Abstract
Enhanced performance of floating PV due to water cooling is widely claimed, but poorly quantified and documented in the scientific literature. In this work, we assess the effect of water cooling for a specific technology developed by Ocean Sun AS, consisting of a floating membrane with horizontally mounted PV modules allowing for thermal contact between the modules and the water. The impact of thermal contact with water on energy yield is quantified using production data from a well-instrumented 6.48 kW installation at Skaftå, Norway. In addition, we apply a thermal model that incorporates the effect of heat transport from the module to the water to estimate the module temperature. By comparing a module string in thermal contact with water with a module string with an air gap between the water and the modules, we find that the water-cooled string had on average 5–6% higher yield compared to the air-cooled string. Also, we find that the system in thermal contact with water has a U-value of approximately 70–80 W/m2K, and that it is necessary to consider the water temperature for a more accurate calculation of the module temperature.
Highlights
Floating photovoltaics (FPV) is growing at a rapid pace
We assess the effect of water cooling for a specific technology developed by Ocean Sun AS, consisting of a floating membrane with horizontally mounted PV modules allowing for thermal contact between the modules and the water
We find that the system in thermal contact with water has a U-value of approximately 70–80 W/m2K, and that it is necessary to consider the water temperature for a more accurate calculation of the module temperature
Summary
Floating photovoltaics (FPV) is growing at a rapid pace. Worldwide accumulated, installed capacity by the end of August 2020 is approxi mately 2.6 GWp, distributed over more than 35 different countries [PV magazine]. The number of available FPV technologies and technology providers is rapidly growing. FPV still needs to compete with land-based PV in terms of cost [PV magazine], there are several ad vantages to FPV that contributes to the increased market share: FPV opens new possibilities for power production where suitable land area for PV plants is either unavailable or expensive. Power production near urban areas can significantly reduce transmission costs. Hybridi zation with hydroelectric power production is emerging as an exciting, and largely unexplored market for FPV. For hybrid applica tions, a range of synergies can reduce the overall power cost, such as improved PV power plant performance, shared transmission infra structure, and improved quality of power, especially in the case of large hydropower sites that can be flexibly operated. The PV capacity can be used to boost the energy yield of the hydropower plants and may help to manage periods of low water availability
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