Reduction of Total Installation Time for Floating Offshore Wind Farms by Improving Actual Unit-Installation Time and Optimizing Operation Windows

Abstract An installation time estimation model for floating offshore wind farms (FOWFs) has been studied and validated based on the cost breakdown structure, and the unit-installation time has been estimated using data from FOWF projects. However, since the unit-installation time includes weather downtime, applying it to other areas with different weather conditions is challenging. In this paper, we propose an installation time estimation model for FOWFs that incorporates weather characteristics specific to the project site, extending upon our previous model. Using installation data from the Fukushima floating offshore wind farm demonstration project in Japan, we estimated actual unit-installation time excluding weather downtime and compared it with that of Hywind Scotland. The results showed that for the pre-anchoring process, the total of the pre-installation time per mooring line and the tensile testing time per anchor in Japan is about 4.1 times longer than those in Europe. As for submarine cables, the time for connecting one side of a riser cable to a floater is 9.3 times longer and the velocity of the trenching cables is 7.5 times slower. Assuming a theoretical FOWF, the total installation time in Japan, Korea, and Taiwan varies from 899 days to 1,214 days. After performing a sensitivity analysis, we found that the total installation time can be reduced by 61% if we adjust the actual unit-installation time and the weather restrictions from the present conditions in Japan to those in Europe. These findings indicate that our model can provide a more general framework for estimating the installation time of FOWF.