Simulation and experimental study of power losses due to shading and soiling on photovoltaic (PV) modules
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- Master's theses (IMT) 
A model for predicting and quantifying the effects of complex partial shading profiles on a PV-module has been constructed by using the simulation tool LTspice IV. The model is constructed according to the two-diode model equivalent circuit for solar cells. Technical specifications from REC255PE were implemented in the model, and partial shade was simulated by applying shade normal to the strings, and along the strings on the module. An experimental basis has been established for quantifying the transmission losses due to the natural accumulation of soiling in Norway. The soiling accumulation is caused by several typical Norwegian weather conditions in the period of 10.25.14-11.23.14. Results show that the transmission is reduced by up to 0.92% and 1.1% during one week for a standard module glass and an anti-soiling coated glass respectively. The results show no positive effect of the anti-soiling coated glass relative to a standard module glass, which is opposing to other previous studies. A longer measurement series is required in order to make a significant conclusion. This experimental basis was also established for measuring the transmittance through snow covers at various depths and implement snow as soft shade in the LTspice model to predict power losses due to snow accumulation. Due to the heat dissipated by the light source on the experimental setup, and the fact that the setup was located indoors, this experimental setup was not sufficient for measurements on snow. The simulation model was used to predict power losses due to partial snow cover on a PV module at a PV plant located at Evenstad, Norway. The simulation results were verified by inverter data at Evenstad. Simulation results showed that if one PV module, where 5 of 10 rows were snow covered, the power output was reduced by 40% for the entire inverter-string, assuming snow depth of less than 10 cm. For thick snow depths, assumingly higher than 10 cm, the power produced from a module string is assumed to be close to zero due to very low transmittance through the snow and the fact that the modules are installed in upraised position. Simulation results show that, for this particular scenario, installing the modules in laying position would increase the power produced by each module with about 19%.