With the US Department for Energy calling for more hydrogen-powered fuel cell cars by 2011, it seems that “hydrogen economy” researches are coming out of the closet. Hot on the heels of the proposed Aluminum pellet hydrogen car, researchers at Virginia Tech, Oak Ridge National Laboratory (ORNL), and the University of Georgia are proposing the use of sugary carbohydrates (polysaccharides) from biomass to directly produce low-cost hydrogen for the so called hydrogen economy.

The US Department for Energy says advances are needed in four areas to make hydrogen fuel an economical reality for transportation: production, storage, distribution, and fuel cells. The scientist driving the sugar-to-hydrogen research, Y H Percival Zhang, assistant professor of biological systems engineering at Virginia Tech (pictured), says his approach overcomes three of these obstacles — production, storage and distribution.

Most industrial hydrogen currently comes from ever more costly natural gas. Storing and moving the gas, whatever its source, is also costly, as well as cumbersome dangerous. And there is little infrastructure for refueling a vehicle.

“We need a simple way to store and carry hydrogen energy and a simple process to produce hydrogen, said Zhang.

Using synthetic biology approaches, Zhang and colleagues are using a combination of 13 enzymes never found together in nature to completely convert polysaccharides (C6H10O5) and water into hydrogen when and where that form of energy is needed.

Polysaccharides like starch and cellulose are used by plants for energy storage and building blocks and are very stable until exposed to enzymes. Just add enzymes to a mixture of starch and water and “the enzymes use the energy in the starch to break up water into only carbon dioxide and hydrogen,” Zhang said.

A membrane bleeds off the carbon dioxide and the hydrogen is used by the fuel cell to create electricity. Water, a product of that fuel cell process, will be recycled for the starch-water reactor. Laboratory tests confirm that it all takes place at low temperature, about 86 degrees F (30 degrees Celsius), and atmospheric pressure.

The vision is for the ingredients to be mixed in the fuel tank of your car. A car with an approximately 12-gallon tank could hold 27 kilograms (kg) of starch, which is the equivalent of 4 kg of hydrogen. The range would be more than 300 miles, Zhang estimates. One kg of starch will produce the same energy output as 1.12 kg (0.38 gallons) of gasoline.

Over the years a number of substances have been proposed as “hydrogen carriers,”such as methanol, ethanol, hydrocarbons, or ammonia – all of which require special storage and distribution. Starch, on the other hand, can be distributed by grocery stores, as Zhang points out.

“So it is environmentally friendly, energy efficient, requires no special infrastructure, and is extremely safe. We have killed three birds with one stone,”he said. “We have hydrogen production with a mild reaction and low cost. We have hydrogen storage and transport in the form of starch or syrups. And no special infrastructure is needed.”

“The next R&D step will be to increase reaction rates and reduce enzyme costs,” Zhang said. “We envision that in the future we will drive vehicles powered by carbohydrate, or energy stored in solid carbohydrate form, with hydrogen production from carbohydrate and water, and electricity production via hydrogen-fuel cells.

“What is more important, the energy conversion efficiency from the sugar-hydrogen-fuel cell system is extremely high – greater than three times higher than a sugar-ethanol-internal combustion engine,”Zhang said.

“It means that if about 30 percent of transportation fuel can be replaced by ethanol from biomass as the DOE proposed, the same amount of biomass will be sufficient to provide 100 percent of vehicle transportation fuel through this technology.”

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Entry was posted on Thursday, May 24th, 2007 at 12:34 pm under Science and technology.

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