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<\/a><\/p>\nFlat plate collectors, developed in the 1950s, are the most common, and are comprised of a dark flat plate (hence the name), with a transparent cover to reduce heat loss, a fluid or gas to transport the heat, and an insulated backing. Once heat is absorbed in the absorber, it is transferred to an area with water pipes where the heat is transferred to the water. From there, the hot water usually goes to an insulated holding tank until it is ready to use.<\/p>\n
Flat plate collector systems are sized at approximately a half to a full square foot of panel per gallon used per day. The absorbers are traditionally made of metal, with copper being the most conductive, but new polymers are being tried in Europe. Polymers are more flexible and also are freeze-tolerant.<\/p>\n
Evacuated tube collector panels are made up of a series of vacuum packed glass tubes with an absorber plate inside that is connected to a heat pipe. The heat from the heat pipe is transferred to the water in a manifold, which is insulated and has a protective cover on it.<\/p>\n
The evacuated tube system is better in colder climates, as the vacuum tubes transfer heat more efficiently, without heat loss due to convection and conduction. This type of system requires less area than a flat plate collector system of the same capacity, though the tube system costs more. Both systems have a long life span \u2013 25 to 30 years.<\/p>\n