The Difference between conventional and a solar hot water cylinders mostly lies with the amount of entry and exit points to and from the cylinders. Solar hot water cylinders should be very well insulated and be made from non-corrosive materials as they are commonly mounted outside.
In a conventional cylinder there are two points:
- cold water inlet
- hot water outlet
In a solar cylinder there are 4 points:
- cold water inlet
- cold feed to solar collector
- hot water outlet for household use
- hot water return from solar collector.
Direct hot water cylinders
This type of hot water cylinder is for use in frost free areas.
In a direct system the water in the cylinder gets circulated through the solar collector to heat up the water.
Indirect hot water cylinders ( freeze protected)
This type of hot water cylinder is for use in areas where frost occurs. In indirect solar hot water cylinders the heating of the water is done by means of a heat exchanger that is usually located at the bottom of the hot water cylinder. Instead of water, a anti-freeze liqued is circulated through the collector and heat exchanger. The electrical heating element is placed in the middle of the cylinder. The reason for this is that the element only heats up the upper half of the storage unit if neccesary and not the whole volume. This differs from conventional geysers where the heating element is located at the bottom of the geyser.
