During the South African Water Week, which is taking place from March 17 to 23, research body the Water Research Commission (WRC) is launching the Bloemwater hydropower project, in an attempt to save on energy costs for the Bloemfontein area.
The University of Pretoria (UP), supported by the WRC, has been engaged in a research project investigating the potential of extracting the excess hydropower energy from water distribution systems in the surrounding area.
Bloemfontein waterboard Bloemwater has been one of the main collaborating organisations on this research project and has taken steps to convert to a sustainable energy source as the main supply of energy for operating their head office in Pellisier.
The Caledon–Bloemfontein potable water supply system supplies the majority of the water demand in Bloemfontein. The water is supplied to the Brandkop reservoir, which is where Bloemwater’s head office is located.
Excess energy from the Brandkop reservoir is dissipated through pressure control valves before being discharged into the reservoir. This type of energy generation, referred to as conduit hydropower, is different from the conventional hydropower generation usually associated with large dams, as the excess energy available in pressurised conduits (pumping or gravity), is transformed into clean, renewable hydroelectric energy by means of a turbine, thereby harnessing what is already available in the existing water infrastructure.
For the Bloemwater project, a 96 kW crossflow turbine and synchronous generator from Italian renewable-energy company Irem is currently being installed. The turbine will be housed in a turbine room currently under construction, located next to the Brandkop reservoir.
Around 30% of the water supplied through the Caledon–Bloemfontein pipeline will be diverted through the turbine. The turbine’s runner will be turned by the water passing through it, which in turn, will start the generator allowing hydroelectric energy to be generated. After passing through the turbine, the water will be discharged through a constructed opening in the roof in the south-west corner of the reservoir.
Control equipment will regulate the flow and pressure through the turbine resulting in the generation of clean stable electricity at the correct frequency of 50 Hz and voltage. The generated electricity will be connected through the control equipment to the main supply of the head office.
Sufficient renewable energy will be generated to supply the peak demand of Bloemwater’s head office as well as meet the electricity requirements of the reservoir terrain. Each year, around 800 MWh could be generated with this micro-hydropower installation.
The energy generation potential at this specific site is around 3.5 times the planned development, which could be exploited in future. There is also additional generation potential in the rest of the supply infra-structure.
The WRC says that hydropower schemes have long lifetimes and high efficiency levels with low operating and maintenance costs.
Conduit hydropower requires a small capital investment and has a short return-on-investment period. “As long as people use water, renewable electricity can be generated,” says the WRC.
Water and Energy in Africa
The WRC highlights that power supply is a necessity for economic growth, and the extension of the generating capacity, as well as the resources used and the impact thereof, required a responsible approach for long-term sustainability.
Energy is the lifeblood of worldwide economic and social development. When considering the current global energy shortages, the emphasis to reduce carbon emissions, development of alternative energy generation methods and growing energy consumption, it is clear that there is a need to change the way energy is generated and used.
South Africa is acknowledged to be not particularly well endowed with the hydropower potential, which is not the case elsewhere in Africa and parts of the rest of the world. However, large quantities of raw and potable water are conveyed daily under either pressurised or gravity conditions over large distances and elevations.
In South Africa, there are 284 municipal-ities, several water supply utilities and mines, all owning and operating gravity water supply distribution systems, which could be considered for small-, mini-, micro- and pico-scale hydropower installations.
Most of these water supply and distribution systems could be equipped with turbines or pumps as turbines, supplementing and reducing the requirements for pressure control valves.
The hydropower may be used on site, supplied to the national electricity grid or fed to an isolated electricity demand cluster.