Performance, degradation, and reliability of Solar Photovoltaic (PV) module under Environmental Field conditions

Abstract

Solar Photovoltaic (PV) system is one of the most promising renewable energy resources globally. However, its utilization has remained low in Kenya. This may be attributed to lack of pertinent knowledge of the potential, opportunities, environmental, and economic benefits of the technology. The PV performance, degradation, and reliability in the East African region have not been documented and little information is available in the literature. The main objective of this research was to determine the performance, degradation, and reliability of solar PV modules under environmental field conditions. The specific objectives were to; evaluate the technical and economic performance of PV modules, analyze the effects of soiling on the performance of PV modules, determine the reliability, degradation rates and mechanism of PV modules. The study area was in Makueni County (semi-arid region), Strathmore University solar PV power plant, and Moi University (tropical-savanna region). The methodology involved review of the historical data of PV power plant and collection of weather data from Kenya Meteorological Department weather station located 300 metres from the solar plant. Secondly, installation of weather station and six PV modules was done in Moi University to establish the effects of soiling. The analysis of the contaminants collected from the PV modules was done using sieves and analytical balance weighing machine. Finally, the measurement of I-V curves, thermal images and visual inspections was conducted on the PV modules installed for more than 1 year. This was done through the use of I-V curve tracer, Infrared camera and PV module check list tool developed by National Renewable Energy Laboratory. The results indicated a performance ratio of 68% and a discounted payback period of 13 years. The model developed indicated that an increase in solar irradiance and wind speed, and decrease in relative humidity, increases the power output. The degradation rates ranged from 0.99% to 1.15%, per annum, which was due to different types of PV cell technology, while degradation mechanisms were established as discoloration of encapsulating materials (36.84 %) in warm semi-arid region and browning of encapsulating material in tropical savanna as the predominant mode. The contaminant contained high percentage of fine particles of less than 0.06 mm in size which caused reduction of short-circuit current. The reliability of the different PV system installation configurations ranged from 35% to 82%, indicating a weighted mean of 67%, which was due to number of components, and connection schemes, majority of modules being polycrystalline. In conclusion the results obtained, provided clear evidence of the technical and economic viability of PV modules in the region as a source of energy. The study recommends parallel connections of components, and regular cleaning to maintain high performance and reliability, and reduction of degradation rates in the region.