Author(s)

OVE T. GUDMESTAD

Abstract

The costs of installation, intervention/maintenance and decommissioning of fixed bottom, founded offshore wind turbine concepts are unreasonably high when using state of the art technology. For such wind turbine concepts, state of the art is to use jackups or crane vessels for said operations. This might not be attractive in view of the large costs of employing sufficiently sized equipment that can operate under most weather conditions. In particular, there is a concern regarding the limited availability of offshore wind turbine installation-equipment in situations where there are larger waves most of the year, as in the North Sea. The investment costs for the wind turbines are thus larger than necessary. There is thus a need for new thinking to develop safe but less costly technology and procedures for these operations. Furthermore, heavy maintenance is particularly difficult for offshore wind turbines, requiring the use of expensive offshore vessels, i.e. vessels requesting high day rates during operations. In view of this, new technical solutions are, in this paper, proposed for the installation, intervention/maintenance and decommissioning of offshore wind concepts. In particular, the use of ballast procedures combined with use of the less costly offshore service vessels to perform offshore operations safely will be investigated. Similarly, the state of art design of the wind turbines requires the use of large cranes for heavy maintenance of said equipment and it might be considered to lower the nacelle to perform such operations. These operations shall not, however, get in conflict with the requirement that the blades shall never touch the sea surface under any activity. The design is extended to floating wind turbines which can be optimized for cost saving fabrication and installation using the method described for the fixed wind turbine designs.

Keywords

wind turbine installation, offshore support vessels, telescope solutions, maintenance, floating wind turbine design