Mighty wings for wind power

A  new wind turbine that promises to advance the harnessing of offshore wind energy through its ruggedness, extra stability and easier access for maintenance has been given the go-ahead.The newcomer could truly bring a wind of change to the public perception of huge windmill-like structures cluttering the seascape. No longer is the structure just a gigantic propeller atop a cylindrical tower, but instead it is a pair of V-shaped arms up to 120 metres high with four rigid 'winglets' along their length.

The wings act as aerofoils with the wind generating the lift necessary to turn the whole structure at about three revolutions a minute, enabling the turbine at the foot of the arms to produce up to 9 MW of electricity. By contrast, today’s conventional turbines generate an average of 2 MW.

The Nova turbine (short for novel offshore vertical axis) has been invented by aeronautical engineer David Sharpe and developed by the UK Wind Power company from Blyth, north-east England.

The firm has already carried out wind tunnel tests on a small-scale version and the results suggest predicted power outputs can be achieved. The new design is said to work in a similar manner to a sideways water-wheel. One commentator said the structure, with its arms linked by steel cable stays, resembled a huge rotary washing line. It has been engineered to overcome the problems that inhibit the present generation of rotor-driven horizontal-axis turbines.

The problem with today’s horizontal-axis turbines is that they are top heavy because the rotors and generators are mounted at the summit of the tower where gearboxes also have to be located to turn the rotors into the wind.

The new design of spinning vertical-axis machine is more efficient in being able to draw wind from any direction and — with the turbine and other mechanisms located at ground level — the structure is bottom heavy and therefore much more stable and easy to maintain.

Furthermore, the V-wing concept faces fewer constraints on scaling up the size of the turbines and this is expected to lead to larger-output offshore wind machines that would cut the number needed.

A totally UK-based consortium now formed by Wind Power to exploit the new technology brings together world-leading research and development groups from the three universities of Cranfield, Sheffield and Strathclyde as well as QinetiQ, one of Europe’s top science and technology companies.

Also involved is the Centre for Environment, Fisheries & Aquaculture (Cefas) with all the project’s inputs being managed and led by OTM Consulting, a specialist offshore energy firm based near London.

Project Nova is one of four developments being backed at a cost of some 20 million pounds by the UK’s recently established Energy Technologies Institute (ETI), a partnership between the government and six global industries represented by BP, Caterpillar, EDF Energy, E.on, Rolls-Royce and Shell.

Three of the projects will focus on new offshore wind turbine technology with the fourth demonstrating a new commercial-scale tidal turbine; all of them are said to have the ultimate aim of providing more affordable, low carbon electricity.

UK Science & Innovation Minister Lord Drayson said: “There is great potential for the UK to harness wind and tidal power to produce renewable energy. These ETI projects will look to turn that potential into reality.

“The government has put record investment into science, including our funding for the ETI. Their work is crucial to achieving a green revolution in Britain and we will be supporting those growth industries and next-generation technologies where we can have a clear global impact. This is also science and engineering at its most exciting,” he added.

The ETI’s Chief Executive Dr David Clarke added: “The projects being announced will demonstrate new technologies which can deliver significant cost savings compared to present renewable energy sources.” The UK aims to be producing 15% of its energy from renewable sources by 2020.

A spokesman for the Nova consortium explained: “The vision for the project is one gigawatt of offshore vertical-axis turbines installed by 2020, via a large-scale demonstrator installed offshore within six years.

“Offshore vertical-axis wind turbines offer the potential for a breakthrough in offshore wind energy availability and reduced life-cycle costs due to their inherent design characteristics of few moving parts, insensitivity to wind direction and the placing of the generator at base level potentially allowing large-scale direct drive.

“Their relatively low centre of gravity and overturning moments in the case of Nova’s Aerogenerator make the turbines highly suitable for offshore installation. In addition, they are potentially ‘radar friendly’ compared with existing horizontal-axis wind turbine technology.”

The plan is for Cranfield University to provide aeronautic structural and materials design know-how for the demonstration turbine as well as working on the support structure. Sheffield and Strathclyde universities will be designing the drive train and power systems. QinetiQ will model and optimise the aerodynamic performance of the wind machine, and Cefas will look after environmental impact issues.

Development work will cover a six-year period and be completed in three phases.