Small wind electric systems require planning to determine if there is enough wind, the location is appropriate, if wind systems are allowed, and if 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 the needs of the system, if zoning codes or covenants 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 estimate your site's wind resource. The wind resource can vary significantly over an area of just a few miles because of local terrain influences on the wind flow. You can use the following methods for estimating your wind resource.
- Consult Wind Resource Maps -- As a first step, you can consult a wind resource map, which is used to estimate the wind resource in your area. The U.S. Department of Energy's WINDExchange has wind resource maps by state.
- Obtain Airport Wind Speed Data -- Another 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. Airport wind data are generally measured at heights about 20–33 feet (6–10 meters) above ground. Average wind speeds increase with height and may be 15%–25% greater at a typical wind turbine hub-height of 80 feet (24 meters) than those measured at airport anemometer heights.
- Observe Vegetation Flagging -- Flagging (the effect of strong winds on area vegetation) can help determine area wind speeds. Trees, especially conifers or evergreens, can be permanently deformed by strong winds.
- Use a 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, the elevation at the top of the tower where the wind turbine is going to be installed.
- Obtain Data from a Local Small Wind System -- If there is a small wind turbine system in your area, you 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 potential zoning and neighborhood covenant issues.
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 machine 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 -- Some jurisdictions restrict the height of the structures permitted in residentially zoned areas, although variances are often obtainable. Most zoning ordinances have a height limit of 35 feet.
- 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 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 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, and resources such as DOE's Consumer Guides for Small Wind can help you get started on some of these estimates.