Wind Power

Power generated from the wind


The theoretically available power in air moving - wind - can be expressed as

P = 1/2 ρ A v3         (1)


P = power (W)

ρ = density of air (kg/m3)

A = area the wind is passing through the wind mill - perpendicular to the wind (m2)

v = wind velocity (m/s)

Be aware that density of air decrease with temperature and altitude and that the major factor in power generation is the wind velocity.

  • 20% increase in wind velocity - increases power generation with 73%

Theoretical and rated wind power generation from typical windmills are indicated in the "wind speed-power curve" below. Cut-in wind speed, rated wind speed, shut-down wind speed and rated power for windmills with 20% and 40% efficiency are indicated.

wind speed power curve

Actual Available Power

can be expressed as

Pa = 1/2 ξ ρ A v3         (2)


ξ = efficiency of the windmill (in general less than 0.4 - or 40%)

Related Mobile Apps from The Engineering ToolBox Engineering Toolbox Apps

- free apps for offline use on mobile devices.

Online Wind Power Calculator

The calculator below can be used to calculate the available power from a windmill:

Density (kg/m3)

Efficiency - ξ

Wind velocity (m/s)

Windmill diameter (m)

Generated Wind Energy

The energy generated by a windmill depends on the power generation as indicated above - and how often, or how many hours the wind blows - or more scientifically - the "wind speed frequency distribution" at the actual location.

The total energy generated over a year can be calculated by summarizing the power generation for all velocities (ranging from the actual windmill cut-in speed to the shut-down speed) multiplied with the no. of hours the wind blows at the actual speeds.

A typical wind speed frequency distribution diagram with energy produced at the different velocities are indicated below.

wind speed frequency distribution diagram

Related Topics

  • Environment - Climate, Meteorology, Sun, Wind and environmental resources ..
  • Fluid Mechanics - The study of fluids - liquids and gases. Involves various properties of the fluid, such as velocity, pressure, density and temperature, as functions of space and time.

Related Documents

Tag Search

Search the Engineering ToolBox

- "Search is the most efficient way to navigate the Engineering ToolBox!"

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your SketchUp model with the Engineering ToolBox - SketchUp Extension/Plugin - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!

Translate the Engineering ToolBox!
About the Engineering ToolBox!

Support the ToolBox

If you find the Engineering ToolBox useful and want this website to be available tomorrow - and the days after tomorrow - enable ads or make a contribution!

Contribute to the Engineering ToolBox