Energy conversion through thermoacoustics and piezoelectricity

Waste or prime heat can be converted into electricity with thermoacoustic-Stirling engines coupled to piezoelectric alternators. An inline arrangement of engines and alternators allows a vibration balanced, multiphase power generator that is compact, light weight and low cost. The engines convert heat into high amplitude ≈400 Hz oscillations in pressurized helium gas. These pressure oscillations cause a thin steel diaphragm to flex like a drumhead. The diaphragm is supported at its perimeter by a ring of piezoelectric elements. As the diaphragm flexes in either direction, it pulls inward on the piezoelectric elements causing a large amplified ≈800 Hz fluctuating compressive stress in the elements which then convert the stress into electricity with high efficiency. The flexible-diaphragm piezoelectric alternator overcomes the large acoustic impedance mismatch between the helium and piezoelectric elements without exceeding the limited fatigue strength of available materials. So far, a prototype generator ha...