Measurement and Simulation of Hot Spots in Solar Cells

Abstract

Solar cells can have various shunts with various origins and current-temperature characteristics. A solar cell with a local ohmic shunt can heat up during partial shadow conditions due to reverse current through the shunt. Depending on the resulting hot spot size and reverse current, the local temperature can be so high that it can damage the solar module. Especially under field conditions, if hot spots are detected, it would be worthwhile to decide on a threshold temperature for which a solar module should be de-commissioned.This work describes experiments where four single cell modules were made with thermocouples embedded close to hot spots. The temperature development in such modules has been measured by an IR camera and simulated by a 3D finite element model. The temperature development of a hot spot was computed as a function of hot spot reverse current, reverse voltage, time, hot spot size, hot spot location and ambient temperature. The temperature development in the module is well described by the model. Temperature trends were shown to be a function of shunt size as well as location relative to the edge of the cell.