There are at least two former CEOs of Eskom active on X. Neither is named “de Ruyter”. Anyway, one of them recently tweeted (Xed?) that power from IPPs is not dispatchable.
I don’t have an opinion on whether he is correct or not, but I do know that I don’t know what the word “dispatchable” means in the context of power grids.
I believe it’s energy (electricity) that can be dispatched immediately.
I think the most commonly referred to are the pumped hydro dams and the open cycle gas turbines. When the demand gets high they let them run and use that.
The same for the new battery storage plants.
So when ‘they’ refer to building reserves I believe that’s pumping water back up the dam and loading diesel. Getting ready to be used again.
I think it’s a conversation that was had before in that these are supposed to be for emergencies, but is now used pretty much every evening and sometimes also during the day in order to reduce the loadshedding stages.
In that sense I would say the former CEO isn’t entirely correct as there are IPP OCGT’s and I beleive IPP batteries too. But I guess they’re referring to the more general IPP being solar panels or wind farms which is not dispatchable as they can’t suddenly generate maximum output at any time and generally contribute what is available.
I know there’s solar farms that stores in salt or whatever, but I’m pretty sure that’s also not dispatchable in that sense and just that they release slowly in order to have more available during the evening peak.
Your understanding of dispatchable is correct, except for this part. It is not only an “emergency” but can be planned and controlled according to the needs of the Grid. You can argue that Coal power stations are also dispatchable.
In terms of the Renewable Energy Independent Power Producer Procurement Program, we utilise a take or pay scenario, thus each kWh generated by the IPPs must be utilised or if curtailed the loss in revenue to the IPP must be paid. (They are changing these rules to allow for certain amount of curtailment of the plants, this is effectively opening up the grid a bit more).
This is also why you might have heard the argument of RE being much more expensive than the kWh paid at the meter as you need Gas or Hydro to back it up for it is “unreliable” or “variable”, this argument has been proven to be mostly ill-informed and in some cases utter BS spun for political purposes.
CSIR previously did some studies on what is required for a grid to be run from RE only and in most cases the end result was a cheaper energy mix.
One of the things (perhaps not so much for solar) that is conveniently forgotten is statistics on generation. If one is to look at the varied dispersion of Wind Facilities in South Africa the likelihood of the generation dropping to Zero oval all wind farms is also almost Zero (Coastal Wind vs In-land wind is negatively correlated in most cases).
You can add PV to the mix in terms of these statistical models.
Yes, you will need something like Battery Storage, Hydro, gas or other “quick” responding generation in such a grid, but the costs (if using the correct models) are not prohibitive in going that direction.
So are the stock standard RE plants dispatchable? No
Is this a problem for the majority of networks with large penetration of RE? No
Can this be a problem for a weak grid like ours? Possibly, yes
Did you mean to say it is not dispatchable? My understanding of a coal plant has always been that it takes time to get it up to full power, it “revs slowly” as I’m fond of saying. You cannot bring coal plants up quickly.
But as I understand it, you can run the boilers hot, but bypass the turbines, which is of course very inefficient but does allow for a coal plant to be ready for peak power in the near future. In that sense, it is fairly dispatchable, but not quite in the same sense as hydro or OCGTs which come online in minutes, and certainly no good for an unplanned shortage.