Wind floating over water

Wind energy technology is moving offshore. This is already occurring in Europe and the United States has a number of offshore wind farms in the planning stages or in the queue.

Building wind farms offshore is decidedly more expensive than onshore. A great deal of that expense is in the support system. foundations have to be able to withstand the rigors of the ocean environment that can include some serious wave action.

As the price of steel increases, it becomes less feasible to consider conventional pile-driven monopile towers for offshore wind systems in waters deeper than 50 feet. As a result, engineers are focusing on floating platform designs.

The late William Heronemus, wind engineer at the University of Massachusetts was not only one of the first people to propose constructing wind turbines offshore, he was also the first to come up with conceptual designs for floating systems! That was back in the 1970's. (GW)

Floating wind turbine may be in sea by 2009

New Zealand News
June 27, 2007

The world's first floating wind turbine could be generating electricity in the North Sea in 2009 under a research pact between Norwegian energy group Norsk Hydro and German engineering firm Siemens.

Floating wind turbines would represent a technological breakthrough for offshore power generation, which has had to rely on shallow sites for turbines installed on the seabed.

"It's attractive to have windmills out at sea, out of sight of land, away from birds' migration routes," said Alexandra Bech Gjoerv, head of Hydro's New Energy division at a signing ceremony to develop floating wind turbine technology.

"We want to build the world's first offshore floating windmill," Bech Gjoerv said. "We want to produce a lot of energy, out of sight."

Under the plan, Hydro will combine its knowledge of floating installations, such as North Sea loading buoys for oil tankers, with Siemens' expertise in building turbines, both on land and standing in shallow waters offshore.

Floating wind turbines are more costly than on land but could supply power both to offshore oil or gas platforms or to coastal cities, cutting emissions of greenhouse gases from fossil fuels and defusing objections that turbines are eyesores.

Hydro said a prototype, costing 200 million crowns ($NZ44.5 million), could be in place in the North Sea in 2009 assuming the firm agreed funding this year. The timetable is two years' later than hoped when Hydro unveiled a floating design in 2005.

If tests of the 5 megawatt wind turbine were successful, a small offshore wind park could be built around 2013-14. Siemens said it would spend several million euros on the research project, on which Hydro has already spent 30 million crowns.

A Siemens unit built the first offshore wind park in 1991, with turbines standing on the seabed off Copenhagen.

"Windmills standing in waters deeper than about 30 metres become prohibitively expensive," said Henrik Stiesdal, chief technology officer of Siemens' wind power unit. Hydro's "is the most elegant and simple solution we have seen."

Hydro's design is an upright steel tube with a concrete base about 200 metres long with 80 metres jutting above the water and three blades 60 metres long.

The wind turbine is tied to the seabed by three cables to keep it steady in seas where waves can be 30 metres high. Hydro reckons it can work in waters 700 metres deep.

Stiesdal said other models for wind turbines at sea relied on more complex designs such as giant tripods mounted on the seabed or turbines mounted on floating boat-like structures.