OSLO (Reuters) - A surge in sea-based wind farms is likely to mean bigger turbines than on land, reaching 10 megawatts by 2020 with blades 85 meters (280 ft) long, the head of Norway’s Det Norske Veritas said on Monday.
Veritas, which tests wind turbines until they snap as part of certification, reckons the industry will need subsidies for years since costs are about 40 to 60 percent above those for land-based wind, Chief Executive Henrik Madsen told Reuters.
A private foundation, Veritas certifies about 75 percent of offshore wind turbines, except Chinese, he said. Veritas says it and Germany’s Germanischer Lloyd are the main groups setting industry standards.
A planned boom so far centered on Britain and the North Sea, part of efforts to slow climate change, was likely to mean bigger turbines offshore than on land.
“They can be larger. It’s easier to transport (turbines) on ships and install them,” he said. On land, heavy cranes and blades often have to be driven along narrow lanes to a remote hilltop, complicating transport.
“We believe you will see larger turbines up to 10 megawatts” offshore, he said. A 10 megawatt turbine would be enough to provide electricity to between 2,250 and 3,000 U.S. households, according to the American Wind Energy Association.
“There’s huge potential,” Madsen said about offshore wind. Big turbines now have about a 5 MW capacity.
A 10 MW turbine would have blades perhaps 85 meters (280 ft) long, giving a 170-meter diameter for a three-blade turbine, he said. The longest blades tested by Veritas at a center with partners in Denmark so far has been 71 meters long.
“We thought of building (the test center) to 100 meters but we decided 85 would do it for the next 15 years,” he said.
Among makers of big turbines, Germany’s Enercon says its E-126, rated at 6 MW and with a 127-meter rotor diameter, can operate at 7.5 MW. Clipper Windpower is working on a 10 MW turbine and Norway’s Sway a 10 MW floating prototype.
Turbine designs and sizes vary widely — carbon fiber is stronger than glass fiber, for instance, but more vulnerable to lightning. Blades are tested to breaking point.
“These blades are extremely flexible, so we need a lot of space. There can be a 10-12 meters deflection until they snap,” he said.
Offshore costs are higher than on land because of problems such as salt corrosion, complex maintenance and linking to the grid. But winds blow more offshore, fewer people complain that turbines are eyesores and larger turbines earn more money.
The price gap between land and offshore was likely to narrow but “I’m not sure it will come all the way down,” he said.
“We believe you will need subsidies, but we also believe that there is a significant potential to drive costs down, in particular related to offshore installations and foundations,” he said. And companies can learn from decades of experience from the offshore oil and gas industry.
Top turbine makers in terms of 2009 market share were Denmark’s Vestas, ahead of U.S. General Electric, China’s Sinovel, Enercon, China’s Goldwind, Germany’s Siemens, Spain’s Gamesa and India’s Suzlon, according to Denmark’s MAKE consultancy.
At the end of 2009, the World Wind Energy Association said wind farms were installed in the sea off 10 European nations and off China and Japan.
Installed capacity offshore amounted to almost 2 gigawatts, or 1.2 percent of world wind capacity. Britain has granted licenses for 32 gigawatts of offshore wind, part of a European Union drive to get 20 percent of energy from renewables.
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Editing by Sue Thomas