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Impact of spectral effects on photovoltaic energy production: A case study in the United States

The time averaged efficiency of photovoltaic modules in the field is generally lower than the efficiency measured in the laboratory under standard testing conditions due to the combined effects of temperature and spectral variability, affecting the bankability of power plant projects. We report correction factors to account for spectral effects ranging from -2% to 1.3% of the produced energy for silicon modules depending on location and collector geometry. In high irradiance locations, the energy yield advantage of trackers is underestimated by 0.4% if spectral sensitivity effects are neglected. We find a correlation between the locations most favourable for tracking, and those most favourable for multijunctions. As the photovoltaic market grows to a multi-terawatt size, these seemingly small effects are expected to have an economic impact equivalent to tens of billions of dollars in the next few decades, far out-weighting the cost of the required research effort.