The performance of crystalline silicon photovoltaic solar modules after 22 years of continuous outdoor exposure

This paper presents the results of 40 silicon‐based photovoltaic solar modules originating from six different manufactures which were tested and characterised originally at the European Solar Test Installation, (ESTI), in the period 1982–1984. These same modules have been re‐measured in 2004 after 20–22 years of continuous outdoor weathering. These modules are a subset ‘Rack C’ of the JRC Ispra outdoor test field where examples of diverse generations of PV technologies have been subjected to long‐term climatic exposure. We have compared the results obtained from these samples with the typical guarantees which are given by module manufacturers and we can see that in general the manufacturers are conservative with their power guarantees. Most modules exceed the minimum power levels given for 10 years exposure, even after 22 years in the field. The results presented in this paper indicate that the degradation observed in the field is comparable to that observed in Type Approval Testing. This result not only validates the testing and stress levels applied in the Type Approval Tests, but also would indicate that (with the majority of modules exceeding the level of 92% of Pmax after 20 years) the actual lifetime of these products is significantly more than 20 years. Copyright © 2005 John Wiley & Sons, Ltd.