Wind Power reveals 10MW turbine design

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A giant 10MW offshore wind turbine that mimics a spinning sycamore leaf has been proposed by British company Wind Power Limited.

The international architectural firm behind the Eden project, Grimshaw, has revealed the design of the massive machine, which will rotate on its axis and stretch approximately 275m from blade to tip. It is believed the first turbines will be built in 2013-14 following two years of testing.

The unveiling of the Aerogenerator X design is the conclusion of an 18-month feasibility study called the NOVA project undertaken by Cranfield University, Qinetiq, Strathclyde University, Sheffield University and Wind Power Limited, supported by consultant engineers and project managers.

Funding for the NOVA feasibility project was provided by the Energy Technologies Institute, a public private partnership comprising BP, Caterpillar, EDF, E.ON, Rolls-Royce, Shell, BP, EDF, EON, Caterpillar, the UK government and Wind Power Limited.

Wind Power Limited is not the only company looking to build 10MW offshore turbines. US wind company Clipper Wind announced plans earlier this year to build the 10MW Britannia turbines in north-east England. Norwegian firm Sway is developing floating wind turbines, anchored by a single flexible tether, which have their backs to the wind.

The main advantage of these large turbines is their economies of scale, which will be an important factor for developers to consider as the UK looks to meet future renewable energy targets.

A recent analysis from PricewaterhouseCoopers (PWC) found that developers will need to raise up to £10bn per year to achieve the annual roll-out rate needed to meet the UK’s commitment to obtaining 15 per cent of its energy from renewable sources by 2020. According to PWC, the UK will need a total of 12GW of offshore wind, compared to the 0.3GW of offshore wind capacity that was completed throughout 2009.

At the unveiling of Aerogenerator X, John Roberts, head of energy at Arup, spoke of the financial challenges involved with offshore wind.

‘Despite the installation of a number of large wind turbines offshore, the problems of increasing capital cost for deeper water remains unsolved, as does the issue of safe operability in the marine environment,’ he said. ‘There is a tremendous opportunity for new ideas to make a difference to the commercial viability and operability of offshore wind power. More cost-effective solutions will be essential if offshore wind power is to make the “hoped for” contribution to the UK’s greenhouse gas emission reduction targets.’

While upsizing conventional onshore wind turbine technology overcomes cost barriers, it also presents significant technical challenges, not least the weight of the blades, which experience a fully reversed fatigue cycle on each rotation, explained Prof Feargal Brennan, head of offshore, process and energy engineering at Cranfield University.

‘As the blades turn, their weight always pulls downwards, putting a changing stress on the structure, in a cycle that repeats with every rotation – up to 20 times a minute,’ he added.

‘In order to reduce the fatigue stress, the blade sections and thicknesses are increased, which further increases the blade self-weight. These issues continue throughout the device. Drivetrain mountings must be stiff enough to support the heavier components inside the nacelle on top of the tower, otherwise the systems can become misaligned and the support structure is also exposed to extremely large dynamic thrust and bending stresses, which are amplified significantly with any increase in water depth.’

Theo Bird, of Wind Power Limited, said that while offshore is ideal for wind power, it is also an extremely tough environment. 

‘The US wind researchers who worked on vertical-axis projects have always regarded the technology as great to work with at sea because it can be big, tough and easily managed,’ he added. ‘We are extremely grateful to the ETI, which had the vision to help us pick up from where the US left off. By facilitating projects such as ours, the ETI continues the heritage of great engineering in Britain.’

Huge turbines that dwarf today’s devices could be the future for offshore wind. Click here to learn more.