Offshore wind biomimicry

Can the design of a spinning sycamore leaf hold the key to developing the world's largest offshore wind turbines? British engineers are discovering that the concepts of biomimicry ("Nature as model, measure and mentor") may lead to a revolutionary approach to scaling wind turbine designs. (GW)

Engineers race to design world's biggest offshore wind turbines

By John Vidal
Guardian
July 26, 2010

British firm to design mammoth offshore wind turbines with 275m wingspan that produce three times power of standard models

British, American and Norwegian engineers are in a race to design and build the holy grail of wind turbines – giant, 10MW offshore machines twice the size and power of anything seen before – that could transform the global energy market because of their economies of scale.

Today, a revolutionary British design that mimics a spinning sycamore leaf and which was inspired by floating oil platform technology, entered the race. Leading engineering firm Arup is to work with an academic consortium backed by blue-chip companies including Rolls Royce, Shell and BP to create detailed designs for the "Aerogenerator", a machine that rotates on its axis and would stretch nearly 275m from blade tip to tip. It is thought that the first machines will be built in 2013-14 following two years of testing.

But the all-British team of designers and engineers, which includes Eden project architects Grimshaw, is in stiff competition with other groups. Earlier this year US wind company Clipper, which has close ties with the US Department of Energy's National Renewable Energy Laboratory, announced plans to build 10MW "Britannia" turbines in north-east England.

Based on a scaled-up version of the conventional wind turbines now common in the British landscape, these giants would be fixed to the sea bed but would stand nearly 600ft high above the waves. If they prove technically and financially feasible, each turbine should be able to generate enough electricity to provide 5,000-10,000 homes and, says Clipper, should create energy equivalent to 2m barrels of oil in their 25-year lifetime.

Meanwhile, Norwegian firm Sway is planning to build massive floating turbines that would stick straight out of the sea from 100m-deep floating "masts" anchored to the sea bed. An EU-sponsored research project is also investigating 8–10MW turbines, and other American and Danish companies are planning 9MW machines. Full-scale prototyes of all three leading designs are expected to be complete within three years.

"There is a wonderful race on. It's very tight and the prize is domination of the global offshore wind energy market," said Feargal Brennan, head of offshore engineering at Cranfield University, where much of the Aerogenerator development work has been carried out.

"The UK has come late to the race, but with 40 years of oil and gas experience we have the chance to lead the world. The new [Aero-generator] turbine is based on semi-submersible oil platform technology and does not have the same weight constraints as a normal wind turbine. The radical new design is half the height of an equivalent [conventional] turbine," he said. He added that the design could be expanded to produce turbines that generated 20MW or more.

The largest wind turbines currently installed are mostly rated at around 3MW. By comparison, coal power stations typically have a capacity in gigawatts, or thousands of megawatts – it would take 180 of the new giant turbines to generate the equivalent capacity of a coal power station proposed this year for North Ayshire, Scotland.

Engineers say that scale is the key to wind power. Doubling the diameter of a conventional wind turbine theoretically produces four times as much power, but weighs eight times as much and can increase costs by a factor of eight. Offshore power is widely regarded as the future of renewable energy because the wind is much more reliable at sea, larger machines are possible to transport and install and there is far less public opposition.

On land, massive cranes and blades have to be driven to remote hilltops, and planning permission can take many years. However, the present generation of offshore turbines are 30-50% more expensive than their terrestrial counterparts, are harder to maintain and are more prone to corrosion.

The market for offshore power is expected to grow to hundreds of billions of dollars a year. Last year the European Wind Energy Association predicted that Europe would increase its offshore wind power from less than 2GW today to more than 150GW by 2030.

Britain, which has little upland space available for large wind farms, overtook Denmark in offshore wind generation in 2008 and now leads the world with 330 offshore turbines installed. It also has the world's most ambitious plans to develop the wind resource, being committed to installing 12GW of offshore power by 2012. This is the equivalent of 2,500 of the largest 5MW machines presently developed.

John Sauven, director of Greenpeace UK, said: "It is critical that the UK government does not hinder the development of offshore wind power by cutting budgets for short-term gain. All our energy needs depend on this."