South Africa is still experiencing a looming national electricity shortfall, with a fledging economy and subsequent electricity demand growth predictions. Solar energy is one of the alternatives
By Busisiwe Dhlamini and Ilana Koegelenberg – staff writers
Solar energy is a topic that is about as hard to ignore as the sun itself on a hot cloudless day. Through modern technology, the use of solar energy is an efficient way to make energy freely available. This is something the plumbing industry knows all too well, considering the vast developments of solar solutions in the market. Most importantly, the use of solar energy is something that the environment smiles upon – and that is why Plumbing Africa continues to present as much information on it as possible.
Advantages and disadvantages
During the past few years solar water heating (SWH) has been improved significantly through research to provide a low maintenance solution, mainly aimed at the residential market. This concept has several benefits, but also disadvantages:
- The main benefit of SWH is a reduction in electricity cost that is normally incurred by electrical resistance heating of sanitary water as found in conventional geysers. The cost of water heating typically contributes between 30% and 50% of a household’s electricity cost. Solar water heaters have been shown to save 55%-70% of water heating costs. It can therefore save a significant fraction of the typical household’s electrical bill of between 17% and 35%.
- Unfortunately the disadvantage of the concept is the high capital cost of acquiring and installing such a unit. Even with recently increased electricity costs, payback periods for typical solar water heater installations still range between 3 to 4,5years.
The SWH industries response to the general negativity regarding pricing has been to offer smaller and therefore less costly systems to clients. Even though these systems still save an appreciable amount of energy, the fraction of savings is impacted negatively for large homes where hot water consumption far exceeds the heating capacity of the smaller SWH. This implies that the rest of the hot water requirements will still be heated by the geyser electrical resistance element.
Factors to consider
When talking about solar water heaters, Sanedi’s Barry Bredenkamp says one first has to differentiate between what is known as high pressure systems (HP) and low pressure systems (LP). The HP systems are typically used in larger, middle-to-high income households, while LPs are much cheaper and typically used in smaller, RDP-type houses.
The LP systems are funded through a fiscus and recipients receive the systems at no charge. The HP systems have been subsidised through a significant rebate from Eskom, which is ultimately funded through the electricity tariff.
Unfortunately there are also cheaper and untested systems entering the market, where the user is willing to pay the full price. A large number of insurance companies are offering SWHs as an alternate option to their customers when replacing burst or damaged conventional geysers.
When it comes to saving electricity on hot water heating, there are basically two domestic options available locally: install a heat pump or put up a solar heat system. Both systems have their challenges and disadvantages;
“A solar system requires direct sunlight to heat the water,” Lea Smith of Watersmith explains. “In cloudy and rainy weather, heating the water becomes an issue, and obviously the same will apply at night when there is no sun.
“With any renewable technology a lifestyle adjustment has to take place to achieve the desired effect or to save electricity. The greater the lifestyle adjustment, the greater the saving achieved. For example if you want to only use direct solar energy to heat your water, without a booster element, you will achieve good electrical savings. However on cloudy or rainy days you may or will not get the desired hot water. You need to find the balance between saving and lifestyle.” According to Smith, a heat pump will give similar savings to a solar panel, as is, but it depends how the process is managed.
Unlike a solar system, a heat pump doesn’t require direct sunlight. It uses environmental energy. It extracts its heat from the air and directs or ‘pumps’ the heat into the water. A big advantage heat pumps have over solar hot water systems is that the existing electrical hot cylinder or geyser can be used, while with solar it’s generally replaced.
|A solar collector designed to collect heat
by absorbing sunlight
When comparing the cost of a heat pump versus that of a solar system, it must first be determined how much hot water is required daily and how much the respective systems would cost to provide an equal amount. Take for example replacing a 150l geyser. With a heat pump that capacity can be matched with equal storage of 150 l.
However, with solar the general rule is that you need more hot water storage capacity than the daily amount of hot water. Double the amount of the required amount of hot water: in the case of 150 l, 300 l of storage is needed to achieve the same effect. The reason for this? If the hot water is depleted during the early evening, it can’t reheat itself with solar during the night to be used again in the morning – unless you have a booster element, which would defeat the objective of a solar system.
“Because a heat pump uses environmental energy, it can extract this heat from the environment anytime of the day or night, come rain or shine. Solar can only draw heat during the day if there’s direct sunlight,” says Smith. “By comparing the systems in this manner, the capital outlay of a heat pump is definitely cheaper to achieve the same result.”
Either way, Smith says it’s always a good idea to invest in a heat pump or solar a system. “Simple maths shows that your return or savings on an initial investment is far greater than any other return that is currently available – and this will only get better as the electrical price increase.”
Any energy that doesn’t have to be generated by burning fossil fuels, should always end up being the cheaper option, says Bredenkamp. “One has to look at the total system, including the size and capital costs of the installation and apply the local municipal energy tariffs, to determine a simple payback on the investment. However, the current and projected increase in electricity tariffs, are making SWH more attractive and viable.”
Although one could view the initial high capital costs of SWH as a disadvantage, Bredenkamp says the total life cycle of the technology must be taken into account to make an informed decision, especially in view of the rising electricity tariffs.
According to Bredenkamp, Sanedi is working with the department of Energy (DoE) and Eskom on the development and maintenance of a comprehensive, user-friendly, web-based Geographical Information System (GIS), which will plot and track each SWH installed throughout the country. “The system uses ESRI’s ArcGIS suite and consists of three components. One is the GIS interactive web-map that will ultimately show all current SWH installations. The second is the handheld mobile data-capturing instrument that uniquely records coordinates, orientation, inclination, size, type, installer, district and other data. In addition, the mobile solution takes photographs and allows for real-time updates to a central database. Thirdly, the mobile solution will also be used for the verification of SWH installations and progress towards the national target of installing 1 million SWH’s in the country by the year 2015.”
This initiative is funded through the South African - German Energy Programme (SAGEN), implemented by GIZ on behalf of Germany, in partnership with the DoE and Sanedi.
The attitude of South Africans
When asked how South Africans are responding to the idea of SWH, Bredenkamp says the uptake has been slower than expected. “Reasons often put forward relate to concerns about a lack of hot water when it is overcast or cloudy, aesthetic impacts on the roof, the high (initial) capital cost of the SWH and the relatively low historical electricity prices in South Africa.”
It is important to only use SABS-approved products. There are lots of cheaper imports entering the market and unfortunately, a large percentage of these products are inferior.
Another important aspect is the potential impact on your water consumption. Often, suppliers advertise SWH’s with a slogan like ‘Free hot water from the sun’. This can be misleading, resulting in consumers taking longer showers or deeper baths than they would normally have. After all, it is ‘free’. However, it is the energy from the sun that is free, not the water…
Water tariffs are also on the increase and becoming a scarce resource and we must take all these things into consideration. We need to become sustainable in all areas of our lives, including the use of energy, water, petrol, waste, and other resources.
Dr. Riaan Rankin & Dr. Martin van Eldik, M-Tech Industrial (Pty) Ltd / North-West University