Wind Energy Systems
Summary
- Overview
- How it Works
- More Physics
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Fig. 1 above shows the old and the new way of building windmills (or wind turbines). The Old mill is a very common sight in the Baltic island of Oland (Sweden); the new wind turbine is the giant 2 MW Tjaereborg turbine (Denmark).
In recent years, development of the new variable-pitch wind turbines, along with
sophisticated electronic controls, has produced machines that can operate at their
rated power output over a wide range of wind speeds.
The idea to capture the energy from the wind is very old, and the wind mill shown
above is a prove that a grasp of elementary aerodynamics was a basic knowledge of
farmers several centuries ago.
The wind can be captured by proper design of the blades. Rotation can be maintained
for as long as there is an axial momentum on the shaft that is balanced by some
resistance (namely an electric generator). The simplest model consists of a
streamtube of air flowing through the rotor disk that looses speed and increases
pressure in the process.
The ability to control three-dimensional unsteady separated flow could dramatically
improve both performance and life span of a wind turbine. Hence the interest in
sophisticated CFD methods.
How it Works
More Physics
Selected References
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