Combined optimization for offshore wind farms

The two main challenges of optimizing a wind farm are the design of the turbine layout and the design of the cable routing. The first task consists in placing each turbine such that overall power production is maximized, the wake effect (wind shadow) between turbines is minimized, and foundation costs are minimized as well. The second task is to select the minimum cost cable routing to connect the turbines with submarine cables, which transfer the produced electricity to a substation and then onshore. Although the typical procedure is to solve the two problems sequentially, we investigate the benefit of solving them together. Few studies in the literature attempt to join these two optimization problems, which are often simplified to keep the computational complexity low. In our work, we model the combined problem with all constraints relevant to practical applications of wind farm design. We also present a novel local search that integrates the two problems, thus allowing the cable routing to give direct feedback to the turbine positions in the layout. We benchmark the combined optimization on a set of realistic industry-scale wind farm instances. Our results show that the combined optimization outperforms the sequential approach, especially for lower energy density wind farms, due to the significant savings in the cable routing which widely compensate for a slight reduction in power production.