WindSurf- A self-starting, active-pitch, vertical-axis wind turbine

Conventionally designed wind turbines only operate efficiently in steady, uninterrupted air. However, most users want to access wind in urban areas or near industrial units where the nature of the wind is more turbulent and swirling. Conventional designs do not work efficiently with the swirling, variable nature of wind at such sites. In this project Swift Energy present a radical re-design of a vertical axis wind turbine, with key technological improvements that will allow efficient operation in small-footprint, urban sites. Such sites have the added advantage that they are close to consumers, minimising transmission losses. WindSurf is a vertical axis, active pitching wind turbine. Swift's patented control technology uses servomotors to continually alter blade pitch, which allows self-starting in wind speeds as low as 3m/s, and optimised energy capture in free and turbulent wind streams. Edinburgh's role in this project is to produce an optimised design of the electrical generator for the WindSurf rated at 16kW, taking into account the environment in which it will be operating. A direct drive generator will be used to eliminate the gearbox, which will improve reliability and efficiency. Both of these contribute to LCOE: reliability through increased availability and reduced OPEX; and improved efficiency will enhance annual energy yield.

An air-cored permanent magnet generator will be designed and built that is optimised for the structure of the Swift wind turbine. In order to achieve such an optimised design an integrated design approach is required, which links electromagnetic design, with structural design and thermo-fluid design. Edinburgh has built up 10 years of experience in the integrated design of direct drive permanent magnet air-cored generators for wind and marine renewable energy applications. Air-cored machines eliminate undesirable magnetic attraction forces that try to close the gap, and thus this topology benefits manufacture, assembly and structural design. A vertical axis wind turbine allows the electromagnetic design of the machine to have a large diameter, out near the blades. A large diameter will result in high airgap velocity and thus have a positive impact on torque density (Nm/kg), reducing the amount of active material, which is the most expensive part of the machine. A novel structural arrangement will be developed for integration into the turbine, which where possible makes best use of the existing structural material, again to minimise material usage and thus cost. A modular design approach will be adopted to ease manufacture and assembly of the generator, but also to make O&M easier. By positioning the generator close to the blades, we will investigate we will investigate methods of "scooping" air from the turbine onto the generator to assist with cooling. Effective cooling will benefit the torque density and the overall performance of the machine. Numerical modelling tools will be used in the design process, such as ANSYS for structural analysis, StarCCM for thermo-fluid analysis, and Infolytica for electromagnetic design. An existing analytical design tool will be refined based on the structural and CFD modelling in order to assist SWIFT in the future design and production of their turbine. Multi-body modelling using SIMPACK will be combined with structural modelling to investigate the impact of environmental loads on the generator in terms of airgap deflection. Once the design is finalised, the machine will be built under subcontract to Fountain Design Ltd, with whom we have worked in the past to build prototype generators. The machine will be tested at the University of Edinburgh on its wind-emulator test rig to verify performance and the design tools developed. A thorough integrated design approach with manufacturing and production techniques in mind supported by laboratory testing will ensure that SWIFT can move towards commercialisation.

Swift TG Energy are aiming to exploit previously untapped wind resources through their game-changing vertical-axis wind turbine technology, WindSurf, which is able to generate power at lower wind speeds compared with conventional turbines. Swift have identified more than 300 potential sites local to their base and have estimated around 30,000 sites in the UK which could utilise WindSurf to generate power where horizontal-axis wind turbines would be deemed unsuitable. This represents a significant market in the UK for small-medium wind turbines. In this project, Edinburgh are developing an electrical generator using an integrated design approach that reduces the cost of manufacture and O&M costs. The generator has high efficiency at variable speed and therefore ideally suited to urban sites with lower turbulent wind speeds. The WindSurf turbine technology coupled to Edinburgh's generator technology will be best positioned to exploit urban sites previously deemed unviable for wind power generation. Swift aim to lead the market in a new generation of turbines and aim to grow turnover to >£100m. The work in this project brings WindSurf closer to commercialization, which will subsequently help to secure additional sales revenue for the industrial partners, and help to grow and sustain UK wide employment for partners in addition to knowledge transfer for all project partners.

Coupled with energy storage, WindSurf can also be a solution to intermittency and costly on-site generation, as well as expensive grid upgrades or the import of fossil fuels. There is an increasing number of small businesses and community groups looking to generate their own secure renewable electricity. The development of WindSurf through this project bring this scenario closer to reality. There is a direct social benefit in increasing security of supply by being able to generate over a wider range of wind speeds and reducing the cost of electricity using Edinburgh's generator technology. The bigger picture is that the work will make a significant contribution to the provision of clean, reliable, and low-cost energy in sites with lower wind speeds and also small businesses and communities living off-grid or those with a weak grid connection. It will improve quality of life and public empowerment through energy independence, behavioural and attitudinal changes towards off-grid sustainability, and also help underpin the autonomy of rural/isolated communities.