Principles of the Sway system

8 years of intensive advanced dynamic simulations and engineering has enabled us to discover nature's own secrets of how to make our technology feasible both technically and economically.





SWAY AS /  C. Sundtsgt. 51 / 5004 Bergen / Norway / Phone: +47-55220900 /
The patented SWAY system is based on a floating tower which extends far below the water surface. The tower consists of a floating pole with ballast in the lower end, similar to a floating bottle. The tower, which is filled with ballast, has its center of gravity located far below the center of buoyancy of the tower. This gives the tower sufficient stability to resist the large loads produced by the wind turbine mounted on top of it. The floating tower is either anchored with a universal joint (articulation) directly to a single seabed anchor in as little as 55m water depth, or at larger water depths, by using a single pipe between the tower and the single anchor. Our patents for the floating pole also include using several slack mooring lines as opposed to our preferred single anchor solution. One non-exclusive license agreement has already been sold for the slack mooring/upwind version of the technology. The turbine can be mounted both upwind and downwind on the tower. However, when the wind hits the rotor the tower is tilting some 5-8 degrees. By tilting the rotor the opposite way which is made possible by placing the rotor downwind of the tower the rotor is kept perfectly aligned with the wind when the tower tilts. When the wind changes direction, the entire tower turns around a subsea swivel at the bottom of the tower by individually pitching the blades to create the necessary yawing moment (i.e. no yaw motors are required) This solution with a passive subsea yawing swivel and the turbine fixed to the tower in one position makes it possible to reinforce the tower on the opposite side of the rotor with a patented tension rod system similar to wire stays on a sailboat mast. Due to the resulting reduction of stresses in the tower, the same tower and anchor system (with a combined total steel weight of only 1200te for a 5MW installation) is capable of carrying a turbine almost twice as big compared to the upwind oriented rotor version. This, in turn, greatly enhances the total economy and makes it possible to deliver power to shore at a similar Cost of Energy as for shallow water wind farms on fixed foundations. To date, we do not know of any other floating foundation systems which can claim the same. The SWAY® systems will be operating in some of the worlds roughest offshore locations, and has been designed to satisfy the strictest regulations for offshore wind turbines and installations. For example, our floater has been designed to withstand impact with a once in a 100-year wave of over 30 m and have a fatigue lifespan of over 20 years. SWAY A/S has, together with its engineering partners, developed advanced calculation software to simulate the loads and dynamics of the entire floating system. In addition, Garrad Hassan & Partners Ltd in Bristol (UK) has carried out independent dynamic analyses of the SWAY system. Sway is using DnV for the certification of the Sway system.