Investigation of seasonal fluctuation of electrical parameters of amorphous silicon modules in ambient conditions

Analysis of continuously acquired electrical data of amorphous silicon (a-Si) modules working under ambient conditions enable us to separate the effects of various factors, as e.g, module temperature, sun spectrum, ambient temperature, influencing a-Si module performance. This results in an improved understanding of the seasonal fluctuations of electric characteristics that can be expected in different ambient conditions. For the test site of Orense, seasonal oscillations lead to electrical power variation of 19% (± 9.5%) around an annual average value with a minimum around January and a maximum around mid of July. Variation of the sun spectrum has the highest impact on the outdoor performance of a-Si modules with amplitude corresponding to about 5.5%. The Staebler Wronski effect has a slightly lower influence with amplitude of about 4 %.