Characterization of commercial thermoelectric modules for application in energy harvesting wireless sensor nodes

Thermal energy harvesting systems commonly exploit thermoelectric generators as power sources. This paper describes characterization of commercial thermoelectric cooling/heating modules, with the aim to select preferable ones for use as generators in energy harvesting wireless sensor nodes. Performed numerical electro-thermal analysis considers generators under three thermally different operating conditions (as standalone devices, with heatsink, and inside the wireless sensor node). Electrical load of the generators is determined by the power management circuitry. Characterization is performed by combining simulation results and current-voltage characteristic of the circuitry. Assessment of the generators is based on voltage and power transferred to the load at various temperature differences. Obtained results are experimentally verified by thermovision and, for the case of standalone devices, compared with an analytical approximation. It is determined that preferable generators can be selected on the basis of the power factor, figure-of-merit, or thermocouple legs length, depending on the imposed thermal operating conditions.