Synchronization of Mid-Frequency Engines for Energy Harvesting.

Thermoacoustic engines convert heat to electricity by producing sound, which generates electricity by a piezo electric device. Multi-device arrays of such mid-frequency (2.5 kHz) thermoacoustic energy converters have been studied in order to raise the power output. Devices with 2 and 3 engines were investigated, eventually leading up to 6 engines. Being self-sustained oscillators with random phase, their synchronizations are crucial in attaining maximum power. Indeed, synchronization was observed; coupling between the engines is attributed to their radiation impedance and reflections from the acoustic cavity supporting them. The observed increased output levels substantiate synchronization through the absence of beats between engines, Fast Fourier Transforms, where a peak due to a common frequency is observed, and resultant common, lowered frequency. A benefit of the array is the reduction of onset temperature such as 50°C for 3 engines, and similarly onset times for oscillations.