I am often asked by prospects interested in wind projects about amount of land required by a wind project.
There are two questions:
- How many MW of wind capacity may be put in 1 SqKm (or 247 acres) of land?
- What is area of land that is made unuseable by a wind project? Meaning how much land is used up by foundation of turbine, roads, substations, storage area, admin offices, etc.? By implication rest of the land is available for agriculture, grazing or other similar purposes.
The correct answer is, detailed micrositing is required in order to accurately determine the land requirements. However, there are several rules of thumb that are employed by practioners to compute a reasonable estimate.
Answer to question 1: About 7.5MW/Sq.Km., or 1/7.5 Sq.Km. per MW or about 33 acres per MW in flat areas.
How is this number computed? Let us do simple back-of-the-envelop calculations. Assume, turbines are separated 3Dx9D, where D is the rotor diameter; in the primary direction of wind the separation is 9D and in the perpendicular direction the separation is 3D. Consider 125MW wind farm consisting of fifty 2.5MW turbines with D=100m, and the 50 turbines arranged in 5 rows. In this idealistic case, wind farm will take up 0.3*10*0.9*5=13.5 Sq.Km; that is, 9.25MW per Sq.Km. in an ideal case. This assumed a perfect array of turbines, which may be a good layout for offshore, but land is never perfect. So, applying a 20% increase in land results in 7.7 MW per Sq.Km.
Important considerations:
-
Terrain: In hilly terrain, acceptable spots for turbines are limited to ridge lines. Therefore, the land required may jump to 60 acres per MW or higher if considering a square plot of land, because valleys and shadow of mountains are not useable by wind turbines.
-
Wildlife areas and protected forests
-
Residential/industrial neighbors
-
Public utilities: roads, transmission, microwave, aviation airspace
-
Others: Primary direction of wind, 3Dx9D and capacity of turbine. Depending on the seasonal wind rose, 3Dx9D may become 5Dx9D. As the calculation above indicate changes in turbine separation, turbine capacity and other parameters will change the land requirement.
Answer to question 2: About 3/1000 Sq.Km. per MW. That is, if 0.1334 Sq.Km. of land is required per MW, only 0.003 Sq.Km. per MW will be used by physical assets of the wind farm. That is, about 2.5% to 3% of land is directly occupied by the wind farm for foundation, roads, etc.; rest of the 97% of land can be used for its original purpose.
Important considerations:
- Size of wind farm; the numbers above are for larger wind farm (>50MW)