The opportunities and ecological risks of floating solar power
Published on 11 September 2026 at 05:43 GMT
By Editorial Team SDG7
Floating solar power turns the surface of reservoirs, irrigation ponds and former industrial water bodies into electricity-generating space. By placing photovoltaic modules on buoyant structures, projects can expand solar capacity without converting farmland, forest or other valuable land. Yet the same design that saves land also changes the boundary between air, sunlight and water, creating questions that conventional solar farms do not face.
The case for floating photovoltaics
The central attraction is spatial. Floating photovoltaic systems use water surfaces that may already serve hydropower, drinking-water storage, irrigation, flood control or industrial purposes. A 2018 assessment by the World Bank Group and the Solar Energy Research Institute of Singapore estimated about 400 gigawatts of technical potential under conservative assumptions, while stressing that this was not a forecast of what would be built.
Artificial and heavily modified water bodies can appear especially suitable because their original ecosystems have already been altered and access to roads or electricity infrastructure may exist. Former quarry lakes, mine subsidence ponds and water-treatment basins can also offer space with limited alternative land value. At hydropower reservoirs, shared grid connections and the different daily and seasonal profiles of solar and hydro generation can create operational advantages.
Avoided land occupation does not mean zero footprint. Anchors, mooring lines, cables, access routes and onshore substations still occupy space. Reservoir shorelines move as water levels rise and fall, and arrays require clearance from dam structures, intake towers, spillways and navigation routes. The National Renewable Energy Laboratory notes that permitting on multipurpose reservoirs can involve water rights, dam safety, recreation, wildlife, cultural resources and existing operating agreements.
Water savings are possible but difficult to generalise
Panels shade the surface and reduce wind exposure, two processes that can suppress evaporation. This makes evaporation reduction a potentially valuable co-benefit in dry regions and in reservoirs where water has high agricultural or municipal value. Small experiments and modelling studies have reported sizeable reductions, but results depend on the proportion covered, panel geometry, wind, humidity, heat exchange and the relationship between the array and open water.
The evidence base remains uneven. A 2021 systematic assessment led by researchers at Lancaster University found that reduced evaporation was regarded by stakeholders as the leading opportunity, but only a small part of the available ecological literature directly examined floating solar. Estimates derived from tanks, shade covers or models cannot be transferred automatically to a full reservoir. Water savings are therefore better treated as site-specific and measured over seasons than assumed from array area alone.
Temperature, mixing and oxygen
Floating arrays intercept solar radiation and shelter the water from wind. Both effects can alter water temperature, daily temperature ranges and mixing. A three-year, whole-lake study published in 2025 compared three lakes with floating solar with three control lakes. It found an average annual cooling of 1.2 degrees Celsius, with reductions of up to 3 degrees on the warmest spring and summer days. Cooling also extended beyond the directly covered area.
Cooling can ease thermal stress for some organisms, while creating less suitable conditions for others. Reduced wind mixing and lower light can also change stratification, primary production and gas exchange. Research across 26 water bodies in China found lower temperature and dissolved-oxygen saturation in panel areas than in control areas, alongside changes in plankton and microbial communities. The study included both floating and pile-mounted systems, so its results describe water-surface solar collectively rather than every floating design.
A separate United States study of three shallow ponds found lower near-surface dissolved oxygen beneath all arrays and cooler surface water beneath the two high-coverage systems. At a pond with active aeration, mechanical mixing altered the response. These findings illustrate why dissolved oxygen cannot be predicted from shading alone: depth, nutrient status, inflows, circulation, coverage and aeration all influence whether oxygen remains available for fish and invertebrates.
Aquatic biodiversity and uncertain trade-offs
Shade reduces the light available to algae, aquatic plants and microorganisms. That can restrain excessive algal growth in some nutrient-rich waters, but it can also reduce food production at the base of an aquatic ecosystem. Changes in temperature and oxygen may favour some species and disadvantage others, while floats and moorings create new hard surfaces for colonisation. Birds may lose open-water habitat or use arrays as perches, and the consequences can differ between resident and migratory species.
The scale of coverage is central. A small array on a large, well-mixed reservoir may produce effects that are difficult to distinguish from normal variation. High coverage on a shallow or poorly mixed pond can create a much larger shift below and around the panels. The 2025 whole-lake experiment warned that cooling could have beneficial or adverse consequences depending on species and ecosystem function. Long-term evidence across climates and water-body types remains limited.
Floating solar is relevant to SDG 7 (Affordable and Clean Energy) because it can expand renewable generation where land is constrained. Its contribution to the goal depends partly on how projects manage site-specific effects on freshwater habitats.
Maintenance on a moving, corrosive surface
Water creates distinctive engineering and maintenance demands. Humidity, ultraviolet exposure, waves, changing water levels and repeated mechanical movement can affect floats, connectors, cables and moorings. Technicians may require boats, walkways, specialist electrical procedures and rescue arrangements. Birds can foul modules, vegetation can entangle equipment, and submerged or wet cables complicate inspection.
A 2025 review by the International Energy Agency Photovoltaic Power Systems Programme found that performance advantages depend on design and site conditions and cannot be generalised. It identified early reliability problems, limited operating data and the need for maintenance strategies tailored to floating plants. Greater accessibility can lower some costs, while remote anchors, underwater components and restricted weather windows can raise others.
Who else uses the water
Reservoirs are rarely empty platforms. Fishers, boaters, farmers, drinking-water operators, hydropower managers, nearby communities and conservation authorities may rely on the same space. An array can exclude navigation, affect views, change access to fishing grounds or restrict future reservoir operations. Construction traffic and security zones may add further pressure. On former industrial waters, contamination, unstable banks or uncertain ownership can complicate a site that initially appears conflict-free.
Project assessment therefore extends beyond avoided land use to the water body, coverage level, design and existing uses. Studies have documented physical and biological changes, although their direction and magnitude vary by site. Monitoring before and after installation can identify changes in temperature, oxygen, light, plankton and species use, but long-term evidence remains limited.
Floating solar can produce low-carbon electricity with less direct land occupation and, under suitable conditions, lower evaporation. Documented ecological effects vary with the water body, array design and coverage, and the human and ecological uses already present.
Written by a human author, edited with AI assistance.
Further information:
• World Bank Group, Where Sun Meets Water: Floating Solar Handbook for Practitioners, used for land-use advantages, reservoir integration and environmental and social considerations. https://documents1.worldbank.org/curated/en/418961572293438109/pdf/Where-Sun-Meets-Water-Floating-Solar-Handbook-for-Practitioners.pdf
• National Renewable Energy Laboratory, AquaPV: Regulatory and Environmental Considerations, used for permitting, reservoir operations and environmental-risk context. https://www.nrel.gov/docs/fy24osti/86325.pdf
• Communications Earth & Environment, Water-surface photovoltaic systems have affected water physical and chemical properties and biodiversity, used for multi-site evidence on temperature, oxygen and aquatic communities. https://www.nature.com/articles/s43247-024-01811-y
• Journal of Environmental Management, Floating photovoltaics strongly reduce water temperature: A whole-lake experiment, used for the three-year lake-temperature findings and ecological uncertainty. https://doi.org/10.1016/j.jenvman.2025.124230
• IEA Photovoltaic Power Systems Programme, Floating Photovoltaic Power Plants: A Review of Energy Yield, Reliability, and Maintenance, used for system performance, reliability and maintenance evidence. https://iea-pvps.org/wp-content/uploads/2025/04/IEA-PVPS-T13-31-2025-REPORT-Floating-PV-Plants.pdf
