Solar DHW Systems

According to the U.S. Department of Energy, a solar water heater is also known as a solar domestic hot water system (DHW). A solar DHW uses the heat and energy of the sun to heat water and reduces the use of electric, gas, wood, propane or oil hot water heaters.

Types

• According to the U.S. Department of Energy, the two basic types of solar DHWs are active and passive systems. Active systems use pumps, controllers and circulators to keep hot water available. A passive system uses insulation techniques to maintain water temperatures; a good example is a hot water tank painted black to absorb the sun's energy.

Back-Up

• The Vermont Solar Energy Guide explains that the majority of Solar DHWs in the United States are designed with a back-up, fossil fuel-powered hot water heater to provide hot water when solar power is insufficient. Solar DHWs are designed to provide a year-round average of 65 percent of a household's hot water.

Process

• The majority of solar DHWs use solar collectors to heat water, according to the Vermont Energy Guide. A solar collector contains an absorber plate coated in dark material that absorbs the heat of the sun and transfers it to pipes filled with water or an anti-freeze fluid. In cooler climates an anti-freeze fluid is used with a heat exchanger that allows the heat absorbed by the anti-freeze to be transferred to residential water without the fluids coming into physical contact.