Ocean Wave-Driven Variability During Offshore Wind Farm Expansion: Wake Development and Power Density

As offshore wind farms expand to the gigawatt scale, understanding their coupled interaction with the ocean surface becomes essential for predicting wake dynamics and power generation limits. Using large-eddy simulations with a wave-parameterized surface stress, this study investigates how different wind–wave regimes influence wake development and the scaling of power density with increasing farm size. Wakes reach a fully developed state after roughly ten turbine rows, beyond which the flow and power output stabilize. Across all cases, power density exhibits an asymptotic decline with farm expansion, with the rate of decline modulated by wave forcing. Under low wind inflow, wind-following swells reduce surface drag and enhance mean momentum advection, increasing power density by up to $46\%$, while wind-opposing swells intensify drag and turbulence, yielding smaller but positive gains of about $11\%$. Although turbine-induced turbulence governs wake recovery, swell effects persist downstream, continuing to influence the power distribution in further farm expansion. The results highlight that ocean waves are a key factor in determining wind farm efficiency and should therefore be explicitly considered in the area requirement estimation and power output prediction for offshore wind projects.