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Talkin’ bout our generation

Since the release of Dr Finkel’s review, the term ‘dispatchable generation’ has been appearing more and more across the NEM. The term does not yet have a clear definition, but seems to be used to refer to generating units whose short-term availability is largely determined by the operator (as opposed to the weather). Dispatchable generation therefore seems to encompass all generation except for wind, solar, and run-of-river hydro.

Despite extensive discussion about the need for dispatchable generation, there has been little analysis of the demand for it. Against this backdrop, this week we look at the historical demand for dispatchable generation in the region of South Australia.

Chart 1: Monthly average demand for dispatchable generation in South Australia

First, we need to establish what we mean by demand for dispatchable generation. We will use a relatively crude definition, ie, regional demand less the generation from all wind, solar, and run-of-river hydro plants. In South Australia’s case, we need only consider wind farms. We have used DEMAND_AND_NONSCHEDGEN in the MMS database as our measure of regional demand.

Chart 1 shows monthly average SA demand, SA wind, and demand for dispatchable generation. By way of explanation:

  • The top panel shows average SA demand, and average SA wind.
  • The bottom panel shows average demand for dispatchable generation (ie, average demand less wind).

You can see that average demand for dispatchable generation reached a record low of 546.6 MW in September 2017.

Chart 1: Demand for dispatchable generation has been declining in South Australia

Top panel: monthly average SA Demand, SA Wind; bottom panel: SA demand for dispatchable generation (2011 to 30 September 2017).

Chart 2: Demand for dispatchable generation by time-of-day

The averaging of outcomes in Chart 1 masks the variability of both demand and wind output. What is the range of demand for dispatchable generation? And what is the profile of this demand over the course of the day?

Chart 2 shows demand for dispatchable generation by time-of-day in South Australia, with each point representing a single dispatch interval. By way of explanation:

  • We show observations for four selected years: 2011, 2013, 2015, and 2017 YTD, showing how outcomes have changed over time.
  • We have added a colour scale showing wind output at each point in time: blue indicates high wind output, red indicates low wind output.

You can see that demand for dispatchable generation has often been negative in 2017.

Chart 2: Demand for dispatchable generation in South Australia is often negative

Demand for dispatchable generation in South Australia by time-of-day, coloured by wind output (2011, 2013, 2015 and 2017 YTD).

My two cents:

  • In Chart 1, the result of 546.6 MW for September 2017 is incredible. To put this into perspective, 546.6 MW is less than the size of one of Loy Yang A’s units. This outcome has occurred despite the introduction of a range of constraints that have curtailed wind output in South Australia.
  • Chart 2 shows that there remain times when we need large amounts of dispatchable generation. The clear trend is that the range or envelope of demand for dispatchable generation is increasing.

As always, all comments are most welcome.