navitronLogo checkatradeLogo

Solar water heating

Solar water heating systems use the energy from the sun to heat water, most commonly in the UK for hot water needs. The systems use a heat collector, generally mounted on the roof in which a fluid is heated by the sun. This fluid is used to heat up water that is stored in either a separate hot water cylinder or a twin coil hot water cylinder inside the building.The systems work very successfully in all parts of the UK, as they can work in diffuse light conditions.

There are two types of collectors used for solar water heating applications - flat plate collectors and evacuated tube collectors. The flat plate collector is the predominant type used in domestic systems as they tend to be cheaper. Evacuated tube collectors are generally more expensive due to a more complex manufacturing process (to achieve the vacuum) but manufacturers generally claim better overall performance.

The diagram below illustrates a typical active solar domestic water heating system. A pump, controlled by the temperature difference controller is used to circulate the heating fluid. The controller constantly monitors the difference between the temperature of the solar collectors and the temperature of the water in the cylinder.

solar diagram

Whenever the collector is hotter than the cylinder, the controller switches on the system's circulating pump. A mixture of antifreeze and water is then circulated through the collectors and the cylinder's heat exchanger, heating the cylinder in just the same way as a central heating boiler.

The heat exchanger in the hot water cylinder transfers the heat from the water mixture to the water in the cylinder. Any excess heated water can either be controlled by the use of a temperature controlled mixer valve or simply dispersed through a heat sink, such as a towel rail or in extreme cases a swimming pool!

Where can solar water heating systems be used?

Ideally the collectors should be mounted on a south-facing roof, although south-east/south-west will also function successfully, at an elevation of between 10 and 60°. The panels can be bolted onto the roof or integrated into the roof with lead flashings. They look similar to rooflights. Solar water heating systems are suitable for any building type that has sufficient year round hot water needs (ideally during the day) and a suitable south-facing roof of sufficient size. This technology is particularly suitable for low-density housing developments. Retail units or offices with canteens and washrooms and/or showers may also have a suitable demand for hot water.

Where possible, solar water heating systems should be placed on roof areas not visible to the road or sight line of other buildings. Some systems can be integrated flush to the roof. The systems are no more intrusive than a roof light (window in the roof) when roof integrated.

Our installations

installation images

Performance of solar collectors

Domestic systems

A 4m2 collection area will provide between 50% and 70% of a typical home’s hot water requirements depending on the quantity of hot water required and the timing of that requirement. The percentage can be increased if:

The system is particularly beneficial for dwellings where residents are at home using hot water during the day, for example, young families or the elderly. Savings from solar water heating are difficult to predict and will in practice depend on how much water the occupants use and at what times they use it.

Our electricity systems more... Our wood burning stoves more...