SOLAR GEYSERS BEAT THE LIMESCALE BLUES IN LIMPOPO

Limescale build up is bad news for geysers, but a SANEDI project in Limpopo could be the key to a solution that protects appliances and make households more energy efficient.

The SANDF’s air force base in Makhado, Limpopo, is the site of an energy-efficiency pilot project aimed at helping households cope with the impact of limescale build up. The project falls under the auspices of a five-year partnership between SANEDI and the military that involves ongoing research to quantify energy, cost and emissions savings through energy-efficient and renewable-energy interventions.

Limescale build up in water-heating systems raises the cost of heating by significantly reducing energy efficiency. It also shortens the lifetime of the geyser or kettle. “A geyser that should last for five years, gives out after 18 months or less,” says Dr Karen Surridge, acting general manager at SANEDI. “Given that parts of Limpopo are notorious for so-called ‘hard water’ – water that has a high mineral content - the SANDF are helping us build a business case for solar technology in high limescale water areas.”

The project kicked off with the installation of 50 indirect high-pressure solar water-heating systems. Seven artisan soldiers were trained to install and maintain this technology that specifically deals with limescale risks to household water-heating systems. An ordinary direct solar water-heating system will calcify with limescale just like an electrical geyser would. Indirect systems work by heating a water-glycol mix (similar to anti-freeze in a vehicle) which runs alongside the normal water and heats it for use. The project compares high-pressure solar heating systems to instantaneous water heating and heat pumps – all of which are more energy efficient than the traditional electrical geyser.

In hot climates like Limpopo, solar water heaters can reach much higher temperatures than what the thermostat of a conventional geyser will allow, meaning that households use less hot water. Using less water more efficiently is critical for people around the Limpopo River basin and other areas most at risk to water insecurity due to climate change.

SANEDI has previously quantified the energy-cost savings from a similar project at a different military base in Limpopo, albeit at a larger scale. The data indicated a return on investment in under three years, accompanied by significant savings in cost, electricity and emissions.

According to Surridge, the Makhado project is the first time that the indirect heating technology is tested, at domestic scale, in an area where hard water is such a severe problem. “We are looking forward to seeing the results. Proving that sustainable and efficient energy technologies are fit for purpose is vital in the energy-constrained environment in which South Africa finds itself.”

While solar water-heating systems store heat for long periods, they do come with back up to ensure hot water is available even during several days without sunshine. The technology cannot deliver results on its own, though. People have to adjust their lifestyles by, for example, using hot water sparingly in the evening to ensure that there is enough hot water in the morning before the sun comes up. “But the benefits, including grid stability, outweigh any inconvenience,” Surridge says. “We are continually making our partners in the military, public, commercial and industrial sectors aware of energy-efficient behaviour as much as of the technology.”