Ordinances

Wind turbine sound and how it is perceived can be impacted by a variety of factors, including the model of wind turbine, atmospheric conditions, distance between the turbine and the listener, existing ambient sound levels, and even individual perception. While there are many ways to measure sound, and no standards currently adopted for ordinances, some communities approach sound limits by establishing a single upper threshold for acceptable maximum sound levels at designated points (such as houses or property lines). Communities can also create separate standards for daytime and nighttime operations. Nighttime levels typically feature a lower allowable threshold than daytime to limit noise when most of the population is sleeping. Another variation may include limited exceptions, temporarily allowing wind turbines to operate at sound levels that exceed maximum limitations during isolated events, usually related to weather such as a high wind event.

More information on wind turbine sound can be found here.

Wind turbine heights can be defined in multiple ways: the distance from the base of the tower to the hub or nacelle, the base of the tower to the tip of a blade when extended vertically, or the base of the tower to the top of the tower. These height definitions are very important for determining requirements and/or constraints on a given project. For example, the Federal Aviation Administration (FAA) evaluates and approves the height of each turbine in a project based on the tip height, or the highest possible measurement above ground level. Some communities may also choose to implement an ordinance that places an upper limit on turbine height in order to address community priorities, whether it be visual impact concerns, airspace use, or other factors.

A setback distance is the minimum allowable distance between a wind turbine and a designated area of concern, which may include property lines, inhabited structures (such as homes or office buildings), public roads, project infrastructure, and other specifically identified local interests. A setback distance can be expressed as a specific distance (i.e. 200 m from the area of concern) or as a multiple of the turbine height (i.e. 1.1 x the height of the turbine from the area of concern)

As it relates to wind energy, a moratorium is a temporary suspension of wind energy development until future consideration warrants lifting the suspension, such as if and when the issues that led to moratorium have been resolved.

A wind energy ban could include prohibiting wind energy development in the expressed area, such as by limiting project output capacity (expressed in MW or kW), or by restricting the offsite use of the electricity generated. A ban could also include regulations that are so restrictive to developers that they can act as de facto bans on wind energy development. For example, a community might set an upper limit on the number of acres of development, or the number of turbines within the county, that has already been met.