RenewEconomy published an article headlined Energy oligopoly using market power to profit under cover of rooftop solar (Wed 12 Feb 2020) by Bruce Mountain and Dr Steven Percy.
The article was written in response to the authors observations of the AEMO 2019 Q4 Quarterly Energy Dynamics Report published on Mon 10 Feb 2020. Here they wrote:
.. in Q4 2019 much more expensive gas generation displaced much cheaper coal generation ..
While more remains to be done to understand this in detail, prima facie this is yet another instance of the exercise of market power by the coal generation oligopoly in New South Wales.
Noting that Eraring and Uranquinty (and Mortlake in Victoria) are owned by Origin Energy, using NEMLog we can replicate the graph in the article (shown below) with the added detail of Uranquinty Station Output, NSW Hydro Output and NSW Dispatch (5 min non-intervention). It was also condensed to Daily Profile Change Graph, comparing 2019 Q4 to 2018 Q4. It is shown below.
An issue with Daily Profile Mean Graphs for Time-Series, is that they can miss the chronology of various underlying events. These events and their impact can get lost in the averaging to create Daily Profile Mean. To unpick this, we can construct the Unit Daily Summary (maximum and minimum output, daily energy and maximum availability) for Eraring Units Daily Summary, Uranquinty Units Daily Summary and Mortlake Units Daily Summary.
Looking at the Eraring Units Daily Summary we can see that Eraring Unit 1 was out-service from the start of 2019 Q4 to Tue 05 Nov 2019 and Earing Unit 3 was out-of-service from the start of 2019 Q4 to the Thu 21 Nov 2019.
We can also see the Eraring and Uranquity Station Outputs for 2019 Q4 (below left) and 2018 Q4 (below right). For 2019 Q4, it would appear that Uranquinty is covering for the outages of Eraring Units 1 and 3. As Eraring Units 1 and 3 come back into service in Nov 2019, the Uranquity output reduces and it would appear to return to its mode of operation.
The following graphs show the Daily Profile Mean for 2019 Q4 compared to 2019 Q4 with each Quarter split into the periods before and after the return to service of Eraring Unit 1 on Tue 05 Nov 2019 and Eraring Unit 3 on Thu 21 Nov 2019. They are show below.