Energy from the sun

The sun has produced energy for billions of years. Solar energy is the sun's rays (solar radiation) that reach the earth. Solar energy can be converted into other forms of energy, such as heat and electricity. In the 183os, the British astronomer John Her-schel used a solar thermal collector box (a device that absorbs sunlight to collect heat) to cook food during an expedition to Africa. Today, people use the sun's energy for lots of things.
Solar energy can be converted to thermal (or heat) energy and used to:
· Heat water - for use in homes, build­ings, or swimming pools
· Heat spaces - inside greenhouses,homes, and other buildings
Solar energy can be converted to electricity in two ways:
Photovoltaic (PV devices) or "solar cells" - change sunlight directly into electricity. PV systems are often used in remote locations that are not con­nected to the electric grid. They are also used to power watches, calcula­tors, and lighted road signs.
· Solar Power Plants - indirectly gener­ate electricity when the heat from so­lar thermal collectors is used to heat a fluid which produces steam that is used to power a generator.
The major disadvantages of solar energy are:
· The amount of sunlight that arrives at the earth's surface is not constant. It depends on location, time of day, time of year, and weather conditions.
·Because the sun doesn't deliver that much energy to anyone place at any one time, a large surface area is re­quired to collect the energy at a useful rate.