Portal frame platform and construction method for large offshore wind turbines

A method for constructing a portal frame platform, comprising

• a plurality of elongate tubular legs extending vertically each comprising an upper section, a mid-section and a lower section;
• a horizontal deck comprising a plurality of circular sleeves equally spaced radially from a center, a base section located at the center and a plurality of horizontal girders each coupled to the base section at one end and each of the circular sleeves at a second end, wherein the circular sleeves having a diameter greater than a diameter of the elongate tubular legs;
• a wind turbine system comprising a wind tower, a nacelle, and a plurality of rotor blades;
• a plurality of suction caisson foundation piles;
• a plurality of link beams;
• a plurality of lateral guides;
• and
• the method comprising:
• STEP I, connecting the suction caisson foundation piles in an upright configuration with the link beams at a top forming a sub-assembly of a symmetrical pattern onshore, and
• lifting the sub-assembly into a water at a quay of an assembly yard and having the sub-assembly stand on a seabed with the top above a waterline;
• STEP II, lifting the horizontal deck onto the top of the sub-assembly with each of the circular sleeves directly above each of the suction caisson foundation piles and the base section at a center of the symmetrical pattern, and coupling the horizontal deck with the sub-assembly by sea-fastenings above the waterline;
• Step III, lifting at least one elongate tubular leg vertically onto the top of the sub-assembly through an opening of the circular sleeve of the horizontal deck on a distal side from the quay and coupling a bottom of the elongate tubular leg to a top of the suction caisson foundation pile on the distal side;
• Step IV, lifting the wind tower vertically and coupling a bottom of the wind tower to a top of the base section of the horizontal deck;
• Step V, lifting at least one elongate tubular leg vertically onto the top of the sub-assembly through an opening of the circular sleeve of the horizontal deck on a proximal side from the quay and coupling a bottom of the elongate tubular leg to a top of the suction caisson foundation pile on the proximal side;
• Step VI, installing each of the lateral guides onto a top of each of the elongate tubular legs;
• lifting and coupling the nacelle to a top of the wind tower;
• lifting and coupling the rotor blades to the nacelle.

A portable frame platform, comprising:

• a plurality of elongate tubular legs extending vertically each comprising an upper section, a mid-section, and a lower section;
• a horizontal deck comprising a plurality of circular sleeves equally spaced radially from a center, a base section located at the center and a plurality of horizontal girders each connecting the base section at one end and each of the circular sleeves at a second end, wherein the circular sleeves having a diameter greater than a diameter of the elongate tubular legs, and each of the elongate tubular legs is concentrically located in an inside of each of the circular sleeves with an annulus space;
• a wind turbine system comprising a wind tower, a nacelle, and a plurality of rotor blades;
• a plurality of driven piles;
• a plurality of pile adaption sections each coupled to a bottom of each of the elongate tubular leg concentrically or with an offset;
• a plurality of mud mats each coupled to a bottom of each of the pile adaption sections;
• a plurality of lateral guides each coupled to a top of each of the elongated tubular legs;
• a quayside assembly configuration in a relative shallow water at a quayside of an assembly yard, wherein each of the elongate tubular legs having substantially more than one half of a length extending vertically upward above a waterline without horizontal or diagonal bracing members between the elongate tubular legs, wherein the pile adaption sections with the mud mats standing on a seabed coupled to the horizontal deck above the waterline by temporary sea-fastenings, and the lower section of each of the elongate tubular legs is concentrically located in an inside of each of the circular sleeves of the horizontal deck, and the base section of the horizontal deck is vertically coupled to a bottom of the wind tower of the wind turbine system;
• and
• an in-service configuration in a relative deep water at an offshore site, wherein each of the elongate tubular legs having substantially more than one half of the length extending vertically downward below a waterline without horizontal or diagonal bracing members between the elongate tubular legs, wherein the driven piles each having a lower section embedded into a seabed and an upper section above the seabed concentrically coupled to each of the pile adaption sections attached to the elongate tubular legs, and the upper section of each of the elongate tubular legs is concentrically coupled to the inside of each of the circular sleeves of the horizontal deck above the waterline forming a rigid connection, and the base section of the horizontal deck is vertically coupled to the bottom of the wind tower of the wind turbine system.