Climate change and local government: Zoning for small wind energy, Part 2
As more local governments explore their roles and responsibilities in climate change adaptation and mitigation, allowing and encouraging small alternative energy conversion systems is one way to address both strategies simultaneously.
In this second part of a two-part series, we further explore some of the issues with small wind energy conversion systems as related to local government zoning regulations. Generally, with small wind energy systems, the issues that most communities regulate include tower height, setback distances, sound, electrical and construction related connections, and safety.
Tower height is a sensitive issue for many communities. When regulating tower height wind energy systems, communities must keep in mind that the potential energy generated by a wind turbine is largely based on its placement and the wind speed. Generally, wind speed is greater and more consistent higher off the ground. So, by regulating tower height, local regulations are also affecting the efficiency and economic practicality of the system. Instead of setting a maximum height, consider setting height standards to allow smaller towers to be constructed by right (i.e. there is no special permitting process) and taller towers to be handled as a special land use with site plan review. The state sample zoning language uses 20 meters (66 feet) to differentiate between these two types of approvals, but other communities set this threshold higher. For instance, Norman Township uses 125 feet as the tipping point beyond which a special land use permit is required for a wind energy conversion system.
Like any other property line setback in a zoning ordinance, a wind turbine tower setback is a safety consideration in the occasional instance of falling debris and the unlikely event of a tower collapse. Essentially, the tower setback recognizes and protects the property rights of adjacent landowners. In the Michigan Sample Zoning for Wind Energy Systems, the recommended setback is equal to the height of the tower and turbine, including the top of the blade in its vertical position. Other communities require larger setbacks such as 1.5 times the tower height. The question to ask when considering a larger setback like this is: what are the public health, safety and welfare concerns for requiring a setback larger than the height of the tower and turbine? Also, keep in mind that setbacks affect whether a given wind energy conversion system and tower combination will be allowed on a given parcel or not. Put differently, a larger setback will necessitate a smaller tower on a given parcel, and a smaller tower will keep the turbine closer to the ground where winds may be lighter and more turbulent.
Another legitimate consideration with respect to siting wind turbines is noise. Best practice states that noise levels should be measured based on a strict, measureable standard, not based on the ear of the complainant. This means that communities should invest in a sound level meter. The State sample zoning language uses a strict standard of 55 dB(A) as measured at the nearest property line, but at least one peer-reviewed article, The Potential Health Impact of Wind Turbines, suggests this standard might be better set at a level closer to 40 dB(A), considering the potential impact on neighbors.
With more states adopting net metering provisions and expanded opportunities for homeowners and businesses to produce alternative energy for utilities through feed-in tariffs, compliance with state construction and electrical codes is a basic standard to require of all wind and solar energy systems. Plus, there may be other state and utility regulatory agency standards related to tall structures, airport zoning, and utility connections that are important to include in reference in zoning ordinances.
Other safety related issues to address in zoning include guy wires to towers being clearly visible to a certain height, towers being clearly marked with ‘do not climb’ signs or made difficult to climb with fencing or other screens, minimum ground clearance for turbine blades, automatic braking or governing to prevent uncontrolled spinning of turbines, and lightning protection. See the Michigan Sample Zoning language for specifics on these issues.
For structure-mounted wind energy systems, which are also growing in popularity, many communities simply regulate these systems as rooftop equipment with a maximum height of 15 or 20 feet. Unlike rooftop heating and ventilation equipment though, screening of structure mounted systems affects system performance, so zoning provisions related to rooftop equipment should be reviewed to avoid contradiction with alternative energy policies and provisions.
There are many other municipal roles and responsibilities with respect to climate change adaptation and mitigation. To explore other resources for local governments related to climate change, visit the Michigan State University Extension Climate Change and Variability website.
Other articles in this series: