Temperature dependence on the photovoltaic properties of selected thin-film modules

摘要

An important requirement in the employment of the different existing PV technologies is the understanding of the performance exhibited by each technology, once installed outdoors. Such records are necessary since the outdoor PV electrical characteristics are different from those corresponding to STC (which rarely occurs outdoors) information listed in manufacturer data-sheets. Therefore the PV monitoring and evaluations, under different environmental conditions, are indispensable for the architects and PV systems installers, in order to accurately size the installations. In this paper the influence of temperature on the photovoltaic parameters of amorphous silicon (a-Si) and copper indium diselenide (CIS) thin film modules has been investigated, as well as the energy produced under actual operating conditions. The current-voltage characteristics and maximum power have been recorded at regular intervals, for one year in the Mediterranean climate city of Patras, Greece (latitude 38°). Patras averages over 4.2 peak sun hours (PSH) per day and module working temperatures between 16 ℃ and 60℃. Our results have shown that, the percentage reduction of the open circuit voltage with temperature increase is greater for the CIS than for the a-Si modules. The short circuit current temperature coefficient for the CIS modules is positive at low and medium temperatures, though over the entire range of working temperature remains approximately constant with a slight tendency to reduce. The maximum power decreases almost linearly, while the efficiency for temperatures higher than 50℃ reduces sharply. It is remarkable that with respect to the temperature increase the a-Si modules efficiency remains very near to the rated value, and the short circuit current temperature coefficient and the power coefficient are positive. The fill factor for these modules decreases linearly and equally as a function of temperature. The series and parallel resistance for the a-Si decrease slightly with temperature increase, whereas for the CIS the series resistance increases and the parallel resistance decreases in a more pronounced way. Maximum year-round energy production corresponds to the tilt angles of about 20 and 50 degrees in the summer and winter respectively.