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 Turbine Size

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Wind turbines can be arbitrarily divided into three classes: small, medium, and large. Small wind turbines are capable of generating between 50 watts and 60 kilowatts of power, and use rotors ranging in diameter from less than 1 to 15 m (3 to 50 ft). Small wind turbines are installed primarily in remote areas where power is needed but access to conventional sources of electricity is either too expensive or too unreliable. Some small turbines, known as micro-turbines, are so compact they can be carried to remote locations on horseback.

Most commercial wind machines are medium-size turbines. Medium-size turbines use rotors spanning diameters between 15 and 60 m (50 and 200 ft), and have a generating capacity ranging from 50-1,500 kilowatts. Most medium-size commercial turbines have a generating capacity in the range of 500 kilowatts to 750 kilowatts.

Large wind turbines are behemoths with rotors spanning diameters between 60 and 100 m (200 to 330 ft), and are capable of generating 2 to 3 megawatts of power. Because the cost-effectiveness of conventional coal-fired and oil-fired power plants increases with the size of the plants, it was originally thought that giant wind turbines would be more economical than smaller turbines. Various countries have attempted to develop commercial multi-megawatt wind turbines, but these machines have proved less economical and less reliable than medium-size turbines