Solar thermal water heating systems use solar collector panels to harness the energy from the sun, which heats up the water in your water cylinder.
There are two types of solar panels, flat plate collectors and evacuated tube collectors.
Flat plate collectors can be integrated into the structure of the roof and look like roof windows. Evacuated tube collectors are more efficient when the sun is not at an optimum angle, and when the sun is not as bright - you get a better result earlier in the morning and in the spring and autumn when the days are cloudier.
Solar Panels are best placed on as near a south facing roof aspect as possible, if you haven't got a suitable roof - for instance if your ridge runs north/south it may be that you can site a collector panel on each face of your roof, what is called an 'East/West' system, where one panel catches the morning sun and the other catches the afternoon sun.
In the majority of solar installations the sun's energy is used to heat up a heat transfer fluid, this is a glycol antifreeze which protects the external parts of the system in the winter. The solar heated fluid then goes into a coil at the bottom of your hot water tank and heats up the potable water for your taps and showers.
The typical installation cost for a basic domestic flat plate collector system is around £4,500. The more efficient "evacuated tube" systems will cost £4,950 - £5,950. Installation takes just a few hours and generally creates little disruption to your home. Solar panels and collectors generally come with a 10-year warranty and require very little maintenance. A yearly check by the householder and a more detailed check by a professional installer every 2-3 years should be sufficient.
How Does It Work?
The diagram below shows a typical solar panel hot water system used to supplement a conventional domestic hot water system.The collector (solar panel) should face south or close to south and lie on a pitched roof that will provide the natural angle to face the sun.
A conventional central heating pump forces water through a coiled pipe in the solar panel where it is heated by the sun. The heated water then flows down and through a second (lower) coil in your hot water cylinder, referred to in the diagram as a solar cylinder. The hot water passing through this coil heats the water in the cylinder.
The slightly cooled water is then returned back to the solar panel via the pump. The controller box continuously compares the temperature in the panel against that in the hot water cylinder (see dotted lines). It switches the pump on when the water temperature in the panel is hotter than that in the cylinder and switches it off when the reverse conditions apply. As long as the water in the hot water cylinder is at the required temperature, your existing boiler will not switch on.
The water flowing around the solar system is used to heat the water in the cylinder indirectly. This means that no water in the SWH system will come into contact with water in your hot water cylinder. The heat is transferred, not the water.
Does it work on cloudy days?
Solar panels depend on radiation not direct sunlight so it works even on dull days. In the autumn, spring and summer, a solar panel can yield surprising results, often not requiring any support from your boiler. Depending upon your system and how and when you use your hot water, you could find that almost all your needs are met by solar panels at these times of the year. However, in winter, although a panel can be effective in helping warm your water, you will still need your existing hot water heater to provide most of your water heating needs.
With a normal hot water cylinder, a solar hot water system is not designed to work in conjunction with your central heating radiators or underfloor heating system - they can only heat your domextic hot water (for your hot taps / showers). We can however design a bespoke system combining a solar thermal collector panel with your other heat sources (be they renewable or fossil fuel fired) via a Thermal Store, which will then give a solar thermally heated contribution to your cenntral heating as well as your hot water requirements.
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