Solar Hot Water

Eco homes 4 U  

Solar water heating

Solar water heating systems use heat from the sun to work alongside your conventional water heater. The technology is well developed

Solar Water Heating (Solar Thermal)

Solar Water Heating (SWH) must not be confused with photovoltaics (solar electricity). Solar Water Heating is a different and much simpler technology.

The basic principle behind every solar water heating panel (or collector) is that DARK COLOURS ABSORB HEAT.

A metal backplate is used to collect the sun’s heat and transfer it to water (or, in the UK, more usually a water/anti-freeze mix – plain water will freeze on a roof) within the panel.

A basic solar water heating panel, with a network of pipes running over a black back-plate, is known as a ‘flat plate’ panel (or collector) A higher-tech type of solar water heater is the ‘evacuated tube’, in which a small ‘slice’ oftube and back-plate is encased in a glass tube with a vacuum inside. A number of tubes (often 20 – 30) are connected in a manifold and mounted on the roof. In winter conditions (with sun but very cold ambient temperatures) a flat-plate panel may be losing heat through convection almost as quickly as it is gaining it. The use of a vacuum limits this heat-loss via convection, and enhances the winter performance.

In most cases the water heated by the panel is passed by a pump through a heat exchanger to heat the water in a hot water cylinder.

Usually a minimum of 2.5 square metres, up to, say, 4 square metres for a 4–5-person household.

The ideal orientation is due South, but anywhere between South East and South West will only cause a slight loss of efficiency.

A 2.5-4 sq m panel can be expected to provide about 50-60% of a household’s hot water over a year, and displace between 1200 and 1600 kWh per year of some other heating fuel. If thatother fuel is on-peak electricity, you will save up to around £160 per annum. If your other form of water heating is a high efficiency condensing gas boiler, your savings will be much less. However, with the price of gas and electricity rising rapidly (March 2006), the savings will increase still further.

A good flat-plate solar water-heating system will normally cost around £2,500 - £3,000 installed. V.A.T. on installations is chargeable at only 5%. An evacuated tube system may cost £3,500 - £4,500. Sadly there are some much higher prices around for similar kit:

Not necessarily, unless you live in a listed building or within a conservation area, but always check with your local planning office first! Retrospective planning permission can be hard to obtain!

Yes. The Low Carbon Buildings Programme (LCBP) currently offers grants for domestic and non-domestic installations.

Energy Network (YREN) for advice on 0845 3304930. E-mail info@yren.org.uk.

Yes. If you are confident with plumbing and roof work, you should find no problems with solar water heating. Solar Clubs and renewable energy advice centres may be able to help with any problems you may have.

Unfortunately, grants are not available for D.I.Y. installations, however proficient you are, and though installed systems only attract 5% V.A.T, 17.5% is payable for D.I.Y systems.

david_wilkins@talktalk.net or octopustrading@freenetname.co.uk 

This site is brought to you by Dave Wilkins.

Author David Wilkins.
Copyright © 2004 by [Octopus Trading]. All rights reserved.
Revised: 14 Dec 2007 12:59:04 -0000 .

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