Performance evaluation of Photovoltaic (PV) modules under different deployment conditions
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Date
2021
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University of Namibia
Abstract
The purpose of this thesis is to evaluate the performance of solar modules, comprising various PV technologies, subject to different climatic conditions. The
assessed PV technologies comprises of commercially available technologies and included Cadmium Telluride (CdTe), Copper Indium diSelenide (CIS), amorphous
silicon (a-Si)and polycrystalline silicon (p-Si) modules. Commercially available photovoltaic (PV) modules currently are comprised of two main groups: crystalline silicon modules and thin film modules. The thin film modules are cheaper due to lower production cost. They also exhibit lower temperature coecients compared to crystalline silicon. There is a perception
in the PV industry that thin film modules exhibit superior performance in hot
climates and that they show better tolerance and performance in lower solar
radiation locations. Our task was to determine if there is scientificc evidence for
such perceptions. Measurements were done at two stations in South Africa with different climates: Port Elizabeth (PE), having a humid, relatively cool and with high cloud cover and Johannesburg (JB), having a warm, semi-arid and low cloud cover
climate. In PE, one year of operation data for power output and module temperature
measured at one minute time resolution were collected from the site while
the GHI and ambient temperatures were measured from the site but downloaded
from the SAURAN website. In JB, the power output and module temperature
data measured at one minute time resolution were collected for a period of 6
months. The assessment was based on the following performance indicators: specific yield (SY), specific yield per unit land/roof area occupied by modules (SY/A) and the relative module efficiency ( rel:) for sunny (high irradiance) days and cloudy (low irradiance) days in each location. Statistical assessment of the performance indicators for each module type was performed with ANOVA test. The Tukey post-hoc test at 5% significance level was used for comparison of the daily SY, SY/A, rel: and average module temperatures between the different technologies at each location. A regression model was created to determine the extent of the impact of ambient conditions on the energy output of the modules. Our findings indicate that the solar radiation and ambient temperature have a strong impact on the module's SY, with the SY increasing linearly with the solar radiation while decreasing linearly with the ambient temperature during sunny days. Our findings further shows that the performance of all PV technology types are comparable in cloudy conditions at both locations. Under sunny conditions, CIS shows the highest SY in both locations, CdTe shows the highest SY/A in the warm and sunny JB climate while p-Si shows the highest SY/A under the cool and cloudy climate of PE, and a-Si shows the lowest SY, SY/A and rel: in PE. Furthermore, CIS remained the coolest and p-Si the hottest in the JB location. In PE, all modules
were equally cool on average. In conclusion, significant difference in performance between different PV technologies is only observed during sunny conditions. In addition, the established differences during sunny conditions were not technology specific but rather dependent of the type of performance indicator assessed. Thin film technologies have shown vast differences in performance between technologies and between climatic conditions. The superior performance of thin film technologies in cloudy conditions could not be established. These results are based only on the first year of module deployment and can be expected to change with time due to module degradation.
Description
A thesis submitted in partial fulfillment of the requirements for the Degree of Master of Science in Physics