UPDATE 12/7/10: Also check out this update on Quora from a wind turbine expert.
Google announced yesterday its investment in Atlantic Wind Connection (AWC), a collection of wind farms and transmission lines near the mid-Atlantic coast, which could provide power to nearly 2 million people by the time its completed (construction could start as early as 2013). On Quora.com, a social networking site for hard-to-answer questions, one user asked "What happens when hurricanes and tropical storms hit wind farms?"
When I saw the map of the proposed site, comparing it in my mind to the map below showing historical hurricane tracks in the same area, I immediately saw their concern. Dozens of hurricanes have passed through the area since records began.
It turns out that no offshore wind projects are currently operating in the U.S., much less Hurricane Alley, although several have been proposed. According to the aforementioned article, only meteorological investigation towers have been erected at these sites to measure winds and waves. The first operational site will likely be Cape Wind in Nantucket, which was officially approved last week.
Media coverage on hurricanes and wind farms is nonexistent, and it's surprising given the dangers. Only one wind farm has publicly talked about being able to stand up to hurricane winds: Wind Energy Systems Technology, CEO'd by Herman J. Schellstede, who has another company that has done custom engineering solutions for the oil industry worldwide. He intends to design 62 turbines for placement off the coast of Houston, Texas, and has said that his turbines are ready for 150 mph sustained winds (gusts to 200), a strong Category 4 Hurricane, using a special tripod design for the tower, and that in fact their prototype tower survived [PDF] the eye of Hurricane Ike in 2008.
"Unlike the single-pole-supported towers used in the majority of the European offshore wind farms, stronger structures are required to support turbines being built off the Gulf Coast. The European model just won't work in the Gulf, Schellstede says, because hurricanes and other cyclonic storms unleash more fierce winds. So, WEST developed a unique tripod designed to support the tower on three legs, which are buried more than 100 feet below the underwater mud line."
In an interview via phone, Markian Melnyk, who developed The Atlantic Wind Connection (AWC) backbone transmission project which Google is sponsoring, says that they won't be involved in the engineering of the turbines. Their company is concentrating on building the offshore electrical grid - they will essentially be the utility company that taps the energy offshore. He said hurricanes are an issue but manufacturers seem to have confidence in the equipment, some of which is based on offshore wind turbines in Europe (where I can tell you that "hurricane-like" storms strike throughout the year). He also pointed out that insurance could be an issue, as could getting engineering certifications that satisfy lenders.
I was glad to find out that my fears have not gone unaddressed by government studies. On Page 93 of the National Renewable Energy Laboratory (NREL) report (PDF) "Large-Scale Offshore Wind Power in the United States ASSESSMENT OF OPPORTUNITIES AND BARRIERS September 2010" they state: "If the offshore wind industry is to be successful, new turbine designs must place a higher premium on reliable designs and low-cost in situ repair methods, from the preliminary concepts to the finished product. Likewise, new materials must be selected for durability and environmental tolerance."
More specifically in regards to "the Mid-Atlantic region [which] comprises the offshore areas of New Jersey south to North Carolina" (where AWC intends to place the Google-sponsored turbines) they say "moderate hurricanes will likely dictate the extreme survival conditions." The NREL is less worried about New England (for example the previously-mentioned Nantucket farm) saying "Extreme conditions are driven by lower intensity hurricanes and more frequent and widespread winter 'nor'easters,' which are usually within the design envelope prescribed by current wind turbine design standards."
Not surprisingly, the biggest concern is the Gulf of Mexico, where Schellstede's windmills will be installed, but the NREL is careful to say that they won't ban them there: "Any offshore wind development in the Gulf of Mexico will have to be evaluated in the context of extreme hurricanes that frequent the region. Hurricanes will not preclude installing offshore wind turbines in the Gulf, but this additional risk factor must be considered in the structural design of any turbines that are put in place."
In the end, they say "risks associated with ice floes and hurricanes, respectively, have not been fully explored and could reduce the gross potential resource even further." I believe what they mean here is that we could be overestimating the amount of power that could be generated due to downtime from tropical storms (for example wind turbines offshore from Denmark had to be replaced in 2004 at a cost of $50 million after they failed due to damage resulting from storm and salt water (something else the engineers need to think about).
Sidenote: Wind turbine blades are typically locked when winds exceed 55 mph because of the potential risk for damaging the equipment and because they are the winds are not consistent enough for the turbines to generate energy efficiently).
The study also states that "More accurate weather forecasting could also become a major contributor in optimizing service for low cost, and this research area has strong synergies with land-based systems." I totally agree.
Could storm surge and high waves be another concern? Probably not storm surge, that far out to sea, but high waves would be. The combination of the two was what destroyed Interstate bridge in Louisiana and Mississippi during Hurricane Katrina.
Markian also reminded me that (theoretically) the danger of a turbine base tower should be less than that with oil rigs that present a much larger surface area if waves crash against their main structure. While that is true, I am also worried about the blades, which no one is really talking about. A report by an anti-wind-energy group [PDF] claims: "By far the biggest number of incidents found were due to blade failure... either whole blades or pieces of blade being thrown from the turbine. A total of 167 separate incidences were found since 1970." They also claim that 84 instances of "structural failure... storm damage to turbines and tower collapse" and I would assume most of those are on land.
In summary: Offshore wind energy efforts in the U.S. will move forward only with specially-engineered turbines that can withstand major hurricanes (likely at a higher build & maintenance cost than land turbines), some of which have already been designed. Unless a Category 5 hurricane moves directly over a turbine, damage should be minimal. However, until a storm passes over an offshore wind farm, we won't know for sure what effect the weather will have.
Sidenote: Will these turbine units be a problem for weather radar? Certainly they have been on land, but it's likely offshore turbines will be too far from the radar tower to be detected since the maximum range I quoted in that article was 35 miles and the radars are generally not right on shore. I would assume the same for NORAD and airplane radars.
Sidenote: I believe in the promise of wind energy, if it can be delivered efficiently, and Google's support of the AWC will help that cause. In 2007, I visited our local wind farm near Altoona, Pennsylvania and documented the construction process for the units (see photos below). I personally didn't see any signs of the negative myths that naysayers associate with the structures, including bird/bat deaths, loud noise, or the ruining of majestic landscapes.
Random "it's a small world" factoid: Herman J. Schellstede & Associates, Inc. designed and built a machine to pick the peppers used in the "Tabasco" brand hot sauce; I visited the factory in Avery Island, LA in 1993.
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