Temperature and thermal annealing effects on different photovoltaic technologies

The effect of temperature on different grid-connected photovoltaic (PV) technologies installed in Cyprus was analyzed in this study. Initially, the performance losses due to the temperature effect on the annual energy yield of each technology were investigated using measurements of module temperature and the manufacturer provided maximum power point (MPP) temperature coefficients, γPMPP. The same methodology was also applied using outdoor evaluated γPMPP coefficients for comparison. When using the manufacturer’s temperature coefficient, the results showed that over the evaluation period the highest average thermal losses in annual dc energy yield were 8% for mono-crystalline silicon (mono-c-Si) and 9% for multi-crystalline silicon (multi-c-Si) technologies while for thin-film technologies, the average losses were 5%. Similar losses were found when using the outdoor evaluated temperature coefficients. Additionally, temperature effects on the seasonal performance of the different technologies were evident on the monthly average performance ratio (PR). For the amorphous silicon (a-Si) technologies, a performance increase from spring until early autumn was observed and was attributed to thermal annealing. The effect of thermal annealing on the performance was evident by filtering dc MPP power measurements at high irradiance (greater than 800 W/m2) and restricting the values at geometric air mass (AM) in the range 1 ≤ geometric AM ≤ 1.5. The extracted dc MPP power was corrected for irradiance and temperature at standard test conditions (STC) using the manufacturer provided γPMPP over a period of two years. Subsequently, the effect of thermal annealing was further investigated by extracting dc MPP power measurements at geometric AM in the range 1.4 ≤ geometric AM ≤ 1.6 in order to minimize the spectral influences on the performance of a-Si technologies. An increase in power for all the a-Si technologies was obvious during the warm summer season and was recorded over the period of March until September for both years.

► The average annual yield thermal loss of the mono-c-Si technologies was 8%.
► The multi-c-Si technologies showed an average annual yield thermal loss of 9%.
► Thermal annealing is a significant factor in the behavior of a-Si technologies.
► Thermal annealing resulted in a power increase of up to 8.4% in some cases.