The water in a solar water heating system needs to be circulated for the system to work. Several methods are used to circulate the water within the system including pumps and the thermo-siphon principle.

Pumped / Active

Active solar water heating systems use a pump to circulate the water within the solar heating system.

One advantage of using a pumped system is that you can easily hide your geyser inside the roof to help improve aesthetics.

The pumps typically used in solar water heating systems are very quiet, draw very little electricity (less than 150 Watts) and are either driven by a solar controller or by a Solar PV panel.

Thermo-siphon

Thermo-siphon systems make use of the fact that hot water rises and cold water sinks. This is a great solution to circulating water within a solar water heating system where the storage tank (geyser) can be installed higher than the solar collector. The solar collector and tank typically need to be close to one another for the process to work efficiently.

A solar collector is the device that is typically placed North facing on your roof which absorbs Sun light and converts it into heat. The heat produced by the solar collector is in turn used to heat the water inside your geyser.

There are various types of solar collectors on the market and the two most popular types are:

• Evacuated tube collectors
• Flat plate collectors

Evacuated tube collector

Demo of how hot evacuated tubes can get in just 30 minutes:

How evacuated tubes are manufactured:

Flat plate collector

Demo of how flat late collectors are used in commercial systems.