Effects of large-scale floating solar farms on hydrodynamics and sediment transport under tidal currents

Large-scale floating solar farms (FSFs) have gained prominence in major coastal cities as a sustainable solution for renewable energy generation. This study investigates the effects of large-scale FSFs on local hydrodynamics and suspended sediment transport in coastal waters, induced by the turbulence modulation of surface boundary layer under tidal currents with the alternating open and covered water surface within the farm. Laboratory experiments were first conducted on a scaled FSF to measure the turbulence modulation of the surface boundary layer. Subsequently, a two-phase numerical model based on the Reynolds-Averaged-Navier–Stokes approach was established and validated by the experimental measurements. The model was then used to investigate the influence of different FSF configurations, water depths, and current magnitudes comprehensively. The results show that the FSF increases the thickness of the surface boundary layer significantly and amplifies its turbulent intensity due to flow detachment, while inducing spanwise secondary currents. The shear stress under the FSF coverage follows a linear distribution that supports the use of a modified logarithmic velocity profile near the boundary. The magnitudes of surface friction coefficient are found to be similar to those of smooth walls, which can act as a reference for the design and environmental assessments of future FSFs. Furthermore, the capacity for suspended sediment transport in the water body is found to decrease significantly due to the presence of large-scale FSFs based on empirical formulas, especially in shallow coastal waters. This reduction can lead to potential long-term sediment accumulation and deposition on the seabed beneath the FSF.