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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Date
April, 2019
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Abstract
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.
Description
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.
Keywords
Evaluation, Risk Priority Number, 2.5 Mw Polycrystalline Silicon Photovoltaic Power Plant, Navrongo, Ghana, Sub-Sahara Africa.