Solar Water Heating

Water heating accounts for about 40% of your electricity bill and this can be considerably reduced with a solar water heater.

The key parts of a solar water heating system are the collectors which sit on the roof and the storage cylinder. Solar water heaters can be combined with other heating methods such as wet-backs, and gas.

Solar water heaters come in two main forms, thermo-syphon or pumped. Thermosyphon systems use the temperature of the water in the collector to induce circulation to the storage cylinder which must be above the collector. Pumped systems use a small, automatic pump and the cylinder can be anywhere in the house. Both types incorporate methods to protect the system in frosty weather.

In very cold areas further protection can be provided by two stage systems in which the collector and exposed pipes are loaded with anti-freeze solution and the heat is transferred into the cylinder via a heat exchanger.

Solar collectors work best pointing North at an angle equal to the latitude but considerable variation is permissible with only a slight loss of performance.

In some situations the collectors can be built into the roof  to provide a less conspicuous installation.

The installed cost of solar water heating systems depends on size and type and is typically between $3500 and $6000 giving a return on investment of 8-12% .which will increase as power prices rise.

When considering solar water heating you should get advice from suppliers who are members of the Solar Industries Association.

 Arthur Williamson PhD

Managing Director, Thermocell Ltd