Performance Evaluation of Monocrystalline and Polycrystalline Silicon Solar Photovoltaic Modules Under Low and High Irradiance Conditions in Kumasi, Ghana

Abstract

One of the biggest drawbacks of photovoltaic (PV) for many applications is the uncertainty in the energy output due to losses attributed to efficiency loss at low irradiance levels. In this study, the electrical performance of as-received monocrystalline silicon (mono-c-Si) and polycrystalline silicon (poly-c-Si) PV modules were evaluated at high and low irradiance conditions in Kumasi, Ghana using I-V Tracer. The low irradiance level of 200Wm^2 was achieved by covering the surface of the PV modules with a calibrated mesh screen. Maximum output power (P_max) of 87.9 W and 136.7 W were recorded for the mono-c-Si and poly-c-Si modules at high irradiance respectively. The corresponding average values at low irradiance were 8.29 W and 12.13 W representing percentage reductions of 90.57% and 91.60% respectively for the two technologies. These results indicate that when irradiance drops to 200 W/m^2 and below, the PV modules generate around only 10% of their nominal output power. This has implications for the number of modules that are required for installation in areas that experience many hours of low irradiance. Efficiency reductions of 64.4% and 59.01% for the mono-c-Si and poly-c-Si modules respectively at low irradiance is reported. The results also indicate that the mono-c-Si is affected more by light induced degradation effect than the poly-c-Si module after a few hours of exposure to the natural light. The novelty of this work is that knowledge of the performance at low irradiance will enable designers determine the number of modules required during the sizing of PV plants.

http://dx.doi.org/10.4314/njt.v40i3.8