Daniel


 * //__Solar Energy:__// **


 * //__ Sun's Energy: __//**

We have used the energy of the sun ever since the the humans have existed.The sun was worshipped as far as 5,000 years back. The sun was a influence in many different religions. Today, the sun is our simplest star. Without it, life on Earth would not exist. Plants use the sun's light to make food. Animals eat plants for food. And decomposing plants creates coal, oil and natural oil. So fossil fuels are actually sunlight stored for millions of years. The sun and other stars are responsible for ALL of our energy.



//__The sun is one of the stars in the middle of the solar system.__//

**//__Solar Hot Water:__//** In the 1980's, solar water heaters were being used all over the United States.They proved to be a big improvment over wood and coal-burning stoves. Artificial gas made from coal was available too to heat water, but it cost 10 times the price we pay for natural gas today. And electricity was even more expensive if you even had any in your town!

By 1920, ten of thousands of solar water heaters had been sold. Then, large deposits of oil and natural gasses were discovered in the Western United States. As these low cost fuels became available, solar water systems began to be replaced with heaters burning fossil fuels.

Today, solar water heaters are making a comeback. There are more than half a million of them in California alone! They heat water for use inside homes and businesses. They also heat swimming pools like in the picture. Panels on the roof of a building, like this one on the right, contain water pipes. When the sun hits the panels and the pipes, the sunlight warms them. That warmed water can then be used in a swimming pool.

//__Solar Thermal Energy:__//
Solar energy can also be used to make electricity. Some solar power plants, like the one in the picture to the right in California's Mojave Desert, use a highly curved mirror called a parabolic trough to focus the sunlight on a pipe running down a central point above the curve of the mirror. The mirror focuses the sunlight to strike the pipe, and it gets so hot that it can boil water into steam. That steam can then be used to turn a turbine to make electricity.

In California's Mojave desert, there are huge rows of solar mirrors arranged in what's called "solar thermal power plants" that use this idea to make electricity for more than 350,000 homes. The problem with solar energy is that it works only when the sun is shining. So, on cloudy days and at night, the power plants can't create energy. Some solar plants, are a "hybrid" technology.

Another form of solar power plants to make electricity is called a Central Tower Power Plant, like the one to the right - the Solar Two Project. Sunlight is reflected off 1,800 mirrors circling the tall tower. The mirrors are called heliostats and move and turn to face the sun all day long. The light is reflected back to the top of the tower in the center of the circle where a fluid is turned very hot by the sun's rays. That fluid can be used to boil water to make steam to turn a turbine and a generator. This experimental power plant is called Solar II. It was re-built in California's desert using newer technologies than when it was first built in the early 1980s. Solar II will use the sunlight to change heat into mechanical energy in the turbine. The power plant will make enough electricity to power about 10,000 homes. Scientists say larger central tower power plants can make electricity for 100,000 to 200,000 homes.

But when most of us think of solar energy, we think of satellites in outer space.