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Hydrogen Is No Gas, Yet

The hydrogen economy is getting off to a shaky start.

Toyota in May recalled its fuel-cell hybrid vehicle in Japan when one of the cars sprung a leak from its hydrogen tank. Last week, researchers from the California Institute of Technology, in a Science magazine report, argued that large amounts of hydrogen leaking into the atmosphere will damage the ozone layer.

By Mark Baard Wired.com

And consumers of natural gas — already the primary source of hydrogen for everything from hydrogenated foods to NASA rockets — learned this week that natural-gas supplies are at their lowest levels in 25 years.

While much of the news has been bad, many scientists believe they can cultivate alternative resources for hydrogen and fix leaky gas tanks. They also cast doubt on the hydrogen leak estimates from the Caltech researchers. But they concede that fuel-cell stacks, which mix hydrogen with oxygen to make electricity, are still too fragile and expensive to be practical for automobile use.

The bad news about natural-gas supplies is a boon to advocates of renewable energy, however. They see hydrogen fuel cells as an aid to the development of energy sources other than fossil fuels. "Fuel cells are a critical technology because of their high efficiency and low impact," said Charles Chamberlin, co-director of the Schatz Energy Research Center at Humboldt State University. "We can use excess wind and solar energy to electrolyze water and produce hydrogen, and then draw that out of storage for use in the fuel cells."

Scientists also said that transporting hydrogen from fossil fuel plants to automobile filling stations will be more difficult than anyone has anticipated.

"There is no infrastructure for getting hydrogen from the oil or gas company to the gas station safely, cost effectively and in a way that is environmentally beneficial," said Andrew Bocarsly, director of graduate studies for chemistry at Princeton University.

The estimates that the Caltech researchers used to predict ozone damage are based in part on leaks from hydrogen in transport. To be moved efficiently, hydrogen must be pressurized, cryogenically stored or mixed in a liquid such as sodium borohydride. But leaks from cryogenically stored hydrogen can be easily recaptured, said Bocarsly, minimizing damage to the Earth’s ozone layer.

The Caltech report, which predicts that 10 percent to 20 percent of the hydrogen produced will leak into the atmosphere, actually came as welcome news to those who want to make hydrogen on demand instead of storing it for long-distance delivery.

HydrogenSource, a company formed by UTC Fuel Cells and Shell Oil, is developing hydrogen processors for use at gas stations. The company also is working on an on-board gasoline-to-hydrogen processor. Users of the on-board system would fill their tanks with gasoline, which would be chemically converted to hydrogen inside the car’s fuel cell.

HydrogenSource’s on-board processor would not release the carbon monoxide, nitrogen dioxide and particles that are products of internal combustion engines. It would, however, release carbon dioxide, a greenhouse gas. "We can’t make this gigantic jump from where we are today," said Ignacio Aguerrevere, marketing manager at HydrogenSource. "We’re creating a bridge from the existing fossil-fuel structure to the hydrogen economy."

Regardless of how hydrogen gets into cars, engineers have yet to build fuel-cell stacks with parts that are affordable and can last 5,000 hours, which translates to about 150,000 to 200,000 miles. "And people are not going to be happy if their hydrogen car is in the shop all the time," said Bocarsly. At the moment, proton exchange membrane, or PEM, fuel cells — which are the most highly developed — only last for thousands of hours when nursed along on laboratory benches.

PEM fuel cells, most notably those using DuPont’s Nafion membrane, decay rapidly under the stresses of chemical reactions, pressures and heat. Nafion membranes for fuel cells are approximately 125 microns thick, and can be easily perforated or torn, Bocarsly said.

Extra membrane layers can prolong the life of a fuel-cell stack, but Nafion, which is closely related to Teflon, is one of the most expensive parts of a fuel-cell stack. "You have to balance cost of the fuel cell with durability," said Noordin Nanji, vice president of corporate strategy and development at Ballard Power Systems, a producer of PEM fuel cells based in Vancouver, British Columbia.

Ballard, which claims 10 of the world’s largest automakers among its customers, is looking into less-expensive, sturdier membranes and components for fuel stacks in an effort to reduce hydrogen leaks. DuPont, 3M, Ballard and other companies are developing alternatives to the current Nafion membrane.

Nanji is confident Ballard can build a robust PEM fuel-cell stack for automobile use. Said Nanji: "We already have had a stationary lab stack run up to 20,000 hours continuously."

http://wired.com/news/technology/0,1282,59322,00.html

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