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SLEEPLESS AT THE SELF-SERVICE PUMP
 

While the “hydrogen economy” of the 21st century seems a distant dream, the prospect of $6 a gallon gasoline is a nightmare that makes many American economists—not to mention consumers—wake up in cold sweats.

Fortunately, researchers in ISU’s Department of Materials Science and Engineering might have just the prescription for more restful nights.

While MSE professor Steve Martin’s work to develop the hydrogen and oxygen fuel cells for powering tomorrow’s vehicles has received a great deal of attention, less well known—but equally critical—are the efforts of two other MSE faculty members: Vitalij Pecharsky, who has turned his attention to storage methods that can make hydrogen-powered cars practical, and Alan Russell, part of a team that seeks to develop materials for purifying hydrogen to fuel truck and automobile fleets.

As with fossil fuels, hydrogen fuels will require a production and distribution chain to deliver usable energy to consumers. More than simply retooling the current petroleum-based system, however, links in the hydrogen chain will need to be forged from the ground up, starting with the very materials that form those links.

Currently, Russell observes, hydrogen from various sources is purified by diffusing it through slender tubes formed of a palladium-silver alloy: “clean” hydrogen atoms are diffused through the tube walls, while impurities continue downstream. But at $7000 a kilogram, palladium is far too expensive to produce hydrogen in quantities that would permit its use on a scale comparable to petroleum products.

“It’s a real problem,” Russell says. “Impurities damage fuel cells, so purification is essential. But there might not be enough palladium in the world to replace gasoline with hydrogen.”

Thanks to a three-year, $2.95 million grant from the U.S. Department of Energy’s National Energy Technology Laboratory program, Russell has joined a team led by Robert Buxbaum of REB Research & Consulting, a Michigan firm that specializes in hydrogen purification technologies. Exploiting Russell’s expertise in intermetallic compounds and transition metal alloys, the team hopes to develop affordable alloys for tubes with sufficient strength, ductility, and diffusivity to purify hydrogen in massive quantities.

“We’d like to see one or more new alloys come out of this that people can actually turn into production alloys to lower costs for these processes,” Russell adds.

Yet any economies in hydrogen production will do little to wean Americans from imported oil without methods to safely store the fuel. That’s a problem Pecharsky has been working on since at least 2000, when a small grant from the Roy J. Carver Trust launched his study of solid-state materials for hydrogen storage. Those early efforts have now moved to the next level with a $1.6 million grant from the Department of Energy, part of the DOE’s $64 million Hydrogen Fuel Initiative.

“Hydrogen storage is a challenge,” notes Pecharsky, who is joined on the project by Ames Lab colleagues Marek Pruski, Victor Lin, and MSE faculty member Scott Chumbley. “Unlike propane, which can be easily liquefied, hydrogen cannot—you have to cool it close to absolute zero to liquefy it.”

Neither is it practical to transport hydrogen in the form of a compressed gas, adds Pecharsky, as any tank large enough to contain sufficient fuel for a typical 400 mile driving range could weigh upwards of 800 pounds. However, a solid synthesized from lightweight elements such as aluminum or lithium that could store 7 to 10% hydrogen by weight would decrease the bulk of a hydrogen fuel system dramatically.

“If you have a material that holds 10% hydrogen by weight,” says Pecharsky, “then to store 5 or 6 kilograms of hydrogen you need only 50 or 60 kilos of a solid, or 120, 130 pounds—which is comparable to the weight of a conventional fuel tank.”

One challenge of any such system lies in managing the excess heat produced by the process of recharging the spent solid with fresh stores of hydrogen. In practical terms, a distribution system for Pecharsky’s technology might involve solid fuel cartridges that, once depleted, would simply be exchanged for fresh ones. The spent cartridges would then be recharged and readied for redistribution under controlled conditions.

That scenario may seem distant, but simple economics are making the technologies of Martin, Pecharsky, and Russell seem less exotic and more inevitable. So if soaring energy prices keep you up nights, take heart: MSE researchers are losing sleep too—and loving it.

“It’s exciting to think that if we get it right,” Russell remarks, “in the year 2030 the whole world fuel economy could be totally different. That’s the kind of thing that gets us scientists out of bed at 5 in the morning.”