An innovative method for determining the junction temperature of a photovoltaic cell

An innovative method for determining the junction temperature T_J as a function of the cell voltage V of a photovoltaic (PV) cell for varying operating power levels at pre-determined values of irradiation levels is presented. Since the junction of a PV cell that is in operation is inaccessible for obtaining a measure of T_J, a novel indirect temperature measurement method suitable for determining the T_J is proposed in this paper. The electronically controllable load required to establish different operating power levels for obtaining the T_J - V characteristic of a photovoltaic (PV) cell is implemented with a MOSFET, suitably controlled to act as a variable load resistor. Microcontroller based hardware with associated software were developed to automate the entire measurement process. Results obtained from a prototype T_J - V measurement unit built and tested establish the efficacy of the proposed method.