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School of Terrestrial Wind Energy

invites you to consider issues concerning

::: Wind System Siting and Placement :::

also see: Wind regime schematics

The first step in the wise selection of a site is to understand the general topography of the land you have to work with.

1. The best site in general is one completely unobstructed for at least 300 yards in all directions.

2. The generator ought to be up high enough so as to clear all obstacles around by at least 15-20 feet, preferably more.

3. Locate wind generators between the direction of prevailing winds and the object(s). Any object higher than the wind generator will cause a disturbance in air flow for approximately 300 yards upstream of the generator and 50-100 yards downstream.

Flat Expanses

The windiest areas are wide open spaces because there is less frictional drag than over rugged terrain. One of the windiest spots in the country is Fargo, North Dakota (with an average ground wind velocity of 14.4). Fargo is located on one of the flattest large expanses of land in the continental United States.

Proximity to Water

Sites near a body of water generally experience higher wind velocity, caused by the temperature differences between the air over the water and that of the air over the land. Count on a daily shift of wind direction both in the morning and in the evening. Temperatures of land masses rise and fall more quickly than water surfaces, i.e., land is warmer than water during the day and cooler at night. During the day the air moves from the cooler water towards the warmer land and at night it shifts direction and moves from the warmer water to the cooler land mass.


Mountainous areas have local wind patterns similar to a site near a body of water. In the daytime, air next to a mountain slope is heated by contact with the ground from solar. This air usually becomes warmer than air at the same altitude, but farther from the slope. Surrounding colder, dense air settles downward and forces the warmer air, near the ground, up the mountain, producing the "valley wind," called thus because the air seems to be flowing up and out of the valley.

Conversely, at night the air in contact with the mountain is cooler than farther from the land mass and so the cooler air sinks along the slope producing the mountain breeze.

These constant temperature differences produce consistently higher wind velocities than in other locales. Hills and ground wells cause an unpredictable variety of wind patterns. At some locations the wind is obstructed completely, at others a venturrie effect is caused by converging winds, thereby creating a very favorable wind generator site.


Barriers produce disturbed areas of airflow downwind, called wakes. In barrier wakes, wind speed is reduced and rapid changes in wind speed and direction, called turbulence, are increased. Because most wind generators have relatively thin blades that rotate at high speeds, barrier wakes should be avoided whenever possible, not only to maximize power, but also to minimize turbulence. Exposure to turbulence may greatly shorten the lifespan of small wind systems.


Since it is likely that buildings will be located near a wind system site, it is important to know how barriers affect airflow and available power. Building wakes increase in height immediately downstream. The wind flows around the building forming a horseshoe-shaped wake, beginning just upstream of the building and extending some distance downstream.

A general rule of thumb for avoiding most of the adverse effects of building wakes is to site the wind system:

* upwind a distance of more than two times the height of the building. Upwind and downwind indicate directions along the principal power direction.

* Downwind a minimum distance of ten (preferably 20) times the building height, or

* At least the building height above ground if the wind system is immediately downwind of the building.


Ridges are defined as elongated hills that reach less than or equal to 2,000 ft. above surrounding terrain and have little or no flat area on the summit. There are three advantages to locating a wind system on a ridge:

1. The ridge acts as a tower.
2. The undesirable effects of cooling near the ground are partially avoided.

The ridge may accelerate the airflow over it, thereby increasing the available power. The first two advantages are not unique to ridges but apply to all topographical features having high relief (hills, mountains, etc.)

The most important considerations in siting wind systems on or near ridges are summarized thus:

1. The best ridges or sections of a single ridge are those most nearly perpendicular to the prevailing wind. (however, a ridge several hundred feet higher than another and only slightly less perpendicular to the wind is preferable.)

2. Ridges or sections of a single ridge having the most ideal slopes within several hundred yards of the crest should be selected. Ridge sites meriting special consideration are those with features such as gaps, passes, or saddles.

3. Sites where turbulence or excessive wind shear cannot be avoided should not be considered.

4. Roughness and barriers must be considered.

5. If siting on the ridge crest is not possible, the site should be either on the ends or as high as possible on the windward slope of the ridge. The foot of the ridge and the leeward side should be avoided.

6. Vegetation may indicate the ridge section having the strongest winds.

Flat-topped ridges present special problems because they can actually create hazardous wind shear at low levels. Siting a wind system at these low levels will cause unequal loads on the blade as it rotates through areas of different wind speeds, will create rapid fluctuations in direction, and could decrease performance and the life of the blades. These problems can be avoided by increasing the tower height to allow the blade to clear the shear zone.

View Wind regime schematics now!

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