Construction and Performance Analysis of a Two-Stage Travellng-Wave Thermo-Acoustic Generator

Thermo-acoustic systems are being considered as a potential sustainable solution for electricity generation where the sound waves can be used for electricity generation through a linear alternator. Thermo-acoustic is actually a field of science that is concern with the interaction between thermal energy (heat) and acoustic energy (sound) with the purpose of inducing cooling or generate electricity. Recently, there have been a significant increase in the development of thermo-acoustic refrigerators as well as thermo-acoustic generators with limited to no moving parts involved. Travelling wave devices have exhibited promising results with respect to their performance whilst working at very lower temperatures. This work describes the construction of a two-stage travelling-wave thermo-acoustic generator. In addition, an experimental investigation into the effect of the heat source on the potential of the device for electricity generation has been conducted in order to evaluate the device performance. The effect of the geometric configurations of the thermo-acoustic engines is examined for series and parallel arrangement. The prototype consists of two thermo-acoustic engine connected through Polyvinyl chloride (PVC) pipes forming a loop for the waves to travel through. A commercial loudspeaker was used as linear alternator in order to assess the potential for sound-to-electricity conversion of the system. Each engine consists of the regenerator, a cold heat exchanger and a hot heat exchanger. The magnitude of the sound generated by the engines, the onset time and the magnitude of electricity generated by the linear alternator have been considered as performance indicators for the device developed. Clear trends showing the effect of inputs parameters on device performance have been presented. The prototype was developed and thenceforth evaluated. It proved to perform better with the parallel configuration, and achieved a faster onset time than with series configuration. A minimum onset time of 3.15 minutes to produce a sound was recorded. The average minimum/maximum amount of heat that has produced a sound was 340/635oC corresponding to sound of 114.1/126.4 dB and a voltage of 387/486 mV respectively. Although the efficiency of the sound-to-electricity conversion was low, this work proves the viability of thermo-acoustic as the alternative solution for electricity generation. Research attention can be invested more on geometric arrangements and configurations of the multistage thermoacoustic devices i.e. the use of a suitable sound-to-electricity convertor, the best location for the alternator as well as whether single or multiple alternators produces better results. This paper provides clarity on the potential for thermo-acoustic system for sound-to-electricity conversion.