Jess Hunt, an energy market designer with the Energy Security Board, posted a comment on LinkedIn to describe how the energy supply in SA was up and down in the week between Christmas and New year 2021-2022.

This week’s energy supply mix in South Australia is a great example of variability that we need to manage in a high VRE [variable renewable energy from wind and solar power] power system – over the course of the week we went from over 130% VRE to less than 4%, with everything in between. The challenge for policy makers is to design a market that can mix and match different types of supply side resources meet demand across the full spectrum of conditions.

Certainly that kind of variability is a major problem for grid managers  but the real challenge is to maintain continuous supply and I think it is clear that VRE has failed due to the problem of windless nights when there is no solar input and little or no wind power available.

The VRE boosters focus on the ever-increasing penetration of RE into the grid and of course as the build continues then inevitably every month or two they can celebrate another milestone on the road to net zero and the elimination of coal power from the grid. This is a radical error because they ignore the “hole in the wall” effect – the fact that the effectiveness of a wall, say for flood protection, is limited by the lowest part, regardless of the highest part of the wall or the average height.

The VRE planners realise that their “wall” is uneven in height but they expect the gaps to be filled by the two kinds of storage – pumped hydro and batteries, collecting power when the supply exceeds demand (the high parts of the wall.)

Jess Hunt and her colleagues underestimate the size of the gaps in the wall that have to be filled and they over-estimate the capacity of pumped hydro and batteries to fill them. First, the size of the gaps. Everyone knows that the sun sets every day but the phenomenon of wind droughts is less well-known because up to date there was no need to bother whether the wind blow or not. Hardly anyone outside particular groups like people in sailboats, golfers and people obsessed with saving power by drying their clothes outside, pay close attention to the amount of wind that is about. The AEMO records of output from the windfarms of SE Australia provide a good record of the vagaries of the wind and several serious wind-watchers have documented the frequency and duration of wind droughts.

For example in South Australia there were spells in August and September last year when SA only survived on the back of coal power from Victoria. This was reported in a post last year. No amount of over-building to provide additional capacity helps on windless nights when there is near-zero RE because multiplying near-zero by five, ten or twenty still falls far short of the amount of power required to keep the grid alive.

The chart shows the amount of wind power generated in South Australia hour by hour through August. The dotted line across the chart at 219MW is close to 10% of the installed capacity of 2,100MW and it marks the upper level of supply that I regard as a “wind drought”.

From the 12^th to the 18^th the supply was mostly under the line and consequently they were importing power every day of that week at breakfast and dinnertime. They were importing at lunchtime as well during that period and this is unusual due to the amount of solar they have.

South Australia may be a net exporter over 12 months but that it practically beside the point because they depend on imports whenever they are in drought. When other states, led by Victoria, get rid of more coal power they will not have spare power during wind droughts to prop up SA.

Another failure at breakfast-time Sunday 5 Sept

 Sunday is a day of low demand but at that time both SA and Victoria were importing power from Tasmania and from Queensland via NSW. Almost half the local generation in SA was gas power and 70% of the local generation in Victoria was coal power.

Getting back to the Christmas to New Year period in South Australia.

As it happens I was watching the power supply in SA like a hawk during that period to maintain a record of the times when SA is importing power from Victoria where brown coal power from Loy Yang and Yallourn account for the vast majority of power generated in the state. SA was constantly in the red from the evening of Tuesday 28 to the morning of Sunday January 2.

After that Christmas to New Year period I decided that there is no need to persist with this regular wind-watching (bearing in mind that it is time-consuming and habit-forming) so I stopped making regular records and just glanced at the situation from time to time. The wind-drought problem does not need more documentation