WIND ENERGY SYSTEMS - Cd3wd

Chapter 9—Wind Power Plants 9–2
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2 SITE PREPARATION
Figure 1: Dimensions of Turbines in a Windfarm
The first step in constructing a windfarm is to acquire the right to use the land. Land
may be either purchased or leased, depending on the circumstances. Leasing land for energy
production, such as oil or gas production, is common and well understood in this country. It
holds the capital costs down to a minimum. It may be the only practical method of acquiring
large tracts of ground from many owners if a large windfarm is planned. Depending on the
type of turbine and the spacing, most of the land may still be usable for agricultural purposes.
For example, a self supported multimegawatt turbine like the MOD-2 requires only a hectare
or so (2-4 acres) around its base for maintenance. The probable density of this turbine would
be perhaps 4 to 6 per square mile in the Great Plains, which would take less than 5 percent
of the land out of production. Leasing should certainly be considered for such an installation.
On the other hand, multimegawatt turbines have not proven themselves cost effective, so
windfarms are installed with smaller turbines, mostly in the 50 - 500 kW range. The smaller
turbines will have a much greater density on the land and therefore interfere with farming
operations to a greater extent. For example, the Carter 300, a guyed turbine rated at 300
kW, with a crosswind spacing of 4 diameters and a downwind spacing of 10 rotor diameters,
would have 8 rows of 20 turbines each on a square mile of land. The access roads and guy
wires would make it very difficult to grow row crops. It may be best to buy the land, plant it
to grass to minimize erosion, and perhaps harvest the grass for cattle feed. The examples to
be given later in the chapter will assume that the land is purchased.
In the Great Plains, land is typically sold by the square mile, called a section (640 acres),
or by an integer fraction of a section. A half section contains 320 acres, a quarter section
contains 160 acres, and so on. A quarter section can be split into two 80 acre tracts, with
the dividing line either east-west or north-south. This places some constraints on the amount
of land that must be purchased. If 80 acres is not enough, then the next allowable size is
probably 160 acres. A half section would probably be the next step after a quarter section,
Wind Energy Systems by Dr. Gary L. Johnson November 21, 2001