Monarch Services

Solar Water Heating
Solar water heating involves the capture of the sun's energy to heat water. Useful heat in the range 20 oC to 100 oC is collected. This is commonly used for domestic hot water or for heating outdoor swimming pools. There are a number of different general designs and systems which can be used for solar water heating. The following types of collector are currently marketed in the UK:

1) evacuated tube collectors
2) flat plate collectors with selective surface
3) flat plate collectors without selective surface
4) unglazed polypropylene collectors (for outdoor swimming pools)
Evacuated tube collectors use metal plate collectors running through vacuum tubes. The vacuum acts as insulation preventing convective heat loss. Flat plate collectors use a metal absorber plate, often coated with low emissivity black paint. They are usually single glazed but can have a secondary glazed layer (sometimes of plastic) allowing higher temperatures to be achieved.

The area taken up by a solar water collector will vary according its design and the hot water needs of the house concerned. Typically it could be anywhere between 2 m2 and 7 m2.

A typical layout for solar water heating system.

If the storage tank is positioned above the collector then there is the opportunity for water to circulate by siphoning. The usual arrangement in the UK with the collector above the tank requires a pump to circulate the water.

In this country it is generally recommended that indirect systems, with antifreeze in the circulating water, are used to avoid potential frost damage. In sunnier climes it is possible to have simpler direct systems with the water circulating through the collector from the cold water intake. Such an arrangement would also be possible in this country if either the system is drained when frost is forecast or it is very well insulated as claimed by at least one product currently on the market.

Savings in running costs of domestic hot water of 40% to 50% are claimed. In the summer the panels may provide all the hot water needs, and the saving in winter whilst lower can still be significant. Energy is captured even on overcast days.

Capital costs range from less than £2,000 to over £4,000 for professionally installed systems. Domestic hot water in a typical household will cost between £50 to £200 to heat. Therefore the simple payback period varies considerably according to circumstance, but is often quite long.

However solar water heaters will look more financially attractive where there is either:

higher hot water use and costs
incorporation into a new building
a bulk order for a number of houses
DIY capability
Savings in carbon dioxide emissions are an important consideration. If the solar water heating is substituting for electric immersion heating then savings in CO2 emissions of over one tonne each year are possible.

Swimming Pool Heating

The simplest solar swimming pool heating systems pump water through unglazed collectors, usually about half the area of the pool itself. They can bring the temperature of the pool up to a comfortable level for bathing.

DIY projects are available, please e-mail for further information mac@monarchservices.co.uk
This information sheet is intended as an introduction to solar water