DISCUSS RENEWABLE ENERGY SOURCES.

There are many sources of energy that are renewable. In some cases, such as wood which is burned for fuel, it can be grown again and again. However, other renewable energy sources do not have to be grown or created; they simply need to be harnessed. Water is one renewable energy source. As you learned in the introduction to this lesson, large dams have been constructed to collect and store water from mountain runoff. Some of the water is used for drinking and other household needs, and some is used for irrigation. The water is also an energy source; it is used to turn equipment that creates electricity. During the last thirty years or so, people have begun to take a closer look at developing other technology to harness more energy sources. Two very promising energy sources are wind and solar energy. In this segment of the lesson, you will read more information that was prepared by the United States Energy Information Administration. You will learn about the processes and technologies that are being used to capture energy from some renewable sources.

Wind energy

Wind is air in motion. It is produced by the uneven heating of the earth's surface by the sun. Since the earth's surface is made of various land and water formations, it absorbs the sun's radiation unevenly. When the sun is shining, the air over landmasses heats up more quickly than the air over water. The warm air over the land expands and rises, and the heavier, cooler air over water moves in to take its place, creating local winds. At night, the winds are reversed because the air cools more rapidly over land than over water. Wind is called a renewable energy source because wind will continually be produced as long as the sun shines on the earth. Today, wind energy is mainly used to generate electricity.

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