The Drop Keel Concept: an Assembly Focused Solution to Commercial Deep Water Floating Wind Turbine Development

Wind is proving to be a commercially viable source for generating electrical power. The UK is exploiting this opportunity with its consistent wind resource using wind turbines fixed to the seabed along its coastline up to 50 metres in depth.

Other coastal regions around the world are considering offshore wind turbine projects and, despite some being too deep for fixed seabed wind turbines, floating wind turbines may provide the solution.

18 miles offshore Peterhead, Scotland, such a test program is in operation. Known as Hywind Scotland, the project deploys five interconnected floating turbines supplying sufficient electricity to power 20,000 UK households.

The next step in development is to design floating foundation structures with commercial potential for mass production. Test level projects may then be scaled up to develop floating windfarms deploying hundreds of interconnected units supplying commercially viable electricity to the world's major coastal cities.

Designs for the floating bases upon which the turbines stand remain a challenge. The Hywind floating bases must be assembled in deep water Norwegian fjords and specialist heavy lift floating cranes for construction which add to the project cost. Alternative floating base designs present different construction challenges such as large widths that make assembly and launch difficult using facilities found in typical ports. Also, the UK currently has to rely on intellectual property rights owned in the US, Norway, France and Japan to take advantage of this new technology.

CPDSYS Ltd is investigating how to optimise floating wind turbine foundation design and intallation. It has developed the Drop Keel concept, a compact, shallow draft design which Atkins Engineering has analysed and identified as possessing operational performance and motion characteristics acceptable for commercial wind turbine operation. Scale model tank tests are planned with Strathclyde University for a 10MW capacity unit followed by further analysis to investigate the relationship between wave motion, aerodynamic performance and motion control systems. The objective is to produce a full scale Drop Keel foundation design protected by UK Intellectual property rights that not only supports renewable power opportunities in the UK's deeper coastal waters but also meets the demands of a global export market.

CPDSYS is also investigating how the Drop Keel concept may support marginal deep water oil and gas fields by providing a source of electricity in remote marine locations that could assist with recovery of hydrocarbons similar to the way that pump jacks (nodding donkeys) power onshore oil wells.