New ideas from Germany's professor of wind energy

By Catherine Simon Mar 8, 2007, 6:05 GMT

Stuttgart, Germany - Model wind generators ranging from palmtop to man-sized fill the office of Germany's first and only professor of wind energy, Martin Kuehn, at the University of Stuttgart.

One, out of Lego bricks and depicting an offshore wind-park, was made by Kuehn's young son. Kuehn himself was fascinated as a boy by the power of the wind, though his interest in building wind generators did not come till he was an adult.

'Nature creates a constantly changing challenge for us,' says Kuehn, 43. 'We devise ways to exploit wind, which is inherently gusty, in a constant and efficient way, in harmony with nature.'

German makers of wind-power equipment are among the world leaders, with German engineers constantly refining the technology.

'The market is booming worldwide,' says Kuehn. 'It is expanding by 20 per cent a year.' Last year, world sales of equipment totalled more than 11 billion euros, with German makers capturing somewhat more than one third of that.

'Of course we are far from the sales volumes of the German automobile industry, but wind-turbine constructors are well out of the stage of being a back-garage industry,' he says.

In absolute terms, Germany has more wind turbines installed than any other country in the world: 18,685. With no direct emissions at all, they feed between 6 and 7 per cent of Germany's total electricity needs.

'Wind is second only to hydro-power as the lowest-cost type of renewable energy,' Kuehn says. The ticket price on a single wind generator is about 2 million euros (2.6 million dollars). Each can provide power 20 years long for about 1,000 households.

Bigger generators can do even more. Increasing the radius of the rotors massively increases the area of wind they can sweep and the energy they produce. Currently the world's largest generators can sweep a circle of 126 metres' diameter.

'The technology itself is very well developed,' says Kuehn, 'but we still have a lot more to do to reduce the costs. In particular, the generators have to become more efficient and more reliable.'

Another key improvement would be to integrate wind power better into the existing energy system.

The Institute of Solar Energy (ISET) at Kassel, Germany recently calculated that Europe's entire electricity needs could be met from renewable energy using technologies that for the most part have already been developed.

The institute said generation costs would be only slightly higher than at present.

'The key to this is combining different sorts of renewable energy sources and energy transport into a trans-continental grid,' explains the professor.

Germany's Wind Energy Federation forecasts that the cost of wind generation will match that of traditional energy sources around about the year 2013. Optimizing wind use is often a question of siting the generators where the wind is strong and steady.

Kuehn say the most promise is held by big wind farms and by offshore sites where there is no scenery to spoil.

'In the sea, close to land, there are enormous wind resources waiting to be exploited,' he said. 'Mean wind speeds and therefore output could be up to 50 per cent more than on land, and there is far more room available off the coast.'

Germany's first pilot offshore wind park is to be built next year, 45 kilometres north of Borkum in the North Sea.

One project under way at Stuttgart is examining how local weather forecasts can be used to accurately predict the wind speed and the energy yield one day in advance, so that a decline in energy output does not come by surprise.

That will make it easier for grid operators to calculate the likely amount of energy from wind so that fossil-fuel plants have plenty of time to get ready for troughs in wind-power supply.

This in turn reduces wear and tear on those plants as well as their carbon-dioxide emissions.

Another university project is using laser instruments to measure the trail of turbulence after air has passed the generator: this is important to know more about the buffeting of structures in a wind park.

Outside Kuehn's office is a 1949 rotor built by Professor Ulrich Huetter, now recognized as the ancestor of the modern wind-generation plant. The blueprints were offered to the US National Aeronautic and Space Administration (NASA) in 1972 at the height of the oil shock.

The German's pioneer rotor has been restored and erected outside the Stuttgart university department where Kuehn teaches as a monument. Kuehn said he aims to ensure that Stuttgart continues to be the fount of cutting-edge wind-power technology for use worldwide.