Solar Thermal Explained

Solar water heating, also known as solar thermal, is designed to assist domestic homes with their supply of solar hot water. Although the system is often called solar heating, very few solar thermal systems do more than just hot water.

How the System Works

Solar water heating works by heating water using free energy from the Sun.

It does this by collecting energy from sunlight in a solar collector and using this to heat and store water in a hot water cylinder for future use.

Typically the solar collector is either a flat plate solar panel or one containing solar evacuated tubes. The panel can be attached to a south facing roof, free standing support and with some products can be installed on flat and vertical roofs and walls.

Both of these panels work by collecting sunlight which they use to heat a fluid that is circulated in pipes underneath the panel's glass surface. The fluid used in the tubes is either plain water or more usually an antifreeze mix containing propylene glycol.

This fluid is quickly heated by the sun and because it is thermally insulated, gets hot even in low sunlight. The hot fluid is then piped into a domestic hot water cylinder where it releases its heat to the water through the process of conduction.

All solar systems require a heating cylinder. This is a twin coil cylinder or thermal store that replaces your existing cylinder and works alongside your normal boiler. The solar panels heat up the bottom of the cylinder, the boiler heats the top.

An average solar hot water system provides up to 60% of a typical household's hot water. However, this is dependent on sunlight hours throughout the year. When days are darker the hot water cylinder can work alongside a traditional boiler which tops up any shortfalls in hot water.