www.plumbingafrica.co.zaVolume 16 I Number 6

Our government sees Solar Water Heaters (SWH) as the ideal way of providing hot water to communities with no burden of monthly bills, and for Eskom, SWH are a means to reduce the ever increasing power generation requirement.

For many however, their recent bad experiences with SWH have led them to ask the question: "Are SWH really the solution?” There is no doubt that SWH are the solu-tion and that they are here to stay. Indeed it is surprising that it took South Africa so long to realise their potential. The systems have been widely used throughout the rest of the world even though, for example, most of Europe cannot harvest more than 1600 kWH/m2 per year. Most of South Africa, by comparison, can harvest in excess of 2000 – 2400 kWH/m2.

It makes so much sense that SWH should be widely used in South Africa, but it is important to make sure that these systems add value and do not end up costing more in the long run. This is where the SABS plays a critical role. There are a large number of standards that a SWH must comply with and the SABS is well equipped to deal with them. The 'parent' specification is SANS 1307 “Domestic Solar Water Heating Systems”. This standard contains a list of requirements including up to 23 addi-tional standards that might have to be verified, depending on the design and construction of the system.

All requirements are equally important – no single requirement is more important than another – but the requirements listed below are regarded as some of the main areas for testing.

Mechanical tests – sans 6210These include a variety of mechanical tests to ensure that the system is of sound construction and will be able to withstand the physical demands of water pressure and extreme weather conditions. The stagnation test involves exposing the system to the sun for about 15 days, with no water in the system. During this test some metal

Solar Water Heaters – enduring South African conditionsSolar water heaters are a hotly debated topic at present. As homeowners, we are in search of ways to use less electricity and keep costs down.

By: Herman Stauss and Karel Deist

components might reach temperatures of over 200°C. Inferior design or materials result in distortion, damage or malfunction during this test.

During the hydrostatic pressure cycle test, the sys-tem is subjected to 250 000 cycles between 0 kPa and the maximum working pressure of the system. A system experiences these cycles in real life because the heating of the water causes thermal expansion of the water. After the cycle test it is subjected to twice the working pres-sure. A typical failure that is revealed during this test is weakness around welded areas.

To test resistance to rain penetration, water is sprayed in a controlled manner over the system. If for instance any seals or the glass cover were compromised during the stagnation test, this test would allow water to enter the panel and reduce its efficiency.

A system that is at the mercy of nature must be able to withstand the sizable hail storms experienced in various parts of the country. During the hail resistance test, 12 ice balls are shot at the system with the energy being 11 J ±1 J.

The aim is to target the weakest spot. In the cold ar-eas of our country the temperatures drop below freezing point in winter. When water freezes it expands and some-thing has to 'give', for example, the pipes or the panels themselves. The resistance to freezing test involves subjecting the system to a temperature of -20°C for a period of four days to test that the SWH freeze protection system functions effectively. The test for resistance to dezincification is commonly performed on all plumbing components to ensure that the corrosion resistance properties of the brass components are up to standard.

1. Karel Deist is Head of Laboratory and technical specialist, plumbing, pipes, mechenical, water meters and solar laboratory.

2. Herman Strauss is Manager: mechanical, fluid and pipes.

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68 did you know...from the SABS labPlumbing Africa

www.plumbingafrica.co.za Volume 16 I Number 6

did you know...from the SABS labPlumbing Africa

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theRMal peRFoRMance test - sans 6211The basis for this test is that the system is filled with water of a known temperature. It is left in the sun for a day while the solar irradiance is recorded and at the end of the day the water temperature reached is recorded. This information is then used to calculate how much of the available solar energy was transferred to the water. The process is carried out over a six day period, while various conditions are simulated. The end result is a formula that can be used to predict the performance of the system for any expected weather condition. For the Eskom rebate program, a “Q factor” is calculated. This is the amount of energy that the system would absorb on a day with a solar irradiance of 16 MJ/m2 and a difference between the ambient temperature and the water temperature of 10°C. This test provides information on the efficiency of the system in heating the water and is an indication of the energy saving that will result.

onGoinG test iMpRoveMentsThe measurement standards used by the SABS are developed by a technical committee comprising experts

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The outer casing of this system was cut open to identify the area where a leak occurred

Karel Deist of the SABS with the hail test machine

A freeze test in progress

Systems on thermal performance test.

from industry and academic institutions. These standards are seen as dynamic and are regularly reviewed and updated as new field information becomes available.

The SABS test laboratory is responsible for performing the tests accurately and without ques-tion to ensure that good quality, safe products are distributed to the benefit of the consumer, and to promote use of sustainable energy.

onGoinG test iMpRoveMentsThe measurement standards used by the SABS are developed by a technical committee compris-ing experts from industry and academic institu-tions. These standards are seen as dynamic and are regularly reviewed and updated as new field information becomes available.

The SABS test laboratory is responsible for per-forming the tests accurately and without question to ensure that good quality, safe products are distributed to the benefit of the consumer, and to

promote use of sustainable energy. PA

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