Solar energy, which radiates light and heat from the Sun, has been harnessed by humans since ancient times using an ever-evolving range of technologies. Solar radiation, along with secondary solar energy resources such as wind and wave power, water power and biomass, make up most of the renewable energy available on Earth. Only a very small fraction of the available solar energy is used.

On 140 acres of unused land on Nellis Air Force Base, Nev., 70,000 solar panels are part of a solar photovoltaic array that will generate 15 megawatts of solar power for the base. (U.S. Air Force photo/Airman 1st Class Nadine Y. Barclay)

Solar power means electricity generation based on heat engines and photovoltaic cells. Solar energy use is limited only by human ingenuity. Partial list of solar applications for space heating and cooling through solar architecture, through drinking water distillation and disinfection, daylighting, solar hot water , solar cooking, and high temperature process heat for industrial purposes. To collect solar energy, the most common way is to use solar panels.

Solar technologies are broadly described as either passive solar or active solar depending on how they capture, convert and distribute solar energy. Active solar engineering involves the use of photovoltaic panels and solar thermal collectors to harness energy. Passive solar engineering includes orienting a building towards the Sun, selecting materials with favorable thermal mass or scattered light properties, and designing spaces for natural air circulation ..