INVESTIGATION OF THERMAL METAMATERIAL DESIGNS TO HARVEST ENERGY BY GUIDING HEAT ENERGY

A novel method to harvest energy by guiding heat using a thermal metamaterial system is presented in this study. Compared to various other promising features that thermal metamaterials are being designed for in the last decade, heat guiding characteristics is one of the unprecedented phenomena which has numerous applications in thermal management and energy harvesting technologies. While thermal metamaterials are envisioned to guide heat in a specific direction, utilizing thermoelectric materials has the potential to significantly increase energy harvesting efficiency. In this study, a numerical model is developed using the commercial finite element solver COMSOL Multiphysics. Using this model, three different types of thermal metamaterial design are investigated to estimate their ability to control the flow of thermal energy through a base material. Initially, the base material is stainless steel whereas the constituents of the thermal metamaterials are high heat conductive Copper and insulator-like Polydimethylsiloxane (PDMS). The unit cell geometries of the thermal metamaterials are designed as circular sectors and varied in such a way that three distinct designs are achieved. In these unit cells, circular sectors are arranged periodically, and the material properties of these sectors are alternatively assigned to Copper and PDMS so that sufficient anisotropy is achieved. While the copper acts as the primary carrier of heat, the PDMS restricts heat energy from being dissipated. The unit cell is placed in the path of heat flow through a rectangular channel. A central circular area is selected near the cross-section to place a thermoelectric patch. The incorporation of thermoelectric materials such as Bismuth telluride (Bi₂Te₃) into the thermal metamaterial system significantly enhances its capability to harvest energy by converting the heat energy to usable electrical energy. A comparison is made by means of the increase in temperature of the central circular area over a range of temperature difference to estimate the efficiency of the unit cell designs. In this numerical analysis, convective and radiative heat transfer are assumed to be zero while only conductive heat transfer is considered.