Study on the Impact of Photovoltaics on Surface Wind and Evaporation over Water Surfaces

Photovoltaic (PV) is the most promising clean energy, and water-surface PVs have been developing rapidly due to less land occupation. For south-facing fixed PV arrays, differences in the wind direction–angle will lead to variations in wind resistance. In this paper, surface wind speed and evaporation near the water surface of a PV-covered fish pond are observed. Results show the ratio of wind speed in the PV area to the reference site (denoted as α) is 0.2~0.3 in the south-biased wind direction, and 0.5~0.6 in the north-biased and east wind direction. A statistical formula for α with wind direction is proposed. The α values agree with previous conclusions from studies of single wind directions. Then the monthly average wind speed reduction ratio is calculated using the environmental wind rose diagram and α. The measured ratio of the monthly evaporation amount from the PV site to the reference site agrees well with that of the monthly wind speed. The method is applied to evaluate evaporation reduction at three PV sites of different latitudes. The results show the evaporation reduction by PVs is more than 50% at all three sites, and the maximum annual amount of 1236 mm occurred with a prevailing wind direction S.