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Norwegian University of Life Sciences (2016)

Effect of Soiling on the Performance of Photovoltaic Modules in Kalkbult, South Africa

Øgaard, Mari Benedikte

Titre : Effect of Soiling on the Performance of Photovoltaic Modules in Kalkbult, South Africa

Auteur : Øgaard, Mari Benedikte

Université de soutenance : Norwegian University of Life Sciences, Ås

Grade : Master thesis 2016

Résumé
With high irradiance, widespread semi-dry, unexploited areas of land, and fortunate economic and political conditions for investments in renewable energy, the potential for utilizing solar energy in South Africa is large. However, in semi-dry areas with little precipitation, dust may accumulate on the module surface, reducing the light reaching the solar cell, and the performance of photovoltaic modules may be reduced. The purpose of this study is to investigate the effect of soiling on the power output from photovoltaic modules for an area in the Northern Cape region in South Africa. The effect of soiling is estimated through analysis of data from a test station at Scatec Solar’s solar park in Kalbult, where the performance of regularly cleaned and uncleaned polycrystalline silicon and CdTe thin film modules is compared. Different cleaning techniques and the effect of an anti-soiling product are also investigated. The data analysis is supplemented by experiments conducted at the test station, including quantification of dust accumulation and measurements of changes in the transmittance through module glass. In the time period considered in this analysis (04.05.2016 – 04.11.2016), it may seem like the losses due to soiling are only significant in the winter months May – July, and that thin film modules are more affected by soiling than polycrystalline silicon modules. The applied anti-soiling product seemed to work against its purpose and increase the dust accumulation on the module surface. In July, when the losses for the recorded data were at their highest, the average power loss due to soiling was 1 % for poly Si-modules without anti-soiling treatment, 2 % for poly Si-modules with anti-soiling treatment, and 4 % for thin film modules with anti-soiling treatment. For the poly Si-modules, it was shown that heavy rainfall cleaned the module surface to the extent that the performance was recovered. For the thin film modules, the performance also increased after heavy rain, although it may seem like the module surface was not completely cleaned. The measurements of the soiling levels suggest a daily dust accumulation of 13 – 22 mg/m2 in October. Compared with results from other studies, this confirms that the soiling levels in the spring months are low, and is an explanation for why there was not observed any significant reduction in performance in the period from August to October. The transmittance measurements confirm that two and a half days with soiling in October is not enough to significant reduce the incoming light on the solar cells.

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