Concept of multi rotor array for deep off-shore wind turbine

Coastal regions in Norway, Spain, Portugal, Japan or the United States comprise over large water depths (> 50 m) making the installation of typical bottom-fixed offshore wind turbines very difficult and expensive. Floating offshore wind turbines might be a more economic option in order to exploit the high energy potential contained in the offshore winds. According to EU-funded ORECCA R&D project these locations were all identified as Level 1 resource capacity with wind velocities ranging 8-11 m/s at 10 m a.s.l. (above sea level) [1]. Different concepts of floating support structures have already been investigated as for the first HAWT prototype, Statoil’s “Hywind” spar buoy turbine, which has been operated off the cost of Norway since 2009 [2]. However, rising costs of operation and maintenance (O&M) as well as manufacturing of large turbine rotors and generators already seriously impair and will impair this branch of energy engineering in the years to come [3]. To address these problems the paper presents a concept of an innovative floating off-shore multi-rotor array turbine.