In this paper, the effect of non-uniform illumination on the performance of conventional polycrystalline silicon solar cell has been experimentally studied. The spatial non-uniform factor α is employed to describe the non-uniformity of illumination. The results show that the maximum power (Pmax) and filling factor (FF) both decrease with increasing α, with the proportional coefficient β =-3.764% and -3.285%, respectively. However, the open-circuit voltage (Voc) nearly remains the same until α=~0.8, and then turns to a slight degradation with β = -3.684%. The analysis reveals that the effect of non-uniform illumination is equivalent to that of temperature raise at some degree centigrade to 10oC. However, solar cells in low-concentrated PV systems always work at 30 – 40oC higher than the standard test conditions (STC). Therefore we draw the conclusion that the power loss in low-concentrated PV systems is not only due to non-uniform illumination itself, but mostly due to non-uniform temperature raise caused by the illumination. Further discussion about α shows that because α just defines the upper and lower limitations of irradiance value, the adoption of α to describe the non-uniformity is more exactly a semi-quantificational method.
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