Magadley, E. - Triangle Research and Development Center, P.O. Box 2167, Kfar-Qari, 30075, Israel; 
 Kacira, M. - Department of Biosystems Engineering, The University of Arizona, Tucson, AZ  85721, United States;
Yehia, I. - Triangle Research and Development Center, P.O. Box 2167, Kfar-Qari, 30075, Israel

This study presents a detailed analysis of the outdoor behaviour of organic photovoltaic (OPV) panels on a polytunnel type greenhouse roof in a Mediterranean climate, looking at the effects of environmental variables and panel orientations on the electrical behaviour and degradation of the panels, thus providing crucial outdoor testing results of greenhouse integrated OPVs in this climatic region. The OPV panel placed at the polytunnel ridge of the roof yielded highest outputs, efficiencies and fill factors during the measurement period. However, the use of panels on the East and West sides of the greenhouse roof, could reduce midday output peaks and therefore provide a more balanced power supply throughout the day. The diurnal variation in OPV behaviour was influenced by simultaneous effects of changing irradiance and temperature. It was found that although output was higher, the OPVs showed dips in fill factor and efficiency at times with high incident irradiance. This was assumed to be due to a reversible degradation phenomenon under high direct irradiance conditions, which led to higher performance during morning hours compared to the afternoon and was followed by a recovery overnight and to some extent in shaded conditions.