Wind Resource Assessments

Is there enough wind on my land to make a wind project profitable?

A precise understanding of your wind resource is the cornerstone of any wind project. While some of the best resources are found on agricultural lands, the power in the wind varies greatly from one location to another.

Wind speed is the most important factor to consider, but you will also need to look at your wind variability, direction, and shear. Wind speed varies from year to year, season to season, with the time of day, and with height above ground. You may determine your sites' average annual wind speed, or compare detailed data showing fluctuations in wind speed to your electric usage. Because the power in the wind has a cubic relationship to wind speed, a site with an average 15 mph wind speed contains nearly 60 percent more energy than a site with an average wind speed of 13 mph.

One way to start determining your site's average wind speed is by reviewing existing wind maps. Wind Powering America has state wind resource maps that will help you determine if your site is in a good location for a wind project. If your site is in a class 4 area or higher, and free of obstacles, then you have good reason to look further into your wind project.

For more information on assessing your wind resource, visit Windustry's Know Your Wind factsheet in our Wind Basics series.

Plains Organization for Wind Energy Resources

The Energy & Environmental Research Center (EERC), with support from the U.S. Department of Energy (DOE) and the North Dakota Division of Community Services (DCS), developed the Plains Organization for Wind Energy Resources (POWER) to serve as a regional center of excellence for wind energy.

You can find a map of the active and inactove monitoring towers in the Midwest as well as a database of wind resource measurements that have already been taken around the Midwest. 

Wind Shear

A term and calculation used to describe how wind speed increases with height above the surface of the earth. The degree of wind shear is a factor of the complexity of the terrain as well as the actual heights measured. Wind shear increases as friction between the wind and the ground becomes greater. Wind shear is not a measure of the wind speed at a site. It is an extrapolation of the difference in wind speed between two different heights above the ground. Thus, high wind shear at a site does not necessarily mean high wind speeds at the site.

Wind Power Class

A way of quantifying on a scale the strength of the wind at a project site. The Department of Energy’s National Renewable Energy Laboratory defines the wind class at a site on a scale from 1 to 7 (1 being low and 7 being high) based on average wind speed and power density to offer guidance to potential developers as to where wind projects might be feasible.

Anemometry Equipment

The set of meteorological measuring and logging devices used to collect wind data for a wind resource assessment study. Equipment set typically includes: tower, anemometer, wind vane, temperature sensors, heating device, and data logger

Anemometer

A device used to measure wind velocity as part of a wind resource assessment study. Cup anemometers are the standard type used today, with 3 cups spinning on a vertical axis. The anemometer typically is installed on a guyed tilt-up tower at the anticipated location and height of the potential wind turbine.

How do I measure the wind resource on my land?

Wind assessment takes place at a number of different levels: consulting a wind map, obtaining previously measured data, and taking your own measurements. The cheapest and easiest way to assess your resource is to consult a wind map. Wind resource maps of your state are available at Wind Powering America

. It is important, however, to remember that wind maps are seldom detailed to the level of individual homesteads and there are many factors, such as hills, buildings, and trees that may further cause variances from the map. Nevertheless, it is a good place to start to give a general idea of your resource and do some basic economic analysis.

The next step is to obtain data that has already been measured by other groups in your area. State governments frequently have weather stations around the state in which they receive wind speed data. Also, airports keep track of wind speeds in their area.

Finally, you can measure your own wind speed by installing a device called an anemometer. Some state energy offices have a loan program in which you can rent an anemometer and data loggers to record your wind speed data. Contact your state energy office to learn more. You can verify that the data you collect is consistent with long-term wind Site-specific measurements using anemometers are considered by some to be the most reliable estimates of the wind resources for a project. However, they can be quite costly and require from one to several years to complete. Other methods also exist where large scale computer weather models are created to extrapolate wind conditions at a specific site from historical data. Many times these computer models of a site’s wind resource can be less expensive than taking meteorological readings for a year or more.

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