Small wind electric systems require planning to determine whether there is enough wind, the location is appropriate, wind systems are allowed, the system will be economical. | Photo courtesy of Bergey WindPower.
Small wind electric systems require planning to determine if there is enough wind in your area on a consistent basis, if the location for the system is appropriate for harnessing wind energy, if zoning ordinances and building codes allow wind systems in your area, and if the system will be economical with all of these elements taken into consideration.
Estimating your Wind Resource
To help determine the suitability of your site for a small electric wind system, you need to develop an estimate for your site's average annual wind speed, or wind resource. The wind resource can vary significantly over an area of just 1 square mile because of local terrain, local structures, and vegetation influences on the wind speed and flow. To assess whether there is enough wind resource in your location to justify contacting an installer to perform a resource estimate is by consulting a wind resource map which can indicate whether you live in a suitable wind resource region. The U.S. Department of Energy's WINDExchange has wind resource maps by state that you can access for free. If you find you are located in an area suitable for wind resources, you will next need to work with a qualified local wind installer to develop a more thorough and exact site estimate. Estimating the wind resource is complex, and your wind installer will likely use a combination of methods to gather information to estimate your wind resource with software. These will likely include;
- Airport Wind Speed Data -- One way to indirectly quantify the wind resource is to obtain average wind speed information from a nearby airport. However, local terrain influences and other factors may cause the wind speed recorded at an airport to be different from your particular location.
- Vegetation Flagging -- Flagging (the effect of strong winds on area vegetation) can help determine the area's prevailing wind direction and speed. For instance, trees, especially conifers or evergreens, can be permanently deformed by strong winds. Examining those deformation can tell an installer a lot about wind energy.
- Measurement System -- Direct monitoring by a wind resource measurement system at a site provides the clearest picture of the available resource. Wind measurement systems are available for costs as low as $600–$1,200. The measurement equipment must be set high enough to avoid turbulence created by trees, buildings, and other obstructions. The most useful readings are those taken at hub height, which is the elevation at the top of the tower where the wind turbine is going to be installed.
- Data from a Local Small Wind System -- If there is a small wind turbine system in your area, you or your installer may be able to obtain information on the annual output of the system and also wind speed data, if available.
Zoning, Permitting, and Covenant Requirements
Before you invest in a small wind energy system, you should research local zoning ordinances and restrictions from neighborhood covenants.
You can find out about the zoning restrictions in your area by contacting the local building inspector, board of supervisors, and/or planning board. They can tell you if you will need to obtain a building permit and provide you with a list of requirements.
In addition to zoning issues, your neighbors or homeowners' association might object to a wind turbine that blocks their view. They also could be concerned about noise. Most zoning and aesthetic concerns can be addressed by supplying objective data.
Some general information about height and noise issues for small wind electric systems:
- Height Issue -- Jurisdictions often restrict the height of the structures permitted in residentially zoned area. Most zoning ordinances have a height limit of 35 feet, although variances are often obtainable if you are willing to absorb the time and cost.
- Noise Issues -- The sound level of most modern residential wind turbines is slightly above the ambient wind noise. This means that while the sound of the wind turbine may be picked out of surrounding noise if a conscious effort is made to hear it, a residential-sized wind turbine is not a significant source of noise under most wind conditions.
For more information, see state and community codes and requirements for small renewable energy systems.
The Economics of a Small Wind Electric System
To help you analyze the economics of a small wind electric system and decide whether wind energy will work for you, you'll want to work with a qualified installer to estimate a number of items, including:
- Cash flow
- Electric bills and electric bill comparisons
- Wind characteristics
- Simple payback in years.
Finding these estimates will help you determine whether wind energy is a good option for your site. If it takes too long to regain your capital investment -- the number of years comes too close to or is greater than the life of the system -- wind energy will not be practical for you. A professional installer should be able to assist with many of these questions. Resources such as DOE's Consumer Guides for Small Wind can also help you get started on some of these estimates.