By JN Bhagwan et al.
Although South Africa has little potential for large hydropower schemes, there is significant potential for the relatively cheap development of small and micro hydropower plants.
South Africa is experiencing serious energy shortages and therefore alternative energy generation methods are being adopted at all levels of the country’s economy. There are 284 municipalities and several supply utilities, all owning gravity water supply distribution systems which could be considered for small, mini, micro and pico scale hydropower installations. Various locations in these systems may be equipped with turbines (or pumps as turbines). The generated hydropower may be used on site, supplied to the national electricity grid or fed to an isolated electricity demand cluster.
A pilot plant has been constructed at the Pierre van Ryneveld Reservoir situated in the Country Lane Estate south of Pretoria. Tests are being conducted to verify the assumptions made during preliminary calculations. Although the site is not one of the municipality’s top 10 sites in terms of hydro potential, it was selected due to the construction of a new reservoir affording the opportunity to construct the first closed conduit hydropower pilot plant in South Africa. It is a ±15 kW installation utilising a cross flow turbine discharging through the roof into the reservoir.
It is planned to use the generated power on site for lighting, alarm, communication etc. The home owners association of the Country Lane Estate have also indicated that it would like to use the power for street lighting. Annually ±131,000 kWh could be generated with this unit, enough to supply 10 households from the pilot plant.
In a desktop study the 10 reservoirs with the highest potential in the Tshwane municipal area were identified. A flow diagram was used as a first order tool for identifying conduit hydropower potential in the municipality. The use of the potential energy stored in the pressurised closed conduit water systems of the Tshwane municipality is however not limited to these sites.
These 10 sites have a potential to generate 10,000,000 kWh/annum. Based on a number of assumptions, the potential annual hydropower generation at these reservoirs, were calculated as summarised. This analysis is a conservative low estimate of the hydropower generating capacity. In the case of the power generation from reservoirs in the Tshwane supply area, the fraction which has been used to calculate hydropower generation is only 12.5% (0.5 x 6/24 x 100) of the potential maximum power generation.
In water is distributed through a large system that includes 160 reservoirs, 42 water towers, 10,677 km of pipes and more than 260 pressure reducing installations (PRVs) that operate at pressures up to 250 m. Geographically speaking, the city of Pretoria has a lower elevation than the bulk service reservoirs of Rand Water which is the main water supply, resulting in high pressures still available.
Hydropower represents a nexus of water and energy and in municipalities and water boards there are several locations where a feasible conduit hydropower scheme can be implemented. It was shown using a first order analysis that economically feasible potential might exist at various PRV stations/reservoirs in Tshwane. Further studies are underway to confirm this potential and optimise the design of hydropower plants. As long as people use water electricity can be generated.
By JN Bhagwan1, M van Dijk2, SJ van Vuuren2, I Loots2 and A Kurtz2&3
1 Water Research Commission, Private Bag X03, Gezina, 0031, South Africa
2 Department of Civil Engineering, University of Pretoria, Pretoria, 0001, South Africa
3 City of Tshwane Metropolitan Municipality, P.O. Box 1022, Pretoria, 0001, South Africa
(Email: firstname.lastname@example.org; email@example.com; firstname.lastname@example.org; Ione.loots@ up.ac.za; email@example.com)