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Eskom has taken Koeberg Unit One was shut down earlier than planned for scheduled maintenance after “an increasing leak rate was observed in one of the three steam generators.”
The unit had been scheduled to go offline for refueling and routine maintenance starting in February. Eskom says it expects the unit to “be operational again during May 2021.”
Koeberg supplies stable and predictable baseline power generation of just over 1.8GW, which was cut in half after 6pm Sunday night when the unit went offline (yellow in chart below). Worrying is the fact that it now has to replace the deficit of around 900MW, especially during the peak of the night.
Source: Eskom
It continues to use pumped storage schemes, designed for peak periods, for base load power generation. On Sunday, for example, it used them to generate between 500MW and 1.8GW throughout the day. Once Koeberg 1 was removed from the grid, their use peaked at 2,071MW (at 7pm). Pumped storage schemes are net energy consumers in the sense that they use more electricity to operate than each unit of energy they produce. This is what makes them so effective peak plants: The “surplus” energy is used to pump water uphill at night when demand is low.
Last week, historically the lowest demand period of the year (lockdown level 5, excluded), the utility was forced to implement stage 2 load shedding overnight. He said this was to “preserve his emergency generation reserves.” From its publicly available control panels, it is clear that Eskom simply did not have enough free space at night to use base load power to replenish its pumped storage schemes (which it was using to increase base load power to throughout the day).
Source: Eskom
From its unplanned outage dashboard, it is clear that these outages increased from around the 9GW level to 12GW between December 28-30. Typically, you could cope with this number of plant breakdowns (and partial losses), but you have deliberately increased planned maintenance to the highest level in at least a year. A total of more than 9 GW of capacity was taken out of service last week, as the utility continues to catch up with maintenance that simply hasn’t been done in recent years.
As plant breakdowns increased, it can be seen from its own data that Eskom was forced to run its open cycle gas turbines (OCGT) overnight on Monday (December 28). Their use peaked at more than 1.3GW before the call was made to implement load shedding. During the afternoon peak on December 29, it also made use of interruptible load supply (ILS), where it cut almost 700MW from its large industrial clients. Did this again during the afternoon peaks of December 30 and 31. On December 30, it asked independent peak gas plant operators to increase supply (in addition to its own OCGT use of around 1GW).
Another cause for concern is that Eskom has relied on approximately 1 GW (and up to 1.3 GW) on so-called “non-commercial generation” capacity since December 23. These are units in Kusile (Units 2 and 3) and Medupi (Unit 1) that are not yet in commercial operation. In the past week, you did not use any of these drives. The two Kusile units are expected to reach commercial operation this month (Unit 2,800MW) and in March (Unit 3,800MW), which will help in some way to alleviate the generation deficit. However, all this capacity is not really available. The utility company identified design flaws at both new power plants in November 2018 and work has begun to remedy them.
Now, with a shortfall of 900MW to take down a unit in Koeberg, Eskom will be forced to recalculate its generation plan. He always planned to have these additional units available in early 2021 (plus, this doesn’t really change the supply picture as he has been able to draw on these units in a similar way to other plants in his fleet).
Only two levers
You actually only have two levers to work with – you can defer some of the planned maintenance (although, in part, this is why the utility has such an unreliable coal fleet to begin with) and you can use emergency OCGT to meet peak demand.
This is the balancing act it will need to perform over the next several weeks as demand increases from the 25GW / 26GW level now to 29GW by mid-month. By the end of this week, those figures are already expected to be between 26GW and 27GW (the difference between so-called residual demand and contracted demand is offset by renewables).
Before Koeberg’s forced blackout, Eskom’s official three-month perspective seemed manageable. At its planned risk level, with unplanned outages of 12 GW plus a 2.2 GW operating reserve, it can be a bit short on certain peaks of the week. It is able to solve this with its available emergency generation resources (pumped storage schemes, its own OCGT, as well as IPP and ILS diesel / gas peak plants).
Source: Eskom System Status Report for Week 52, 2020
The only way Eskom prevents head loss is by giving yourself more headroom (doing less planned maintenance, which is unlikely) or by ensuring (read: hoping) that you can keep unplanned breakdowns well below the level of 12GW. We’ll know if you chose the former once your weekly system health reports are released for this week and next.
It will be a difficult few months.
- This article was originally published on Moneyweb and is used here with permission.
