Sound makes electricity for space

Generating electricity is all about changing one source of energy into another.

Researchers from Los Alamos National Laboratory and Northrop Grumman Space Technology have built a compact generator that converts heat to electricity with the relatively high efficiency of 18 percent.

The generator is simple, making it potentially long-lived and easy to maintain. This makes it especially appropriate for generating electricity aboard spacecraft, according to the researchers.

The generator uses a small version of a thermoacoustic sterling engine developed at Los Alamos in 1999. That engine converted heat to acoustic energy using no moving parts. Compressed helium cycles between heat exchangers, and the movement of the gas generated sound waves.

In the generator, the sound waves from the engine drive a piston, which moves a coiled copper wire. As the wire moves through a magnetic field produced by a permanent magnet it produces electricity.

Existing spaceship thermoelectric power converters are about seven percent efficient, and produce 5.2 watts per kilogram. The researchers' thermoacoustic sterling heat engine could eventually produce 8.1 one watts per kilogram, according to the researchers.

The researchers' next steps are to better match the engine and alternator to make the engine more efficient, and to reduce the engine's volume.

A space power application could be practical in two to five years, according to the researchers. The work appeared in the August 9, 2004 issue of Applied Physics Letters.