Solar Thermal

What is it?

Solar water heating systems use free heat from the sun to warm domestic hot water. A conventional boiler or immersion heater is then used to make the water hotter, or to provide hot water when solar energy is unavailable.

How does it work?

Solar water heating systems use solar panels, called collectors, fitted to your roof. These collect heat from the sun and use it to warm water which is stored in a hot water cylinder.

The panels work throughout daylight hours, even if the sky is overcast and there is no direct sunshine.

A solar water heating system comprises of three main components:

Solar panels

Solar panels are fitted to a roof and retain heat from the sun and transfer this heat to a fluid. 

There are two different types of panel:

  • Flat plate collectors - these consist of pipes passed through a metal absorber plate (often coated with low emissivity black paint).  The pipes absorb solar radiation and heat is transferred to the fluid passing through the pipes (typically water treated with anti-freeze).  An insulated housing and transparent cover provide weather protection and reduces heat losses.  They can be fixed on the roof tiles or integrated into the roof.
  • Evacuated tubes – these occupy a smaller area, tend to be more efficient, and more expensive than the flat plate collectors.  The absorber fluid is enclosed in a vacuum in order to minimize heat losses.

Hot water cylinder 

The heated fluid is passed through a heat exchanger in the hot water cylinder.  The cylinder stores the hot water that is heated during the day for supply when hot water is required.  A boiler or immersion heater can be used as a back up to heat the water further to reach the temperature set by the cylinders thermostat when the solar water heating system does not reach that temperature. (The cylinder thermostat should be set at 60 degrees centigrade).

The plumbing system

The plumbing system is made up of simple piping and sometimes a pump which moves the fluid around the system to point of use.

Is it suitable?

You'll need around 5 square metres of roof space for a family of 4.  If the roof space is limited consider using an evacuated tube as output is usually higher.

To maximise hours of sun the building should be south facing or within 35 degrees of south, and there should be no shading from neighbouring buildings or trees.

The panels don't always have to be mounted on a roof, they can be fixed to a frame on flat roofs.

If a dedicated solar cylinder is not already installed then you will need to replace the existing cylinder with a dual coil cylinder, or add a dedicated dual cylinder with a solar heating coil.

Most conventional boiler and hot water coil cylinder systems are compatible with solar water heating. If your boiler is a combination boiler (combi) and you don't currently have a hot water tank then a solar hot water system may not be compatible.

In England most solar water heating systems don't need planning permission, but it is always best to consult your local planning office if you live in a Listed Building, or a building in Conservation Area or World Heritage Site. If you live in Wales, Scotland or Northern Ireland you will need to consult your local authority.

What are the benefits?

Maintenance costs are very low. Most solar water heating systems come with a 5-10 year warranty and require little maintenance. You should take a look at your panels every year and have them checked more thoroughly by an accredited installer every 3-5 years, or as specified by your installer.

A solar water heating system can reduce your water heating bill by between £50 and £85 per year

It will also save up to 570kg of CO2 emissions, depending on what fuel you will be replacing.

Hot water throughout the year: the system works all year round, though you'll need to heat the water further with a boiler or immersion heater during the winter months.

Contact Us

Tel: 01304 872128