In this study, the snow melting behavior of several photovoltaic technologies, all installed at the same location under identical conditions, is analyzed based on the time-dependent changes of the snow cover, which is extracted from images of a monitoring webcam, for various temperature and irradiation conditions. From this study, conclusions can be drawn for the optimum module technology for a given location with respect to snow-dependent yield losses. In particular, the melting behavior is analyzed regarding its dependence on the ambient temperature and the irradiation level. Finally, the relevance of snow cover-related losses is discussed. The study shows that comparably large frameless modules exhibit the highest snow shedding rates. Hence, they are snow-free for longer periods, thereby increasing their potential for electricity generation in snowy regions. In summary, this paper reveals the beneficial snow removal properties of large frameless modules for snowy areas by applying a novel image processing technique for the determination of the snow-covered area fraction of the modules.
In the presented paper, we introduce an approach to rate the performance of modules under specific real weather conditions, since solar modules are rated according to standard test conditions which do not give evidence of the performance under real outdoor conditions. Therefore, we categorize the daily weather at a photovoltaic test site into 7 different climatic-day classifications and multiple cloud scenarios. Two different approaches to evaluate the cloud conditions were investigated. Furthermore, we use the developed approach to rate the performance of 8 different commercially available photovoltaic modules that have been installed and measured in Germany. The evaluation shows that module properties (eg, temperature coefficient, spectral response, and mechanical construction) have a major influence on the performance of photovoltaic modules under different weather conditions. In existing studies, mostly specific module technologies were investigated under outdoor and/or laboratory conditions according to their specific yearly or seasonal yield, 3-7 ageing behaviour, 8-11 behaviour on spectral or thermal influences, 12-15 or light soaking effects. 16,17 Therefore, we present an approach to categorize the weather and cloud conditions at a specific site to rate the specific outdoor performance of PV modules. Furthermore, we use the developed approach to investigate 8 different commercially available modules in the period from August 1, 2015 to July 31, 2016. We also discuss the influence of different module parameters (eg, low light performance and temperature coefficient)as the presumable root causes for the performance differences under various weather scenarios.At first, we describe the test site as well as the data acquisition system followed by the determination of the different weather scenarios.Afterwards, we present and discuss the results of the investigation and sum up in a conclusion and present an outlook on future research activities.
PHOTOVOLTAICS TEST SITEThe measurement equipment as well as the investigated PV modules were installed at the ZAE Bayern test site in Arzberg, Germany.
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