As soon as you hear the word “solar” you know that it somehow involves the energy of the sun. This bit is easy. You will also be aware that you can get solar power from panels on your roof and use this energy as electricity in your home. But what about solar thermal? How is this different and how does it work?

Solar thermal energy harnesses the solar energy from the sun and uses it to heat water for use in your home. It is different to photovoltaic technology which uses solar panels to create electricity as solar thermal concentrates the light from the sun and turns it into heat.

A solar thermal system will usually consist of two separate modules. The first will be some way of collecting the sunlight. This usually takes the from of a flat plate which is placed on the roof of your house. This looks like a normal solar panel. The second part of the process is a storage tank which holds the water you are heating.

The solar radiation is absorbed by the flat plate collector which heats the water and this is pumped through the collector. In some cases this heating can occur in your domestic water storage tank via a heat transfer fluid. This water is then stored in a hot water tank in your home ready for use.

This process does not need to happen constantly as it is only switched on when your water storage tank reaches a temperature which is lower than that on the collector. The water is then circulated through the system to reheat it .

In most cases a solar thermal heat system will provide around two thirds of the water you require under normal circumstances. Obviously during the winter you may need to have a back-up system such as a boiler or immersion heater to generate enough hot water.

You can also use this method of heating water to heat your home. This would require the water to be circulated through your central heating system.

Not all homes will find this way of heating water suitable. You will need a sunny place to put the collectors – usually on a south facing roof. You will also need space inside your home for a large water cylinder to hold the hot water. A new cylinder will need to be used as it needs a special solar heating coil.

The good news is that you won’t need planning permission to install a solar thermal heating system unless you live in a conservation area or have a grade 2 listed home.

You can expect to pay around £5,000 for a solar thermal system and the savings are fairly small – generally less than £100 per year. However it is worth noting that the government has started offering a tariff for those home owners or businesses which have this type of technology installed. This is called the Renewable Heat Incentive and can provide a significant income for a period of 7 years.

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