Solar domestic hot water (SDHW) systems collect and store the sun’s radiant energy to produce and store hot water for use in the kitchen, bath and laundry. SDHW systems used on Long Island utilize a roof-mounted flat plate collector panel. Fluid in the collector, heated by the sun, is circulated into the house where it transfers its heat into the domestic water in an insulated tank. The fluid, now at a lower temperature, is pumped back to the roof to gather more heat. A thermostat indicates if additional backup heat is required to supplement the solar heated water.
The SDHW system used on Long Island is an active system with circulating pumps and controls. Passive systems are not typically used in climates where temperatures fall below freezing.
Solar water heaters require a well-insulated storage tank, similar to a conventional water heater, but with additional connections to and from the collector. In two-tank systems, the solar water heater preheats water before it enters the conventional water heater. In space-saving one-tank systems, the back-up heater is combined with the solar storage tank.