Assessment Of Risk Priority Number Of 2.5 Mw Polycrystalline Silicon Photovoltaic Power Plant At Navrongo, Ghana In Sub-Sahara Africa.

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Understanding failures of photovoltaic (PV) modules is one key factor in enhancing the reliability and service lifetime of PV modules; and hence reducing the cost of PV systems and financial implications on investment. This study seeks to identify the field failures associated with installed PV modules in the Ghanaian climatic condition, which minimize the performance of modules, and pose reliability issues to the solar plants as well as financial implications to manufacturers and investors in the PV sector. Physical examination of the modules using visual inspection checklist and their corresponding electrical performance parameters (I-V characteristics) measurement using multimeter and I-V tracer were performed on two models of the five (5) year old 2.5 MW PV power plant at Navrongo. A MatLab program was used to evaluate the failures and degradation modes of 144 Polycrystalline silicon (Poly-Si) framed modules under the hot dry climate of Navrongo. The program is a statistical reliability tool that uses Risk Priority Number (RPN) to determine the dominant failures by means of ranking and prioritizing the failure modes. The visual inspection revealed front glass slightly soiled, junction box lid fell off, cell interconnect discoloration and backsheet crack between cells as the peculiar failure issues either affecting the performance of the modules and/ or posing safety concern to personnel and properties on site. Mean degradation rates of 1.11%/year and 1.23%/year were respectively computed for Model A (Jinko solar) and Model B (Suntech technologies) types of modules for the power plant studied. These degradation rates values are beyond the standard warranty limit of 1.0%/year reported in literature. In addition, short circuit current (Isc) and fill factor (FF) were determined as the dominant I-V parameters affecting the power degradation rates of the Model A and Model B modules respectively. The study also determined the total Global RPN value of 606 for the Model A type of modules for this plant, whereas that for Model B is 583. These RPN values fall within the reported values ranging from 500 to 755 in literature. With this information, investors can have an insight on the worth of a PV Plant and viability of their investment before making a decision. From this study, it can be concluded that, the five years old PV plant in operation is not performing very well and needs urgent attention to avoid loss based on the degradation rates of the fielded modules.
A Thesis Submitted to the Department of Mechanical Engineering, Kwame Nkrumah University of Science and Technology, Kumasi in partial fulfilment of the requirement for the award degree of MASTER OF PHILOSOPHY IN MECHANICAL ENGINEERING