Sunday, February 19, 2017

The big South Australian blackout revisited

Reliance on "renewables" was the problem

Let’s recap on exactly what happened based upon the actual reports written after people knew what had happened, rather than before. First a little background on South Australia’s electricity system.

We had about 6,000 mega watts (MW) of capacity in 2015-16; which means when all of these sources of electricity were running flat out, we could light up about 60 million 100 watt globes. But because about 2200 MW of this capacity is wind and solar PV, then that would be impossible except perhaps on a hot and very widely windy day. On a windless night, that 2200 MW will produce bugger all. Since then, we have lost about 1,000 MW of baseload capacity. The word baseload is a little misleading, the right word is despatchable… meaning you can choose when you want it rather than with wind and solar, which operate according to the whims of the wind and weather.

Our maximum demand is only about 3,400 MW, but because of our high renewable mix, we not only need interconnectors to handle windless nights, we needed to upgrade the biggest of these in 2016. The flow of electricity into South Australia over the past decade has been steadily growing as our despatchable power stations close.

If all of our 4,800 mega watts was despatchable power, then we’d never need either of our interconnectors; Murraylink (220 MW) and Heywood (recently upgraded to 650 MW).

On the 28th of September, the Heywood interconnector was supplying 500 MW with Murraylink running at 110 MW. When the storm knocked over the transmission towers and some wind farms shut down, the system lost 445 MW of capacity.

Imagine sucking a drink through three straws and one of them blocks, then the suck on the other two rises. This is what happened when the wind farms shut down; the combined demand, the suck, was transferred to the interconnectors. Remember, Heywood was upgraded to handle a 650 MW suck and was running at 500 MW. When the wind farms died, the suck on Heywood surged to 850 MW and it turned itself off to prevent catastrophic damage. The rest is history; a cascade of failures.

Had we had 4,800 mega watts of despatchable power, then we wouldn’t have had such a load on the interconnectors and they would easily have had the capacity to absorb the additional load when the wind farms shutdown.

Was the SA generation mix a factor in the blackout? Of course. Are there generation mixes which would have prevented it? Of course; I just gave one.

The great thing about the interconnectors is precisely that they can function to satisfy demand during the loss of capacity. But if that function isn’t available because your interconnectors are already saturated making up for renewables which aren’t currently doing much, then you have a problem.

What enrages me so much about the debate on this issue is that everybody has an opinion about why the blackout occurred without understanding what actually happened. If you don’t know the simple facts of what happened, they how can you imagine you understand why?

I’ve deliberately ignored important things like frequency control and spinning reserves in an effort to keep things simple. But our renewable mix has various other complicated effects on our grid to make it less robust in the face of disturbances.

The short-term answer to our problems is to change the NEM rules which discriminate against despatchable systems. This will allow gas operators to make money and stay running. This will also allow investment in clean despatchable systems, meaning nuclear, that can solve both our reliability and climate problems simultaneously. Remember, the main reason that the Nuclear Fuel Cycle Royal Commission found that nuclear would be uneconomic in SA is that under the current NEM rules, all despatchable power is uneconomic. When reliability isn’t considered worthy of a price premium then it will vanish, exactly as we have seen.

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