A promising approach in converting heat or waste heat to electricity is in using the thermoacoustic effect. When heat generates a temperature... » More

A promising approach in converting heat or waste heat to electricity is in using the thermoacoustic effect. When heat generates a temperature gradient along a stack of large-surface area material inside an acoustic resonator, an intense sound can be generated. This type of energy converter, which is a self-sustained oscillator, has been developed so that the sound can be converted inside the unit to electricity using a piezoelectric device. Such devices are simple, and they have essentially no moving parts. They consist of an acoustic resonator which contains the stack and a heat exchanger at each end of the stack. The operating frequency is determined by the size of the resonator; frequencies are in the range of 2 kHz to 24 kHz. Power output can be increased by combining the devices into arrays. Important applications are in harvesting waste heat.

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