Solar Geysers 101

A solar system comprises a solar heat collector coupled to an insulated storage tank. The collectors are of two types - evacuated tubes and flat panels. The evacuated tubes are made of glass. Each has its advocates.

Evacuated tubes deliver most heat, but heat delivery in SA can be excessive.  Evacuated tubes were developed for use in Europe, and if they are applied here they must have a thermostat.

Flat panels are stronger.  Proponents of evacuated tubes say they are cheap and easy to replace if broken by hail, by an envious neighbour, or rioters throwing stones. But it is really hard to damage when there are fragments of glass in the insulation and in the O-ring seals to ensure a proper seal after a repair.

Before you buy you should ask for the supplier for the SABS test report.

SABS: Specs vital

People who have high quality systems properly installed are delighted with them.  Eskom insists on SABS-tested systems and installers who can issue certificates of compliance.

Installing a solar system is complex. You have to bleed out the air and make sure that it is correctly piped and pitched at the correct angle to the sun. Some are split systems that require a small 12-volt circulation pump, sometimes powered by the sun, sometimes by mains power. Others are "thermosyphonic" and circulate water by convection. Wrong installation can destroy the efficiency of the best system. A drip tray, vacuum breakers and a safety valve are mandatory.

As with motor cars, the most expensive systems are generally the best - but, as with cars, some middle-cost solar systems are of very high quality. 

Some cheapies are good but most are less robust and won't last as long.  But no matter how good the components, a badly installed system will at best not be economical and, at worst, dangerous.

Pressure, hail and freeze tests

Systems that pass the SABS test are pretty robust. They are subjected to pressure, hail and freeze tests. They are tested at minus 20 degrees to ensure they stand up to frost, and when they are bombarded with hail stones the size of golf balls. They also undergo thermal testing. All of this takes up to four weeks.

Many sellers of solar geysers are claiming you can save 40% of your domestic electricity costs. That is true only of a low-income family.  For those who have underfloor heaters, automatic dishwashers, tumble driers and who use their electric stoves and heaters extensively, the saving is perhaps only 20%.

The full article first appeared on Moneyweb.co.za