Piping hot and efficient: Wits to save millions using the sun
The varsity now has SA’s largest solar thermal system, and expects to recoup the cost within three years
Wits University has launched SA’s largest solar thermal system that will produce enough warm water for more than 1,000 students in 14 residences.
At a cost of R15m, the investment is expected to be recovered within three years through lower electricity and water usage.
A solar thermal system is a new technology that cuts out the need to generate electricity to heat water. A normal solar system uses light to create electricity, while a thermal system directly heats up the water.
“The normal rooftop solar geysers are not as efficient in providing hot water for the whole building, as this thermal system is,” said Dr Karen Surridge of the SA National Energy Development Institute (Sanedi) who worked with Wits to install the system.
Surridge said one reason solar geysers were not as effective as a thermal system was because it required long pipes to take water to the tap.
“One reason it is not as efficient is that using solar geysers, you run pipes quite a long way from the tap to the panel.
“But now the new ring piping system at Wits runs all around the building so you literally only have a couple of metres where hot water has to come out of the pipe. So you have instant hot water.”
The system heats 94,000 litres of water for showers, cooking and laundry use a day.
“It is one heating system for 14 buildings for over 1,100 students. At Wits junction [a set of 14 residences] they got rid of the electrical wiring and stripped out the 200 solar geysers.”
Dark panels with water inside were installed on a large rooftop area at Wits. This water is pumped to three 300,000-litre insulated storage tanks in an operating room.
Two kilometres of piping was installed to run in a ring around the 14 buildings, carrying hot water to all of them.
Wits Junction is above the underground Egoli gas line.
The system uses the gas as a backup to heat water on a cloudy day or when the water temperature is too low.
“You always need a backup, but solar is the primary energy source,” said Surridge.
Wits University spokesperson Buhle Zuma said: “The university is delighted with the savings being realised to date, and are proud to own the current largest solar thermal district heating system in the country. There are already several similar projects in the pipeline for implementation in the near future.”
Also involved in the Wits project was Soltrain, an Austrian government-sponsored project set up with an Austrian company, AEE INTEC, to roll out their solar thermal power technology to sub-Saharan Africa.
Soltrain, Stellenbosch University, AEE INTEC and Sanedi worked together on the Wits project and on a project in the Karoo.
Werner Weiss, director of AEE INTEC, said the beauty of solar thermal heating was to reduce electricity demand and in the process lower greenhouse gases and pollution.
“Electricity is the centre of global political discussions. Half of the total energy demand globally is for heating and cooling. Half of all residential electricity usage is for heating water,” said Weiss.
“What could be the solution? In Northern Europe, we heat water in summer, [with solar thermal panels] store it for six months and take it out in winter. If we could do it [heat water] with low radiation in northern Europe, we can do it with your [South Africa’s] radiation.”
Also launched on Wednesday was a 600m² solar water heating system for the Klein Karoo tannery, which makes leather from ostrich skins.
A tannery is highly energy-intensive, since hot water is needed for the process of stretching out skin into leather.
The solar collector system was implemented by the Oudtshoorn Klein Karoo Tannery to reduce costs.
The Karoo is also home to Kathu, a solar power generating system using light to create electricity.
The groundbreaking Kathu plant uses giant curved mirrors to track the sun and focus its light into a pipe.
The energy is taken by pipe to water that makes steam to push a turbine to create power. A specialised system allows Kathu to store energy and produce it even after the sun sets.