Formulation and Analysis of Offshore Installation Time Estimation Model for Floating Offshore Wind Turbines

In this paper, the authors propose the offshore installation time estimation model for floating offshore wind turbines, hereinafter FOWTs, in order to analyze the efficiency in each offshore installation process. The total offshore installation time as the sum of operational time for (1) pre-anchoring, (2) ultimate holding capacity verification, (3) towing, (4) mooring, and (5) the other operational processes is defined. This study introduces "installation time per mooring line" as benchmark to measure of efficiency. Firstly, the authors applied this proposed model to Japanese and European FOWTs project data, and it is found that in Japan, the installation time per mooring line for (2) ultimate holding capacity verification and (4) mooring was reduced by 69% and 95%, respectively from the initial time. Secondly, the authors also applied this model to the offshore installation of a large-scale wind farm, by changing the benchmarks when the number of mooring lines of FOWT and the distance from the port were varied under the constraints of the port occupancy duration. To satisfy the duration of pre-anchoring port occupancy, it is concluded that the summation of installation time per mooring line for (1) pre-anchoring and (2) ultimate holding capacity verification should be reduced to the same level as that of Europe, and by almost 84% from the present level.