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What is a solar thermal system?
Solar thermal is a renewable energy source that uses the sun’s energy to heat water for use in kitchens and bathrooms.
Capable of meeting around 50 per cent of a UK property’s annual hot water demand, solar thermal systems deliver significant annual savings, which will only increase if energy prices continue to rise.
Solar thermal energy is harnessed from roof-mounted tubes or panels called solar collectors. The hot water that’s generated is stored in a large cylinder or tank until needed.
Solar thermal is different to Solar PV (PhotoVoltaic), which is designed to generate electricity.
Whilst electricity from solar PV systems can be used to heat water, solar thermal systems are more efficient, needing less roof space to generate the same amount of energy. That’s why some properties use a combination of solar thermal and solar PV systems.
How do solar thermal water heating systems work?
Solar thermal hot water systems work by using solar collectors to absorb the energy radiated by the sun.
The two types of solar water heating collectors are:
- Evacuated tubes – banks of glass tubes mounted on the roof tiles
- Flat plate collectors – that are fixed on the roof tiles or integrated into the roof.
Both work by transferring the absorbed energy into a fluid which is pumped around a sealed circuit and into a coil within a specially designed hot water cylinder.
Because the level of solar energy varies, the hot water cylinder needs an alternative energy source to enable water to be heated in winter or bad weather.
The top-up can be provided by a conventional boiler, an immersion heater or from a renewal source such as a heat pump.
Which type of solar collector is best?
Evacuated tubes are the most efficient form of solar collection. They require less space and perform best in different weather conditions where there is less direct sunlight.
Flat plate collectors are less efficient but are cheaper to purchase. They may also blend in better.