you have to have base load generating capacity that isn't reliant on weather. The technologies you have mentioned are part of solution sure, but they are not sufficient on their own.
Our coal fleet is old. It must be retired at some point. We must have base load capacity to replace it.
Base load is another word for inflexible generation.
It's really a thing created to justify Nuclear to be honest.
You need sufficient generation to cater for usage. Usage climbs and drops based on the time of day. Lowest late evening through to morning. Highest at dinner time.
Large monolithic generation like Nuclear still needs to be backed up with equivalent generation in case it drops out. Similar to large scale coal.
Solar and Wind will add additional generation in smaller increments on a country wide basis. We have enough of a geographical spread to safely say its always sunny somewhere in SA during the daytime, and its always windy somewhere any day in South Africa.
Solar generation could basically cover our "base load" daytime, and then some. This leaves the evening peak.
Wind will take some of that, but our traditional go-to for that is pumped storage.
Pumped storage allows us to time shift our excess generation to another time.
Traditionally this would be overnight, then reused early day, supplemented daytime, then reused again in the evening. Generation failures mean that this isn't happening.
So, we need additional generation.
We could build additional coal, or we could add more solar or wind. Both of those options are cheaper to run than coal, cheaper to build than coal, and have little to no environmental impact (at least in comparison to coal).
No-brainer right? Sadly, coal makes money for the people sticking their fingers into the pies, so they're less interested in renewables. There are profits to be made in renewables too, but they aren't as glorious as the existing coal or diesel profits.
Anyway, we still need storage to cater for when that cheap generation isn't available.
Our current coal generation has worse reliability than solar. So that - but we need "base load" generation argument is a bit redundant when it can't even work 30% of the day.
Supplement renewables with pumped storage, CSP, and other large scale storage mechanisms, with some battery to cater for short term requirements, and you're pretty good, and at cheaper pricing than Nuclear.
Don't need to take my word for it, studies have been done in South Africa proving it already.
Renewables aren't a 100% solution, but we can easily triple or quadruple what we have without any issues, remove our non functioning coal, and have a cheaper more environmentally friendly solution.
No brainer really, our only issue is that it doesn't make financial sense for the people in control of things, cough Gwede cough, as they don't make tons of money off of it*.
* our last REIPP phase was mainly supplied by Squirrel's brother, and at costs roughly double what we're seeing in other countries for renewables. Even so, they still came in cheaper than current coal stations costs.