Positive effective temperature coefficient of power of +0.75/°C in flexible a-Si modules in building integrated installations

摘要

The paper analyses and discusses the effect of temperature on the performance ratio of Flexcell's a-Si based PV modules and plants. As a first finding, a relatively high annual cycle amplitude of 20% of performance is found for central European locations. Secondly, annealing experiments in the lab of light-soaked modules yield an activated annealing behavior, and stressing the importance of peak cell temperature, and with significant annealing rates at temperatures as low as 60°C. As a next step, the performance rate during outdoor exposure is correlated with the daily peak module temperatures reached by the exposed modules. Here, a unique linear relation is found to relate these two parameters, defining an "effective" positive temperature coefficient with a magnitude about +0.75%/°C. Further, back side isolation is found to clearly improve the performance ratio and thus the energy yield of exposed modules significantly through the increase of the daily peak module temperature; the improvement is of 8%; the corresponding increase of 12°C in the daily peak module temperature is thereby corroborating the amplitude of the effective temperature coefficient. In addition, the linear peak module temperature dependency of the performance ratio is further confirmed by a first data from a larger grid connected flat roof plant that has started to operate in January 09 in southern Switzerland.