Hotspot selection and complementarity for combined offshore wind and wave energy utilization in the China East Adjacent Seas

The intermittent characteristics of offshore wind and wave energy bring difficulty to their grid connection, and combined utilization can help improve the utilization situation. This study takes the China East Adjacent Seas as an example, based on the ERA-5 reanalysis wind field data and wave hindcast data calculated by the Delft3D-Wave numerical model, evaluated the resource characteristics and combined development potential of offshore wind and wave energy. Considering the resource density, variability, correlation, and effective energy frequency of wind and wave energy, an improved co-located feasibility index is proposed. Four combined development hotspots, Zhoushan, Taizhou, Xiapu and New Taipei, are selected, where not only have abundant energy density and great stability, but also have significant complementarity of wind and wave resources. Through further comparison of the three electric field modes, it can be found the combined power generation can significantly reduce the volatility of power output and the zero production rates, and improve the capacity factor, especially in seasons two resources are scarce and complementarity is significant. Compared with the single wave power farm, the combined power farm in the hotspots reduces the coefficient of variation by 12.8 %–28.49 %. Two optimal wind and wave resource ratios of 50 %:50 % and 60 %:40 % have been proven can achieve a balance between output efficiency and stability, providing a reference for the practical application of combined development.