Design and construction of a two-stage thermoacoustic electricity generator with push-pull linear alternator

Abstract

Traveling-wave thermoacoustic heat engine is capable of converting heat to acoustic power which in turn can be used to generate electricity by a linear alternator. The thermoacoustic heat engine can work in a wide range of heat quality, giving it the ability to be used for waste heat recovery. In this paper, a new configuration of looped-tube traveling wave thermoacoustic engine is proposed, which consists of two identical stages each having a power extraction point, and the linear alternator connecting these two points working in "push-pull" mode. This enables a more effective acoustic impedance matching compared to the use of multiple linear alternators known in the literature. The laboratory demonstrator has been designed, built and tested. The applied heat source temperature is similar to that of the internal combustion engine exhaust gases in order to explore the potential of using the device for waste heat recovery from road transport. In experiments, the maximum electric power of 48.6 W at thermal-to-electric efficiency of around 6% was achieved with helium at 28 bar as working fluid and 297 K temperature difference across the regenerator. The performance of the device has been analysed and compared to modelling performed using DeltaEC simulation tool.

Experimental investigations of the performance of a thermoacoustic electricity generator

“…Figure 8b shows that the increase of heating power increases the net generated acoustic power, acoustic power delivered to each side of the linear alternator and the piston displacement. However, the acoustic power phasing becomes unfavourable to the linear alternator (explained in Hamood et al [15]) at higher heating power as the acoustic-toelectric efficiency decreases with increasing of heating power as shown in figure 9a. The thermal-to-electric efficiency decreases between 700 W and 1300 W, as the rate of generated electricity is less than that of the heating power.…”

Numerical and experimental study of a looped travelling‐wave thermoacoustic electric generator for low‐grade heat recovery

“…Hamood et al established a two‐stage TEG with push‐pull linear alternator (LA). They reported a maximum electric power of 48.6 W with a thermal‐electric efficiency of around 6% when the temperature difference was 297°C . Wang and Qiu carried out a numerical investigation on a four‐stage LTTEG, with which a relative Carnot efficiency around 20% could be achieved when the hot end temperature was 300°C, but no experimental data were reported.…”

“…They reported a maximum electric power of 48.6 W with a thermal-electric efficiency of around 6% when the temperature difference was 297°C. 20 Wang and Qiu carried out a numerical investigation on a fourstage LTTEG, with which a relative Carnot efficiency around 20% could be achieved when the hot end temperature was 300°C, 21 but no experimental data were reported. Zhao proposed the convection-driven Rijke-Zhao tube with two bifurcating daughter branches to harvest the heat source at about 350°C, and the piezoelectric transducer was used to convert acoustic power into electricity.…”

Optimization of standing-wave thermoacoustic refrigerator stack using genetic algorithm

“…Another area of applications of thermoacoustic effect is thermoacoustic engines (or prime movers), by which thermal energy is converted to acoustic energy [7], [10]- [11], [12] .…”