What are the types of the available solar collectors?

Answer: 

Flat Plate Solar Collectors: Flat plate System is designed with a well insulated, waterproof box containing a dark absorber plate under one or more translucent or transparent covers. Water passes through pipes located below the absorber plate.

Flat plate collectors can be very efficient in hot and sunny climates, although they do not have insulating benefits of the evacuated tube (below) that affects their performance in colder sunny climates.The Evacuated Tube Solar Collector. These collectors have multiple evacuated glass tube which heat up solar absorbers and, ultimately, solar working fluid in order to heat hot water or for space heating. The vacuum within the evacuated tube reduce conducted heat losses, allowing them to reach considerably higher temperatures than most flat-plate collectors.

 

For this reason they can perform well in colder conditions. In recent years the production volume of evacuated tube has exploded, resulting in greatly lower manufacturing and material costs. The result is that evacuated tube are now similar in price to flat plate, but with the insulating benefits of the evacuated tube, they are set to become the default choice for thermal solar applications worldwide.A difference in evacuated tube over the flat-plate type is that the constant profile of the round tube means that the collector is always perpendicular to the sun's rays and therefore the energy absorbed is approximately constant over the course of a day. Due to the high temperatures that can occur in evacuated tube, special system design considerations are made to avoid or mitigate overheating conditions.

Concentrating Collectors. Concentrating collectors are utilized to achieve temperatures in the range of 100-200 Degrees Celsius for industrial and commercial application where steam, district heating or cooling, and power may be required. The collectors are usually parabolic troughs that use reflective/mirrored surfaces to concentrate the sun's energy on an absorber tube containing heat-transfer fluid, or the water.

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