In a solar hot water system the storage and management of the energy is as important as the initial capture of solar energy.

A solar hot water cylinder differs from a regular hot water cylinder in three main ways.

1. It has two heat exchange coils instead of one. The coil that transfers heat from the solar panels is at the bottom of the cylinder where the cold mains water enters. The second coil transfers heat from the gas boiler when needed at the top of the cylinder where hot water leaves.
2. It is taller and narrower than a traditional cylinder, in order to promote ‘stratification’ or the layering of water, so that the water is cooler at the bottom and hotter at the top. As the solar panel circuit will be adding energy to the water store when it is hotter than the water store, locating it in the part of the cylinder where the cold mains comes in and the water is cooler increases the amount of energy transferred. Water is drawn off from the top, where the water is hottest, minimising the amount of time the gas boiler is required to top-up the temperature.
3. They are larger than traditional cylinders, typically by up to 50%. This is to allow maximum use of the solar energy captured. On a hot day a small cylinder would be heated up quickly by the solar panels and additional solar energy would go to waste. By heating a larger volume of water you enable that energy to be captured, stored and carried through ‘for a rainy day’.

Like all cylinders, they should be well insulated to preserve the heat stored in the water as long as possible.

The choice between vented and un-vented cylinders will depend on your specific situation and we can advise on this during the survey.