South Africans on Wednesday awoke to news that Eskom was cutting more power as the utility scrambles to top up emergency reserves it said were “being depleted faster than can be replenished”.
The power utility on Monday announced so-called stage 2 load-shedding, or removing 2,000MW from the national grid, and the following day said the cuts would continue until Saturday. Stage 4 (4,000MW of cuts) was announced on Wednesday morning, which Eskom estimates will cost the economy about R1bn a day.
The utility’s emergency generation capacity is supplied by the open-cycle gas turbines and through pumped storage hydropower generators. These can deliver a maximum of 5,700MW to the grid to supplement capacity lost when there are breakdowns at the coal-fired power stations.
Eskom has been using 9-million litres of diesel a day to power its open-cycle gas turbines, Ankerlig and Gourikwa, said COO Jan Oberholzer.
Oberholzer said an additional three to six stages of load-shedding would be required if emergency reserves were depleted, removing as much as 10,000MW from the system.
Eskom’s load-shedding schedule at present provides for as much 8,000MW of cuts, but further levels could be implemented if more load-shedding hours were required, he said.
To avoid this “it is critically important to balance these emergency resources to make sure we manage the power system safely while making sure we keep the stage of load-shedding as low as possible,” he said.
CFO Calib Cassim told a media briefing on Wednesday that the reliance on emergency generation capacity was a source of great concern due to the escalating cost of diesel. The spike in crude oil prices in the wake of Russia’s invasion of Ukraine could affect the amount of diesel Eskom would be able to afford to power the gas turbines, he said.
Besides the cost concerns there are also logistical challenges to delivering enough diesel to Ankerlig where delivery had to be made by road.
Eskom’s fleet of coal-fired power stations remained fragile, said Oberholzer. In addition to unplanned outages of about 15,500MW on Wednesday morning, there were 16 units with combined generation capacity of about 5,600MW that are at risk of breakdown. That includes three units with generation capacity of 1,088MW that were “at very high risk”, he said.
Phillip Dukashe, Eskom’s group executive for generation, said the energy availability factor — a measure of the available generation capacity as a percentage of total installed generation capacity — was about 62% across the entire generation fleet and about 58% on the coal-powered fleet.
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