Mooring renewable energy systems
A mooring system for a floating electric power producing unit such as a wind turbine or a wave energy converter comprises a buoyant element held beneath the surface and a swivel supported by the buoyant element. The swivel comprises a static part that is held against angular movement about an upright axis and a rotating part that is movable angularly relative to the static part about the upright axis. A mooring link extends between the power producing unit and a mooring point supported by the buoyant element. A conductor link extends between the power producing unit and a connector supported by the buoyant element. The mooring point and the conductor link are movable angularly about the upright axis together with the rotating part of the swivel. Angular movement of the mooring link about the upright axis drives corresponding angular movement of the conductor link about the upright axis.
1 . A mooring system for a floating electric power producing unit, the system comprising:
an upwardly elongate sub-surface buoyant element comprising a central longitudinal spine supporting a stack of modules providing buoyancy extending upwardly toward an upper end of the buoyant element from a lower end of the buoyant element;
a foundation;
an upright tensile member extending between the lower end of the buoyant element and the foundation, the tensile member being held in tension by upthrust of the buoyant element;
a swivel supported by the buoyant element, the swivel comprising a static part that is held to resist angular movement about an upright axis and a rotating part fixed to the buoyant element that is movable angularly relative to the static part about the upright axis;
a mooring point supported by, and in fixed angular relation to, the buoyant element;
a mooring link extending between the power producing unit and the mooring point;
a connector supported by the buoyant element; and
a conductor link extending between the power producing unit and the connector, wherein the conductor link is in fixed angular relation to the buoyant element;
such that rotational movement about the upright axis of the mooring point, the buoyant element, the rotating part of the swivel and the conductor link are coupled, so that angular movement of the rotating part of the swivel and the conductor link about the upright axis is driven by angular movement of the mooring link and the mooring point about the upright axis, and
wherein the mooring point is vertically separated across the height of the buoyant element from the point of connection between the conductor link and the connector.
2 . The mooring system of claim 1 , wherein a lower end of the conductor link is attached to the buoyant element.
3 . The mooring system of claim 1 , wherein a lower end of the conductor link is attached to the rotating part of the swivel.
4 . The mooring system of claim 2 , wherein the lower end of the conductor link is supported by an arm that extends radially from, and is movable angularly about, the upright axis.
5 . The mooring system of claim 1 , wherein the mooring point is on the buoyant element.
6 . The mooring system of claim 1 , wherein the mooring point is on the rotating part of the swivel.
7 . The mooring system of claim 1 , wherein the swivel defines an interface between the buoyant element and the tensile member and enables angular movement of the buoyant element relative to the tensile member about the upright axis.
8 . The mooring system of claim 1 , wherein the mooring point is at the lower end of the buoyant element.
9 . The mooring system of claim 2 , wherein the mooring point is at the upper end of the buoyant element.
10 . The mooring system of claim 1 , wherein the connector is accommodated within the spine.
11 . The mooring system of claim 1 , wherein the connector extends downwardly from the conductor link to an export cable at the lower end of the buoyant element.
12 . The mooring system of claim 11 , wherein an upper end of the export cable is in fixed relation to an upper end of the tensile member.
13 . The mooring system of claim 1 , wherein the connector extends from the upper end to the lower end of the buoyant element.
14 . The mooring system of claim 1 , wherein the conductor link joins to the buoyant element at an intermediate level between the upper end and the lower end of the buoyant element, and the connector extends from that intermediate level to the lower end of the buoyant element.
15 . The mooring system of claim 14 , wherein the buoyancy of the buoyant element extends above and below the intermediate level.
16 . The mooring system of claim 1 , wherein the connector comprises a sinuous or coiled portion or a sliding link for enabling relative angular movement of adjoining parts of the connector in response to angular movement of the conductor link about the upright axis.
17 . The mooring system of claim 1 , wherein the mooring point is vertically separated across the height of the buoyant element from the point of connection between the conductor link and the connector by at least half of the height of the buoyant element.
18 . The mooring system of claim 1 , wherein the conductor link is joined to the connector at a level above the mooring point.
19 . The mooring system of claim 1 , wherein a vertical clearance is defined in water between the buoyant element and an underside of the power producing unit.
20 . The mooring system of claim 1 , wherein the mooring link and/or the conductor link hang in a catenary shape between the buoyant element and the power producing unit.
21 . The mooring system of claim 1 , comprising more than one conductor link, more than one mooring link, more than one mooring point and/or more than one power producing unit.
22 . The mooring system of claim 1 , wherein the mooring point is offset angularly from the conductor link about the upright axis.
23 . An offshore electric power generation installation comprising at least one mooring system as defined in claim 1 .