Modeling the thermal runaway effect in CPV modules

Abstract

In this work current injections into solar cells due to parallel connection within CPV modules are investigated. A current injection into a solar cell increases its temperature. If the current injection is above a certain threshold a thermal runaway is started. The current injection into a solar cell is limited by the short circuit current generated by a string of parallel connected cells. The value of the short circuit current is determined by the number of cells in parallel and by the concentration factor of sun light used in the CPV module. In this work the value of current injection is calculated above which a thermal runaway is triggered. For these calculations a model is introduced and tested with an experimental setup. The model shows a satisfying agreement with the measurement. The model is used to calculate the maximum number of solar cells for which the temperature increase due to current injection is limited to 20 K and a thermal runaway is prevented. This maximum number is presented in dependence of the concentration factor of sun light.