12 point checklist to buying a solar geyser

Posted by: Yes Solar Cape (Cape Town, South Africa) – 29 October 2010

When purchasing a solar water heating system consider the following 12 points, and evaluate each one before committing to a system.

Yes Solar installation - evacuated tubes

1. Certification – what kind of certification does the system have? First prize is SABS Mark Approval. This is a higher form of certification than just an SABS Test Report. Mark Approval means that the entire supply chain of the product has been inspected and that SABS are confident that the product will consistently meet their standards.

2. Also look out for Solar Keymark certification (EU), and the German TUV standard.

3. Direct versus Indirect systems – basically, if you live near the coast you can install a direct system (no intermediate heat transfer fluid), but if you live somewhere that is prone to frost (i.e. temperatures drop below 4 deg), then you have to go for an indirect system. Where possible, go for a direct system, the heat loss between panel and geyser is lower.

4. Evacuated Tube versus Flat Plate collector – the respective suppliers / manufacturers of these systems place too much emphasis on this question. Rather look at the build quality, efficiency and durability of the collector, regardless of the type of technology it employs. Pay special attention to corrosion resistance – low quality stainless steel and shoddily galvanized metals will start to rust after a couple of years.

5. A quick way to measure efficiency is to look at the rebate a system enjoys. The rebate is simply a multiple of the Q factor of the system (which is a measure of its efficiency). But be careful to compare systems of the same size, e.g. a 200 litre system with a 200 litre system. Continue reading

Solar Water Heating – Split Systems

Posted by: Yes Solar Cape (Cape Town, South Africa) – 08 September 2010

Unlike a Thermosyphen System that is normally a complete on-roof hot water system; a Split System uses a pump to move a glycol liquid through the collectors and into the heat exchanger of the storage tank, where the heated, pumped glycol solution heats the household water.

Flat Plate Collectors used in a Split System

Although this system has more components than a thermosyphen system and consequently more expensive, it has two advantages:

1. The storage tank (geyser) does not need to be placed directly above the collectors, allowing the tank to be placed up to 20 m away from the collectors.

2. The system is more efficient as the pump regulates the flow rate of the glycol solution through the system.

Two types of pumps are available to circulate the glycol:

  • Electric, which relies on grid electricity; and
  • Photovoltaic, which are carbon neutral and make the installation independent of the grid.

Split Systems are available with either Flat Plate or Evacuated (vacuum) Tubes.