How pumped-storage power works at Ingula
See how water moving between an upper and lower reservoir can store energy and support the electricity system when demand changes.
BhoSpark team · 21 Oct,2026 · 5 min read
Pumped storage works like a large rechargeable energy store. Instead of storing energy in chemicals, it stores energy by moving water to a higher reservoir.
At Ingula, on the border of KwaZulu-Natal and the Free State, an upper and lower dam are connected through underground waterways and a powerhouse. The same pump-turbines can move water uphill or let it flow downhill through generators.
Store energy by lifting water
When the electricity system has enough available power, the machines pump water from the lower reservoir to the upper reservoir. That input electricity is converted into gravitational potential energy because the water is now stored at a greater height.
Generate when demand rises
When more electricity is needed, water is released from the upper reservoir. It moves through the waterways, turns the turbines and drives generators before entering the lower reservoir. The water can later be pumped uphill again.
Pumped storage does not create extra energy. Pumping and generating both involve losses, so less electrical energy comes back than went into the cycle. Its value is that energy can be stored when it is more available and returned quickly when the system needs support.
What determines the result?
The useful output depends on the height difference, the amount and flow of water, the turbine-generator design and losses from friction and turbulence. Engineers must also consider geology, waterways, grid connections and the surrounding environment.
Investigate the idea with a model
A small turbine model cannot reproduce an entire pumped-storage station, but it can show the first half of the cycle: stored water moves downhill and produces rotation. Keep the water volume and test time the same, then change the release height or flow and count the turbine turns.
For a useful conclusion, state what your model showed and what it could not show. It does not pump the water back uphill, connect to a national grid or measure the full efficiency of the cycle.
Continue with the Eskom overview of Ingula and its peaking power stations, then sketch the energy changes during pumping and generating.
Put moving water to the test
Build the turbine model, choose one condition to change and record how the rotation responds.