Researchers from Germany’s FH Aachen University of Applied Sciences have developed a novel dynamic model of spray cooling for floating PV (FPV) systems.
“This work takes a system-level perspective on spray cooling for floating PV. While cooling itself isn’t new, the focus here is on a very simple and low-cost spray system that could realistically be implemented in practice,” corresponding author Nico Oellers told pv magazine. “It combines detailed dynamic modeling with validation and applies the concept to different climates, showing how strongly performance and optimal operation depend on location.”
He added that, beyond cooling, spray cooling might also be useful for cleaning, snow prevention, and fire protection on FPVs. “We also plan full-scale long-term testing to validate the results and to investigate additional use cases and environmental effects, including impacts on the lake ecosystem and evaporation,” he added.
The dynamic model the team has created couples thermal behavior, electrical performance, and active cooling for floating PV systems. It takes various meteorological data as inputs and computes solar heating, convective and radiative cooling, as well as evaporation and condensation effects to determine module temperature. This temperature is then fed into an electrical model where efficiency decreases with rising temperature.
When a defined temperature threshold is exceeded, the method activates a spray-cooling model. This model quantifies the effects of both sensible and latent heat removal from water droplets impinging on the PV module, while simultaneously accounting for the electricity consumption of the water pump. It ultimately evaluates the net energy impact of cooling under different climatic conditions and operating scenarios.
Image: Solar-Institut Jülich (SIJ) of the FH Aachen University of Applied Sciences, Solar Energy, CC BY 4.0
To validate the model, the team compared its outputs with measurements from a real floating PV installation at a water reservoir in Weeze, north-west Germany. The system has a total capacity of approximately 750 kW and uses 395 W modules with an efficiency of 19.5%. A spray-cooling system was installed on a limited section of the plant in its central area, where modules are arranged in both east- and west-facing orientations. The setup consisted of a 2.2 kW submersible pump connected to an agricultural sprinkler operating at 2.3 bar, with a jet length of 23 m and a flow rate of 10.4 m³/h.
The model showed strong agreement with the experimental results, with a mean absolute deviation of 0.98 C. Subsequent annual simulations were conducted for four climatically distinct lakes: Lake Kinneret in Israel, Lake Garda in Italy, Lake Tahoe in the USA, and the full Weeze installation.
“Across all sites, spray cooling substantially reduced module temperatures, with annual mean reductions ranging from 12% to 22% and peak-temperature reductions of up to 42%,” the researchers stressed.
They also found that the magnitude of the cooling effect and the resulting energy gain depended strongly on climatic conditions, with the highest relative energy gain of 3.8% being obtained at Lake Kinneret. In contrast, the cooler climates of Lake Garda and Lake Tahoe yielded smaller relative gains of 2.7% to 3.1%, despite lower mean module temperatures, while the temperate site Weeze showed the smallest effect of 1.9%.
The research findingds were presented in “Dynamic modeling of spray cooling for floating photovoltaics with application to different climates,” published in Solar Energy.
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