# >> College & Higher Education >> College

How to Determine the Average Wind Speed at Hub Height

Wind speed changes with elevation above the ground. Near the Earth's surface, air is slowed down by friction from the terrain, trees or even buildings. As you gain elevation, friction is greatly reduced and airspeed increases. The change in speed greatly affects the planning for wind farms and the construction of turbines. Because of their huge size, turbine blades experience different forces from the wind as they rotate. The blades at the top are hit with higher winds than those at the bottom. As a result, knowing the wind speed at hub height is very important for turbine engineers.

Instructions

- 1
  Determine the shear exponent for the terrain around the turbine. The shear exponent represents the roughness of terrian based on hills, buildings or vegetation. A smooth surface has a value of 0.10, but a very rough surface is closer to 0.30. The shear exponent is labeled using the variable "n."
- 2
  Measure or calculate the hub height for the turbine in feet. Record this value as "H2."
- 3
  Measure or estimate the wind speed near the ground in miles per hour, a standard height for weather stations is 10 meters or about 33 feet. Make sure to record the height at which the speed is recorded. Record the height as "H1" and the speed as "V1."
- 4
  Divide the hub height (H2) by the height of your known wind speed (H1) near the ground.
- 5
  Raise the result from Step 4 to the power of the shear exponent (n).
- 6
  Multiply the result from Step 5 by the velocity at or near the ground (V1). This number is the wind speed at hub height in miles per hour.

Contextual Factors in Qualitative Research

How to Number the Pages of College Essays