Wind Availability and Location Optimization for Wind Turbines

12:08 PM No Comments

Wind Availability

Whether constructing a wind turbine is economically viable at your home or farm depends most strongly on the quality of your wind resource. Generally, average annual wind speeds of at least 4.0-4.5 m/s (14.4- 16.2 km/h; 9.0-10.2 mph) are needed for a small wind turbine to produce enough electricity to be cost-effective. A very useful resource for evaluating a site for its wind energy potential is a wind resource potential map. 

Wind Map for Eastern Ontario. (a.g.l. = above ground level) 

It may be useful to check wind speed measurements that have been recorded at a local weather station. It is important to consider that sitting factors at these weather stations, such as nearby trees and buildings, might influence any wind speed measurements. Also, keep in mind that the equipment at these stations is often located close to the ground, and that weather stations located at airports are usually sheltered from the wind.

Wind Map for Southwestern Ontario. 

This means that wind speed measurements recorded at these stations might under represent the wind potential at your site.

For the most precise evaluation of the wind speed at your site, you need to purchase a wind resource evaluation system. While wind resource evaluation systems can be expensive, if your property is hilly and has unusual terrain features then it might be worth obtaining one.

The most important component of a wind resource evaluation system is an anemometer. Anemometers are typically designed with cups mounted on short arms that are connected to a rotating vertical shaft.

The anemometer rotates in the wind and generates a signal that is proportional to the wind speed. If you do purchase an anemometer, you will also need to purchase something to record the readings made by the anemometer, and a tower or tripod to mount the whole system on.

For as little as $500 you might be able to purchase a wind totalizer, which is a very simple type of wind resource evaluation system where the anemometer is linked to an odometer. The odometer is similar to those found in cars. After a period of time, the number recorded on the odometer, which represents the total "distance" the anemometer has turned, can be divided by the time passed since the odometer was last checked in order to determine the average wind speed over a period of time at a location.

If there is a small wind turbine system in your area, you may be able to obtain useful information from its owners about the annual electrical output of the system and, possibly, wind speed data. Such information could be extremely valuable as an alternative to installing a wind resource evaluation system.

 Wind turbine schematic. (Modified image from Natural Resources Canada)

Picking the Best Location for a Wind Turbine

Where you choose to build your wind turbine is important. Remember that if nearby houses, tree lines and silos obstruct the full force of the wind from your wind turbine, you will not be able to generate as much power.

Also keep the following in mind:

• Wind speeds are always higher at the top of a hill, on a shoreline, and in places clear of trees and other structures.
• Remember that trees grow over the years; wind turbine towers do not.
• Inform neighbours of your plans to avoid conflict later on.
• Be courteous. Keep the turbine as far away from neighbours as possible. 250-300 m away is typical.
• Check with the local government for any other laws and regulations about zoning.

Wind speeds tend to be higher on the top of a ridge or hill, and for that reason it is a good idea to locate wind turbines at hilly locations. Just remember to keep your turbine away from high turbulence. Neighbours must also be taken into consideration when picking a spot to build your turbine. The farther your wind turbine site is from neighbouring houses, the better.

Do not expect your wind turbine to generate the same amount of power all the time. The wind speed at a single location may vary considerably, and this can have a significant impact on the power production from a wind turbine. Even if the wind speed varies by only 10%, the power production from a wind turbine can vary by up to 25%!

 Example of wind speed distribution by hour of the day. Values shown are monthly averages of measurements made by anemometers.