On harvesting residual thermal energy from photovoltaic module back surface

Abstract

In Brazil, photovoltaic (PV) plants have been increasing their importance in the country’s electricity matrix mainly because its annual irradiation can achieve up to 2400 kWh/m2. On the other hand, the high temperature levels along the PV modules impose a negative effect on the electrical efficiency. For instance, in a PV plant in the Brazilian Northeast region, the PV modules temperature can reach 70 °C in a sunny day while the ambient temperature is around 30 °C. This difference can be used to generate heat as a residual thermal energy, but, in general, it is wasted to the surrounding environment. In other context, currently, there is an increasing development of Renewable Energy Monitoring Systems (REMS) for monitoring PV plants. In this paper, we present an experimental study on the potential of harvesting PV-module residual thermal energy using thermoelectric generators (TEGs) for powering low-power wireless sensor for REMS to monitor the whole PV plant itself. From the experimental results, 3.3 V is achieved from stepping up about 220 mV harvested from monthly average temperature difference of 15 °C. In addition, it is shown that 528 mW can be harvested every burst of 30 ms, which is enough to power low-power devices.