Dynamic analysis of offshore wind turbine installation based on a novel integrated mating method

摘要

With the size of the wind turbine and water depth being continuallyincreasing, offshore wind turbine (OWT) installation has become amajor challenge for the development of offshore wind energy. Thetraditional OWT installation methods either use a crane vessel toachieve a single lift installation of the integrated wind turbine onto thepre-installed foundation, or use a jack-up vessel to conduct modular liftinstallations for the different pieces of OWTs such as the tower, nacelle,and blades. The crane vessel method is limited by the lift capacity andheight of the crane vessel, and is sensitive to the environmentalexcitations. The modular lift method by jack-ups generally entails alarge number of offshore lifts and a protracted period for offshorehook-up and commissioning, resulting low installation efficiency andhigh costs. In addition, the working water depth of the jack-upinstallation vessels in the market is generally limited to 35 meters. Theincreasing interests in exploiting offshore wind energy in deeper watermay bring new challenges to the installation of OWTs. Therefore,many novel installation methods have been proposed by practitionersand academia. This paper presents a novel integrated mating methodbased on a ship-type installation vessel with the capacity oftransporting 4 integrated wind turbines on one route. By this method,the blades, rotor, nacelle and tower are assembled as one piece at theshipyard, which is then loaded out onto the installation vessel. Duringtransportation, the 4 integrated turbines are horizontally placed on the8-legged frame mounted on the ship deck. The installation of theintegrated turbines involves anchoring and prepositioning of theinstallation vessel, erection of the integrated turbine by the hydraulicjacking system and mating of the tower stabbing cone with the preinstalledfoundation. This installation approach is an analogy to thefloat-over deck installation method for the offshore platforms. A casestudy of offshore wind turbine installation onto a pre-installedmonopile foundation by the new installation method is conducted inthis paper. By using ANSYS-AQWA, numerical simulations arecarried out to investigate the hydrodynamic characteristics of theinstallation vessel and the nonlinear dynamics arising from the matingoperations. In addition, parametric studies are performed to study theeffects of the motion control systems such as the mooring system,fender system and shock absorber within the monopile, on the vessel motions and mating forces.