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Very Large Installations and Light Concentration

Light Concentration

While Photo voltaic panels are the most appropriate method for capturing light energy in domestic solar power installations, for larger scale systems, light is usually concentrated to produce heat, which in turn is used to generate electricity.
There are three main systems in use.
All photographs on this page were taken at the Platforma Solar de Almeria experimental station in southern Spain, the main facility for this type of research in Europe.

Central Receiver or Tower System

image of heliostats and tower receiver

With this system, an array of mirrors or heliostats, whose angles will be computer controlled, reflect sunlight onto a receiver at the top of a tower. The heat at this point will be used indirectly to generate steam or air that will drive a turbine, generating electricity.
The image shows an experimental system capable of producing 7MW of electricity, consisting of 300 heliostats (not aiming the light on the tower at the time of the photograph)

Parabolic Trough

The parabolic trough

The parabolic trough system is the one that is most widely used at present in commercial systems, and consists of a number of long parabolic mirrors focusing light onto a tube which carries either water or oil. This heated liquid can then be used to indirectly generate steam to drive a turbine.
Again, the angle of the mirrors will be computer controlled, maintaining the light focused on the tube.

Parabolic Dish with Stirling Motor

parabolic reflector dish with sterling motor

The parabolic reflector and stirling heat engine combination have been used in smaller commercial systems. The one shown here was not in use at the time and is pointing downwards with the stirling motor just above ground level.
In use, the circular dish reflects light onto a sterling motor which only requires heat to make the motor turn. A generator is attached to the stirling motor.