Brian Hand, Andrew Cashman, December 2017
Large-scale floating vertical axis wind turbines (VAWTs) are an attractive and economical solution to harness superior offshore wind resources in deep water locations. This paper presents the conceptual design of a VAWT for this application using a developed aerodynamic modelling strategy. A comprehensive examination of several critical VAWT design parameters was undertaken which included the turbine solidity, blade number, blade aspect ratio and non-prismatic strut design.
This study identified a low solidity turbine (σ = 0.263) gave the best aerodynamic performance, while a two-bladed VAWT design is recommended. The results also indicated a blade aspect ratio in the range 10 ≥ H/c ≥ 20 gives favorable performance. Finally, the geometrical details and operating specifications for a 5 MW VAWT design are presented.
Nicolas Parneix, Rosalie Fuchs, Alexandre Immas, Frederic Silvert, Paul Deglaire, 2016
Improving the performance of Vertical Axis Wind Turbines is the key to make VAWTs commercially successful. Scientists have investigated several interesting concepts for that purpose: increasing the swept area, especially to the limit the losses due to 3D effects, or using flap and pitch systems to control the flow around the blades. Nenuphar, with the Twinfloat concept, propose to take advantage of all these concpets combined with an aerodynamic effect called counter-rotating effect. The turbine is made of two 2.5MW VAWT on only on floater, to reach a rated power of 5MW. The proximity of the two rotors generates a contraction of the streamtubes that flow in the area between the rotors, thus increasing the air flow rate going through both the swept areas and thereby the performance of the VAWT.
Paul Dvorak, Windpower Engineering Development, 18 April 2016
There are still many advantages to Vertical Axis Wind Turbines (VAWTs) over the conventional three-blade designs, especially when considering offshore duty. Engineers at Sandia National Labs are working on models for an offshore VAWT and offered this mid-project report. "The goal of the project is to advance the rotor technology of large offshore vertical axis wind turbine from concept to lab-scale prototype stage through four major research thrusts,” says project supervisor D. Todd Griffith.
Sandia National Laboratories
This project seeks to advance large offshore vertical-axis wind turbine (VAWT) rotor technology from concept to lab-scale prototype stage through four major research thrusts; innovative aeroelastic rotor conceptual design, deep-water system design and cost analysis, rotor material and manufacturing strategies, and subscale rotor prototype design & testing.
Vrije Universiteit Burssel and NENUPHAR work together on R&D projects related to the performance of vertical-axis wind turbines. Together they are performing tests to compare performance of VAWTs and HAWTs of similar size and power rating. They believe they would be able to provide a substantial cost reduction for offshore VAWTs.
Michael Borg, DTU Wind Energy, Technical University of Denmark 1 October 2015
Presentation by Michael Borg discussing the potential life-cycle cost reductions for offshore floating wind energy. He discusses the offshore wind life cycle value chain, the floating wind turbine system, alternative concepts, improved design tools for cost reduction and case studies.
The SKWID is a floating wind and current hybrid power generation system capable of converting to inexhaustible ocean energy sources into abundant power. By harvesting renewable energy from never-ending currents and strong and continuous ocean winds, the pioneering technology of the SKWID provides cost-effective power generation with minimal environmental impact.
Christos Galinos, Torben Larsen, Helge Madsen, Uwe Paulsen, SciVerse ScienceDirect, 2016
Multi megawatt Vertical Axis Wind Turbine (VAWT) seem to be re-gaining a general interest in the wind energy sector as an alternative to Horizontal AxisWind Turbine (HAWT). Current guidelines for certification of wind turbines as e.g. IEC 61400-1 ed.3  covers any type of onshore wind turbine. However, as it has mainly been used for HAWTs during the development it is a bit uncertain whether the load-cases are also representative for VAWTs. This paper describes the results from the study on the applicability of the IEC 61400-1 ed.3 minimum design requirements in the case of an onshore Darrieus VAWT. It reveals potential critical design aspects of VAWT emerging from the Design Load Case (DLC) simulations. A comparison of basic DLCs is made between an equivalent rated power HAWT and the Darrieus wind turbine, as well. The study is based on aeroelastic simulations in time domain using the HAWC2 code, which has been validated for both HAWTs and VAWTs.