Floating Solar (FPV) & Evaporation
Floating photovoltaic arrays shade the water they cover, cutting evaporation under the panels while generating power — a dual benefit at high capital cost.
What it is
Floating solar — floating photovoltaics (FPV) — places solar panels on pontoons that float on a reservoir or pond, anchored with an engineered mooring system. The primary purpose is electricity generation, but because the panels and their floats sit over the water, they also shade it and reduce evaporation underneath. That combination is FPV’s distinguishing feature: a dual benefit.
How it works
The panel array shades part of the surface and shelters it from some wind, lowering the radiation and exposure terms that drive evaporation (see what is evaporation). At the same time the water below helps keep the panels cool, which can modestly improve their electrical efficiency — a reinforcing loop between the two functions.
How well it works
The honest framing here is qualitative rather than a single suppression percentage: FPV reduces evaporation under the panels and generates power. The key limit is coverage. A solar array is sized for energy output and electrical spacing, so it typically occupies only part of the water surface — the panel footprint — leaving open water between and around rows. Evaporation continues on that uncovered water at the full rate.
This means FPV is best judged on its combined value: a partial evaporation benefit plus a stream of generated electricity. Where the goal is to maximise evaporation suppression alone, a dedicated full-surface cover does more — but it generates no power.
Trade-offs
- Capital and complexity. FPV is the most capital-intensive option in this comparison, and it adds electrical, structural and mooring complexity beyond a simple cover.
- Permitting and grid. Grid connection, permitting and interconnection agreements add lead time and cost.
- Coverage choice. Denser arrays shade more water but raise cost and can complicate maintenance access.
Where it fits
FPV suits large reservoirs near electrical demand or the grid, and operators who value energy generation alongside water savings. Where evaporation suppression is the sole objective, compare full-coverage options such as suspended covers and modular floating covers. The full methods comparison places FPV against the dedicated covers.