The fingerprint of solar and wind on import/export balance

The subject of previous post is how South Australia, having a high share of solar and wind, balances its grid. While crunching the numbers, I noticed that there generally is more import when electricity production by solar and wind is low and that there is more export when electricity production by solar and wind is high. This reminded me of a post I wrote about the German Energiewende in which I looked at the import/export balance and compared it with solar, with wind, with solar plus wind and with lignite. The import/export balance clearly followed the solar plus wind curve, but the peaks were somewhat topped off.

This made me wonder whether the same is true of the South Australia data. Let us first look at the same graph from previous post, but overlayed with the import/export balance curve in red (click to enlarge for a much clearer view):

In the AEMO data, negative values signify import (more import than export in that time frame) and positive values signify export (more export than import in that time frame). This import/export balance indeed seems to follow solar and wind pretty well, but just as in Germany, the import/export balance of South Australia is topped off (there is a limit to how much can be exported to Victoria). It is now also clear that overall there is more import than import.

There is a lot going on in that graph. When decluttering it and adding fossil fuels output (predominantly from gas, but also a speck of diesel oil) as a comparison, this is the result (I had some more data gathered in the meanwhile):

The fossil fuel curve does not resemble the import/export balance curve at all, maybe even heads towards the opposite. Which is not exactly hard to understand, it are the fossil fuels that largely fill in the gaps left by solar and wind.

There is however quite a resemblance between the top curve (solar and wind) and the middle curve (import/export balance). When solar and wind output go down, generally the import/export balance curve also goes down and vice versa. This resemblance can have several reasons, but one thing is sure: this export is the direct result of policies of promoting intermittent power sources without the ability to balance that power, therefor the need to export the problems abroad.

Exporting the surplus is a pretty neat balancing strategy, but one need to have good neighbors for it to work. Although those neighbors will get that electricity very cheap (or even for free), they will have to deal with that electricity and balance it on their own grid (solar and wind power are not necessarily produced when there is a need for it). However, if those neighbors also start to focus on solar and wind, then that strategy become lees effective because they then will encounter the same issues on their own grid.

It seems that South Australia is going for increasing their import/export capacity in order to balance their grid. There is an interconnection planned between South Australia and New South Wales (h/t Chris Morris), expected to be completed from 2022. More capacity for export will probably mean more export and an import/export balance curve that even closer resemble solar and wind.

The capacity of this planned interconnector between New South Wales and South Australia is 800 MW. If the current constraints on the Heywood and MurrayLink interconnectors are lifted, then we are talking about a capacity of 800 (new interconnector) + 650 (Heywood) + 220 (MurrayLink) = 1,670 MW available in a couple years. That seems quite a lot, it would allow South Australia to export as much electricity from solar and wind as they currently can produce potentially and they also will have enough import capacity to cover their demand for most of the time.

That is of course good news for South Australia. Investing in an interconnection is probably much, much cheaper than building their own balancing capacity (like for example batteries) and it would allow South Australia to add more intermittent sources to its grid and/or decrease its fossil fuels capacity at the expense of its neighbors. If that much interconnecting capacity is available, South Australia could then just rely on reliable electricity from its neighbors and it also could just dump the (ever increasing) excess of solar and wind production abroad, leaving it to its neighbors to balance that surplus on their own grid. That is probably why The Lead article about the New South Wales interconnector writes (my emphasis):

The 900km interconnector linking Robertstown in South Australia’s Mid North with Wagga Wagga in central New South Wales is expected to provide grid stability and lower electricity prices in South Australia when completed from 2022.

That makes perfect sense. Basically, it will be South Australia’s neighbors that will provide reliability for the South Australia grid and will have to take care of balancing the (increasing) share of intermittent output on the South Australia grid.

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