Just curious…If all solar was suspended from 12h00 to 13h00 on a particular day what would happen? Do open cycle gas turbines kick in to compensate or are areas switched off? Maybe private home solar is too small to affect the national grid and it’s a stupid question. The thought just occurred to me around the speculation that the ANC Government is burning diesel as an election ploy and by extension private solar is assisting them to this end 
Well there are plenty of days when the weather is overcast for an hour or so, which would have the same effect.
We mustn’t just think of private home solar. Haven’t you seen hospitals and shopping malls with solar panels all over the place?
Anyway, the total of all this rooftop solar is significant because it reduces demand. Eskom don’t know where it all is, but they see the reduction in demand.
The burning of diesel isn’t happening. The figures for output from the OCGTs are in the public domain, updated daily. Extrapolating April 2024 to date Eskom are going to burn about 50% less than in April 2023.
Speculation should be expanded to include the coming into service of some big IPPs. And the reduction in demand that private solar is leading to.
Probably the worryingly long spell of uninterrupted service is down to a combination of
- Significant amounts of private roof top solar
- IPPs coming on line
- Eskom doing a not necessarily great job but a better job
- Change in usage habits as awareness grows and tariffs increase
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Well, you have to prevent a brown-out, so let’s say there is a full solar eclipse for an hour and all the solar in the country goes offline. When that happens, the emergency reserves (which are OCGTs, and pumped storage) come online immediately, and then within the next couple of minutes a decision is made (by the grid operator) whether they need to increase/start load shedding.
If the outage can be repaired easily, if there are some plants coming out of maintenance soon, or if the solar eclipse is going to be over anyway, they may decide to keep running the OCGTs and bridge the gap. If not, they will shed some of the load (in a somewhat orderly fashion), in order to preserve the emergency reserves, and switch the OCGTs off.
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