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Every home should have one:
Solar thermal systems have been around for a long time, they work well, and are generally seen as the most flexible, efficient and most economically viable of all the renewable energies.
Solar water heating systems are straightforward and reliable, they need minimal maintenance and have a proven life span in excess of 20 years. The panels work throughout daylight hours even when there is no direct sunlight.
About 100,000 Homes in the UK have some form of solar hot water heater and this number is growing by several thousand a year. Most solar water heaters take the form of a flat metal plate or a set of vacuum tubes on the roof of the house.
In the UK about 60% of all energy collected comes from diffuse light, i.e., when the sky is overcast. Heat from the sun is transferred via a pump to a special solar coil at the bottom of the hot water cylinder. Hot water is then drawn from the cylinder as required with no noticeable difference except lower fuel bills.
Adverts for these products claim that they can replace 50 to 70 per cent of the energy used for heating water. The truth of this statement depends upon the relationship between the size of the installation on the roof and the hot water demand of the household. Inherently, there is only sufficient solar energy during six months of the year give us enough solar energy to get water anywhere close to a high enough temperature to avoid using the boiler. Solar collectors will heat water from mains temperature of about 10C up to 80C or more.
This means that in the summer months, the system can actually provide almost all your hot water needs without the boiler being switched on but, will only supplement conventional water heating in the winter months.
The size of the system is determined by the amount of hot water being used i.e., number of occupants and the amount of solar radiation available. You must have a sufficient area of material, known as the absorber plate, to absorb heat energy that can be transferred to the water.
As a rule of thumb, an average household in the UK with 2 adults and 2 children would require 45 litres of hot water per person per day which relates to a 4m2 system, as recommended by British Standards. Other factors may also need to be taken into account such as the size of the property and roof orientation .
Ideally your roof orientation should be within 25 of due South and sloping at between 20 and 50. You can add additional panels or install a split system to compensate for East/West orientations.
Flat roofs are ideal as panels can usually be mounted on aluminium A frames facing due South. You should always check your roof to ensure that trees or other buildings do not overshadow it.
The savings in gas or electricity both depend upon the amount of the Suns energy falling on the collector panels and the efficiency with which it is collected. In southern England, 1m2 of surface area receives about 1,200kWh/year in solar energy.
On a typical June day a 4m2 solar collector plate will receive about 20kWh to 24kWh, compared to no more than 2kWh in December (the total energy received in December is about one-tenth of the June level).
People often ask whether a solar thermal system can be used for central heating. The answer, unfortunately, is that when heating is required there is so little solar energy reaching the UK that it would require a huge collector plate to capture more than a fraction of the heat energy we would need. The typical house requires 65kWh a day of heating, and 2kWh from a 4m2 solar collector plate provides less than 5% of this requirement.
For more information http://www.perfectheat.co.uk
For more information http://www.lowcarbonbuildings.org.uk/micro/solartherm/ |
