Foundation for offshore wind turbine and method and means for its transportation and installation in deepwaters

Abstract

The main goal of the proposed by present invention compliant guyed tower is to increase the depth in which offshore wind turbines can be installed from present limit of 50 meters to 200+ meters. The specifics of compliant guyed towers, which are widely used by offshore oil industry for installation platforms in water depth starting from 300 meters and up to 1,000 meters, is in their long mooring lines, which have springiness that allows to mitigate dynamics of wind and waves forces acting on platforms. The length of mooring lines for wind turbines installed in the relatively shallow waters is not sufficient to have required springiness. By present invention the mooring line are attached to anchors on seabed through a pneumatic hydraulic spring, which provides to the mooring line the needed additional springiness. The other innovation is in the method and means for simplification and expedition of the process of delivery and installation wind turbines foundation by using specialized Catamaran Foundation Installer and Transfer Pier.

1 . A foundation for offshore wind turbine and the means for transporting it from transfer pier, to the destination site, installing and anchoring it there, comprising:
 a said foundation for offshore wind turbine, which is based on the concept of Compliant Guided Tower, consisting of Tower and three Mooring Lines attached to three Anchors,   a said transfer pier consisting of upper structure, supported by piles, along said upper structure are positioned at least two carriages that moves on rails along the said upper structure,   a said means for transporting said tower assembled with said mooring lines to the destination site, installing and anchoring them, are in the form of Catamaran Foundation Installer, which includes Lead Catamaran and Support Catamaran.   
     
     
         2 . The foundation for offshore wind turbine according to  claim 1 , wherein said foundation for offshore wind turbine, which is based on the concept of Compliant Guided Tower, consisting of Tower and three Mooring Lines attached to three Anchors, comprising:
 Tower, consisting of upper and lower parts;
 said upper part of said Tower includes:
 a connector, through which said wind turbine is connected to said Tower and which contains inside it a shock absorber that will reduce impact during the process of lowering said wind turbine on the said Tower of said Foundation for offshore wind turbine; 
 a landing platform, 
 three receivers for hydraulic cylinders, that would tension said mooring lines during the process of said foundation for offshore wind turbine installation; 
 three sets of clamps with guides for fixing said mooring lines to said tower at the end of the process of installing said foundation for offshore wind turbine; 
 a bulkhead inside said tower upper part that forms buoyancy force that keeps said tower floating vertically during the processes of its installation an anchoring; 
 a pair of journals serving as the lifting points and as a rotating axis for said tower during the processes of its lifting and installation; 
 
 the said lower part of said tower includes:
 lifting gear; 
 foundation base, which is in the form of a typical suction bucket that consists of cylindrical body and the upper plate on which are placed vacuum pump and the universal joint through which said foundation base is connected with said tower lower part; as the innovative feature the said foundation base includes scorching prevention ring with upper and lower position stoppers. 
 
   three said Mooring Lines each having upper end engaged with said clamps on said upper part of said Tower and their lower ends engaged with hydro-pneumatic springs located on the top of said anchors;   said three Anchors, based on a typical design of suction bucket, each having a cylindrical body and a top plate, which supports vacuum pump and said hydro-pneumatic spring;   said hydro-pneumatic spring consists of:
 central hydraulic cylinder with piston and rod, to which the lower end of said Mooring Line is connected; 
 several vessels-accumulators, located around said central hydraulic cylinder, each containing mix of gas in their upper part and liquid in their lower part; 
 said lower parts of said vessel-accumulators are interconnected by fixed conduit with upper part of said central hydraulic cylinder; 
 a common base on which said central cylinder and said several vessels-accumulators are assembled; 
 a said common base is connected to upper plate of said suction bucket type foundation through a chain type connection. 
   
     
     
         3 . The foundation for offshore wind turbine according to  claim 1 , wherein said means for transporting said Tower assembled with said mooring lines to the destination site, installing and anchoring them, comprising:
 a Catamaran Foundation Installer includes Lead Catamaran and Support Catamaran, which are interconnected by pair of towing lines, each towing lines by one end is fixed to said Support Catamaran and other end is winded up on a towing winch on the said Lead Catamaran, thus allowing to control the distance between said Lead Catamaran and said Support Catamaran;   a said Lead Catamaran includes:
 two pontoons, 
 a front and rear cross frames, 
 a deck interconnecting cross frames, 
 a gantry crane consisting of a traveling frame with two crane carriages, each of said crane carriage has heavy lift hoist arrangement and auxiliary winch for handling said vacuum pumps on said Anchors; 
 a pair of horizontal guides, 
 a pair of Tower centering and grabbing arrangement, each consisting a base to which, through hydraulic cylinders are attached two arms, which can center and grab said Tower, each said arm has on its end a contact roller; 
   a said Support Catamaran includes:
 two pontoons; 
 two mooring arrangements consisting of a bit and engaging bar, which includes a slot and a stopper; 
 a cross-frame, which is fixed to said pontoons through four legs and having in its middle a Quick Connect-Disconnect Arrangement consisting of: 
 a frame, a which is positioned on the top of said cross-frame, 
 a sliding column inside of said frame is suspended through a hoisting line from a said winch, on the lower part of said sliding column is positioned hydraulically operated engager consisting of: 
 a base, a pair of pivoted hooks and a pair of hydraulic cylinders. 
   
     
     
         4 . A method of lifting completely assembled Tower from Transfer Pier, transporting it to destination site, installing and anchoring it there, comprising the following steps:
 the Lead Catamaran lifts up the upper part of said completely assembled Tower from transport carriage on Transfer Pier using Gantry Crane both crane carriages;   the Lead Catamaran pulls assembled Tower, which lower part is supported by transport carriage, along the Transfer Pier, when Quick Connect-Disconnect Arrangement on the Support Catamaran aligns with lifting gear then the Quick Connect-Disconnect Arrangement engages with lifting gear;   after the transport carriage moves out of contact with Tower and by this transferring all weight of Tower to the Lead Catamaran and to Support Catamaran, the caravan consisting of Main and Support Catamarans interconnected by Tower floats to the destinations site.   at the destination site the Support Catamaran disconnects from the Tower, which in a free fall would be rotated around the pivot journals on the upper part of the Tower and finally would come into vertical position;   when Tower reaches vertical position the crane carriages on the Gantry Crane would lower Tower further down until its foundation, which is in the form of a suction bucket, would penetrated seabed on a some distance;   by the following steps the vacuum pump on the foundation would be actuated and by this it would create a conditions under which under hydrostatic force the foundation would be fully pressed into seabed;   since the Tower is connected with foundation through universal joint and its upper part would not be flooded the Tower would float in vertical position and would be capable of withstand wind and wave actions, and by this allowing the Catamaran Foundation Installer placing Anchors, which are already preattached to Tower through mooring lines, around the floating Tower;   after all Anchors, which are suction buckets, are firmly entrenched into seabed the Catamaran Foundation Installer gets back to Tower and pretension simultaneously all three mooring lines through the preinstalled Portable Hydraulic Cylinders;   after the pretension of mooring lines would be completed and Tower would be in the exact vertical position the mooring lines would be clamp to the Tower by hydraulically actuated wedges;   as the final step of foundation installation the preinstalled Portable Hydraulic Cylinders would be removed from the Tower.