concentrating solar collector
A solar furnace harnesses the Sun's energy by focusing its heat, using large lenses or mirrors. This furnace at Mont-Louis in France gets hot enough – 3,000°C (5,430°F) – to melt metals. The heat, which is completely clean and uncontaminated by fuel gases, cold be concentrated on a boiler to raise steam for domestic heating or for driving a turbine for generating electricity. Generally, a set of flat mirrors is arrange to follow automatically the path of the Sun and reflect its rays on to the stationary furnace mirror. The tracking mirror is called a heliostat and may be driven by an electric motor so that it moves through exactly 15 minutes of arc every hour. Alternatively, the angle of the heliostat may be controlled by a photocell or thermocouple that detects the absence of light or heat rays.
A concentrating solar collector is a solar collector that uses reflective surfaces to concentrate sunlight onto a small area, where it is absorbed and converted to heat or, in the case of solar photovoltaic (PV) devices, into electricity. Concentrators can increase the power flux of sunlight hundreds of times. This class of collector is used for high-temperature applications such as steam production for the generation of electricity and thermal detoxification. Concentrating collectors are best suited to climates that have a high percentage of clear sky days.
The main types of concentrating collectors are:
A PV concentrating module uses optical elements (Fresnel lenses) to increase the amount of sunlight incident onto a PV cell. Concentrating PV modules/arrays must track the sun and use only the direct sunlight because the diffuse portion can't be focused onto the PV cells.
Concentrating collectors for home or small business solar water heating applications are usually parabolic troughs that concentrate the sun's energy on an absorber tube (called a receiver), which contains a heat-transfer fluid.
|Parabolic trough collector.