CFD modelling to derive U-values for floating PV technologies with large water footprint

Abstract

Floating photovoltaics (FPV) systems are an emerging and increasingly competitive application of solar PV. Although lack of land is the main reason for assessing the technology against land-based PV, favourable cooling conditions, justified by the fact that air above a water body is typically colder and windier than on land, is often also used as an argument. Few have quantified this effect, and the aim of this work has been to use Computational Fluid Dynamics (CFD) to derive U-values for the most used FPV technology today. Our results show that the presence of a float with large water footprint promotes a significant non-uniform temperature field in the wafer layer. The study confirms that the cell temperature rises by decreased wind and by increased solar irradiation and air temperature. We found that the water temperature does not significantly affect the cell temperature. Radiative heat transfer between the back of the module and water was estimated to reduce the cell temperature typically less than 1 °C. Because the technologies are not identical but still represent systems with large water footprint, U-values from the study were considered to compare well to reported values derived from FPV field data in Singapore and the Netherlands.