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November 15, 2007

Renewable energy is an energy that quickly replaces itself and is usually available in a never-ending supply. Renewable energy comes from the natural flow of sunlight, wind, or water around the Earth. With the help of special collectors, we can capture some of this energy and put it to use in our homes and businesses. As long as sunlight, water and wind

continue to flow and trees and other plants continue to grow, we have access to a ready of supply of energy.

KINDS OF RENEWABLE ENERGY 

¯    SOLAR ENERGY

The sun has produced energy for billions of years.  Solar energy is the solar radiation that reaches the earth. Solar energy can be converted directly or indirectly into other forms of energy, such as heat and electricity. Solar energy is used for heating water for domestic use, space heating of buildings, drying agricultural products, and generating electrical energy. Electricity can be produced from solar energy using photovoltaic devices.Photovoltaic energy is the conversion of sunlight into electricity through a photovoltaic (PVs) cell, commonly called a solar cell.

¯    WIND ENERGY

The History of Wind

Since ancient times, people have harnessed the winds energy. Over 5,000 years ago, the ancient Egyptians used wind to sail ships on the Nile River. Later, people built windmills to grind wheat and other grains.

Americans used small windmills to generate electricity in rural areas without electric service.

Wind energy is really just another form of solar energy. Wind is simple air in motion. It is caused by the uneven heating of the earth’s surface by the sun. Since the earth’s surface is made of very different types of land and water, it absorbs the sun’s heat at different rates. During the day, the air above the land heats up more quickly than the air over water. The warm air over the land expands and rises, and the heavier, cooler air rushes in to take its place, creating winds.

HOW WIND MACHINES WORK

Like old fashioned windmills, The wind flows over the airfoil shaped blades causing them to turn. The blades are connected to a drive shaft that turns an electric generator to produce electricity.

There are two types of wind machines used today: horizontal–axis wind machines and vertical-axis wind machines. Most windmills are the horizontal-axis type. One wind machine can produce 1.5 to 4.0 million kilowatthours (kWh) of electricity a year. That is enough electricity for to power 150-400 homes.

there is some other kinks of renewable engery that we will speak in an other lesson

More entries: Renewable energy

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