Power from wind


How much power is there​ in wind?

The power in the wind is proportional to the cube of the wind speed.

The power output of a wind generator is proportional to the area swept by the rotor, and it's efficiency.

Albert Betz, a german physicist in 1919, concluded that no wind turbine can convert more than 59.3% of the kinetic energy of the wind into mechanical energy. If all the wind's energy was removed, it would stop, and wouldn't turn the blades. This is the Betz Limit.

When you allow for friction etc, the real world wind turbine can only reach up to 80% of this 59%= 47%. So:

Max power = 0.59 x .8 x Swept Area x Air Density x Velocity3..


The condensation shows the turbulence in the wake of wind turbines.

The maximum design output of this turbine is 2 MW

Each turbine is designed for maximum efficiency at a certain wind speed. Faster or slower than this and the efficiency drops.As well, the windusually blows about 30% of the time. Once the turbine reaches its design power output, any extra wind energy is not used.

A wind turbine is designed to produce a maximum of power at wide spectrum of wind speeds. All wind turbines are designed for a maximum wind speed, called the survival speed, above which they do not survive. The survival speed of commercial wind turbines is in the range of 40 m/s (144 km/h, 89 MPH) to 72 m/s (259 km/h, 161 MPH). The most common survival speed is 60 m/s (216 km/h, 134 MPH). The wind turbines have three modes of operation:

Below rated wind speed operation
Around rated wind speed operation (usually at nameplate capacity)
Above rated wind speed operation


Wind power calculator: Danish wind power assn.

Wind atlas of Canada


The CSIRO has produced an excellent "Planners Guide" to wind energy.

Prof Diesendorf (UNSW) has produced a Submission to Senate Public Inquiry on the Social and economic Impact of Rural Wind Farms  This is an excellent list of the advantages of wind power and answers to various objections.

Great website on South Aust. wind

How wind is changing SA generation (An answer to a weird article in the Australian newspaper explaining that coal fired power stations burnt the coal anyway so wind saved no CO2.)