Spar-type floating wind turbine foundations have been deployed successfully for deep-water offshore wind power generation using the conventional installation method involving horizontal wet-tow of the hull and a large floating crane vessel for lifting the wind turbine tower and rotor system onto the hull. Due to the high cost and limited availability of large floating crane vessels, offshore installation has been identified as one of the key areas for technical innovation in order to reduce overall cost and schedule for large scale commercially viable development of deep-water floating wind farms.
In this study, a novel self-installation method for installing a new concept triple-column Spar floating wind turbine system is proposed, which not only accelerates the installation process, but also drastically reduces the associated cost. By employing the self-installation method, the wind turbine tower and rotor system, the Spar deck structure and hull, consisting of three individual columns connected to a soft tank at the keel, are initially connected upwards in installation configuration inshore at the quayside, and subsequently wet towed offshore with the assistance of reusable temporary stability modules. Once arriving at the deep-water wind farm site, the Spar hull is first lowered to certain depth freely under gravity with the wind turbine tower mounted on the deck structure connecting to the stability modules. The operating draft is achieved by adding ballast water into the hull columns, and at this point the deck structure is then permanently connected to the hull. Feasibility study of the proposed self-installation method is carried out by simulating the dynamic response of a 5MW triple-column Spar-type floating wind turbine over the self-installation process. Simulation results indicate the installation process can be completed successfully thus proving the technical feasibility of the self-installation method preliminarily. The next step will be to perform model tests to further investigate and validate the triple-column Spar concept and the self-installation process.
