Solar Hot Water (Solar Thermal)

Because sunlight heats the bottom of a body of water, such as a lake, the water itself gets warmed up. It's free solar water heating from the sun. This phenomenon can be used to heat water used in buildings and swimming pools.

Solar water heating systems for buildings have two principal parts: a solar collector and a storage tank. Collectors can be either "flat-plate" or "evacuated tubes. "

A typical flat-plate collector is mounted on a rooftop, usually facing south. It is a rectangular panel with a transparent cover looking at the sun. Small tubes run through the box and carry the fluid, either water or an antifreeze solution, to be heated. The tubes are attached to a black absorber plate and as heat builds up in the collector the fluid passing through the tubes is heated.

The storage tank, usually a modified hot water heater, holds the hot water. Swimming pool systems simply use the pool to store the hot water.