Evaluation and correction of the impact of spectral variation of irradiance on PV performance

Spectral shift from the ASTM G173-03 reference spectrum was calculated for different cell types from measured quantum efficiency and predicted spectral irradiance using the Bird Simple Spectral Model with measured aerosol optical depth and water vapor. Our predictions correlated well with measured spectral shift for different sites and cell technologies. However we observed significant differences between spectral correction methods. We found that the factors affecting spectral shift differ depending on cell technology, making the formulation of a single linear expression of all factors difficult for all technologies. Predicted power at several geographically different sites using the Sandia Array Performance Model with its spectral correction function versus our predicted spectral shift showed seasonal variations.