HELP > FREQUENTLY ASKED QUESTIONS
General Solar Questions
Solar Water Heating is a system for heating water using energy from the sun. Solar energy is collected by a panel, which is connected by pipes to a hot water storage device such as a hot water cylinder.
Solar water heaters use two natural events in order to function: dark coloured objects absorb heat (solar energy) and hot water rises. Technology has made this natural phenomenon a working reality for a reliable source of hot water in our homes and for a range of other applications.
A solar water heater is a combination of three elements:
Solar collector an energy device, designed to absorb solar radiation and transfer the energy to the energy transfer fluid or material passing through the collector.
Energy transfer medium – is a medium that through the process of conduction or convection, transfers the absorbed heat to the water. The type of material used is dependant on the design and needs of the installation. Where freezing of the transfer medium is a concern, the liquid used should be mixed with a non toxic coloured anti freeze liquid and a corrosion inhibitor.
Solar water system tanks/storage vessels should always be larger than conventional household geysers. This is because the sun is heating the total volume of hot water that is required for the day. For your conventional 150 liter electric geyser to heat 300 liter it will need to cycle and heat the extra body of water. A thermally insulated hot water storage vessel or geyser with a protected inner lining, copper, steel or a polymer should be used. There are solar water heating systems that work on a low pressure, but most are pressurized from 100 kPa to 600 kPa, depending on the materials used.
Solar water heaters can be plumbed in series to pre feed your existing geysers, or can completely replace existing geysers. The complete system can be mounted on top of the roof, if the structure can hold the mass, or the hot water storage vessel can be mounted under the roof at a high level or at ground level in a utility room or cupboard. Solar water geysers/storage vessels function best when mounted vertically. However if there are physical or aesthetic concerns the geyser can be mounted horizontally.
Solar water heaters can help save water heating costs by reducing the amount of gas and electricity needed to heat water. By using sunlight to heat water instead of combustible sources or fossil fuel-produced electricity, fewer pollutants are being introduced into the environment. Solar energy is not affected by the current shortage of electricity and does not stop providing hot water during load shedding.
A solar water heater can provide between 50 and 90 percent of your total hot water requirements, depending on the climate and model of heater.
By how much will replacing a conventional geyser with a solar powered system reduce electricity consumption?
The electrical geyser uses 30 – 50% percent of your household’s monthly electricity bill. Replacing your conventional geyser with a solar powered system will reduce that percentage of your electricity consumption by up to 70 percent.
Standard geysers are not designed to be utilised with solar collectors as they do not have sufficient inlets and their linings are often not designed to withstand the temperature experienced from solar energy. The supplier should evaluate the existing geyser and, based on your needs, the supplier can evaluate the possibilities of using the existing system.
Solar water tanks are better insulated than electrical geysers and can keep water hot for a longer period of time. This ensures that there is always a tank full of hot water (and a back-up of hot water) in the early evenings/mornings provided the tank size is correct. An electrical back up system is allowed on the programme provided it has a timer switch that ensures it does not operate during Eskom’s peak demand periods.
Most solar systems heat the water to between 55 - 65 degrees Celsius. You should have a timer installed with your system, as it has been shown that this will give you the maximum energy saving and ensure you have hot water in peak periods.
What is the life-cycle expectation of the system and more significantly the total energy savings on it?
Each piece of equipment has a different savings profile which depends on various elements such as geographical area, water usage profile, number of users and the size of the system. However, on a 200 liter system, the SABS average is 5.67kWh per day at 16MJ input power. The expected life of the equipment is 10 to 15 years; most systems are guaranteed for 5 years.
The specifications on solar water heaters focus on three main areas, i.e. quality, performance and safety. Testing systems verify these requirements. As the payback periods are very important it is vital that the solar water heater is of a quality that ensures the longevity of a system. The mechanical performance tests e.g. hail, freezing and pulsation test are conducted to ensure that the minimum quality standards are met. The performance tests are conducted to determine how well the system works, the safety test determines if all the safety requirements are met including electrical and mechanical safety criteria.
The SABS mark takes the test report and adds an evaluation of the manufacturer’s ability to consistently produce quality solar water heating systems. This means that if the testing indicated a high quality, durable and safe solar water heater design, and the manufacturing quality audit indicated that the manufacturing facility can manufacture high quality products consistently, the SABS will allow the manufacturer to use the SABS mark.
The installation of a solar system, to qualify for the incentive, has to be done by an approved installer. Even though the concept of the system may look simple, many areas can be damaged if the system is not installed by a qualified tradesman. Accredited suppliers register their installers and undertake to oversee the installations to ensure that they comply with programme and building regulations and other applicable legal requirements. Guarantees can also be lost if it becomes evident that someone without the correct technical expertise has tampered with the system.
Costs can only be provided taking into account your specific hot water usage habits but an approximate cost can be given here. Installing a 200 liter solar water geyser costs approximately R10 000 with an additional R4500.00 installation fee. The upfront cost of a solar water heater (including installation) is higher than electric or gas water heaters but the savings on your electricity bill will compensate for this over time. Once you have paid back your system, your hot water is for free!
Programme Related Questions
The cost of installing a solar geyser varies between R 12 000 to R 35,000.00 depending on the size, type, and source (i.e. imported or locally manufactured).
A geyser uses between 30 – 50% of the electricity used in a home. Typically taking overcast weather and usage patterns into account, 70% of this energy can be displaced by a solar system.
If a 100,000 geysers were to be installed this would offset 300 MW worth of connected load. However if we take diversity and usage into account this equates to a 63 MW load that is actually removed during our peaks.
What are the stumbling blocks in getting solar water heaters rolled out in SA, even with our abundant sunshine?
Currently the stumbling blocks are the high price of solar systems, and supplier capacity. Historically South African's did not use solar to generate hot water, thus the industry is underdeveloped and needs time to develop. The skill required for installers is a concern but Eskom is working with SESSA's solar division and the ESETA to develop new training programs to train installers.
Paybacks are typically between 5 to 10 years, depending on geographical area, water consumption patterns, number of people in the household, type of system chosen, and energy cost.