Micro-hydropower lights up village
There is hidden potential for small hydropower plants in South Africa
South Africa’s first microhydropower plant supplying electricity to a rural area has been developed in the village of Kwamadiba in the Eastern Cape, powering about 50 households.
The department of science and innovation funded the pilot project through the Water Research Commission (WRC), in work led by the University of Pretoria.
“This is the first one that supplies electricity to a rural community,” says Marco van Dijk, a lecturer at the University of Pretoria’s department of civil engineering, who implemented the project together with his team.
“There are a number of run-ofriver schemes which range in size from small pico installations used by a farmer to larger installations such as the 42 megawatt Colley Wobbles power station on the Mbashe River, which Eskom owns and operates.”
He says the pilot project proves that small hydropower technology can provide grid quality electricity to rural areas. “Such plants can provide renewable options for communities that are currently off the mainstream electricity grid but living near rivers or existing dams that can be retrofitted.”
The technology components are housed and retrofitted in a prefabricated shipping container at the bottom of Thina Falls. The waterfall is on the Thina River just before its confluence with the Tsitsa River. A small, diverted flow at the top of the falls fed into a pipe provides the necessary head to turn the turbine.
“This run-of-river, modular unit turns the potential energy of water flowing into clean electricity,” Van Dijk says. “It’s turbine and generator harness energy from water, of which there is plenty all year round.”
Such installations, he says, provide an alternative renewable source of electricity, particularly for people living far from the national grid. “It provides a baseload supply and further eases the burden on the national grid.”
The system is clean, efficient, dependable and cost-effective, according to Van Dijk.
Aqeelah Hassan, of the Africa programme of International Rivers, said that hydropower generation at such a small scale, for example, benefiting a village otherwise not connected to the grid, generally has few adverse impacts on the environment.
“This approach has been extremely successful in expanding access to electricity in rural areas. For conventional, large-scale hydropower, it’s generally worse environmentally to have multiple small dams on a river than having a single large one. This doesn’t necessarily apply at the village level.”
Hydropower, especially run-ofriver designs, is highly seasonal, Hassan said. “It’s also very site-specific, so what may work for one village might not in others. Areas that are prone to drought or receive little rainfall much of the year might not get much benefit and household solar is likely a better option. Solar is generally cheaper and easier to maintain. Solar can also be generated and consumed by a single household so it reduces the problem that mini-grids have of some using more than their share.”
The effect on the environment are based on the size of an installation, says Van Dijk. “If a new weir needs to be constructed across the river, this means the fish cannot migrate upstream and this would require other mitigating measures to be implemented.”
The idea is to focus on locations where any potential negative environmental effects can be mitigated successfully, he says. “As an example the minimum flow over the Thina waterfall is 1500 litres per second and we are only using 10% of this. The way in which we release the water at the tailrace will not cause any scouring and the water is not polluted when passing through the turbine.”
The effects on the environment need to be quantified and assessed. “For small installations these impacts are, in many cases, insignificant. If, for example, water is released from a dam for the reserve flow downstream then why not add a turbine to that outlet and first extract any potential power from this before releasing the water?
“This would actually have an environmental benefit as the energy is dissipated by doing this and not released downstream,” he says.
Small hydropower schemes can play a critical role in providing energy to remote areas in South Africa, “as stand-alone isolated mini-grids or to alleviate the burden on municipalities by making them more sustainable”.
Jay Bhagwan, an executive manager at the WRC, says the project offers huge potential for several other villages in areas such as the Oliver Tambo district municipality that are near an adequate water source.
The Kwa-madiba plant has a projected lifespan of about 40 years, and the local municipality now owns the project and will be responsible for its operation and maintenance.
A vast water infrastructure network has been developed to dam, store, control, measure and convey water to end users because South Africa is an arid country, says Van Dijk.
“There is hidden potential for hydropower at many of these locations, ranging from a pico-, micro,or even mini-hydropower scheme, to possibly supply a school or clinic, a cultural village centre, or even a whole community.”
Van Dijk and his team are compiling a national hydropower atlas as part of another Wrcfunded project, to help identify areas where hydropower projects of different sizes can potentially be implemented.
There is uncertainty about the hydropower potential in the country’s rivers and water infrastructure “but there are many dams that could be retrofitted with hydropower. For example, the water that is being released from the Vaal Dam for the natural reserve flow can be turbined to first extract the energy from it,” says Van Dijk.
The atlas will examine “unconventional opportunities” in water infrastructure.
“For example the water that flows under gravity in a Rand Water pipeline from Midrand to Pretoria is controlled at the end with pressure reducing valves, which provides an opportunity to add a turbine in parallel and extract this ‘conduit hydropower’ from it before flowing into the end reservoir.
“The outflow from a wastewater treatment work is a relatively constant flow of effluent back to the river and some electricity could be extracted to assist in the wastewater treatment works’ needs.”