Thermosiphon Systems

Schematic diagram of a thermosiphon system. Illustration: Heindl Internet AG

Usually, the Collector is placed on the rooftop and the water tank in the basement. This means that circulating pumps have to transport the heat-transfer fluid from the tank up to the collector in order to keep the entire system working.
Thermosiphon systems work differently: the water tank is also mounted on or under the roof, but, most importantly, it is above the collector. This set-up makes it possible to use gravity for circulation.
The principle is simple: the Solar Radiation heats the heat-transfer fluid, whose density then decreases as its temperature increases. The fluid becomes lighter and rises – a phenomenon known as natural convection – inside the circulation pipes. An extra pump is not necessary. A Regulator, or Controller, is also not necessary because the sun controls the flow of the heat-transfer medium: When it shines, the heated heat-transfer fluid rises in the standpipes. The potable water is heated over a Heat Exchanger with a large surface area. The heat-transfer fluid which has cooled down then flows back to the collector – the process is back where it began.

Further information:

• http://www.solahart.com.au/

Previous Topic:
Thermal stratification (solar heating)

Next Topic:
Thermosiphonic Tank (Solar Heating)