Solar energy - is electromagnetic radiation, concentrated mainly in the wavelength range 0.28 ... 3.0 microns. The solar spectrum consists of:

ultraviolet wavelength 0.28 ... 0.38 microns are invisible to our eyes and make up ~ 2%;
light waves in the range 0.38 ... 0.78 mm, representing approximately 49%;
infrared wavelength 0.78 ... 3.0 mm, which accounted for most of the remaining 49%.

The remaining part of the spectrum plays a minor role in the thermal balance of the Earth.
Thus, the practical interest are only the visible and infrared part of the spectrum.
The sun provides us with 10 000 times more free energy than is actually used throughout the world.

Using solar energy can reduce heating costs by 70-80%.Next