Solar Water Heating

A typical solar water heating system uses a roof mounted collector, angled towards the south to capture heat from the sun. About 1m2 of collector area is needed for each person in the household, with a minimum size of around 2.5m2. The collector may be a flat panel, or a series of vacuum tubes: in both cases it contains a heating fluid which is warmed by the sun's rays, and then pumped through a heat exchange coil in the hot water tank. As this coil warms up, it transfers the heat to the water in the tank. An expansion vessel built into the system allows for any expansion or contraction of the heating fluid as it warms and cools.

Today solar collectors are typically integrated into the slope of the roof. This method of installation gives the solar collector the appearance of a quality, opaque, glass skylight. In most cases, since the piping is not seen, it actually improves the appearance of the home because it looks like an elegant, expensive skylight. Derby Solar's installers offer a free solar site survey to determine the location of the solar collector, and to verify that you will not have any collector shading problems.

Any solar-based system will still need a conventional water heater - powered by gas or electricity - to provide back up. However, in hot weather solar energy should be sufficient to provide all the hot water needed, and even on a cool day it will help to raise the temperature of the water a little, meaning the conventional system doesn't have to work as hard.

In some cases the conventional water heater is used to heat a main water tank, with the solar heating system warming water in a second tank which feeds into the main supply via a diverter valve. It is simpler and more efficient, however, to have two heating coils in a single tank. One is heated by solar energy, and the other by the conventional heating source. The conventional heater takes over when a thermostat in the tank warns that the water temperature has fallen.

Only 1% of the heat generated in the UK comes from renewable sources. The rest is generated from conventional fossil fuels such as gas, oil, coal, as well as electricity. The Government has been set the target of generating 15% of the UK's energy from renewable sources by 2020 in order to reduce our dependence on fossil fuels. So by installing a Renewable Energy system you can help the Government meet these targets. So as well as saving money and earning money from installing a renewable heating system, you will also be reducing your impact on the environment.

The chart below shows an estimate of how much heat a Solar thermal system would produce per m2, based on an installation 40 degrees West of due South with a 200 litre tank.

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