Performance Evaluation of Silicon-Based Photovoltaic Modules Found in the Kenyan Market
Njeru, Elosy Gatakaa
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Various kinds of photovoltaic (PV) modules have been developed and practically deployed as PV systems over time. The performance of PV modules found in the Kenyan market has not been documented and therefore their reliability and stability in providing an alternative source of energy has not been sufficiently established. In this study the I-V data of Silicon-based mono crystalline, poly crystalline and amorphous modules was collected. The choice of the modules was done randomly depending on their availability, the cost of the modules and their power rating. They were selected randomly from PV module vendors within Nairobi Central Business District (CBD). The manufacturers’ specifications were taken. The modules were then mounted at an optimum fixed tilt angle of 15 degrees. Initial measurements of short circuit current Isc, open circuit voltage Voc, ambient temperature and module temperature were taken immediately on mounting the modules. Measurements of current and voltage to obtain I-V data was done daily at solar noon for four months. The back of the module temperature and ambient temperature at the time of measurement was measured using thermocouple while the irradiance at the time of measurement was measured using a pyranometer. The pyranometer was mounted at the plane of array of 15 degrees as the modules. The collected I-V data was normalized and I-V curves were plotted. Performance parameters of the modules were then calculated from the I-V curve. There was a decrease in Voc of the modules with time with the amorphous modules clearly showing the Staebler-Wronski effect. The Isc of the modules showed little variation while Pmax of the modules had reduced significantly. The Pmax of most of the modules was found not to match with the manufacturers specifications provided in their data sheet. On inspection of the modules, the 10W polycrystalline module revealed a defect which was as a result of overheating of the cells that contributed greatly to its poor performance in comparison to the other polycrystalline modules. The efficiency of the amorphous modules ranged between 3%- 5% while that of mono crystalline and polycrystalline was above 10%.