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Stellenbosch University (2021)

The Influence of albedo and cooling on the yield of floating PV systems

Patel, Shahina Salim

Titre : The Influence of albedo and cooling on the yield of floating PV systems

Auteur : Patel, Shahina Salim

Université de soutenance : Stellenbosch University

Grade : Master Degree (Electrical and Electronic Engineering) 2021

Floating PV (FPV) technology is an innovative technique of deploying PV modules on water bodies. Floating solar PV plants conserve the land areas and operate under lower temperatures, which lead to higher power outputs due to the cooling effect from the water. Due to the reflective and evaporative properties of the water surface, the performance of FPV systems is affected by the water surface reflectance and the heat transfer between the PV modules and the atmospheric environment. In the absence of measured reflected radiation from water, a default albedo value of 0.2 is commonly used to simulate PV systems as varying water surface albedo is currently not integrated into the PV simulation software. Therefore, the research work provides the modelling of the time-varying water surface albedo with the change in solar elevation ; as changes in weather patterns strongly affect the radiation received on the FPV modules and the reflection off the water surface. Results show that the water surface albedo is affected by the spectral and angular dependencies of the irradiance ; and that the albedo is lower at higher solar elevations and higher at lower solar elevations. Furthermore, this research studies Ocean Sun’s FPV technology that uses the concept of using floating PV modules on a flexible polymer floating structure on the water surface. Performance analysis shows that the water-cooled string, which is in thermal contact with the floating canvas, performs between 3.17 % to 7.32 % better than the air-cooled string, which is lifted 32 mm above the floating canvas using 32 mm polypropylene pipes. A thermal model is also being investigated to estimate the cooling effect of an air-cooled and a water-cooled FPV string in comparison to a ground-mounted PV string. Average U-values of 30 W/m2.K and 89 W/m2.K for the air-cooled and water-cooled string is observed, respectively. Higher U-values corresponds to a better cooling effect due to the direct thermal contact of the PV mod- ules with the floating canvas on the water surface. An average U-value of 27 W/m2.K is observed from the ground-mounted PV system. The research also tests the ability of solar PV simulation software, PVsyst, to successfully simulate FPV systems and to compare the energy yield of an FPV system with hypothetical tilted strings and increasing U-values in the same location. The influence of the tilted panels at different tilt angles on the energy yield of the FPV system using the default albedo versus the modelled albedo is analysed. PVsyst simulation shows that the energy production increases with an increase in U-values and the energy difference increases with an increase in the tilt angles due to the lower irradiance experienced at higher tilt angles.


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