1. Useful energy that is immediately derived from the sun; for example, a system that collects and uses the heat of the sun to warm a building or to generate electricity.
2. In the larger sense, any energy source that can be ultimately traced to the action of the sun.

A proposed system to supply power from space for use on the earth.

The SPS system, or solar power satellite system, would have a huge array of solar cells that would generate electrical power to be beamed to earth in the form of microwave energy sent to a central receiver.

An energy conversion system that uses a large field of independently adjustable mirrors (heliostats) to focus solar rays on a near single point on the top of a fixed tower (receiver).