Field Investigation of the Effect of Spectral Response Upon Photovoltaic Energy Yields

Abstract

The operating efficiencies of multijunction photovoltaic (PV) cells are sensitive to changes in the spectral distribution of solar irradiance. Previous studies suggest that optimizing a cell's spectral response can improve energy yields. To examine how this affects their performance in the field, two sets of triple-junction photovoltaic cells with different spectral responses are being characterized side-by-side outdoors in Nicosia, Cyprus. High-resolution measurements of the solar spectrum are also being recorded at this location, allowing a detailed examination of the cell performances under varying spectral conditions. Using spectral matching ratios to analyze the data has indicated that daily changes in the fill factors of the cells can be attributed to their spectral responses. However, average performance ratios over the period of testing are similar for the two cell types. An in-depth analysis reveals that this is due to a combination of both the spectral responses and the spectral resource at the test site, where both cells operate close to their optimum. This indicates that customizing the spectral response of a cell may only be advantageous for applications under an extreme spectral resource distribution.