Reliability testing of cell assemblies for photovoltaic concentrator modules

Correlation of artificial thermal cycling with field operation through two separate experimental investigations is described. The first is a study of two sets of identical cell assemblies: one used in the field and the other stored. For the degradation mechanism of cracks in the solder attaching the feet of the top contact to the cell, 125 thermal cycles were found to cause the same amount of degradation as 4.7 years of use in the field. The second investigation involves thermal cycling at temperatures simulating field operation but at higher cycling frequencies. By comparing identical parts cycled at different frequencies, the effect of frequency on rate of degradation is determined. A number of thermal cycles at a higher frequency then related to an equivalent number of thermal cycles at the lower frequencies encountered in actual use.