Hot spot tests for crystalline silicon modules

Hot spot heating occurs when a module's operating current exceeds the reduced short circuit current of a shadowed or faulty cell or group of cells within the module. In order to determine whether a crystalline silicon module is adequately protected against hot spots, two hot spot test have been developed and utilized as a part of IEC 61215 "Crystalline silicon terrestrial photovoltaic (PV) modules - Design qualification and type approval" and as part of UL 1703 "UL Standard for Safety for Flat-Plate Photovoltaic Modules and Panels". Each of these tests has some problems. Working Group 2 of IEC Technical Committee 82 on photovoltaics is developing a revised hot spot test as a modification to IEC 61215. Major features of the revision include 1) a new way of identifying low and high shunt cells by measuring a set of IV curves for a module with each cell shadowed in turn, 2) selection and testing of 3 low shunt cells and one high shunt cell, 3) providing modified procedures to determine the worst case shadowing for the selected cells and 4) testing of the low shunt cells for 1 hour and of the high shunt cell for a longer time (still to be determined).