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Cape turbine failures during storm stir up concern  

Credit:  By Doug Fraser, Cape Cod Times, www.capecodonline.com 16 March 2010 ~~

When the 100-foot-tall wind turbine at Bartlett’s Ocean View Farm hurled one of its broken blades nearly 200 feet Jan. 18, it was a statistical anomaly. Wind energy experts claim, and statistics seem to show, failure rates are low.

But when a second 100-foot-tall turbine, this time in Marstons Mills, shed its blades in a northeaster this Sunday, it seemed to some the start of a troubling trend.

That is especially relevant as the Cape sees an ever-growing demand to add more wind power, whether in people’s backyards and businesses or on municipal property. Then, there’s the 130-turbine project in Nantucket Sound.

“There’s a growing interest in (turbines) because a lot is being paid for by public dollars,” said Lisa Linowes, executive director of Industrial Wind Action Group. The New Hampshire-based national advocacy group is pushing for more analysis of cost, danger and benefits of wind energy.

Linowes said there are better places to locate turbines than in New England’s harsh coastal environment.

“There’s only so much testing going on with (wind turbines), and the different environments they are being sited in pushes them to the limit,” she said.

Gusts of 60 MPH

This weekend, the gusting winds, at times measuring over 60 mph, prompted Conrad Geyser to check in on the turbine he owns at Peck’s Boats Inc. on Route 28 in Marstons Mills.

“I was looking and listening, and I didn’t see anything off the chart,” he said yesterday. “The thing was going like crazy and moving around a lot, but nothing any more extreme than we’d seen already.”

Geyser said he believes sometime in the early morning Sunday a big gust may have hit especially hard and knocked the blade tips off. He’s not sure how far they landed from the tower. Wind turbine blades can be subjected to enormous pressures, especially in the Cape’s notoriously stormy weather.

“They’re light,” he said. “But anytime you have something falling from the sky, there is concern.”

Of greater concern are the relatively heavy blades on larger models. But, of course, the larger the turbine, the greater the level of sophistication and safety features built in to avoid just such a scenario.

Hyannis Country Garden installed its 126-foot-tall wind turbine in 2008. It sailed through last weekend’s storm without incident.

Specially designed software monitors wind conditions and applies brakes to slow the spin of the blades if the wind speed exceeds design criteria for efficient and safe power generation.

If the wind hits storm levels with sustained winds of over 50 mph, with gusts up to 60 to 80 mph, the computer begins shutting down the turbine, and the brakes can stop the rotation within a couple of spins.

The turbine performance, blade spin and weather conditions are also monitored remotely by technicians in Vermont. The computer sends an e-mail alert if it detects any major aberration.

“I feel this is a safe machine,” said Country Garden owner Diana Duffley. She researched and purchased the Northwind 100 in part because the property is in a relatively densely populated area.

Five miles offshore

The same cannot be said of Cape Wind, whose 130 towers would be 258 feet tall, with blade tips stretching up to 410 feet; the turbines would be more than five miles from shore in Nantucket Sound. The technology, proponents insist, is much more sophisticated than that of smaller turbines. They insist blade failures are rarely, if ever, seen.

“These are things that have not happened in offshore wind (power),” said Cape Wind spokesman Mark Rodgers. As evidence, he offered that large-scale turbines are online, producing power, 98 percent of the time the wind is blowing.

“Large turbines rarely have failures,” said John Dunlop, a senior project engineer with the American Wind Energy Association. Technology, he said, has changed dramatically in the past decade.

Where turbine blades used to be fixed to the hub, they now can be rotated so that, in storms, they actually dump wind and become less efficient. Much as a sailor lets out the mainsail to avoid capsizing in a gust, the blades pivot to offer less surface area to the wind.

They do this because the turbines that produce the electricity reach full capacity in a 25 mph wind. By feathering the blades, and using brakes, the turbine can continue to produce power with less strain than a rapid spin would cause.

“There’s less stress because they’re only extracting the amount of energy it takes to reach capacity,” Dunlop said.

When winds reach 50 to 60 mph, he said, the leading edge of each blade faces into the wind, presenting the smallest profile, and the brakes hold them in place.

Extreme force

But some critics say the larger size and greater sophistication don’t guarantee faultless performance.

“While the larger turbines may be manufactured more solidly, the force of having blades that are 165 feet long is extreme,” said Audra Parker, executive director of The Alliance to Protect Nantucket Sound.

Parker said the recent incidents involving smaller turbines are warnings of what could happen in Nantucket Sound.

“What happens if you do get a blade throw with ferries passing within two-tenths of a mile?” she asked.

But Industrial Wind Action’s Linowes thought the chance of a blade from an offshore wind turbine striking anything was pretty slim.

She was far more concerned about what she’s seeing on land.

“It’s tough to justify these projects being built 1,000 feet from a home,” she said.

Source:  By Doug Fraser, Cape Cod Times, www.capecodonline.com 16 March 2010

This article is the work of the source indicated. Any opinions expressed in it are not necessarily those of National Wind Watch.

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