedrich Prinz, a professor of chemical engineering at Stanford University, says such a network could perhaps cost a trillion dollars, "and today, that's not feasible." It also presents a classic chicken-and-cgg dilemma: Energy companies won't invest in building an infrastructure until they're confident there will be enough hydrogen cars to use it; and auto manufacturers are reluctant to mass produce cars that aren't easily refueled.

While hydrogen is clean, current methods for obtaining it are not. Most hydrogen is produced from natural gas or coal, and the dreaded carbon dioxide is a byproduct. "The real question is, 'Can we produce hydrogen sensibly at a manageable cost?'" Heywood explains. "The ideas that we have now are primitive and not very developed." And, true, electrolysis is a super clean technology. But 85 percent of our electric power today comes from fossil-fuel plants. So using electrolysis to make clean hydrogen in, say, Atlanta, is pointless if the electricity is coming from a coal-fired plant 70 miles out of town. As Guezennec says, "It's displaced pollution."

That means we also need simultaneous breakthroughs in solar (photovoltaic) and wind technologies. Solar cells that most effectively convert light to energy need high-grade silicon semi-conductors, and that's expensive. Thin-film technology that relies on amorphous silicon is cheaper, but it's also less reliable and the film quickly degrades. But new types of stronger, more efficient thin-film cells that use cadmium teluride or copper indium diselenide are starting to appear. Advances in the manufacturing of wind turbines make wind energy promising. Already in some European countries, like Britain, electricity generated from catching the wind is competitively priced.

Capturing hydrogen from the natural gas produced at oil wellheads may be another option. The resulting carbon dioxide could be "sequestered," or injected into the earth, a process that also makes the pumping of the oil more efficient. But as MIT's Heywood points out, we're not sure that shunting massive amounts of carbon into the ground is environmentally benign. And at the end of the day, the idea is to move away from fossil fuels entirely.

Clean machines

ASEE Prism, Sep 2003 by Grose, Thomas K

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