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SOLAR COLLECTORS

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Solar water heating systems are a two part system: the storage tank and the solar collectors. There are also two types of solar water heating systems: (1) active: which have circulating pumps and controls and (2) passive: those that don't ave the pumps and controls.

Solar water heaters should have, and some even require, a well-insulated storage tank. Solar storage tanks have an additional outlet and inlet connected to and from the collector. In two-tank systems, the solar water heater preheats water before it enters the conventional water heater. In one-tank systems, the back-up heater is combined with the solar storage in one tank.

There are three types of solar collectors that are used for residential applications:

Evacuated-tube solar collectors - The evacuated tub solar collectors have parallel rows of transparent glass tubes. Each tube contains a glass outer tube and metal absorber tube attached to a fin. The fin's coating absorbs solar energy but inhibits radiative heat loss. These collectors are used more frequently for U.S. commercial applications.
Flat-plate collector - Glazed flat-plate collectors are insulated, weatherproofed boxes that contain a dark absorber plate under one or more glass or plastic (polymer) covers. Unglazed flat-plate collectors—typically used for solar pool heating —have a dark absorber plate, made of metal or polymer, without a cover or enclosure.
Integral collector-storage systems - Also known as ICS or batch systems, they feature one or more black tanks or tubes in an insulated, glazed box. Cold water first passes through the solar collector, which preheats the water. The water then continues on to the conventional backup water heater, providing a reliable source of hot water. They should be installed only in mild-freeze climates because the outdoor pipes could freeze in severe, cold weather.