Solar Hot Water

Solar thermal systems include a rather large category of energy collection and distribution devices for pool heating, domestic water heating, and space heating via radiant floor heating or water-to-air heat exchangers.

Installing a solar domestic hot water (SDHW) system is one of the best investments homeowners can make to reduce their electric or natural gas water heating bills, with typical financial paybacks at less than eight years. Depending on the size of the system you install, your local climate, and your hot water use, SDHW systems can cut your water heating bills by 40 to 80 percent. Systems have been designed for all types of applications. Whether you live in the farthest reaches of Alaska, in cloudy Seattle, or by the beach in Jamaica—an SDHW system can work for you.

A collector is used to collect the solar energy using a heat transfer fluid. There are three basic types of collectors:

• The flat plate collector is the most common type of collector. It consists of an insulated weatherproof box containing a dark solar absorber plate under one or more transparent covering layers.
• The evacuated-tube collector is made up of rows of parallel, transparent glass tubes. Each tube consists of a glass outer tube and an inner tube, or absorber, covered with a selective coating that absorbs solar energy well but inhibits radiative heat loss. The air is removed from the space between the tubes to form a vacuum, which eliminates conductive and convective heat losses.
• Concentrating collectors for residential applications are usually parabolic troughs that use mirrored surfaces to concentrate the solar energy on an absorber tube, called a receiver, containing a heat-transfer fluid.