South Africa is a water-scarce country, but there is plenty of sun. A group of University of Stellenbosch researchers has effectively used solar energy to produce drinkable water in isolated rural communities — cheaply, reliably and with very low maintenance.
The device is simple but highly effective, making use of science and technology: a solar panel attached to a catchment container, which comprises the solar still, creates sufficient heat to evaporate salt-heavy, brackish underground water not fit for human consumption.
This distillation/desalination process produces between 10 and 15 litres of drinking water per solar still each day. And communities are part of the project: members are trained to look after the stills — the glass panel needs to be wiped down once a day — and maintain them. The stills are made of cheap, locally available materials.
‘We do it to give people water. It [the solar stills] will go into rural areas that have no electricity. We have to go in with easy technology,” says Dr Ron Sanderson, director of the Unesco Centre at the University of Stellenbosch’s chemistry department.
Already two remote communities at Ladismith in the Western Cape — Kerkplaas and Algerynskraal — are benefiting from a secure water supply. A third, under the auspices of the Department of Water Affairs and Forestry, will be established before the end of the year.
‘If we don’t save water together, we will die together,” read one of the placards designed for the official handover of the solar stills at Algerynskraal in May this year. That installation was completed and handed over to the community in less than three months. The first, at Kerkplaas, took about a year.
Research started in 1996 after Sanderson saw how fresh water was obtained by residents of Leupelfontein, a hamlet on the Cape West Coast. A wall had been built around a granite rock and condensation accumulating on it was collected for use.
Back at the University of Stellenbosch chemistry department the aim was to develop a solar still that was cheap, easily maintained and used local products. The main challenge was effectively to waterproof the catchment container, which, for cost reasons, was to be made of wood.
Eventually the researchers developed their own polymer, a plastic- based coating, which would withstand up to 90°C heat.
Doctoral student Ian Goldie, who headed this part of the research, says the process identified the necessary characteristics and the best way to obtain them. Researchers experimented with various commercially available products, including expensive silicone, before successfully ‘cooking up” their own polymer coating.
Such polymer research has also improved the water yields from fog nets set up in Namibia and elsewhere. Roughing up the polymer of the nets resulted in a substantially increased water yield.
The solar stills were initially tested in the Namib desert and at Brand- vlei to ensure they withstood harsh weather conditions. There master’s student Andrew Theunissen monitored water yields of the units and also investigated potential improvement of the solar stills’ workings.
A key element of this phase was to ensure that everything needed to repair the stills was available at the local hardware store, he says, adding: ‘There are very poor people and very little water.”
In conjunction with two companies, the researchers have developed a commercially viable solar still to supply safe drinking water to South Africa’s rural communities, where extending the water and sewerage grid could be prohibitive.
The unit price of the stills is R1 000, less than a tenth of the price of American products. ‘It’s a purely South African design and it’s inexpensive,” says Sanderson.