Mad scientist Doc Brown powers his time machine by feeding coffee grounds and other biowaste into the DeLorean in Back to the Future.
While time travel is still in the realm of science fiction, carbon-based fuel cells are about to become science fact -- rendering a similar scenario all the more possible. SRI announced in November that it has developed direct carbon fuel-cell technology.
The process is 70 percent efficient, double that of traditional coal power plants, according to Larry Dubois, vice president of the physical sciences division at SRI.
SRI researchers have shown that in a single step, they can take pulverized coal -- or anything else that contains carbon, including human waste or banana peels, for example -- and directly transform the fuel's chemical energy into electricity by electrochemically oxidizing the carbon.
The byproduct is carbon dioxide -- but it is emitted in such a pure form, Dubois said, that it's easy to contain. "If you have a conventional gas-fired coal plant and capture the (carbon dioxide) -- 75 percent of the cost is separating carbon dioxide from air," he said.
The new technology could also help to reduce dependence on foreign oil, he said.
"(The United States has) a 250 year supply of coal," he said. "If you think about that as a strategic asset for the U.S., exploring the ability to use coal in a clean efficient manner is beneficial."
Dubois said that while it is theoretically possible to power a small business, a home or even a car with carbon-based fuel, SRI has its eyes on larger power plants.
Another bonus is that unlike hydrogen, the other alternative-energy option, carbon fuel is very easy to come by, said Roberta Gamble, an energy analyst at Frost and Sullivan.
Despite its benefits, however, carbon fuel cells may be too costly, she added.
"If it's prohibitively expensive you'll be hard pressed to find a restaurant that's going to give up perfectly good traditional energy," she said. She suggested it might take a decade before a carbon fuel system paid for itself, which is probably longer than most users are willing to wait.
"We're finding if (new fuel sources) can provide an economic benefit within five years then there is a potential benefit to that," she said.
For now, the carbon fuel cells are producing small amounts of power on the scale of a few watts at SRI's laboratory in Menlo Park, California. But Dubois expects their capability to rise to 10 kilowatts by 2009, to 100 kilowatts by 2011 and to 500 kilowatts by 2015.
"Is this early stage?" he said. "Absolutely. Is it risky? Absolutely. But the payoff potential is tremendous."
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