Modeling of enhanced micro-energy harvesting of thermal ambient fluctuations with metallic foams embedded in Phase Change Materials

Abstract

We present an enhanced micro-energy harvester to transform ambient thermal fluctuations into electricity. The design consists of a Thermoelectric Generator (TEG) joined to a thermal storage unit improved with a Phase Change Material within a metallic foam (pPCM). We show how the augmented effective conductivity of the heat storage unit multiplies the production of electric power through voltage generation in higher and shorter sprouts. The porosity of the metallic foam accelerates the heat transfer and permits higher volumes of the heat storage unit to be effective in harvesting more energy from the surroundings. The pPCM/TEG device is a robust and cost-effective means to optimize the output of TEG based systems to power low-consumption electronics. The potential of this design is demonstrated with examples of micro-energy harvesting under ambient thermal conditions in an aircraft and ground solar irradiation. In these applications, a single TEG module with a moderate merit figure is used and found that pPCM allows a substantial optimization of energy conversion. As an example, the pPCM/TEG devices produce about twenty times more electric energy at even small volume fractions of the foam ε=0.95 than PCM/TEG systems in solar micro-energy harvesting on ground conditions with low thermal gradients.