Reporting on the contribution of the windmills at the evening peak of demand from early December. The point is to demonstrate the significance of the lowest levels of wind supply (choke points) when they coincide with peak demand in the morning and evening (breakfast and dinner).
This display shows the daily cycle and the contribution from different sources.
Some features of interest. Black coal is the foundation of the system and it ramps up and down between 9.2 and 16.1. These are the limits that I have seen since I started to take notice. The peak is almost twice the level of the trough, a vivid indication of the efficiency (and profitability) that are lost by making coal stand in line behind the more expensive and subsidised unreliables that get first access to the grid. Brown normally runs steady and does not adjust to track demand like black coal, water and gas.
Water has capacity up to 5 or more but lately it has spent a lot of time at 0.5 presumably to husband the supply of water in the dams
Extreme heat is expected today and we are warned that problems at Loy Yang (brown coal) persist and also one of the four 500MW units at Liddell will close for repairs. Loy Yang went down in May and from that point the Brown Coal supply ran steady at 3.1GW until it came up in December and peaked at 4.6 at 4pm on Christmas Day. Since then it has been up and down with the latest changes in the last day when it dropped suddenly from 4.2 to 3.6 at 8.15pm last night, then eased up after midnight to reach 4.2 in the early morning and run steadily since then (fingers crossed).
On the bright side, there is less demand in the weekend.
The wind supporters talk in terms of installed capacity, sometimes allowing that the average is a good deal less (like a third) but the real crunch is the minimum. We breathe air containing 20.95% oxygen most of the time (a bit less in crowded spaces) but when we are choking or under water we are dead in five or ten minute. Similarly the grid needs a constant supply of power or bits of it will die by managed or unmanaged load shedding and in the worst case (SA 2016) large parts will die.
This display shows the variability of the wind supply in December expressed as the percentage of installed capacity. The data points are three hour intervals. The range is 64% to 4.1% and the average is a bit over 30%
You can also see the picture for the amount of power with the range from 4.4GW to 0.273 but the default is the percentage and you can toggle to the volume. The installed capacity is 6.7GW so the average is about 2.2GW. Compare with Liddell (coal fired) at 1.7GW.
The Wind Contribution at the Evening Peaks
From 8 December the daily figures for the % of demand provided by the wind at 6.30pm (NSW Vic and Tas) are
7, 7, 9, 10, 10, 11, 5, 12, 4 (and 2% at noon), 3.5, 5, 6.5, 10, 8.5, 7.2, 8.5 (2.8 at noon), 11.5, 9, 6.5, 5.5, 4, 10, 7, -, 5.5, 6.
What happens when we lose Liddell or any other coal-fired power station?
Before Daniel Andrews put Hazelwood out of business there was a slim reserve most of the time to cater for really difficult periods. Since then we have been running on the rims and the danger of the situation has been obscured because there has been just enough power most of the time, give or take occasional blackouts.
Take out the best part of 2GW and then what happens at the evening peaks.
Adding another 7GW of windpower translates into less than one GW if the system is running under 10% of plated capacity or less and you can see from the display above that situation arose nine times in December. Of course there are times when it runs well below 10% (say 2%) but in the larger scheme of things under 10% is next to nothing when demand is peaking.