ASEE Prism Magazine - September 2003
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Clean Machines

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 CAR” 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.

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-egg 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 semiconductors, 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.

One of Prinz's chemical engineering colleagues at Stanford, Jim Swartz, is working with a team on “a hydrogen genesis project . . . a direct pathway to capture solar energy and convert it to hydrogen using microorganisms.” An enzyme called hydrogenase “is very efficient at collecting sunlight and converting it into hydrogen,” Swartz explains. The problem is the process also produces oxygen, which kills the enzyme. So his team wants to bioengineer a version of the enzyme resistant to oxygen. If it succeeds at that, it must then design a bioconverter. Swartz envisions “energy farms,” several square miles of untillable land that would be set aside for the collection of sunlight and its conversion to hydrogen. “We've got significant amounts of land not suitable for agriculture that could be used,” Swartz says. The problem with producing hydrogen in remote areas—from wellheads or energy farms—is one of transport. “How do you get it to where people want it?” Heywood asks. You can build hydrogen pipelines, but they're hard to manage.

Another possible solution is to initially piggyback on the existing oil-based infrastructure. Hydrogen could be produced in the cars themselves using onboard reformers that convert either gasoline or methanol to hydrogen. The advantage would be getting consumers used to driving hydrogen-powered cars with the hope that eventually petroleum-based hydrogen would be replaced by a more cleanly derived fuel. The obvious issue is that onboard reformers still produce carbon dioxide. As Guezennec says, “It's an expensive exercise . . . that would produce cars that are not much better than the (internal-combustion engine) cars we produce today.”

Sticker Shock

Fuel cells are not cutting-edge technology. They were invented in 1839 in England. But the first practical application didn't come until the 1960s, when NASA used them on its Apollo and Gemini rockets, at astronomical expense. But advances in materials and technology in the ‘90s have made them feasible. Says Guezennec: “Fuel cells are for real. The make or break issue is not the science, it's the cost.” Fuel cells are still very expensive. Walter Russell, an assistant professor of civil and construction engineering at Iowa State University, says the cost of generating a kilowatt of power from a fuel cell is $4,500. A diesel generator will do the job for about $350, while an auto engine can do it using just $50 of gasoline. Manufacturing of fuel cells on a larger scale will ultimately cut costs. “Once you find one market for fuel cells it drives down the costs by increasing production,” Russell says.

Other problems that need to be addressed include size and weight, temperature, and the purity of the fuel source. Today's fuel cells are big and bulky. And they are susceptible to cold weather, because they require a certain amount of humidity to work. And heat's an issue, as well. Jason Keith, an assistant professor of chemical engineering at Michigan Tech, says fuel cells are typically stacked to produce enough power, “and as you scale up, they get warmer, from the chemical reaction.” That heat has to be controlled. And most fuel cells require pure hydrogen. If trace amounts of carbon dioxide remain in the hydrogen, “that will poison the catalyst within the membrane,” Keith says.

Onboard storage of hydrogen isn't easy, either. “In its compressed form, hydrogen is the most flammable chemical there is,” Keith says. Indubitably, the gasoline we lug around in our cars today is also highly explosive, but well-designed fuel tanks mitigate the risk. Eventually, hydrogen tanks can be made just as safe. But the technology still requires some upgrades. High-pressure hydrogen tanks now available are heavy and of limited capacity. It's also possible to store hydrogen as a liquid, but that requires keeping it at very low temperatures, “and that poses significant technology issues,” Prinz says. One promising solution is storing it as a solid within metal hydrides that release the gas as they're heated. But that's a fairly slow process, and we're used to cars that start in an instant and are ready to roll. The answer may be the addition of a battery that can store enough power to start and run a car for the few minutes it takes for the hydrides to release their hydrogen.

A possible scenario for breaking through the which-comes-first impasse is initially using fuel cells to power buildings—particularly office buildings—where weight and bulkiness matter less. Hydrogen would be produced in situ, using electrolysis. Eventually, some of the hydrogen that's produced could be used by fuel-cell vehicles, most likely corporate fleet cars. Those cars, because it's environmentally benign for them to continuously idle, could be plugged in to generate power to feed the grid, providing owners with a revenue stream that helps defray their cost. Ultimately, the growing use of fuel cells and hydrogen-powered cars would bring down prices, creating bigger markets and stand-alone hydrogen filling stations.

That plan sounds feasible, but it's decades away, engineering academics say. In the short term, many would like the government to do more to promote hybrid cars. Hybrids combine gasoline engines with small electric motors that kick in when the cars accelerate or need a power boost, and they are capable of obtaining 60 to 70 miles per gallon. So far, only Toyota and Honda have introduced hybrids, but other automakers are planning to market them, as well. Currently, consumers pay a premium of around $5,000 for a hybrid compared with a similar gas model. That premium is so hefty that it can't be fully amortized by the resulting savings in fuel. Nevertheless, a recent MIT report coauthored by Heywood said that because there are no clean methods for producing hydrogen, for the time being, fuel-cell cars are not as environmentally friendly as hybrids. He'd like to see more government incentives to expand the hybrid market while the technology for hydrogen production evolves. If hybrids become more popular, the premium will fall to a point where the fuel savings will compensate for the extra cost. Also, Yann notes, the electronics used in hybrids can be used in fuel-cell cars, as well. “It builds on a common technology.”

Hybrid cars, engineering academics say, are a “bridge technology,” a means of getting from A to C not by one big leap but by first taking a smaller step to B. And many believe the bridge it offers is the best route toward making the Freedom Car a reality.

Thomas K. Grose is a freelance writer based in Washington, D.C.
He
can be reached at tgrose@asee.org

 

 

 
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