Offshore wind turbine stands up to gusts, waves

PORTLAND, Maine — A scaled-down offshore wind turbine has withstood winter storms that included the equivalent of waves exceeding 70 feet, providing confidence that a full-scale version can handle the harshest weather that the North Atlantic can throw at it, the head of the University of Maine’s advanced composites center said Thursday.

The 65-foot-tall turbine deployed last summer off Castine performed as engineers expected even as the waves exceeded the platform’s design limits in November and December, giving them confidence as they prepare to build larger platforms and taller turbines, Habib Dagher said after addressing the Environmental and Energy Technology Council.

“We feel very confident now that we have something we can build that will survive a 100-year storm in the state of Maine. So am I worried about the ‘perfect storm’ coming in and wiping out offshore wind farms? No, I’m not. I think we’re in good shape,” he said.

The university and its partners have formed a joint venture called Maine Aqua Ventus to build two larger units to be deployed nearly 15 miles off shore near Monhegan Island. Maine Aqua Ventus officials have estimated that the project could create 340 full- and part-time jobs during the three years of planning and construction.
The Public Utilities Commission gave initial approval to the project Tuesday.

The project is expected to generate enough power for as many as 7,000 Maine homes and at 23 cents per kilowatt hour it will cost customers roughly $9 more a year on their utility bills. If successful, officials believe a large wind farm 20 miles offshore could generate up to 500 megawatts of electricity and cut electricity costs by at least half.

But first, the one-eighth scale model had to be deployed to prove the technology works.

Instead of using a steel structure, the University of Maine and construction company Cianbro Corp. used cement to create the 90,000-pound floating platform that’s tethered to the ocean bottom.

Video during the presentation at the University of Southern Maine showed that the platform and turbine remained stable even as the tugboats bobbed up and down while deploying the unit.

Dagher acknowledged that there were some anxious moments as the first big storm rolled through the Gulf of Maine on Nov. 1.

“None of us slept on that day as the storm went through. We could watch this thing live on video. It was beaming data back to us,” he said.

He and other researchers kept close watch on data from 70 sensors aboard the platform during that storm and several others that battered the platform in November and December. The platform and turbine bobbed and leaned at a maximum of 5.9 degrees, just as engineers anticipated, Dagher said.

With PUC approval for installing two larger turbines off Monhegan, Maine Aqua Ventus hopes to win a $50 million federal energy grant in May to move forward with full-scale turbines.

If those are successful, then the goal will be to use the 83 of the 6-megawatt turbines to create a 500-megawatt wind farm that’s 8 miles long and 4 miles wide, Dagher said. By contrast, the Maine Yankee nuclear power plant generated about 800 megawatts of electricity when it was in operation.