The hypothesis of this project is that a new wind turbine concept developed specifically for offshore application has potentials for better cost efficiency than existing offshore technology. Based on this hypothesis the objectives are: i)to explore the technologies needed for development of a new and simple floating offshore concept with a vertical axis rotor and a floating and rotating foundation, ii)to develop calculation and design tools for development and evaluation of very large wind turbines based on this concept and iii)evaluation of the overall concept with floating offshore horizontal axis wind turbines.Upscaling of large rotors beyond 5MW has been expressed to have more cost potentials for vertical axis wind turbines than for horizontal axis wind turbines due to less influence of cyclic gravity loads. However, the technology behind the proposed concept presents extensive challenges needing explicit research, especially: dynamics of the system, pultruded blades with better material properties, sub-sea generator, mooring and torque absorption system, and torque, lift and drag on the rotating and floating shaft foundation. In order to be able in detail to evaluate the technologies behind the concept the project comprise: 1) numerical tools for prediction of energy production, dynamics, loads and fatigue, 2) tools for design and production of blades 3) tools for design of generator and controls, 4) design of mooring and torque absorption systems, and 5) knowledge of friction torque and lift and drag on rotating tube. The technologies need verification, and in the project verification is made by: 6) proof-of concept testing of a small, kW sized technology demonstrator, partly under real conditions, partly under controlled laboratory conditions, 7) integration of all technologies in demonstration of the possibility of building a 5MW wind turbine based on the concept, and an evaluation of the perspectives for the concept.