Getting serious about setbacks

This week, utility giant National Grid teamed up with Nantucket High School in Massachusetts to erect a 100 kilowatt wind turbine on school property. The 158-foot turbine [1] is located immediately adjacent to the school's football and baseball fields and by the road that runs behind the school.

According to the Nantucket Independent, the high school originally proposed locating the tower immediately west of the Newtown Cemetery to provide for an adequate "fall zone" but the plan changed after concerns were raised about the visual impact of the tower on the historic burial ground. The turbine was moved to its present location.

This aerial image of the school sports fields shows a circle with a radius of approximately 50 feet to denote the location of the turbine.

Nantucket High School turbine location

Apparently, the school reconsidered the need for a safety zone which would have to be at least four times that size.

Perhaps they were unaware of the three turbine collapses in the Northeast alone since September 2008.

In one of these instances, the turbine detached at its base and fell full-length in a field. In another, the turbine malfunctioned and went into over speed. When a spinning blade hit the tower the turbine exploded and fell to the ground. Firefighters were called out to extinguish flames caused by the collapse.

Catastrophic failures are more common than the public has been led to believe. In 2009, three small-scale turbines at the Perkins High School in Ohio sent blades flying after a wind gust apparently caused a blade to flex and hit the support pole. Earlier this year, two turbines sited on Cape Cod in Massachusetts blew apart in high wind conditions. Many more incidences of fire, blade throw, and collapse have been documented.

GE Energy explains that we do not have a good understanding of what happens to turbines when operating in extreme wind conditions. If GE is recommending caution it would be prudent to understand the risks other manufacturers are citing. The coastal areas of New England are well known for severe wind and weather conditions.

Ice shedding is a separate but real issue. According to GE Energy's Wind Application Engineering Group, wind energy siting in cold climates, at a minimum, should be based on the following formula for calculating a safe distance: 1.5 * (hub height + rotor diameter). Using this formula, the Nantucket high turbine could fling ice nearly 300-feet away, well into areas where students play and gather. This e-mail characterizing ice-shed at the Searsburg, Vermont wind facility provides some insight into the problem. (Note: the turbines at Searsburg are 198-feet tall).

It's hard to imagine the parents whose teenagers attend Nantucket High School were aware of the risks of siting a turbine so close to populated areas. And the question of safety must have been just a fleeting thought for school officials since they agreed to the present location. Unfortunately, the Massachusetts Renewable Energy Trust (now part of Massachusetts Clean Energy Center), who partially funded the project, is silent on the safety question.

When Windaction.org asked about setbacks in reference to the Newburyport, MA turbine, also funded by the Trust and sited close to homes, we were informed by e-mail that: "Massachusetts Renewable Energy Trust's goal is to support the installation of renewable energy projects and expansion of the clean energy industry in Massachusetts for a cleaner environment and stronger economy. The Trust evaluates projects at a high level and seeks to support projects that have a high likelihood of success and are deemed suitable by the communities in which they are located. The Trust is not a permitting agency; rather, permitting decisions for wind turbines are in the hands of each community."

There is a consistent pattern across the U.S. of small communities approving wind turbine proposals with little consideration, or apparent understanding, of the serious safety risks of erecting towers near public areas, rights-of-way, and residences. It surprises us that the insurance industry has not responded to the heightened risks. Hopefully, we will not see persons injured, or worse, before those making the decisions start taking the risks seriously.

[1] The NHS turbine has a hub height of 134 feet and a blade length of 24 feet, which totals 158 feet to the top of the blade when in a vertical position.

(Note: The distances referenced in this editorial pertain to the risks of flying debris from operating turbines. Setbacks to mitigate for turbine noise, shadow flicker and visual impacts are not considered.)

OCT 1 2010
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