Text: Sound Can Power Engines 11.45 a.m. ET (1545 GMT) May 30, 1999 By Mark Prigg LONDON - Sound could be the key to engines of the future according to American researchers. A team at the Los Alamos National Laboratory in New Mexico has developed an environmentally friendly engine with no moving parts that is powered by sound waves. The new engine is made from steel tubing and is cheap to produce. Called a thermoacoustic Stirling heat engine, it consists of a long baseball-bat-shaped resonator with an oval chamber instead of a handle. The engine is filled with compressed helium and when heat is applied to the "handle" acoustic energy in the form of sound waves is produced. This can be used to drive a piston and create electricity. The team is also working on a similar system to cool refrigerators. Scott Backhaus, one of the inventors of the engine, says: "Conventional engines are limited by the laws of thermodynamics and their complexity. Typically the most efficient engines are the huge turbines used in power stations. "Our small engine is actually 10 percent more efficient than the best turbine, largely because of its simplicity," he says. The engine is also maintenance-free as it has no moving parts. The team is working on a way to use solar energy to power the engine and considering a system that uses a car's exhaust heat to power its air-conditioning system. A home version of the engine, also under development, could be used both to generate electricity and provide domestic heating. The principle behind the engine was discovered by Robert Stirling, a 19th-century Scottish inventor, who found that cooling and heating gases could drive a piston.

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