Researchers have analyzed how floating photovoltaic (FPV) structures, when co-located with offshore wind farms, alter hydrodynamics and stress the seafloor in ways that extend well past the visible solar array footprint, says Tech Xplore.
Their work is based on a high-resolution three-dimensional hydrodynamic simulation (using the COHERENS model) applied to a site in the Belgian sector of the North Sea where existing offshore wind infrastructure is present.
In the baseline scenario (wind turbines alone) flow conditions are well understood. When FPV installations are added, especially in a dense configuration (~252 MW solar capacity) over the same area, the model finds that surface currents drop by up to 20.7% compared with wind-only conditions. Meanwhile, bottom shear stress (the force water exerts on the seabed) changes locally by as much as 63% in the dense FPV case.
Perhaps most striking: the area of seabed showing more than a 10% change in shear stress extended to 1.8 times the wind farm area and more than 23 times the surface area covered by the solar panels themselves. In other words, the impact zone underwater is far larger than the array footprint.
Although the study found only modest sea surface-temperature changes (a cooling of ~0.006°C on average, up to 0.03°C directly underneath) in summer, the effects on currents and sediment transport are much more pronounced. The authors link this to the greater amount of submerged structure in FPV systems, i.e., floats, moorings, support frames, which act as obstacles to flow and stir up turbulence and sediment.
Combining floating solar with offshore wind may optimize space and power output, but it also comes with non-trivial underwater ecological and physical engineering costs. Design, layout density, anchoring and monitoring will need careful attention if seabed habitats and sediment dynamics are to be preserved. The study emphasizes that good intentions in the energy transition must still account for marine-environment engineering at the seabed.