Experimental study and modeling of thermoelectric energy harvesting in low temperature dynamic condition

Low power energy harvesting from low temperature sources usually features dynamic regime. Periodic and non-periodic temperature variations are due to transient heat sources, environmental conditions and load. Moreover, the time dependent behaviour of temperature difference, and thus output power depends on mass and thermal properties of thermoelectric module, heat sink and hot source. As a consequence, the evaluation of a thermoelectric generator under dynamic thermal load presents difficult tasks to solve. In particular, with natural convection cooling, the main issue is to evaluate the performance of a heat sink of given geometry and material with a varying heat source. In this work, we present a transient numerical thermal model of simple thermoelectric generator, whose behaviour has been experimentally studied with a custom-built setup working at low temperature. The numerical model has been used to evaluate potential thermal storage effects due to the coupling of elements with different heat capacity. Particular attention has been focused on modeling the transient buoyancy-driven airflow to evaluate the evolution of heat transfer coefficient in natural convection. Moreover, we investigated with experimental measurements the minimal requirements of the thermoelectric generator to achieve increasing electrical power storage under temperature varying conditions