Solar Hot Water

Solar hot water is water heated by the use of solar energy.

Solar heating systems are generally composed of solar collectors and a fluid system to move the heat from the collector to its point of usage. The system may use electricity for pumping the fluid, and have a reservoir or tank for heat storage and subsequent use. The systems may be used to heat water for a wide variety of uses, including home, business and industrial uses. Solar pool heaters, underfloor heating or energy input for space heating or cooling are more specific examples.

How the solar water heating system is pumped and controlled determines whether it is a zero carbon or a low carbon system. Low carbon systems principally use electricity to circulate the fluid through the collector. The use of electricity typically reduces the carbon savings of a system by 10% to 20%.

Conventional low carbon system designs use a AC powered circulation pump. Electronic controllers used by some systems permit a wide range of functionality such as measurement of the energy produced; more sophisticated safety functions; thermostatic and time-clock control of auxiliary heat, hot water circulation loops, or others; display or transfer of error messages or alarms; remote display panels; and remote or local datalogging.

Newer zero carbon solar water heating systems are powered by solar electric photovoltaic (PV) pumps like the Laing Solar Pump. These pumps typically use a 10-30W Photovoltaic Solar Panel which faces in the same direction as the main solar heating panel. This represents a zero operational carbon footprint and is becoming an important design goal for innovative solar thermal systems.

The pump is typically controlled by a simple Solar Powered Differential Temperature Controller (SPDTC). Newer SPDTC's are just as sophisticated as their AC powered counterparts.

The most commonly used solar collectors are the insulated, glazed, flat plate type. Less expensive panels, like polypropylene panels (for swimming pools) or more expensive and usually higher-performing ones like evacuated tube collectors, are often used.

In many climates, a solar hot water system can provide up to 85% of domestic hot water.