Offshore Floating Structures Suitable for Mounting Wind Turbines
Over the last forty years or so, the offshore oil and gas industry has designed and developed various floating structures to support hydrocarbon production platforms. Most of these designs are suitable as support structures for offshore wind turbines; the more popular types are listed below;
These structures are comprised of hulls fabricated from large horizontal pontoons onto which vertical steel columns are welded. The columns and horizontal pontoons are interconnected and braced by a lattice of tubular steel supports.
The structures are held to the seabed by anchors, whose chains are maintained in a catenary mooring mode by winches situated on the main deck.
Various structures have been examined for potential use as floating supports for offshore wind turbines, including a multi wind turbine support. However, this type of semi-submersible would require automatic weathervaning, controlled by satellite navigation that would turn the structure into the wind without interfering with the mooring system.
Semi-submersibles can be self-propelled using their own marine diesel engines; the non-propulsion type is towed to the required location.
Semi Submersible Production Platform for Offshore Oil and Gas
The offshore oil and gas industry has used semi-submersible floating structures for many years both as drilling rigs and production platforms, operating in depths of water of up to 6,000 feet.
- Tension Leg Platform (TLP)
This is a floating platform fixed by high-tensile solid steel round tie rods, attached to a specially designed template piled and grouted onto the subsea bedrock. The tie rods are kept in tension by overhead winches located under the main deck. TLPs can operate in depths of 6000 feet.
The spar is just a large floating round hull that can be fabricated from steel or concrete. It has several sections built inside the hull which serve as ballast and oil storage tanks, being tethered to the seabed with conventional chains and winches. Spars can also operate in water depths of 6000 feet.
The Petronius Spar hydrocarbons production platform, weighing 45000 tons, is currently operating at a depth of 1750 feet in the Gulf of Mexico.