Energy Harvesting from Thermal Variation with Phase-Change Materials

Abstract

Phase-change materials with temperature-dependent thermal conductivity have drawn lots of attention recently. They have exhibited promising potentials in devices such as the thermal diode, thermal memristor, etc. Here we investigate the heat exchange between two reservoirs through a bare phase-change material. In the presence of temperature variation in one of the reservoirs, we find a unidirectional thermal flux between those two reservoirs though they share the same average temperature, i.e., no temperature bias. By mapping such a system to the heat exchange between two reservoirs through a regular material with a constant thermal conductivity, we obtain an effective temperature difference ${T}_{\mathrm{eff}}$, which should present to maintain the unidirectional thermal flux. We then provide a semianalytical formula for ${T}_{\mathrm{eff}}$, which works well over an extensive parameter range. The parameter dependence of ${T}_{\mathrm{eff}}$ and the temperature dependence of the thermal capacity are then studied in detail. Our work thus provides a useful tool for calibration of heat conduction within phase-change materials and leads to potential applications related to energy extraction from the thermal variation of the environment.