A photovoltaic system uses solar cells for converting energy from the sun into electricity. Photovoltaics were initially used to power small and medium-sized photovoltaic systems, from the calculator powered by a single solar cell to off-grid home solar systems powered by a photovoltaic combination.
Concentrated Solar Systems
The technology of concentrated solar power (CSP) involves the use of solar thermal applications. There is a wide range of these solar systems. Concentrating solar power systems exist mostlyin form of a parabolic trough, the concentrating linear fresnel reflector, the Stirling dish and the solar power tower. These solar power systems all work similar: lenses, mirrors or tracking systems are used to concentrate the light of the sun into a beam. The beam heats a working fluid which runs a generator or sterling engine to generate electricity.
Solar troughs are the most widely deployed concentrated solar power systems. A parabolic trough consists of a linear parabolic reflector that concentrates light onto a receiver positioned along the reflector's focal line. The receivers in these solar systems are tubes positioned right above the middle of parabolic mirrors and are filled with working fluid. One of the largest solar power systems using CSP is the 354 MW SEGS installation in the Mojave Desert of California.
Stirling solar dish solar systems combine a parabolic concentrating dish with a Stirling engine which normally drives an electric generator. Parabolic dish systems give the highest efficiency among concentrating solar power systems.
Instead of parabolic mirrors, compact linear fresnel reflectors are solar systems that use many thin mirror strips to concentrate sunlight onto two tubes with working fluid. These solar power systems can be used in large or very compact solar systems.
A solar power tower uses an array of tracking reflectors to concentrate light on a central receiver on top of a tower. Power towers are very efficient solar systems with a good energy storage capability.
In contrast, solar thermal panels are usually used in smaller solar systems for residential water heating. They are not used as photovoltaic systems and do not generate electricity.