Wind power is the conversion of the energy of the wind into a useful form, such as electricity.  The blades of a wind turbine capture the energy of the wind as they rotate.  This energy is then transferred through mechanical connection to a generator.  The rotating blades cause the generator coils to spin inside a magnetic field generating electrons that then travel through wires to a place of energy demand.  This movement of electrons is electricity.  The amount of energy contained in the wind is a function of the wind speed cubed.  That means relatively small increases in the wind speed result in quite significant increases in the wind energy.  The amount of power a wind turbine can generate however is determined by its individual power curve.  This power curve varies depending on the type of technology and the specific unit that you select.  Please see our RENEWABLE ENERGY CALCULATOR for a comparison of some different wind turbine technologies.  The map below shows the averaged wind speeds over the United States provided by NREL.

The two major types of wind turbines are vertical axis and horizontal axis.  Vertical axis wind turbines function better in low wind speed and turbulent conditions; however they are much less efficient at high wind speeds than horizontal axis wind turbines.  Vertical axis wind turbines are growing in popularity for areas in which space is a premium and wind speeds are below those normally used for Horizontal axis turbines.  Horizontal axis turbines are by far the most common wind turbines because they offer the highest efficiency in converting wind energy into electrical power.  There are also two different types of rotor designs available for horizontal axis wind turbines:  a lift design and a drag design.  In the drag design the wind pushes the blades out of the way as it blows by.  These designs usually have many blades spaced very closely together.  The drag design produces low rotational speed but high torque.  The drag design is best for direct uses such as pumping water.  In the lift design rotor blades are shaped like airplane wings and produce high rotational speed with relatively low torque.  In these designs the blades are spaced far apart on the turbine in order to minimize turbulence between blades.  The high rotational speeds produced by the lift design are ideal for electric power generation.  As the blades spin they rotate the wire coil inside the generator’s magnetic field generating electricity.  The picture below shows a diagram of how the lift rotor design works.   

 

The implementation of a residential wind turbine requires more property considerations than that of solar hot water or solar PV.  In general wind installations require a property of 0.5 acres or greater.  The wind turbine height should be at least 2 times the height of any upwind obstruction; the rotor height should be about 30 feet higher than any obstruction within a 300-foot radius.  Typical residential tower heights are between 60 and 120 feet.  For wind turbine investments, in general the taller the tower the shorter the payback time.   

Residential scale wind turbines range in output from 1 to 100 kW with an averaged installed cost of $2,000 to $3,000/kW.  Homeowners utilizing grid tied systems do not need to supply 100% of their power needs, they can start with 50%, 25% or even 10%, then add on later as desired.  Just be sure that other components like inverters (if necessary) are sized correctly if you plan on expanding in the future.  The typical life of a wind turbine is between 20 and 30 years.  Pay back periods for this investment vary depending on local conditions and individual power requirements but can be as little as 5 years.  Please see our RENEWABLE ENERGY CALCULATOR to estimate the required investment, payback and power output for your specific location.