熱音響自励振動を利用したエネルギー・ハーベスティング

抄録

This paper reports a novel method of energy harvesting by exploiting thermoacoustic self-excited oscillations in a looped tube filled hermetically with atmospheric air. The oscillations are excited spontaneously by imposing a temperature gradient on a porous stack made of ceramics sandwiched by hot and cold (ambient) heat exchangers. A pair of identical stacks is placed in the tube at diametrically opposite positions so that the temperature gradient may be in the same direction. A single Wells turbine with a DC generator connected coaxially is installed inside the tube near a pressure node of the 1st mode or the 2nd mode of oscillations. The turbine starts to rotate spontaneously and generates a voltage from oscillatory airflow of 24 Hz (1st mode) or 49 Hz (2nd mode). The maximum voltage of about 10 volts is generated across two open terminals of the generator, while the maximum power of about 1.3 W is extracted at 6.4 V when a resistor of 30 Ω is loaded for the 1st mode of the oscillations. It is found that the Wells turbine, which was originally developed for energy harvesting from an oscillating water column of low frequency, can be applied to generate electricity from the thermoacoustic oscillations of high frequency.