Concerns are rising for South African as Eskom has taken Unit One of Koeberg offline earlier than planned for scheduled maintenance after “an increasing leak rate was observed on one of three steam generators”. The unit was scheduled to be taken offline for refueling and routine maintenance starting in February. Eskom says it expects the unit “to return to service during May 2021”.
The power station supplies stable and predictable baseload power generation of just more than 1.8GW, which halved after 6pm on Sunday evening when the unit was taken offline (yellow in the chart below). Of concern is the fact that it now has to replace the about 900MW shortfall, especially during the evening peak.
On Sunday, for example, it used these to generate between 500MW and 1.8GW throughout the day. Once Koeberg 1 was removed from the grid, the usage of these peaked at 2 071MW (at 7pm). Pumped storage schemes are net consumers of power in that they use more electricity to operate than each unit of power they produce. This is what makes them such effective peaking plants – “excess” power is used to pump water uphill overnight when demand is low.
According to Moneyweb, Eskom has been relying on approximately 1GW of so-called ‘non-commercial generation’ capacity since 23 December. Of further concern is that Eskom has been relying on approximately 1GW (and as much as 1.3GW) of so-called “non-commercial generation” capacity since 23 December. These are units at Kusile (Units 2 and 3) and Medupi (Unit 1) that are not yet in commercial operation. In the week prior, it used none of these units. The two Kusile units are slated to achieve commercial operation this month (Unit 2, 800MW) and in March (Unit 3, 800MW) which will go some way to alleviating the generation shortfall. However, all of this capacity is not actually available. The utility identified design defects at both new power plants in November 2018 and work has begun to remedy these.
Now, with the 900MW shortfall from taking the one unit at Koeberg offline, Eskom will be forced into recalculating its generation plan. It always planned on having these additional units available in early 2021 (plus this doesn’t really change the supply picture as it has been able to call on these units in a similar way to other plants in its fleet).
Only two levers
It really only has two levers to work with: Some planned maintenance can be deferred (although this is partly why the utility has such an unreliable coal fleet to begin with), and it can use emergency OCGTs to meet peak demand.
This is the balancing act it will need to perform for the coming weeks as demand ramps up from the 25GW/26GW level now towards 29GW by mid-month. By the end of this week, those figures are already forecast to be between 26GW and 27GW (the difference between so-called residual demand and contracted demand is made up by renewables).
Before the forced Koeberg outage, Eskom’s official three-month outlook looked manageable. In its planned risk level, with unplanned outages of 12GW plus a 2.2GW operating reserve, it may be slightly short at certain peaks in the week. It is able to work around this with its available emergency generation resources (pumped storage schemes, its own OCGTs as well as IPP diesel/gas peaking plants and ILS).
The only way Eskom avoids load shedding is to give itself more headroom (by doing less planned maintenance, which is unlikely) or by ensuring (read: hoping) that it can keep unplanned breakdowns well below the 12GW level. We’ll know whether it’s chosen the former once its weekly system status reports for this week and next are published.
Main Image: Solidariteit