How Solar Thermal Works | Ra Energy: Solar Hot Water Solutions

Solar thermal water heaters vary in their details, but they all do the same basic things - gather heat in a solar collector, transfer the heat directly or indirectly to the water supply, and store the heated water until it’s used. These systems use relatively simple, time-tested technology, which is one reason they are a best bet in renewable energy.

Closed loop antifreeze systems are the most popular and versatile type of solar thermal system installed worldwide. The following are the basic system components:

one or more collectors
insulated piping
a circulating pump
an expansion tank
a hot-water storage tank
a heat exchanger
solar fluid (usually a solution of water
and non-toxic propylene glycol anti-freeze)
a controller
valves and gauges

The piping loops from the collector panels to the heat exchanger and back again. This closed loop keeps the antifreeze solution inside the collectors and piping at all times.

Whenever the sun shines on the collectors the circulating pump comes on and the solar fluid circulates within the closed loop. The fluid gets hot inside the collectors and travels through the piping to the heat exchanger.

The heat exchanger transfers the heat from the fluid to the water inside the storage tank, which stores the heated water for your use. As the fluid heats, it expands, so the expansion tank is included to relieve pressure in the system.

When the sun is not shining, the circulating pump simply turns off, and the fluid stops circulating.