Swedish company SeaTwirl has been granted a U.S. patent for its dynamic wind turbine.
The floating turbine can fold its blades to become flat and can be placed where there is risk of hurricanes, cyclones or typhoons. A regular turbine dimensioned to withstand such extreme winds would be a lot more expensive to build, says the company.
SeaTwirl uses a vertical axis wind turbine with a tower that is placed on an underwater structure that reaches deep below the surface. The underwater structure consists of a buoyancy element and, at its lowest point, a keel. The wind turbine, tower and underwater structure are fixed together and rotate as a single unit. The water carries the full weight of the structure, and when the wind turbine captures wind energy the structure is stabilized by the keel much like on a sailing boat.
The generator is placed low on the turbine but above the water line, giving it a low center of gravity. This also facilitates boat access for maintenance. The placement of the wind turbine on the floating underwater structure means the bearings don’t need to carry the weight of the wind turbine. This is unique, says SeaTwirl, and implies that the bearings will be exposed to lower loads than other wind turbines.
SeaTwirl use a vertical wind turbine which can absorb wind energy independent of wind direction. There is no need for a yaw system for the turbine to face the wind as required by traditional horizontal axis wind turbines. A pitching mechanism to turn the rotor blades is not needed either. Therefore, a vertical wind turbine contains fewer moving parts which imply lower maintenance costs and more available operating hours, says the company.
SeaTwirl launched and installed its 30kW SeaTwirl S1 prototype turbine at a site in Lysekil, Sweden, in 2015. The device had endured all weather conditions including heavy storms, and the company is now in the process of developing a full-scale unit – SeaTwirl S2 – a 1MW turbine planned to be completed by 2020.
The company has seven other patent applications pending in different jurisdictions.