Solar Geysers

Solar Geyser FAQ

How soon can I pay back my Green Power solar water heating system through my electricity savings?

Every client is unique with different energy consumption habits and water usage. Eskom claims that your water geyser consumes about 40 to 60% of your monthly energy bill.

From our experience, if your monthly electricity bill is R600 per month and electricity tariffs continue to rise by 15% per annum, you should pay back a 150L system in less than 5 years through accumulated savings.

What happens if the weather is very bad?

Vacuum tube solar water heating is the leader in solar heating technology, operating very effectively even in cloudy and overcast conditions. Vacuum tubes use the light radiation from the sun. For e.g. if you go to the beach and it’s overcast you still burn, the same principle applies with the vacuum tube. If the weather is constantly “bad” there are electric backup elements installed in your geyser for those rare “weeks of continuous rain and poor weather”.


How hot does the water get in a solar geyser?

This is dependent on the amount of light UVA/UVB radiation but the water can reach temperatures of up to 97o C in summer & 70o C in winter.

Can I retrofit a Green Power Solar Water heating solution to my existing geyser?

Yes. There are various valves and fittings on the market to retrofit your existing geyser.

What happens when the power goes off?

Nothing. The water gets heated in the panel and as it’s heated, the water pressure increases and pushes the hot water through to the geyser. Additional expansion from the hot water will be relieved by the pressure release valve (PRV). Green Power has researched other alternatives like battery back-up systems and also small PV panels to run the pump and controller. Both options are available on request.

Why do I need a pump and controller?

The controller is there for safety and efficiency and has built in safety features. For example if the water in your geyser reaches 90 degrees it shuts down the pump and stops more water from being unnecessarily heated. Once the geyser temperature drops, the panel and pump will run again and the water will be heated again.

In the case of freezing or if the panels’ temperature drops below 2 degrees the system will intelligently pump water through the panel to ensure the pipes don’t freeze up.

Efficiency- the Green Power system works on a temperature differential i.e. if the panel is hotter than the geyser it tells the pump to kick over a cycle of water and vice versa. The water then heats up and returns to the geyser, and the process starts all over again. The pump does not run continuously but rather heats the water up in cycles, making the system run not only efficiently, but cleverly too.

How does a vacuum tube heat the water?

A vacuum in its very basic form is merely a natural insulator, providing for a heat-loss factor of merely 7%. In other words 93% of the radiation that enters the glass tube is retained and transferred to the water. The vacuum (similar to our ozone layer) assists in prevention of radiation and convection. Another example is a flask that you put your coffee in to keep warm. The vacuum tubes use the same principle except they keep the sun’s radiation in.

How do you install a solar geyser?

Solar elements can be installed on the face of any North-facing wall or preferably on the roof. Water is pumped from the ordinary 3-port internal geyser, in circulation, over the solar element and returned to the internal geyser. Tiled or corrugated roofs work fine, while flat concrete roofs are ideal. The system is mounted onto the roof with each leg bolted to the beams within. Water proofing by means of flashing and sealants is accomplished relatively easily, because the panels are relatively light.

Do the glass tubes break very easily?

According to South African Bureau of Standards (SABS) testing, the vacuum tubes resist hail up to 35mm in diameter. This is the largest hailstone that the SABS tests with! They might break as often as the windows in your home i.e. not very often! Should a vacuum tube break, the system continues to operate without interruption. An optional polycarbonate cover can be installed in heavy hail regions or where baboons are in the area. Replacement of a vacuum tube costs roughly R 220.00.

Can the solar geysers handle urban water pressure?

Yes! Up to 400 kPa (4 Bar).

What is a 3-port geyser?

Most geysers currently manufactured by ordinary geyser manufacturers have three ports. One port is taken up by the temperature/pressure (T/P) safety valve and cannot be used thereafter. Solar water heating systems require the geyser to have one additional water outlet to allow them to be easily coupled together. This makes a 4-port geyser. The Cobra geyser solves the problem by way of a Banjo type t/p safety valve which also acts as an outlet.

Why is vacuum tube technology more suited to moderate climes like the coast as opposed to flat plate technology?

Flat plate collectors are susceptible to “wind Chill” which affects their efficiency. In addition to this, flat plate collectors are only efficient at solar noon when the sun is perpendicular to the collector. In contrast vacuum tubes are round, and all panels are installed with a reflector which enables them to track the sun, focusing all light on to the copper tube within the vacuum tube.

As well as this, vacuum tube technology is much less expensive in terms of maintenance and repair.

What is Eskom’s involvement in the solar water heating programme?

In order to reduce the growing demand for electricity, Eskom is embarking on energy efficiency and alternative energy programmes that promote energy savings on a large scale in order to mitigate system constraints. Eskom is working towards a goal to meet government’s target of 10 000 gigawatt hours of renewable energy generation by 2013.

How does the programme work?

The programme is structured around a rebate which reduces the selling price of a SABS approved solar water heating system. The reduction in price is based primarily on the performance of the solar water heater and its associated electricity saving potential. You receive a rebate directly from Deloittes, the facilitating auditors of the programme.

Only registered products, complying with the following criteria, qualify for the rebate:

  • It must be a high-pressure system with pressure higher than 100kPa.
  • The system must have a timer to optimise energy savings and regulate everyday usage. Alternatively, a load management device, i.e. a geyser buddy or ripple relay, to control the usage in crisis situations must be installed.
  • The system must be appropriate for the household and area in which it is installed, in terms of size, frost protection and water quality compatibility.
  • It must have a comprehensive guarantee of at least five years.
  • The system must have passed the South African Bureau of Standards (SABS) tests, and comply with the South African National Standards (SANS) for thermal and mechanical performance and safety.
  • The supplier of the system must be registered with SESSA (Sustainable Energy Society of South Africa) solar water heating division.
  • The system must be installed by a registered installer and the customer will only be able to claim the rebate once facilitating auditors receive a final invoice from their supplier.

How do I ensure the quality of the system I have purchased?

Purchasing a system that is registered on the Eskom programme ensures that the system and the supplier have been checked and audited, not only safeguarding you as a consumer but also giving you greater assurance of the system’s quality. Buying an Eskom registered system means you qualify for a rebate, making your purchase good value for money.

end faq

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