We are members of
the Solar Trade Associaton

We have BPEC Certification.
This means that
we have met
their standards
for installing
solar water
heating.

Technical information:
How solar heating works and system design

There are many different designs of household solar water heating system, pictured here is the most common. Each design may be considered to have its own advantages and disadvantages.

Water from the cold supply provides water for the dedicated solar pre-heat storage, which is heated by the solar collectors. The pre-heated water is then heated to the required draw off temperature by a domestic hot water appliance, such as a boiler or electric immersion heater. A typical arrangement is to combine the solar pre-heat store and the store heated by the domestic hot water appliance in one vessel. The illustration shows an indirect solar circuit.

Because unclouded solar radiation cannot be relied upon at all times, solar water heating systems do not totally replace the more conventional means of providing hot water such as solid fuel, oil, gas or electricity. They are an addition to these systems, pre-heating the water and therefore reducing the energy that the conventional boiler needs to provide to meet the hot water requirements of the household.

A solar water heating system should absorb solar energy efficiently and transmit that energy to the storage cylinder with minimum loss. It should also have a life comparable with that of other building services.

Has Britain got enough sun?

There is a widely held opinion that the UK does not have enough sun to make solar systems worthwhile. In fact parts of the UK have annual solar radiation levels equal to 60% of those experienced at the equator.

The DTI commissioned a 2 year monitoring programme of 4 domestic hot water solar systems in differing locations. The results showed that systems provided an average of approximately 70% of the annual hot water requirements at the 4 locations. All 4 systems workd in winter as well as summer with 16-17% of hot water needs being met in January and December and almost 100% of hot water needs being met in both July and August.

Maximum power on a cloud free day occurs at solar noon at any location. The Meteorological Office has been recording solar radiation for more than 30 years and has produced maps showing the geographical distribution of solar radiation for the UK.

The map on the right shows variations in annual mean values of solar irradiation on a south facing 30º inclined plane in the UK in kWh/m2.

NB. Change in the weather from year to year can give variations in system output of up to 10%.

The available energy decreases as one goes north, because of the lower altitude of the sun and because the radiation has a longer distance to travel through the atmosphere. There are also subtrantial local differences in the amount of solar radiation that is available, since geographical features such as mountains and proximity to the sea also affect the availability of solar radiation.