Multiple Energy Harvesting Based on Reversed Temperature Difference Between Graphene Aerogel Filled Phase Change Materials

Abstract

We demonstrated a thermo-electric energy harvesting system that utilized the temperature difference between two graphene aerogel filled composites. Two phase change materials (PCMs), polyethylene glycol (PEG) and 1-tetradecanol (1-TD), were used to absorb or release a large amount of heat of fusion during the phase transitions. Since the temperature of cold side can be higher than that of hot side in the heating and cooling processes, unwanted energy loss may occur in the PCM system. Therefore, the amount of energy harvesting is quite limited. In this sense, we designed a new energy harvesting system by integrating two kinds of PCMs to enhance the amount of released heat energy and its time duration. The energy harvesting based on thermo-electric conversion was performed by combining multi-PCMs with N and P type semiconductors (PN TEGs). Based on the different temperature gradients generated in melting and crystallization processes, the electric energy was harvested for 2,200 s and 850 s at the first thermo-electric conversion and for 2,700 s and 1,500 s at the second thermo-electric conversion. In addition, the numerical simulation of the system was carried out using the finite element method (FEM), and the predicted results were close to the experimental results.