Matter & Energy


Matter is composed of atoms or groups of atoms called molecules. The arrangement of particles in a material depends on the physical state of the substance. In a solid, particles form a compact structure that resists flow. Particles in a liquid have more energy than those in a solid. They can flow past one another, but they remain close. Particles in a gas have the most energy. They move rapidly and are separated from one another by relatively large distances.

Wind Energy System Components

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Modern wind energy systems consist of three basic components: a tower on which the wind turbine is mounted; a rotor that is turned by the wind; and the nacelle, which houses the equipment, including the generator, that converts the mechanical energy in the spinning rotor into electricity. The tower supporting the rotor and generator must be strong. Rotor blades need to be light and strong in order to be aerodynamically efficient and to withstand prolonged use in high winds.

1. Tower
Improvements in structural design and construction materials have led to the construction of taller towers, allowing rotors to be mounted farther off the ground, where winds are typically stronger. Small wind turbines (less than 1 kilowatt) are installed on simple guyed (cable-anchored) poles ranging in height from 10 to 20 m (30 to 65 ft). Turbines from 1 to 30 kilowatts are installed on lattice or tubular towers ranging in height from 20 to 40 m (65 to 130 ft). Medium-size wind turbines are typically installed on tubular steel towers ranging in height from 25 to 50 m (80 to 165 ft). Wind turbine towers, which house the cables that conduct electricity from the generator through the base of the tower, can be constructed from metal, reinforced plastics, and concrete.

2. Rotor
The rotor, which spins when driven by the wind, supports blades that are designed to capture kinetic energy in the wind. Nearly all modern wind turbines have rotors that spin about an axis parallel to the ground. The spinning rotor turns a shaft which converts the wind’s energy into mechanical power. In turn, the shaft drives the generator, which converts mechanical energy into electricity. Although some modern wind turbines have rotor blades made of composite wood, most modern wind turbine blades are made of fiberglass, a lightweight, strong material typically composed of polyester resins and glass fibers. Unlike the American farm windmill, contemporary wind turbines do not use blades made from aluminum or steel; aluminum is unable to withstand continuous stress from flexing in strong winds, and steel is too heavy. Small wind turbines (see Wind Turbine Size section below) typically use a tail vane to keep the rotor pointing into the wind. Most medium-size wind turbines use an electric motor to mechanically aim the rotor into the wind.

3. Generators
The generator converts the mechanical energy of the spinning rotor into electricity. Most wind turbines use a generator and transmission in combination. Many of these wind turbines use two generators, a small generator for light winds and a large generator for strong winds. Other wind turbines use a single generator that contains dual electric windings. These dual electric windings accomplish the same task as the combination of a small and a large generator. Some wind turbines use another type of specially designed generator that is driven directly by the rotor without a transmission.