Solar Thermal (Solar Hot Water)
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 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 – 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
Climate Change Officer
Property, Leisure and Waste Management
White Cliffs Business Park
Dover
Kent CT16 3PJ
Email: energy@dover.gov.uk
