Eskom generating so much electricity it’s switching units off

Eskom’s generation fleet is performing so well that the power utility is placing some of its units on cold reserve due to excess capacity, Sunday Times reports.

Eskom head of generation Bheki Nxumalo says generation units are typically switched off for a few days, which helps the power utility save money and resources when capacity dramatically exceeds demand.

He said Eskom typically switches off units at its plants that are the most expensive to run. These generally are the power utility’s older power stations.

However, other factors, such as the reliability of returning the generator to service, must also be considered.

Nxumalo added that the process is normal for a large interconnected power system.

Placing units on cold reserve involves careful planning. Nxumalo says Eskom forecasts the demand for electricity for every hour of every day up to 18 months in advance.

“Based on this, planned maintenance of generators is scheduled for periods of lower demand after ensuring there are sufficient operating reserves to cater for short-term generator breakdowns,” Sunday Times quoted Nxumalo as saying.

Restarting units can take up to 72 hours, so Eskom avoids placing too many units simultaneously at one power station on cold reserve to ensure adequate power to restart generators.

Nxumalo noted that Eskom produced more than 35,000MW daily in the last week of July, approximately 3,000MW higher than peak demand.

He said Eskom last achieved such high generation figures in July 2018.

Nxumalo previously said Eskom’s decision to fix its existing generation fleet rather than build new generation capacity is paying off and saving the entity a lot of money.

He explained that capacity losses had fallen below 9,000MW, roughly 7,000MW less than at the same time in 2023.

He said the investment required to add that amount of new capacity would be around R100 billion. Fixing their existing power stations was much cheaper.

“If you look at the amount of money that was spent, this was a cheaper option from where I’m sitting and where we are at Eskom, to say lets fix the current fleet,” said Nxumalo.

He added that two of Eskom’s most problematic power stations (which is also its newest) — Medupi and Kusile — are now the top-performing stations in its fleet.

“We had some teething issues during the start up but now those stations are performing exceptionally well,” said Nxumalo.

The South African National Energy Development Institute’s Professor Sampson Mamphweli believes load-shedding could be history by the end of the year, made possible by an improved energy availability factor, fewer breakdowns, and lessened demand.

“I am very much optimistic that we may be able to continue to sustain this until we start the beginning of summer, and if we go through the beginning of summer without load-shedding, we might see the end of load-shedding,” he said.

He added that he’s confident the government will declare the end of load-shedding between November and December 2024.

Electricity and energy minister Kgosientsho Ramokgopa said Eskom’s improved performance, which has allowed for an extensive load-shedding break since 26 March 2024, is sustainable.

“Since the beginning of this year, Eskom’s plant availability has been trending upwards, supported by a decrease in unplanned losses,” said Ramokgopa.

“All indications suggest that this performance trajectory is sustainable.”

He added that government is continuing efforts to complement the coal fleet with new generation capacity, including converting open-cycle gas turbines from diesel to gas and from open to close-cycle systems.

Ramokgopa said Eskom’s generation fleet is performing far more reliably going into 2024’s summer than at the same time in 2023

“Generation has been able to maintain the unplanned losses below 14,000MW throughout the winter period while leveraging the improved performance to conduct additional short-term planned capacity loss factor,” he said.