The site needs to have a good wind resource. Unlike a gas generator, a wind turbine will not work at every site. Without enough fuel (wind), a wind turbine cannot run at its designed efficiency and will not produce the expected amount of power. A good wind resource includes a sufficiently high wind speed and minimal turbulence.

Most wind systems are grid-tied as opposed to battery based systems. This means that there is no need for batteries and the electricity generated by the wind system will be used directly by the loads at the site and any excess will be “stored” on the utility power grid. This is good news for wind systems because it eliminates the expense and maintenance of a battery bank, and the system is more efficient. The only downside is that when the utility grid goes down (during a power outage) the wind system also shuts down for safety reasons and no energy will be delivered. This is not a significant concern in areas where power outages are rare.

The surrounding terrain should be relatively free of clutter. Wooded and urban areas are considered very cluttered. Obstructions around the turbine, such as trees or buildings, cause turbulence, which not only reduces the efficiency of the turbine; it also shortens its life due to the additional wear and tear. Taller towers may be needed to get the system above any turbulence created by ground obstructions.

The energy generated by a wind turbine is directly proportional to the “swept area”. The area that is encompassed by the blades when they are spinning. Power is actually proportional to the square of the blade length; Increases in blade length significantly increase the power output. 

Wind turbines need to be on tall towers. Because of the friction between the wind and the earth, wind speed increases rapidly with increasing distance from the ground, especially in the first 60’. This effect is magnified when there is a significant amount of ground clutter and turbulence. A general rule for determining the tower height is that the bottom of the turbine rotor should be 30’ above the tallest obstruction within 500’. For trees, this means the mature tree height over the 20 to 30 year life of the turbine, not the tree height when the site assessment was done. For residential or small business sized wind systems, towers of 100’ to 140’ are common. 

The site for the wind system must be accessible, either for a crane or with space enough for a tilt-up a tower. Most wind systems, even residential sizes, need a crane during installation to raise the tower and/or to lift and place the turbine on top of the tower, and in case of major maintenance or repair. Accessibility issues include steep ridges, low overhead power lines, dense woods, crossing streams, etc.

A Certified Site Assessment will provide you site-specific information on how a wind or solar (PV) system would perform at a specific location, including information on system options, minimum tower height, shade analysis, installation concerns, the available resource, estimated energy production, estimated costs, and financial incentives. We have Wind and Solar Site Assessors on staff Certified by the Midwest Renewable Energy Association (MREA). Site assessment reports provide all the information you will need to make an educated decision on whether a renewable energy system will work for you, and the next steps to take.