Solar Water Heater

Solar hot water systems can be a cost effective way to generate hot water for your home. They can be used in any climate, and the fuel they use, sunshine, is free.
Solar water heating systems include storage tanks and solar collectors. Most solar water heaters require a well-insulated storage tank. There are three different types of solar collectors used to heat the water in the system :

• 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.

• Evacuated-tube solar collectors

  They feature 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.

(provided by the u.s. department of energywebsite)

Heres a diagram of the system