Design and implementation of conduit hydropower plants in the City of Tshwane Marco van Dijk Chantel Niebuhr Anja Bekker
The Hydropower Research Group in the University of Pretoria’s Department of Civil Engineering has been involved in the development of conduit hydropower plants for the past 10 years.
As a water-scarce country, it is often presumed that South Africa does not have the most prevalent hydropower conditions, as may be found elsewhere in Africa and the rest of the world. However, large quantities of raw and potable water are conveyed daily over large distances and elevations under either pressurised or gravity conditions. Within these systems exists the opportunity for conduit hydropower generation. In water distribution systems, excess pressure, which can be exploited for conduit hydropower, is generally dissipated by employing equipment such as orifice plates and pressure-reducing valves. Conduit hydropower differs from more conventional hydropower development in that it is not located on natural rivers or waterways, and does not involve the potential negative types of environmental impacts that are usually associated with hydropower projects. The water supply and distribution systems consist of a complex network of interconnected pipes, service reservoirs and pumps that deliver water from the treatment plant to the consumer. The Hydropower Research Group has been actively involved in the following activities: • • • • • • •
South African policy and legislation Feasibility studies Site evaluations Small-scale hydropower plant development Turbine development and design Numerical computational fluid dynamics modelling Guideline and software tool development
A Memorandum of Agreement, cementing the collaboration between the University of Pretoria and the City of Tshwane, endorsed the research group’s opportunities to evaluate, plan, design, experiment and develop conduit hydropower plants on the water infrastructure of the City of Tshwane.
Three pump-as-turbine installations at the Annlin Reservoir
The Otter turbine installed on a bypass in parallel to pressure-reducing valves
A new reservoir was recently completed in Doornkloof. An 8 kW prototype “Otter turbine” was installed as part of this construction. This conduit hydropower plant was recently commissioned and supplies the site with power for lighting, telemetry, cathodic protection and an alarm system. A student completing his master’s degree in the Department of Civil Engineering is now optimising the design and monitoring the functioning.
In 2011, the Pierre van Ryneveld conduit hydropower plant was launched, showcasing a 15 kW cross-flow turbine installed on the reservoir roof.
The research group also assisted in the development of the Annlin Reservoir conduit hydropower plant, which consisted of three 50 kW pump-as-turbine installations, with two grid-connected units and one unit supplying the reservoir complex. Unfortunately, this site was vandalised (a reality for most municipalities) and requires refurbishment.
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