Large-scale floating photovoltaic systems impact the water quality of deep sand extraction lakes in the Netherlands

The growing demand for sustainable energy has increased interest in floating photovoltaic (FPV) systems on inland waters, especially in densely populated areas like the Netherlands. Current knowledge on FPV effects on deep sand extraction lakes is mostly based on literature and models, with limited field data. This research evaluates the impacts of large-scale FPV systems on water quality in deep sand extraction lakes and identifies shortcomings in current monitoring strategies. Long-term water quality data from two lakes partially covered by FPV systems were analyzed. The Oudehaske case study monitored light, temperature, dissolved oxygen, chlorophyll-a, and turbidity, while the Beilen case study focused on temperature, dissolved oxygen, and phytoplankton composition. Key conclusions: 1. FPV systems can cool the water, creating a shallower thermocline. 2. Shading from FPV systems can reduce oxygen levels, especially in isolated lakes. 3. Light reduction effects depend on the scale of coverage. 4. FPV systems can reduce water mixing by blocking wind. 5. Phytoplankton diversity may be higher under FPV systems, though data is limited. Recommendations include researching biodiversity enhancement within FPV installations and extending studies to include eutrophic organisms. Establishing a reference site monitoring strategy before FPV construction is essential for accurate environmental impact assessment.