Solar Radiation in the British Isles
The DTI has calculated that there is sufficient solar radiation levels received across the whole of the UK for solar water heating to be a viable supplement to existing domestic water heating.
The Solar Trade Association states:
"Solar energy in the UK is far greater than most people imagine. In the summer, when items such as car bodies are often too hot to touch we become aware of the Sun's heat. However, even in the spring and autumn and on clear winter days we receive very useful amounts of solar energy.
By tilting a surface to an angle the amount of solar radiation falling on it will be greater than that falling on a flat surface in this country."
They draw the conclusion:
"... figures bring out the remarkable fact that the amount of solar energy falling on the total roof area of an average house is many times that required to provide all its heating and hot water."
The solar hot water heating system does not rely just on direct sunlight. It uses diffused radiation so they still work effectively on cloudy days.
Naturally, summer will provide the largest amount of solar hot water heating but a useful contribution will be provided by the other seasons as well.
As an indication, a well sized typical installation will provide the following proportion of the household domestic hot water requirement:
- Spring – 40 to 50% of domestic hot water requirements
- Summer – 80 to 90% of domestic hot water requirements
- Autumn – 40 to 50% of domestic hot water requirements
- Winter – 20 to 30% of domestic hot water requirements
So over the whole year this translates to approximately half of the typical annual domestic hot water requirement.
