Abstract: As a new energy production mode, floating photovoltaic strengthens a comprehensive utilization of water areas, restrains water surface evaporation effectively, and alleviates the current energy crisis and land crisis. However, certain issues emerge in the research of water surface evaporation in the construction areas of floating photovoltaic stations, such as lack of empirical monitoring data, unclear mechanism of water surface evaporation under photovoltaic panels, low accuracy of evaporation calculation models. In this study, data series were collected through in-situ monitoring at the Panji floating photovoltaic station of 150 MW capacity in Huainan, Anhui, including the surface evaporation from natural waters in Mar. 2022 - Jan. 2023, and the under-panel surface evaporation of the photovoltaic modules in Jun. - Nov. 2022. We develop a new whole evaporation model for calculating the construction water area, using an improved Penman model to calculate its surface evaporation from natural waters, and construct an energy-conservation numerical model of under-panel evaporation. And this new model is verified against the in-situ data collected. The results show that the photovoltaic module can reduce under-panel evaporation effectively, and the evaporation model gives R2 greater than 0.85 and RRMSE less than 0.25, quite accurately reflecting the real case under the influence of construction. For a water-saving design of this floating system with its 45% coverage of the water area, calculations reveal its annual water saving is as much as 1.47 million m3 that would generate a remarkable benefit.

Key words: floating photovoltaic, Penman model, evaporation numerical model, in-situ monitoring, evaporation under the module panel