Challenges during installation of floating wind turbines

Abstract

Floating wind turbine substructures are an expanding sector within renewable power generation, offering an opportunity to deliver green energy, in new areas offshore. The floating nature of the substructures permits wind turbine placement in deep water locations. This paper investigates the installation challenges for the various floating offshore wind types and suggests priority areas for future development to help reduce costs. Specifically tailored design for installation includes expanding the weather window in which floating substructures can be transported to and from site and making mooring and electrical connection operations simpler. The simplification of installation methodology will reduce time spent offshore, by installation vessels, and minimise risks to personnel. The paper reviews best towing practice for offshore installation and the possible return to port for maintenance. The installation process for a floating offshore wind turbine varies with substructure type e.g. Barge, semi-submersible, Spar and TLP which are discussed in detail. TLPs will need temporary buoyancy or specialised offshore crane vessels to enable installation of these substructures. Spars require deep water for construction and tow out. Return to port for maintenance is only feasible for Barges and semi-submersibles Floating offshore wind structures require an international collaboration of shipyards, ports and installation vessels, The installation phases, in particular the maximum draft of the substructure, are affected by the construction materials i.e. steel or concrete. . Steel Semi Submersibles and Barges, have a smaller draft than concrete substructures, and thus require out-fit quays with less water depth. In order to facilitate the installation and to minimize costs, the main aspects have to be considered strategically i.e., the required vessel types, the distance from fit out port to site and the weather restrictions. The fit-out port should be as close as possible to the offshore installation site to minimise weather downtime during tow-out. Of the main substructure types, the Spar has the greatest average installation cost, driven by the vessel requirements and the sheltered/calm conditions required for turbine assembly. The nature of the Semisubmersible substructure and its moorings lead to lateral movement of the turbine, which presents a challenge for the export cable connection. This paper will be useful for researchers and stakeholders in the offshore wind and offshore engineering sector offering or considering technology solutions for floating offshore wind installations