Off shore wind energy installation foundation system

An offshore structure comprising:

• a foundation system including three or more suction buckets configured to be installed in the seabed, the three or more suction buckets being disposed at corners of an imaginary polygon, viewed in top view, to act as the foundation system or a part of the foundation system to carry an upper offshore structure supported on the seabed, the three or more suction buckets carrying a connector body configured to carry a payload;
• and
• a single vertical tower disposed centrally between the three or more suction buckets, seen in top view, formed by a single tube and made of steel, the single tube carrying a gondola of a windmill at a top thereof, the gondola having rotor blades at least 20 meters above the local water level, the single vertical tower resting on top of the foundation system and the connector body resting on top of all of the three or more suction buckets, the tower being disposed completely above an underside of the connector body, the tower being hollow and having a wall thickness between 20 and 200 millimeters, the tower being above the water level, prismatic over its entire length and being rigidly mounted to the connector body,
• wherein the offshore structure is made of steel and configured as an offshore wind energy installation of at least 9 MW extending upwards from the seabed at an offshore location where the seabed is at least 10 meters below the local water level, the offshore wind energy installation configured to be connected with an electricity cable run on land to carry the offshore-generated electricity,
• the connector body has a star shape, seen in top view, the connecting body having the same number of external corners as the number of the three or more suction buckets, the connector body having a plurality of arms extending from a central part of the connector body radially outwardly to each of the respective suction buckets, all of the plurality of arms of the connector body extending from the central part of the connector body radially outwardly in a horizontal direction or at an angle of less than 20 degrees relative to the horizontal direction to each of the respective suction buckets, the external corners being formed by the radial outwardly-extending arms which provide the star shape, each of the suction buckets is a vertical steel cylinder having a wall thickness of at least 3 millimeters and a diameter between 10 and 15 meters, each of the vertical steel cylinders being closed in an airtight manner at a top end by a top plate, each of the vertical steel cylinders being open and extending into the seabed at a lower end thereof that is in fluid communication with a suction space inside the respective suction bucket, the vertical steel cylinders being in the seabed by hydraulic underpressure generated in the suction space inside the respective cylinder, the hydraulic underpressure being generated by an external suction pump connected at the top plate provided with a suction port with a suction valve in fluid communication with the suction space, the vertical steel cylinders being penetrated into the seabed, the three or more suction buckets having a mutual spacing of at least 5 meters and providing a statically balanced or overbalanced support for the connector body,
• the respective suction buckets being attached thereto at ends of the arms, the connector body having a flat underside and being a completely closed body and being completely hollow, the connector body having a closed, monocoque construction having external walls that carry the loads,
• the cross-section of the arms of the connector body being box-shaped with an angular cross-section, the arms of the connector body extending horizontal and being made from flat plates, four flat sides including a top side, a bottom side, a left side, and a right side of each of the arms connect to each other via angular corners,
• the tower, the connector body, and the suction buckets being rigidly mounted so that all loads including vertical and horizontal loads, bending moments, and torsion are transmitted from the tower to the three or more suction buckets via the connector body, the the tower is attached to the connector body with a beam of which a single longitudinal end is fixedly wedged so that the tower extends vertically upwards from the connector body as a cantilever beam, the tower being above the connector body with respect to the seabed, the tower being free from structures that transfer mechanical loads from the tower onto the seabed,
• the foundation system extending a maximum of 15 meters above the local seabed and being disposed completely below the highest point of the connector body and only in the area downwards from the highest point of the connector body extend structures that are to the tower attached and transfer all loads, from the tower to the seabed.