State-owned electricity group Eskom is warning that its use of the country’s diesel-fuelled open cycle gas turbines (OCGTs) is set to remain elevated in the coming months as the utility seeks to avoid load-shedding in a context of rising planned maintenance and the ongoing risk of unplanned breakdowns.
Eskom has already spent R5.5-billion for the year-to-date to run its own OCGT plants and a further R3-billion to purchase electricity from the private Avon and Dedisa plants, as the energy availability factor (EAF) from its coal fleet slumped to 62.9% against a target of 70%.
Despite operating the OCGTs at far higher capacity factors than planned, the utility has nevertheless been forced to implement record levels of load-shedding during the current financial year, with 51 days of cuts between April 1, 2021, and January 24, 2022, compared with 31 days in the prior period.
For 2021 as a whole, the picture is even bleaker with 1 150 hours having been affected by rotational cuts and 1 773 GWh not supplied to customers, representing the worst-ever performance for the level of energy shed.
Group executive for transmission Segomoco Scheppers said the outlook for the rest of summer, or until the end of March, pointed to a continued over reliance on the diesel plants.
The precise level of OCGT use would depend mainly on the level of unplanned losses, he explained during a briefing on the state of the system.
Should unplanned breakdowns remain below 12 000 MW until the end of summer, Eskom expects to spend R500-million more on diesel and avoid load-shedding.
Should breakdowns rise to 13 000 MW or 14 000 MW, the number of load-shedding days will rise to two and 29 respectively, while its diesel spend would climb to R1.7-billion and R4.1-billion respectively.
However, Scheppers warned that, in reality, there would have to be more load-shedding days at higher stages, as logistical constraints made it difficult for Eskom to spend more than R1.2-billion on diesel in a single month.
Similar sensitivities would prevail between April and August, but Eskom would only finalise its winter plan in March.
During recent hearings into the utility’s request for a 20.5% tariff hike, CFO Calib Cassim confirmed that Eskom was seeking R6.5-billion to operate its OCGTs in 2022/23, largely because of a material lowering in its coal EAF assumption for the year from 72% to 62%.
As a result, Eskom is expecting to operate its OCGT generators at a load factor of 7%, rather than the 1% initially assumed.
There was much debate during the hearings about the prudence of allowing Eskom to use the OCGTs other than as peaking plants, but the utility defended their use on the basis that load-shedding carried a cost to the economy (estimated at R9.53/kWh) that was three times that of producing OCGT electricity.
COO Jan Oberholzer said that, while Eskom would do what it could to limit load-shedding, it would not be at the expense of its reliability maintenance programme, which remained key to stabilising the performance of its unreliable coal fleet.
“We continue to drive our planned maintenance programme with a focus on the effectiveness of outages.
“This will contribute to the risk of load-shedding during times of capacity constraints,” Oberholzer said during the briefing.
While Eskom reported some progress in the implementation of its reliability maintenance programme, group executive for generation Phillip Dukashe warned that the backlogs remained large and would take time to address.
These backlogs were presenting primarily in the form of vacuum issues across many stations, delays to control and instrumentation refurbishment projects, persistent boiler tube leaks, overdue environmental projects and water treatment plants that were in a state of disrepair.
The programme also remained beset by skills and liquidity challenges, however, which had resulted in the deferral of 40 of the 84 outages initially planned for 2021/22.
“As of January 19, 2022, of the 84 outages planned for 2021/22, 33 have been completed, nine are in execution, two are remaining and 12 have been deferred within the financial year, while a further 28 outages have been deferred to 2022/23,” Dukashe reported.
Outages could also be affected by the fact that Eskom planned to increase its energy utilisation factor across its operating plant, to mitigate the slump in the EAF.
“Resolving the issues sustainably requires extensive maintenance outages and implementation of refurbishment projects,” Dukashe said.