Review of photovoltaic module energy yield (kWh/kW): comparison of crystalline Si and thin film technologies

The energy yield (kWh/kW(STC)) reported from photovoltaic (PV) installations were reviewed to look for consistent trends in performance between module technologies. The effect of higher operating temperature and lower light intensity are discussed in terms of different locations and module technologies. Both of these losses can favor thin film PV under controlled laboratory conditions but may not be significant under real field conditions. As received, PV modules suffer from a minimum +/- 5% uncertainty because of binning (+/- 3%) and calibration (+/- 2%). Differences between initial nameplate kW(STC) and the actual field-tested values cause larger uncertainty. Thin film modules suffer additional uncertainty because of calibration and stabilization issues. A recent study comparing 12 different module technologies in Nicosia and Stuttgart concluded that when properly measured and stabilized, thin film technologies could have a 1-4% advantage because of smaller temperature losses and 3% advantage due to improved low light efficiency but the tolerances and uncertainty in kW rating were greater at +/- 5-10%. Energy yield data from utility scale installations in sunny hot locations finds that CdTe outperforms c-Si by similar to 5-6%. Data for a-Si is complicated by initial versus stabilized module ratings and summer annealing. Gains with Cu(InGa)Se2 (CIGS) are expected to be even less than CdTe or a-Si. Analysis of data-driven simulation finds at best a few percent advantage in kWh/kW for thin films. We conclude that any differences between thin film and c-Si module technologies are much smaller than reported previously, and are often smaller than the measurement uncertainty especially between different locations. (C) 2012 John Wiley & Sons, Ltd.