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Snagged cables, hurricanes and insurance; risk assessment for offshore wind turbines  

Credit:  By Dan West, The Block Island Times, block-island.villagesoup.com 30 March 2012 ~~

In coastal New England the threat of hurricanes is ever present. They come in the late summer and down trees, drive boats up on shore and, at their worst, blow roofs off houses and send deadly storm surges up Narragansett Bay. But what would those storms do to Deepwater Wind’s proposed wind farm just off Block Island?

A Carnegie Mellon study published last month in the Proceedings of the National Academy of Sciences attempts to quantify the risk. It looks at possible sites for offshore wind farms around the U.S coast, including two sites comparable to the island.

The study calculates the probability of a 50-turbine wind farm losing between a single turbine and half of its turbines over a 20-year period. The authors looked at four locations: one in the Gulf of Mexico, one off North Carolina, one off the coast of New Jersey and one off Massachusetts.

According to the study, the two southern locations are in much greater danger of damage from hurricanes than those closer to here.

Most of the damage to wind turbines from hurricanes came from Category 4 and 5 storms, which the study says might not even be possible this far north in current climate conditions. No hurricanes that strong have made landfall in New England since record keeping began in 1850.

In the worst case scenario, the wind farm in the Gulf Coast would have a 60 percent chance of losing one turbine over 20 years, and a 30 percent chance of losing more than half its turbines. North Carolina also has a 60 percent chance of losing one turbine, but a 9 percent chance of losing more than half.

The two northern sites faired better. Even under the worst case scenario, the study says, there is between a 10 and 15 percent chance of losing a single turbine, and a less than 1 percent chance of losing more than half the turbines over a 20-year period.

The worst-case scenario calculations are based on critical safety systems not functioning. Those systems, which allow turbines to yaw or pivot, keep the turbine blades facing the wind, reducing wind resistance. If those safety systems are in place in the northern sites, the study finds “there is approximately a 99 percent probability that none will buckle in 20 years.”

The authors of the study say that it isn’t unreasonable to assume that the motors that allow the turbine to yaw quickly with the wind could be rendered useless. In many cases, those motors rely on grid power, and in a storm that power could be knocked out.

Deepwater Wind says that won’t be an issue in the Block Island project. Company President Chris van Beek says the Siemens turbines that will be used off Block Island employ a number of safety systems, including wind speed sensors, rotation per minute monitoring, and vibration sensors that will shut down the turbines if winds exceed 50 knots.

The turbines also feature yaw motors that can rotate the turbine up to 10 degrees per second, van Beek said. The blades are pitched to reduce wind resistance. And the entire system will be equipped with a battery backup in case the mainland grid fails.

If those safety systems hold, the Carnegie Mellon study suggests a less than 1 percent probability that any turbine would suffer a catastrophic failure.

Cooneymus Road homeowner Michael Hickey is skeptical, saying he is concerned that the hurricane risk will drive up the insurance cost on the Deepwater project. Hickey, investment director for Fidelity Management Research, says that he expects a high premium due to the danger of hurricane damage.

Hickey is also worried about the possibility that Deepwater Wind will “self insure” the project.

“There are no rules and regulations on insuring and de-commissioning these projects,” Hickey said. “For the most part, the state will be ‘making it up as they go’ or maybe worse – relying on Deepwater Wind to produce estimates.”

He said that Deepwater’s parent company, DE Shaw, could establish a new Limited Liability Corporation to insure the project, which could allow the company to abandon the project if it suffers significant damage early on. That could leave the island with no one to help it deal with damaged turbines, he says.

“There is a material risk that this project is a burden on this island 20 years from now,” Hickey said. “As Reagan said in the eighties about the Soviets, trust but verify.”

Van Beek said that Deepwater will not be self insuring the project, but will go through a third party and insure the full cost of the project.

The Times confirmed that Deepwater has contacted at least one outside insurance provider, GCube Insurance Services Inc. GCube is an international insurance company that insures more than 30,000 megaWatts of wind power globally.

Among its clients are more than a dozen offshore wind farms in Europe – all larger than the proposed Block Island project. John McLane, President of GCube Insurance Services Inc., says that the company has had informal talks with Deepwater that he says have been positive.

McLane says the most critical issues with offshore wind farms is not damage to the turbines, but damage to the undersea cable, which can render a wind farm inoperable for an extended period and be costly to repair or replace. Cables can be damaged in a number of ways, he said, from snags on passing ships to the construction phase of the wind farm, especially if not buried deep enough in the ocean floor.

Roland Godfrey-Davies of GCube added that around 70 percent of the claims made on European offshore projects are related to the cable.

McLane explains than another concern is an offshore farm’s remote location. With onshore wind turbines, he said, there are periods with relatively calm weather when maintenance and repairs can be performed. With offshore wind, the remote location and higher average wind speeds can mean there are longer periods when turbine operations might be interrupted.

“Damage to the submarine cable, and business interruptions, weigh more heavily on the underwriting,” McLane said. “In the total scheme of things, damage to the turbines is relatively minor.”

The cost for insuring the Block Island project, McLane estimated, would be between 1 and 1.25 percent of the project cost, or an annual premium between $1.75 million and $3 million. Those numbers are rough estimates and would vary depending on many different factors, McLane said.

Those factors will include things like who will be the contractor managing the installation, who will do the construction and who will supply different parts of the project.

Hickey, meanwhile, says it’s time for greater engagement from the town and Block Island residents. He says that the state’s Coastal Resources Management Council, which has not reviewed a project of this scale in the past, does not have the expertise to regulate things like insurance or the eventual decommissioning of such a large project.

“Our local government needs to take some ownership of these issues, because we can’t rely on the CRMC,” Hickey said. “Block Island needs to be engaged on the details. The town should find the money to hire our own experts.”

Source:  By Dan West, The Block Island Times, block-island.villagesoup.com 30 March 2012

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

The copyright of this article resides with the author or publisher indicated. As part of its noncommercial effort to present the environmental, social, scientific, and economic issues of large-scale wind power development to a global audience seeking such information, National Wind Watch endeavors to observe “fair use” as provided for in section 107 of U.S. Copyright Law and similar “fair dealing” provisions of the copyright laws of other nations. Send requests to excerpt, general inquiries, and comments via e-mail.

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