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.

Reliability of Wind Energy

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Wind energy is a promising source of electrical power because it is a clean and renewable resource. However, because wind speeds vary by time of day, season, and even from one year to the next, wind energy is an intermittent resource. At windy sites it is common for wind turbines to operate 60 percent of the year. Even when operating, however, the wind may be insufficiently strong for wind turbines to generate at full capacity. Overall, turbines installed on windy sites operate at an average of 25 to 35 percent of full capacity. In comparison, coal-fired power plants usually operate at an average of 75 to 85 percent of full capacity.

The intermittent nature of wind energy does not affect consumers when wind turbines are tied to an electrical network, or power grid. Many wind turbines in North America, Europe, and parts of Asia are connected to large electricity networks. The effect of windless days can be offset by production from other power-generating sources, such as coal-fired plants and hydroelectric plants that are connected to the power grid. Such a system helps provide reliable power supplies to consumers. People located in remote sites that rely on electricity from wind turbines often use batteries or a backup generator to provide auxiliary power during extended periods without sufficient wind.