Difference between direct and indirect solar hot water

One of the questions we get asked here at Sunwatt is, "what is the difference between indirect and direct solar hot water systems?"

With direct solar hot water systems, the solar water heaters work by absorbing energy from the sun’s rays in roof mounted solar collectors. This energy is transferred to heat water stored in the storage tank. Ground mounted systems rely on inbuilt pumps to push the water through the system, whereas roof mounted systems rely on a natural ‘thermosiphon’ effect. 

Typically water passes through channels in the solar collector where the water is heated. As the water moves out of the collector and into the tank, the tank gradually gets hotter until the water reaches its maximum stored temperature.

The story is a bit different with indirect solar hot water systems. Indirect models are designed for frost prone areas and work in much the same way as direct models but rather than heating water ‘directly’ in the solar collectors, heat exchange fluid with anti-freeze properties is heated. This in turn ‘indirectly’ heats the water. Indirect heating prevents water freezing and damage to collectors.