South Africa’s largest underground power station takes shape
Ingula is Eskom’s fourth pumped storage scheme. Constructed inside a mountain, 116 storeys below ground, it is South Africa’s largest hydro power project to date.
Royal HaskoningDHV has been involved at Ingula since the project began in 2005, as part of Braamhoek Consultants, a joint venture company set up to deliver five contracts within the bigger project. These include design and construction supervision for Ingula’s two dams – Bramhoek and Bedford, access roads, visitors centre and administration building and main underground works..
Pumped storage is a tried and tested solution for delivering energy to the national grid at peak demand times. Pumped storage schemes are also a sustainable option because they partially use hydroelectric power.
Advantages of PSS
- Provides rapid response to system load changes
- Improves power factor of the system
- Permits continuous operation of base load plants
- Contributes to reliable stability
- Provides ‘black start’ capability
In order to function, pumped storage schemes require two dams or reservoirs. At Ingula, the upper Bedford and lower Bramhoek dams are located 4.6 km apart and connected by underground waterways. During times of peak energy consumption, water will be released from the upper dam and flow through 4 x 333 MW turbines to generate 1332 MW of electricity. At times of low energy demand, the pump turbines will drive water 470m from the lower to the upper dam where it will be stored in readiness for the next peak event.
Jacques du Plessis, Project Manager, Royal HaskoningDHV said: “Constructing the largest powerhouse complex yet built in mudrock was a unique challenge. The team used a three phase rock support system and extensive instrumentation to overcome this. Excavation of the very steep headrace tunnels required specialist techniques and equipment and close cooperation between all parties.”
Desigan Padayachee, Engineering Manager, Eskom comments: “The Ingula pumped storage project is integral to our new build programme and will add the peaking capacity South Africa needs to meet the demands of a modern economy. It will also enhance the lives of millions of urban and rural dwellers who can look forward to enjoying the benefits of reliable electricity.”
- The design of Bedford Dam made provision for wetland protection, landscape aesthetics and artificial bird cliffs.
- Three million m³ of rock were excavated
- Excavations created the largest mudrock cavern in the world, totalling 200,000 m³.
- Animal and plant fossils dating back 255-million years were discovered indicating that the region was covered by an inland fresh water lake many millennia ago.