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An Energy Idea that’s Heating Up

September 18, 2009
by Andrew Becker
Image source: Michael Wertz

Anyone whose car has overheated has caught a glimpse of wasted energy. Arun Majumdar, a professor of mechanical engineering, sees such waste everywhere he goes. But he and other Berkeley researchers may have found a way to turn that loss into an opportunity that could help cut down on fossil fuel dependency.

Researchers led by Majumdar and Rachel Segalman, a chemical engineering professor, have generated electricity by trapping organic molecules, potentially paving the way to a new, inexpensive source of energy.

In his fifth-floor office in Etcheverry Hall, the soft-spoken and affable Majumdar explains that it all starts with molecules similar to the precursors to plastic. His team coated gold electrodes with the organic molecules benzenedithiol, dibenzenedithiol, and tribenzenedithiol—petroleum byproducts—and heated them to different temperatures, generating an electrical current, a phenomenon known as the Seebeck effect. (The temperature difference between the junctions of two metal electrodes causes a small current to flow between them.)

Most power generation—satisfying about 90 percent of the world’s energy needs—comes from burning fossil fuels to create steam, which powers turbines to generate electricity. In the process, a lot of heat is lost; organic molecules could help convert much of that heat to electricity.

“We’re still early in the game, but this new direction people have not considered before could be quite interesting,” says Majumdar.

The team is now amassing a library of organic molecules—most as cheap as Styrofoam—at a rate of about two a week.

Although researchers are working on a scale not much bigger than a nanometer, and voltage levels are modest, they are optimistic. Potential applications include capturing heat loss from engine turbines by placing a device that conducts organic thermoelectricity inside a heat exchanger.

“How good we can get is a long-term kind of thing,” says Segalman. “We just figured out we can use organics at all. The sky is the limit in terms of how far we can optimize.”

From the May June 2007 New Food and Farming issue of California.

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