When pointing to the huge fluctuations of solar and wind production in previous post, I wrote that these fluctuations will only grow when South Australia advances on its path towards 100% renewable energy. Looking at the fuel mix and demand data that I had gathered until then, I noticed a fine example of exactly that. Just look at the fuel mix and demand data:
Let’s focus on the minimum on September 5 at 20:00. That is around the time that I looked for the first time at the overview panel (see previous post). The data showed that the total production of solar and wind was 4.341 MWh, which is 0.29% of what was produced at that moment. Contrast this to the peak of 1,258.486 MW the next day around 22:00, just after the evening peak when energy demand was slowly starting to decrease. It is this dynamics that will lead to the fluctuations that I wrote about.
Solar and wind produced virtually nothing (wham in the middle of the evening peak) and just one day later they produced more than needed, this time just after the evening peak when demand was still high.
Now look what happens when we multiply the observed production in that period, simulating a capacity increase. Pay close attention to the difference in growth between the bottom value (just before the September 6 grid line) compared to the peak value (just before the September 7 grid line) when we multiply by even higher numbers:
That is not hard to understand. Multiplying the tiny value of 4.341 MWh by 4 will result in a still tiny 17.36 MWh (+ 13.02), while the same multiplier will blow up the peak value of 1,258.486 MW to a huge 5,0033.94 MWh (+ 3,775.45).
In the following graph shows a comparison between these minimum and maximum values growth between the original value and 4 times the original value. The maximum is illustrated by a gray dotted line and the minimum by a red dotted line:
You now might object that there are only gray dotted lines in those graphs, but that is not the case. The red dotted lines are actually there, but way too small to see, even when viewing the graph full screen. When zooming in on that part of the graph, the red dotted lines are clearly visible (100x magnification):
That is quite a difference between growth of the minimum compared to the maximum values when adding solar and wind capacity. The consequence is that the need for backup capacity will not shrink easily. Even taking an (unrealistic) increase of 4 times the current solar and wind capacity, it would theoretically only decrease the need for backup capacity by 13.02 MW. While at the other end the peaks will become ever larger. This is good news for those who want to declare record production of solar and/or wind during small time frames, but not for those who want to balance the grid.