While everybody was in the dark, literally and figuratively, we now know more about why load shedding is worse than ever and might still get worse too.
The chaotic and dramatic escalation that went from Stage 2 to 3 and then Stage 4 on Saturday, is the loss of imports of 1 100 megawatts (MW) that we got from Mozambique. Or so they say….
The extensive damage that cyclone Idai caused also damaged transmission lines that carry power from Cahora Bassa to South Africa.
According to Eskom, they have to maintain an operating reserve of 2 000MW at all times, hence the need from Saturday to curtail load through load shedding.
The current underlying problem in Eskom’s generating unit, though, is worse than simply what happened in Mozambique on Saturday. On Friday, it announced that load shedding would continue until Sunday.
Along with the announcement on Friday came the ‘forecast’ that Stage 2 load shedding would continue until “the middle” of this week. This is unprecedented. And the only reason that this forecast was/is “only” until Wednesday is because a de facto long weekend starts on Thursday! With imports off the table for days (if not weeks), expect the forecast to deteriorate.
What Eskom hasn’t said explicitly is that it relied (heavily) on its pumped storage schemes to keep the lights on during Saturday. These schemes – Drakensberg, Ingula and Palmiet – together (nominally) produce 2 724MW. They are not intended to produce base-load power for the simple reason that they are net users of electricity!
In other words, they use more power than they produce.
The schemes are used to supply electricity during peak periods, with water being pumped back up during off-peak periods, i.e. overnight.
The details are generally couched in opaque references to “water reserves”, but on Saturday night Eskom for the first time stated that Stage 2 load shedding would continue through the night “in an effort to build up necessary water reserves in the pump storage scheme”.
Presumably, it is referring to at least both Drakensberg and the new Ingula power station, which together can generate 2 300MW. The decision to continue with load shedding through the night was another unprecedented one (it has never before continued beyond 11 pm) and points to the utility once again using the pumped storage schemes for base-load power through Sunday.
It must also be noted that recent instances of load shedding run for longer, often starting at 8 am and ending at 11 pm. Previously, load shedding would run until 9 pm only. This suggests far less of a peak problem (which was the case, historically), and more of a base-load generation issue.
Eskom’s (now outdated) infographic about Stage 4 load shedding explains matter-of-factly that “should there be a need to go beyond Stage 4, Eskom and the municipalities will implement contingency schedules”.
But late last year the utility published schedules for load shedding all the way to Stage 8, something it was forced to do by the National Energy Regulator of South Africa. This is a good thing, as one wonders whether these “contingency schedules” were as detailed and robust as they ought to have been.
Part of the decision to use the pumped storage schemes as baseload power sources in an unexpected emergency was sure to ensure that the utility avoided – at all costs – a situation where load shedding shifted to Stage 5. It has never before removed more than 4 000MW of demand from the grid (under the old Stage 3 and new Stage 4 regimes).
Because of this, a scenario where it is forced to cut demand by 5 000MW or 6 000MW inherently carries a number of risks. A lot is made of the fact that it would be politically unpalatable to shift to Stage 5, but the country is hurtling towards an election with load shedding almost certainly a regular occurrence until then.