Eskom only meets peak demand half the time

Eskom only meets peak demand half the time

South Africa power utility giant Eskom imposed severe and highly unpopular power rationing, known as load-shedding, for ten consecutive days in March 2019. Picture: AFP / File / MARCO LONGARI

The risk of load shedding remains, but the outlook has improved as it slowly catches up on its maintenance backlog, and as it brings new units at Medupi and Kusile online.

Eskom has only managed to meet peak demand with its own fleet on 49 of the 106 days between the most recent instance of load shedding on March 23, and July 7.

An analysis by Moneyweb of data published by the utility shows that for just more than half the time over the past three months, Eskom has not generated sufficient electricity to meet peak, night-time demand. This shortfall has ranged from just 30 megawatts (MW) to 3 097MW, and was in excess of 1 000MW for 35 of the 57 days.

Generation performance deteriorated noticeably over the two weeks to Sunday (July 7), with Eskom’s own fleet only able to meet peak demand itself on two of the 14 days (June 29 and 30).

Peak demand has not exceeded 33 000MW yet this winter, with the highest demand (32 949MW) reported on May 28. On that day, Eskom reported 35 265MW of available generation, its highest total in many months. It must be remembered that there were a number of public holidays over this period, including the Easter weekend, Workers’ Day and Election Day, which would have depressed demand.

Source: Eskom

In the joint briefing by the minister of public enterprises and Eskom executives at the beginning of April, it was clear that to avoid load shedding this winter, Eskom had to ensure that unplanned outages (plant breakdowns and trips) were kept below 9 500MW. With this headroom, Eskom said it planned to “execute proper maintenance” this winter, a departure from previous years where planned maintenance was cut to about 1 000MW. The utility has forecast planned maintenance of as much as 4 000MW at a time during the winter months.

The extent to which it has been able to execute this maintenance is not known, but running a negative operating reserve margin seems to suggest it is comfortable it can take plant out of service for repairs because of capacity from other sources.

Alternative sources

Chief among these, obviously, are the independent power producer (IPP) gas (diesel) peaking plants, Avon and Dedisa, which together provide 1 005MW. It is clear these are being used when Eskom is unable to meet demand.

Renewable energy from other IPPs is also available and being fed into the grid. Already, wind and solar photovoltaic (PV) and concentrated solar power (CSP) are consistently supplying just under 2 000MW of power through the day. But, given that the evening peak is at around 6pm, only wind is able to provide a significant amount of capacity at that time. There is some supply from CSP, likely around 200MW.

We know that, together, wind and CSP are able to provide around 1 000MW of supply during the peak.

Eskom is also able to use its so-called ‘virtual power station’ to manage demand. This allows it to effectively remove demand (load) from contracted customers. In the utility’s 2018 integrated report, it discloses that its “demand response programme achieved an average certified capacity of 1 296MW during the year”. It is unlikely this number is substantially higher currently. This means it can remove demand of over 1 000MW during peaks.

A shortfall in available generation capacity of around 1 000MW to 2 000MW is therefore comfortably made up by a mix of the above sources. The gap of 3 097MW on Wednesday, June 26, would’ve been a big ask.

Supply mix

Each IPP project supplies Eskom at a contracted price, and the utility will buy a mix of supply at the cheapest possible rate when it is unable to meet demand. For instance, if its demand-side management agreements with large customers cost more than running the diesel peaking plants, it will favour the latter.

Eskom has given itself additional headroom to do maintenance on its coal fleet by synchronising a total of three units at its Medupi and Kusile power stations to the grid ahead of its revised schedule.

Unit 2 at Medupi was first synchronised to the grid on October 7, 2018, and reached full load on November 12, 2018. Kusile Unit 3 was synchronised to the grid for the first time on April 14, which it says is eight months ahead of schedule. Eskom has not yet announced that this unit has achieved full load, meaning that it is contributing less than this to the grid when it operates.

Eskom is able to use this capacity, typically up to 600MW from each unit, to supplement its supply.

Medupi Unit 3 fell into this category too, as it was first synchronised to the national grid on April 8, 2018, reached full load (796MW) on May 16, 2018, and has been ramping up over recent months. This unit, however, achieved commercial operation on June 28, meaning that its additional 796MW is now formally part of the utility’s installed capacity.

While it plans to achieve commercial operation of Kusile Unit 3 in November this year (much earlier than the scheduled August 2020 date), Medupi Unit 1 is the only other unit from the new-build programme slated to achieve commercial operation next year.

Improved outlook, but risks remain

The risk of load shedding remains, with Eskom noting this at the April briefing. The outlook, however, has improved significantly as it slowly catches up on its maintenance backlog, as plant performance improves, and as it brings new units at Medupi and Kusile online.

Three-month outlook published on Wednesday, May 15

Source: Eskom

Three-month outlook, published on Wednesday, July 10

Source: Eskom

Hilton Tarrant works at YFM. He can still be contacted at

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