Can Eskom keep lights on?

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 had been scheduled to be taken offline for refuelling and routine maintenance in February. It’s now expected to return to service in May.

Koeberg supplies stable, predictable baseload power generation of just over 1 800 megawatts (MW), which halved on Sunday evening when the unit was taken offline.

Concerningly, it must now replace the shortfall, especially during the evening peak.

It continues to use pumped storage schemes – designed for peak periods – for baseload power generation.

On Sunday, for example, it used these to generate 500MW to 1 800MW throughout the day.  Once Koeberg 1 was removed, usage peaked at 2 071MW.

Last week – historically the lowest-demand period of the year – the utility was forced to implement stage 2 load shedding to “preserve its emergency generation reserves”.

From its public dashboards, it’s clear Eskom didn’t have sufficient headroom overnight to use baseload power to replenish its pumped storage.

Based on its unplanned outage dashboard, these outages spiked from about 9 000MW towards 12 000MW between 28 and 30 December.

It would typically be able to cope with this number of plant breakdowns, but it has deliberately ramped up planned
maintenance to the highest level in a year.

Over 9 000MW of capacity was taken out of service last week as it continues to catch up on neglected maintenance.

As plant breakdowns spiked, Eskom was forced into using its open cycle gas turbines (OCGT) overnight on 28 December.

Their usage peaked at over 1 300MW before it implemented load shedding.

During 29 December evening peak (and on 30 and 31 December) it also used interruptible load supply (ILS), cutting nearly 700MW from large industrial customers.

On 30 December, it asked independent operators of gas peaking plants to augment supply (in addition to its 1 000MW OCGT usage).

Of further concern, Eskom has been relying on as much as 1 300MW of “non-commercial generation” capacity since 23 December. These are units at Kusile (units 2 and 3) and Medupi (unit 1) not yet in commercial operation.

The two Kusile units are slated to achieve commercial operation this month (unit 2, 800MW) and in March (unit 3, 800MW) which help to alleviate the generation shortfall.

However, this capacity isn’t 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 Koeberg unit offline, Eskom is forced into recalculating its generation plan.

It has only two levers to work with: deferring some planned maintenance (unlikely) and using emergency generation capacity (OCGTs) to meet peak demand.

This is the balancing act it will need to perform for coming weeks as demand ramps up from 25 000MW/26 000MW towards 29 000MW by mid-month.

This article first appeared on Moneyweb and was republished with permission.