Wind Turbines: Three Critical Factors for a Successful Site

 As fuel prices rise and the climate warms everyone is looking for alternative sources of energy to power our lives and wind is an obvious source.  Wind turbines have been used to capture energy from the wind for many years.  In the 1920’s there were approximately 12 manufacturers of wind turbines including the Zenith Wincharger which could be purchased through the Sears catalog.  Turbines like the Wincharger brought electricity to remote areas enabling farmers to have some basic electrical devices such as radios.  Small wind turbines became a common sight throughout rural America.   However, in the 1930’s electric power lines began crossing the country to bring electricity to these farming communities.  The result was to drive the wind turbine manufacturers out of business.

Now, with a desire to produce electricity from clean sources, the wind turbine is making a long overdue comeback.   Today’s turbines are more efficient, quieter and will supply more power, but before we make the choice to install a wind turbine in our neighborhood, back yard, or community, it is important to understand three basic factors about effective wind turbine siting.

Wind:  For a wind turbine to be effective there must be a good source of wind.  The best way to determine if your site has adequate wind is to install a meteorological tower and to measure the wind for at least a year.  If this is not feasible, there are several resources online which can give a rough estimate of your wind resource such as http://firstlook.3tiergroup.com/.  These online resources do not replace measuring at your specific site, but they provide useful general information.

Wind speed:  When extracting power from the wind, the most critical factor is the wind speed.  The power in the wind is a cubic function of the wind speed (Power = ½ air density x swept area x velocity³).   Doubling the wind speed will mean 8 times more power.  Each wind turbine has a range of wind speeds at which it will generate electricity.  On the low end is the ‘cut in’ speed where the turbine will begin spinning fast enough to generate a small amount of electricity; then there is the ‘rated’ wind speed which is the speed at which the turbine is designed to produce its’ rated power (i.e., the speed at which a 10kW turbine is designed to produce 10kW); and, on the high end, there is the ‘cut-out’ wind speed which is the speed at which the turbine will shut down to protect itself from dangerously high winds.  Although wind speed fluctuates at every site, it is important to find a site where the average wind speed is close to the rated wind speed for your selected turbine.

Hub height:  The height of the hub of your turbine can determine success or failure.  There are two primary things to consider when determining how high a tower needs to be to enable an effective wind turbine.  The first is that the speed of the wind will increase with height.  So, in most cases the wind turbine will be able to extract more power from the wind if it is installed on a higher tower.  The second consideration when determining height is turbulence avoidance.  Air turbulence is trouble for a wind turbine.   Turbulence will decrease the effectiveness of the turbine resulting in decreased electricity generation and it will increase the wear and tear on the turbine resulting in increased maintenance.  Turbulence is caused by objects in the path of the wind including buildings, trees, bushes, and hills.  A general rule of thumb is to install a wind turbine at least 30 feet higher than any obstruction (trees, buildings, etc.) within 500 feet.

If you have a site with a strong wind resource, which provides good wind speed and will support the installation of a tower well above any local obstructions, then you have the basic foundation in place to explore installing a turbine to generate electricity from wind.