Facts On Solar In The UK

For more than 30 years The Meteorological Office has been recording solar radiation in the UK. Look at the map, it shows an annual average of solar irradiation on a suitable house in the UK in KWh/m2. Properties will normally have a solar collector area of 3-4m2. (NB. Change in weather from year to year can give variations in systems outputs of up to 10%).

As you can see, Wales and West Wales in particular are good areas to have a solar powered water heating system.

Solar radiation comes in 2 forms, Direct Radiation and Diffuse Radiation. The easiest way to explain the difference between the two is to say that when you can see the sun, that is direct radiation. On a cloudy day when the sun is behind the clouds we still get diffuse radiation. To put it another way, when the sun is behind the clouds there is still daylight, without diffuse radiation it would go dark!

Now thankfully for us in the UK diffuse radiation powers the solar collectors! During a test measuring the amount and type of solar radiation on a solar hot water system, it was found that a total of 985kwh m² was collected in a year. Of which 573kwh m² was direct radiation and 448kwh m² was diffuse radiation.

(All above information was sourced from the BPEC Domestic Solar Hot Water Heating Systems training manual)