Hot spot investigations on PV modules-new concepts for a test standard and consequences for module design with respect to bypass diodes

Solar cell manufacturers should provide information to module manufacturers about the operation of their cells under reverse biased conditions. The inhomogeneous behaviour of cells under reverse biased conditions needs further investigation. In particular, cell damage during manufacture should be evaluated. To guarantee resistance of the module design to thermal overload due to partial shading, the number of cells in a sub-string should be limited to 20. The hot-spot test procedure of IEC 1215 should be generalised for all types of cell interconnection circuits. The selection of the worst case cell should be improved by measurement of the module current at the characteristic break point of the I-V characteristic.