Optical Measurement of Cell Temperature in a Solar Array

Summary

We present a method to measure the operating temperature of photovoltaic cells in an array. We use temperature shift of optical parameters of the semi-conductor which induce a variation of spectral response. This variation is large for wavelengths near the cut off wavelength λ_c= E_G ⁻¹ hc.

We describe how to measure, at the panel terminals, the voltages σ_a et σ_b which arise from illumination of a single cell by two mono-chromatic beams superposed on the solar illumination. We show that the knowledge of the ratio ρ = σ_a/σ_b allows to find the temperature of this cell. This work leads us to study the impedance values and to propose a way to detect defective cells in an array.

Supported by COMES-contrat n°79127