A startup company has developed a new type of engine that could generate electricity with the efficiency of a fuel cell, but costs as much as an internal combustion engine. Etalim, based in Vancouver, Canada, says its engine, roughly the size of a basketball, could improve the economics of electricity production for the cogeneration of power and heat in homes, and as a way to harness the heat produced at concentrating solar collectors. The company has created a prototype, but has yet to achieve the kind of efficiencies (in excess of 40 percent) that its computer models indicate are within reach. Encased within the core of Etalim's engine is a plate of metal that replaces the function of a piston in a conventional Stirling engine. When pressurized helium on the top side of the metal plate is heated, sound waves traveling through the gas are amplified, causing the plate to vibrate, and a metal diaphragm below (separated by a cooler layer of helium) to push down on a shaft. All mechanical friction is eliminated. The shaft is attached to an alternator that produces electricity. The vibration of the plate only moves the shaft two-tenths of a millimeter per cycle, so not much helium is being moved with each cycle. But the engine achieves a rapid 500 cycles per second. A first prototype, completed last year, demonstrated that the concept works, but relatively low heat was used, so its efficiency was only 10 percent. A second prototype that aims for 20 to 30 percent efficiency at 500 °C is expected this spring. A commercial product with 40 percent efficiency running at 700 °C is targeted for 2012. It will initially be sold as a cheaper and longer-lasting competitor to fuel cells used for residential cogeneration. The company believes it can manufacture the engine for less than $1 per watt, and has a long-term target of 15 cents per watt, which would make it less expensive than a comparable internal combustion engine. For more information visit: http://www.etalim.com/technology.php
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