Understanding wind farm power densities

Kirby et al. (J. Fluid Mech., vol. 953, 2022, A39) adapted the two-scale momentum theory (Nishino & Dunstan, J. Fluid Mech., vol. 894, A2) to large finite-sized farms. They demonstrated that analytical estimates agree excellently with large eddy simulations, and that the model provides a good upper limit of the power production for a given array density. Crucially, they introduced the concepts of farm-scale losses, caused by the atmospheric response to the whole farm, and turbine-scale losses, owing to internal flow interactions in the wind farm. These two new theoretical concepts offer a novel way to analyse the performance of extended wind farms. For large offshore wind farms, losses at the wind-farm scale are typically twice as high as at the turbine scale. This demonstrates that there is limited potential for layout optimizations of extended arrays. Instead, optimization strategies should focus on developing methods to increase the energy entrainment into the wind farm. This work provides an exciting roadmap for analysing the effective efficiency of large wind farms.

Automated summary

Kirby et al. adapted the two-scale momentum theory to large finite-sized wind farms and demonstrated good agreement with simulations. They introduced the concepts of farm-scale and turbine-scale losses, providing a novel way to analyze wind farm performance. Layout optimizations have limited potential, and increasing energy entrainment into the wind farm should be the focus of optimization strategies. This work offers an exciting roadmap for analyzing the efficiency of large wind farms.