Introduction
Sun
The heat of the sun is about equivalent to burning a billion trillion tons of coal an hour. Even though only a small fraction of that heat ever reaches the earth it is still more then enough to power the whole world.

People seemed to realize the importance of the sun around 30,000 BC. This was when people first started planting crops of wheat. They realized plants did better when planted in the sun over the shade. This caused them to worship the sun as a God. Many cultures built large and extravagant temples to worship the sun in. Other cultures built places to observe the sun in, such as Stonehenge in England.

Different Types of Solar Panels
There are three main types of solar panels. They are flat plate collectors, focusing collectors, and solar cells.
The first kind is a flat plate collector. Flat plate collectors are fastened on the top of the roof of a house. They usually either heat the house or its water.  A flat plate collector consists of a black rectangular frame, two or three sheets of glass, and copper plumbing. A flat plat collector uses the greenhouse affect. The sunrays go through the glass but can’t get out through the glass. The sunrays heat the water-filled copper tubes. Then the water is used to heat the home or water.

Another type of a solar panel is a focusing collector. They consist of a mirror or mirrors which are focused in one spot. Some focusing collectors are solar furnaces, parabolic dishes and troughs and power towers.

The first type is a solar furnace. A solar furnace consists of many mirrors that are aimed at a large curved mirror that is aimed at a large steel building. This building can get as hot as 5,790 F. Scientists use solar furnaces to run experiments to see how certain materials react to extreme heats. They are also used industrially to melt metals.

The next kind of focusing collector is a parabolic trough and dish. A parabolic dish looks just like a satellite dish except the dish part is to reflect the sunrays onto the vocal point which is filled with oil. The heated oil is used to produce steam to turn a turbine. A parabolic trough uses the same principles as a parabolic dish. The only differences are how they look, the mirror is shaped like a large feeding trough and the vocal point is an oil filled tube. These are used for either commercial such as in a power plant.

The last focusing collector is a power tower. A power tower has many mirrors all focused on a large tower. This tower gets extremely hot. The tower is filled with oil. When the oil is heated it is piped to a power plant where it is used to produce steam that turns a turbine. These are used for power plants.

The final type of solar panel is a solar cell. A solar cell usually consists of two layers of silicon that produce an electric charge which is picked up by wires that are laid across the silicon. Solar cells can be used for anything from powering an isolated phone booth to a whole city or even an airplane.