Friday, November 14, 2008
Wind turbine bylaw takes shape
The Alternative Accessory Clean Energy Generation Committee met on November 3 to iron out details of the proposed alternative energy bylaw and determine the remaining steps to its presentation at Town Meeting next May. The following committee members attended the meeting: Chair Bob Koning, Elizabeth DeMille Barnett, John Dalton, Keith Therrien and Bill Tice.
The Wind Energy Conversion Systems section of the proposed zoning bylaw was adapted from an equivalent section in the bylaws of Hamilton, Massachusetts. Committee members modified the wording to fit the situation in Carlisle. It requires a special permit from the Zoning Board of Appeals in order to install a wind energy system. Details of the bylaw were discussed and altered at the meeting. The next step is to have Town Counsel review the draft. Then the proposal will be circulated to all town boards for review. The committee hopes to have the comments by mid-to-late December. Finally, the Planning Board will hold a public hearing to help interested citizens learn about the bylaw. The committee members agreed that they could not complete these tasks before the January Town Meeting, so the May meeting is the target date for a Warrant on the bylaw.
The committee members also discussed the need for a solar energy section in the bylaw, particularly considering the clear-cutting issues that can arise when installing solar systems on the ground rather than on a roof.
Hamilton’s bylaw refers to “windmills,” but the committee decided to use the technical term “wind turbine.” The draft requires an applicant to provide a certified plot plan showing its location, along with certified engineering drawings of the tower and its foundation. The wind turbine tower must be set back from the property lines by a distance equal to that of the tower height plus the rotor radius. This ensures that a tower collapse would not encroach on abutting property. An abutter may grant an easement to reduce this requirement.
The tower may be of the lattice or monopole variety. Guy wires are not allowed, nor are advertising signs. The applicant must show that the turbine has a minimum capacity factor of 10% based on Massachusetts Technology Collaborative, Truewinds, or similar approved data. This means that the turbine must generate at least 10% of its maximum power capacity over time, based on its design and the prevailing wind speed at its location. The committee pointed out that otherwise, the tower serves little purpose and might be considered a blight on the landscape. The Building Inspector may revoke a wind turbine permit if it has been abandoned for more than 12 months and may require the owner to dismantle it.
The proposed bylaw covers only one turbine per site. It does not cover, and therefore does not allow without a variance, community windfarms or large turbines generating over 50 kilowatts.
Wind in Carlisle
The power capacity of a wind turbine is determined by the average wind speed at the elevation of the rotor along with the specific design of the turbine. According to data from the AWS Truewind Web site (navigator.awstruewind.com), the average wind speed in Carlisle at an elevation of 80 meters ranges from 5.0 to 5.19 meters/second (approximately 11.4 miles/hour). Surrounding towns are similar, although speeds increase as you move east. A wind speed of 4.0 meters/second is generally considered sufficient for a small turbine. ∆
© 2008 The