Solar Power Systems
Photoelectric and Concentrating Solar Power Systems
Solar power systems convert sunlight into electricity either directly using photovoltaics, or indirectly using concentrating solar power technologies. Photovoltaics convert light into electric current using the photoelectric effect. Concentrated solar power systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam.
Photoelectric Solar Power Systems
Photoelectric solar power systems use photovoltaic cells to convert energy from the sun into electricity. Photovoltaics were initially used to power small- and medium-sized solar power systems, such as the calculator, which is powered by a single solar cell, and off-grid homes, which are powered by a photovoltaic array.
Concentrated Solar Power Systems
The technology of concentrated solar power (CSP) involves the use of solar thermal applications. There is a wide range of concentrating solar power systems. Most developed are the parabolic trough, the concentrating linear fresnel reflector, the Stirling dish, and the solar power tower. These solar power systems all work similarly in that 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 dish at Ben-Gurion National Solar Energy Center in Israel
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 receiver is a tube positioned right above the middle of the parabolic mirror and is filled with a working fluid. One of the largest solar power systems using CSP is the 354 MW SEGS installation in the Mojave Desert of California.
The Stirling solar dish combines a parabolic concentrating dish with a Stirling engine that 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 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 plants.
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 and have a good energy storage capability.
In contrast, solar thermal panels are usually used in smaller applications for residential water heating. They are not used as solar power systems and do not generate electricity.