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How do windmills convert moving air into mechanical energy?
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energy conversion
Before the Industrial Revolution, power came from three main sources: humans, draft animals, and water.
The ingenuity people used in harnessing waterpower can be seen in this medieval-style mill. The waterwheel is turned by a stream and is connected to a shaft that leads into the building. At the other end of the shaft is a gear. The connection of a series of gears translates the power from the stream to a shaft that drives a millstone, which grinds flour from grain.
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Windmills, or wind turbines, convert the kinetic energy of moving air into mechanical energy through the interaction of wind with the device's blades.12
The process works as follows:
- Blade Design: The blades are mounted at an angle or given a slight twist, similar to an airplane propeller.32
- Force Division: When wind strikes these slanted blades, the force is divided into two components. One component acts in the plane of the blades, which imparts rotational motion to the rotor.3
- Mechanical Transmission: The blades are attached to a shaft (or windshaft). As the wind pushes the blades, they rotate, causing the shaft to spin. This spinning shaft serves as the source of mechanical energy, which can be used directly to power machinery—such as grinding grain or pumping water—or connected to an electrical generator to produce electricity.431
To operate efficiently, the blades must be positioned to face the wind squarely, a task often managed by automatic mechanisms like a fantail or by rotating the turbine's cap or body.3