Solar energy is a term that usually means the direct use of sunlight to produce heat or electric power. The sun's energy is plentiful, but it is thinly distributed over a large area and must be collected and concentrated to produce usable power. As a result, solar energy is a more expensive power source than fossil fuels for most applications. Solar technology is improving rapidly, though. Someday, it may provide a clean and abundant source of power.
There are two chief ways that sunlight may be converted into electric power: (1) directly, in a process called photovoltaic conversion, or (2) by solar thermal conversion, which converts light to heat and then to electric power. Most solar thermal devices heat water to produce steam, which drives a steam turbine.
Nearly all the energy that we use is actually solar energy
