What Is Solar Energy?
Every day the sun radiates
, or sends out, an enormous amount of energy. It radiates more energy
in one second than people have used since time began.
Where does all this energy come from? It comes from within the sun itself. Like most stars, the sun is a big gas ball made up mostly of hydrogen and helium gas. The sun makes energy in its inner core in a process called nuclear fusion.
Only a small part of the solar energy that the sun radiates into space ever reaches the earth, but that is more than enough to supply all our energy needs. Every day enough solar energy reaches the earth to supply our nation's energy needs for one and a half years!
It takes the sun's energy just a little over eight minutes to travel the 93 million miles to earth. The solar energy travels to earth at a speed of 186,000 miles per second, the speed of light.
Today people use solar energy to heat buildings and water and to generate electricity.
Heating with solar energy is not as easy as you might think. Capturing sunlight and putting it to work is difficult because the solar energy that reaches the earth is spread out over a large area. The sun does not deliver that much energy to any one place at any one time. How much solar energy your town receives depends on the time of day, the season of the year, the cloudiness of the sky, and how close you are to the earth's equator.
A solar collector is one way to capture sunlight and change it into usable heat energy. A closed car on a sunny day is like a solar collector. As sunlight passes through the car's windows, it is absorbed by the seat covers, walls, and floor of the car. The absorbed light changes into heat. The car's windows let light in, but they don't let all the heat out. A closed car can get hot!
Solar Space Heating
Space heating means heating the space inside a building. Today many homes use solar energy for space heating. A passive solar home is designed to let in as much sunlight as possible. It is like a big solar collector. Sunlight passes through the house's windows and heats the walls and floors inside the house. The light can get in, but the heat is trapped inside. A passive solar home does not depend on mechanical equipment, such as pumps and blowers, to heat the house.
An active solar home, on the other hand, uses special equipment to help heat the house. An active solar house may use special collectors that look like boxes covered with glass. These collectors are mounted on the roof top facing south to take advantage of the winter sun. Dark-colored metal plates inside the boxes absorb sunlight and change it into heat. (Black absorbs sunlight more than any other color.) Air or water flows through the collector and is warmed by the heat. The warmed-up air or water is then distributed to the rest of the house just as it would be with an ordinary furnace system.