Actual PV module performance including spectral losses in the UK

STC efficiencies are not sufficient to compare photovoltaic devices of different semiconductor material or device configurations. The energy yield changes as the variables of STC deviates from their original values when the modules are placed in various climatic conditions. The magnitude of this change for different modules is not always clear and needs to be investigated and modelled. A modeling and analysis method named site specific conditions (SSC) is demonstrated which is a measure-correlate-predict approach. It allows an accurate estimation of the actual energy yield for different sites based on the measurements at one single site. The method takes into account the effect of the physical operating environment and translates this to other meteorological conditions on the basis of physics related formulae. Our results show a large seasonal variation for modules for the different effects. For crystalline modules losses of up to 12% in the summer is due to the temperature effect while the multi-junction thin film losses of more than 30% in the winter is due to spectral changes and incidence angle effect for the UK.