Eskom using diesel to keep load-shedding miracle alive

Eskom has increased its use of diesel-fuelled Open-Cycle Gas Turbines (OCGTs) to prevent load-shedding during the evening peak as it struggles to return some units to service on time. 

Eskom’s OCGTs are referred to as peaking stations, which are plants used to manage short periods of elevated demand. 

In recent years, as load-shedding escalated, these stations were used more regularly to prevent higher stages of load-shedding. This resulted in Eskom’s diesel expenditure soaring to R23.4 billion in the 2023 financial year. 

Over the past five years, the utility has spent R64.8 billion on diesel. 

Eskom’s improved performance in 2024 has largely negated any need for these power stations, resulting in diesel expenditure declining by 75% from April to August 2024 compared to last year. 

This translates into R10.6 billion in savings for the utility, which can be allocated to maintenance or expanding its generation capacity. 

Eskom has forecast a continued decline in the use of OCGTs throughout the rest of 2024 and early 2025. 

However, in recent weeks it has had to ramp up the use of these power stations as Koeberg’s Unit 1 was shutdown on 11 September for repairs, and there have been delays to the return of some units at Medupi. 

In response to questions from Daily Investor, Eskom said it has been strategically using its peaking power stations, including pumped storage and OCGTs, to manage demand in the evening peak from 17:00 to 22:00.

“Diesel consumption remains significantly below projected figures and is considerably lower than in the past two years,” it said. 

Diesel expenditure stood at R6 billion as of 10 October 2024 from the beginning of its financial year on 1 April, 67% less than the R18.03 billion spent during the same period last year. 

The OCGT load factor for 1 April to 10 October 2024 was 5.79%, compared to last year’s figure of 18.63%.

The OCGT load factor for 1 October to 10 October 2024 was 4.35%, significantly lower than the 11.54% for the same period last year, Eskom said. 

Operational efficiency has met summer expectations, with unplanned outages averaging 12,087 MW during the past seven days, compared to 15,065 MW in the corresponding week last year.

The graph below shows Eskom’s increased diesel usage in recent weeks. 

The ramp-up in diesel usage to meet demand during the evening peak can largely be attributed to the shutdown of Koeberg Unit 1 on 11 September due to an equipment fault. 

“The unit was shut down to restore redundancy of the steam pressure relief system in line with the operating technical specifications,” Eskom said. 

This means Koeberg, with a capacity of 1,840 MW, has been completely offline for over a month as its second unit has been shut down for maintenance. 

Energy analyst and MD of EE Business Intelligence, Chris Yelland, said Eskom had delayed the return of Koeberg Unit 2 from June 2024 to December 2024. 

This delay will be compounded by delays in returning Medupi’s Unit 4, as its generator repairs will only be completed in March 2025. 

Electricity Minister Kgosienstho Ramokgopa admitted that Eskom has been unable to meet its own targets in returning these units to service. 

The primary component of Koeberg Unit 2’s maintenance is replacing its steam generators. In July 2024, Eskom noted that it would soon return to service. However, Ramokgopa says the power utility’s target has slipped.

“We said it would come on this date, and it has not come on that date. So, that’s something we are attending to,” the minister said.

Ramokgopa also raised concern about the performance of Medupi, saying a lot of money has been invested in the power station without much to show for it. 

“Medupi is a big concern. A number of units had gone out and the like. It’s a concern because it’s one of our newest. It’s a concern because we have invested a lot of money,” he said.

“It’s a concern because we’re pricing that money in the tariff, and then it’s not performing.”

He added that the issues at Medupi are something that Eskom’s teams are focusing on.

The coal-fired Medupi plant is one of South Africa’s newest power stations, but it has been fraught with problems since construction began.