Eskom, the South Africa-based company that supplies 95% of the country’s energy, is unable to generate at full capacity at two of its pumped-storage facilities mainly operated during periods of peak electricity demand. The hydroelectric projects have a total capacity of 1,400 MW, but due to a combination of maintenance, supply and demand issues, Eskom recently announced it was entering Stage 1 load shedding to maintain water levels at its pumped storage facilities.
According to Eskom officials, Stage 1 allows for up to 1,000 MW of South Africa's electricity load to be shed from its national grid, Stage 2 for up to 2,000 MW, and Stage 3 for up to 4,000 MW. To date, Eskom has applied Stage 1 load shedding on Jan. 28.
Eskom’s operational pumped-storage schemes include 1,000-MW Drakensberg in the mountains of the Northern Drakensberg of KwaZulu Natal and 400-MW Palmiet, 2 km upstream of Kogelberg Dam on the Palmiet River near Cape Town.
Eskom ended Stage 1 load shedding, which resulted in rolling power cuts, at 2 p.m. on Jan. 28, after initially announcing it would implement power cuts from 10 a.m. to 10 p.m. to manage water levels at its two operating pumped storage.
Eskom has a third pumped-storage site, 1,332-MW Ingula, scheduled to open later this year. It is being constructed 55 km from Ladysmith, within the Drakensberg range, on the border between the Free State and KwaZulu-Natal provinces.
Eskom said the water levels in the upper reservoirs at its two pumped storage schemes are below normal because in order to meet power demand the stations have had to shorten pumping cycles, making the projects unable to pump enough water from the lower reservoir to return the upper reservoir to full capacity.
The company said this time of year it normally conducts maintenance at several of its facilities, necessitating that those facilities not generate electricity. Eskom operates several hydroelectric projects, fossil fuel-fired plants and the 1,940-MW Koeberg nuclear power facility. Eskom said it expects the South African national power grid to remain “constrained” for the rest of the summer.
However, the utility is receiving help from neighboring Namibia. Namibia’s state-owned NamPower is providing up to 200 MW of surplus energy capacity to Eskom to ease the burden on South Africa’s national grid. The utility supplies bulk electricity to regional electricity distributors, mines, farms and local authorities throughout Namibia.
The Drakensberg pumped-storage plant was commissioned in 1982 and uses water pumped from the Thukela River, over the Drakensberg escarpment into the Wilge River, a tributary of the Vaal. The Palmiet facility, commissioned in 1988, transfers water from the Palmiet River catchment into Steenbras Dam to supplement Cape Town’s water supply.