Eskom didn’t really keep the lights on because of the rugby

Eskom managed to stave off load shedding for almost 10 days, until the unwelcome sight of “Stage 2 and Stage 3” was implemented from 4pm on Sunday – with Stage 3 implemented overnight and Stage 2 in place on Monday.

For the past week – and this had nothing at all to do with the Rugby World Cup and the achievements of the Springboks (seriously!) – the utility has managed to avoid implementing load shedding since 10pm on October 19.

Quite a few things went Eskom’s way when it came to generation in the last 10 days.

First, the return of two units at Kusile Power Station way ahead of schedule on the temporary recovery plan (following the flue duct collapse last year) added as much as 1 600 megawatts (MW) to generation. In reality, this was closer to 1 000MW as those units ramped up to full production.

It is unclear at this point whether these units have even reached this point, given the difficulties in returning units to service after being offline for 12 months.

The return of this generation capacity was a welcome boost for Eskom, which, together with a significant – yet temporary – improvement in the efficiency of the coal fleet, allowed for the longest break in load shedding since September last year.

The coal fleet has consistently been producing more than 20 000MW, which is a solid performance considering that at various points in the depths of winter, it barely managed 18 000MW from those power stations. Kusile only counts for half of that improvement. (In fact, last week, there were a number of hours where the coal fleet was producing more than 22 000MW!)

This has certainly been a major contributor to Eskom’s energy availability factor, or the measure of generation capacity available, hitting a high for the year of 60.46%.

Before the week ending last Sunday, Eskom had not managed to get to the 60% mark (its previous best was 59% in week 23). It will only publish a report for the week to Sunday at the end of this week, but based on data from Eskom, its performance is likely to have been almost as good.

Other contributors

But it’s not just the coal fleet that has contributed to the absence of load shedding. The generation from that core has actually slipped somewhat in recent days.

Two weeks ago, Eskom barely relied on its open cycle gas turbines (OCGTs), with those being used in fewer than 10 hours for the week. In the past week it’s been a different a story, with a large reliance on burning diesel since Monday. According to Eskom data, it has run its OCGTs since 5am on Tuesday consistently until Friday night (and likely beyond, but this data is not yet available).

At the peaks (such as 8pm on October 25), it has relied on as much as 1 800MW of generation capacity from burning diesel. At that point, it was also leaning on Avon and Dedisa, the two independent power producers (IPPs), for above 800MW of generation.

Beyond this, however, the contribution from renewable producers, particularly wind, was a massive help.

Two weeks ago, wind was contributing as much as 2 500MW of generation capacity, and this repeated last week. Wind generation was muted from Tuesday, which meant the increased reliance on diesel. The cold front and associated weather since Friday has certainly helped the capacity from wind.

During the day, solar photovoltaic produces between 1 500MW and 1 900MW, but given the nature of this Eskom has baked this into its supply profile. Of course, there is an additional almost 4 000MW installed by businesses and residential customers. This is not included in any of Eskom’s figures, but serves to supress demand – at least during daytime – by a material amount.

Eskom says “breakdowns are currently at 16 150MW of generating capacity while the capacity out of service for planned maintenance is 5 950MW”.

Monday night peak demand is expected to be 27 557MW. This is about 5 000MW lower than the peak demand profile in winter.