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June 06, 2007

Small 40% efficient heat - sound - electricity converter

From the New Scientist, new ways of turning heat into sound waves - and then into electricity - may be the next step toward a practical new source of alternative energy.

40% of waste heat from power plants could be converted to electricity if this works and can be scaled up and installed on power plants. Whereever the heat is not being used like for cogeneration systems, then extra electricity could be generated.

A team of University of Utah researchers plan to show they’ve succeeded in miniaturising and optimising [acoustic heat engines], which then turn the sound into usable electricity.

If true, the advance could open the door to super-efficient power plants, cars, and computers, as well as a new generation of solar cells.

To improve their prospects, Orest Symko and his team built smaller engines ranging from 11 to 18 centimeters long. At 40% efficient, the engines rival gasoline and diesel engines at energy conversion.

The team’s discoveries have also raised some eyebrows, however. "I realise anything to do with energy is really important these days," says Scott Backhaus, who studies thermoacoustics at the Los Alamos National Laboratory. "But we’re working on some applications for diesel engines, and I can tell you we’re not getting anywhere near 40% efficiency. I’m sceptical."

The Utah researchers have also built the smallest known acoustic heat engines, which at 1.8 millimeters long could produce 1 Watt of electricity per cubic centimeter when clustered together. Symko speculates that the clusters could be used as the 'cells' in a new type of solar panel.

He plans to test the devices within a year to produce electricity from waste heat at a military radar facility.

“It looks very promising, but at this point there is still much work to be done. We’re still working on an array,” he says, adding that he hopes to begin mass-production of miniature engines within the next year.

If all goes well, they could be installed on natural gas and coal-fired power plants shortly thereafter. The team will present their research on Friday at the annual meeting of the Acoustical Society of America in Salt Lake City, Utah.

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