Energy and exergy analysis of phase change material based thermoelectric generator with pulsed heat sources

Abstract

Previous studies focus on the generation capacity of phase change material based thermoelectric generator (PCM-TEG) under a steady-state heat source or single pulsed heat source, which cannot fully reflect the dynamic characteristics of TEG under a diversified actual heat source. Meanwhile, the actual heat sources have unstable characteristics of intermittence and fluctuation, resulting in troubles for TEG to maintain effective thermal management and stable generation. In this work, a three-dimensional transient numerical model of PCM-TEG is proposed to characterize its energy harvesting process under multiple pulsed heat sources, including square, triangular, linear and sinusoidal patterns. The effect principle of heat fluxes and heat source periods on PCM-TEG is sensitively performed, aiming to detect the evolution laws of the temperature field and electric field. The energy and exergy analysis of PCM-TEG is determined to indicate its transmission and conversion process. A comparison analysis of PCM-TEG and TEG is carried out to appreciate the thermal management of PCM from temperature difference and failure-free cycle times. The power generation coupling mechanism of PCM-TEG is further developed concerning the phase transition process and power generation process. The results demonstrate that the temperature difference and output power of PCM-TEG change periodically with the pulsed heat sources. The electrical energy and exergy efficiencies of PCM-TEG under square pulsed heat source are 0.10% and 0.45%, higher than other heat sources. Simultaneously, the maximum output power and the electrical energy efficiency of PCM-TEG can be improved by 173.29% and 80% respectively with the enhanced heat flux. Furthermore, although the transient power generation capacity of TEG is weakened by integrating PCM on the hot side, it can alleviate the thermal fatigue of thermoelectric device and meet its thermal management requirements. This paper is informative to understand the dynamics characteristics and power generation coupling mechanism of PCM-TEG for energy harvesting.