The Australian Energy Market Operator has sought to play down the risk of widespread curtailments or shut-downs of large scale solar farms in northern Queensland, saying that any severe limitations would be unlikely and would only happen if synchronous generation in the region fell to historically low levels.
On Monday, as RenewEconomy reported at the time, AEMO issued a market notice warning that nine solar farms located from Gladstone to north of Townsville could have their output reduced to zero under certain circumstances – depending on the number of synchronous units operating in the region and the amount of load in the system at the time.
The nine solar farms affected are Clare (110MW), Collinsville (42MW), Daydream (80MW), Hamilton (58MW), Hayman (58MW), Kidston (50MW), Ross River (128MW), Rugby Run (128MW), and Whitsunday (58MW).
This warning came on top of the constraints that are more regularly placed on two other solar farms – Haughton and Sun Metals – and the Mt Emerald wind farm due to emerging “system strength” issues in the region. None of these assets have been permitted to generate in the last two weeks.
AEMO told Reneweconomy this week that it was keen to point out that the new constraints on the additional nine solar farms would be a rare event, and only likely when some coal generators in central Queensland were sidelined by planned, or unplanned maintenance, and if demand levels were also low – which can be the result of increased rooftop solar production or lower overall demand.
“AEMO has informed market participants of temporary network limits impacting several generators due to a large volume of planned maintenance on synchronous generation units in central Queensland,” it said in an emailed statement.
“The market notice includes network limits that may result in moderate levels of constraints on inverter connected generation (wind and solar farms), along with more severe limitations in the unlikely scenario that synchronous generation in central and north Queensland falls below historic minimums. This information is required to ensure market preparedness should this unlikely event occur.”
The recent Quarterly Energy Dynamics report for the second quarter produced by AEMO highlighted that average black coal generation in Queensland fell by more than 600MW over the quarter. This was driven by reduced operational demand, partly from Covid-19, displacement by solar and gas generation, and increased outages at Tarong North and Callide power stations:
- The issue of constraints and restrictions has become a significant problem in the grid – a result (depending on who you talk to) of grid congestion, insufficient network planning, ageing coal plants, new modelling that has unveiled hitherto unsuspected potential problems, and an ultra-cautious approach.
Five solar farms in Victoria and NSW had their output cut in half for more than seven months because new third party modelling identified the potential of voltage oscillations in some contingency events. System strength issues have also been identified in South Australia, Tasmania, and elsewhere in NSW, as well as Queensland.
Indeed, the latest Integrated System Plan highlights the risk of insufficient synchronous generation in Victoria should rooftop solar increase to the point where brown coal generators were sidelined by their inability to flex and accommodate low demand. Unless other storage investment or new links are made, AEMO warned of the risk that large scale generation could be constrained.
That’s worth a story in itself, but it does underline the need for planning, the ISP, and for changes to the regulatory regime and market rules.
So far, to the frustration of everyone in the industries, some of the remedies proposed to deal with emerging system strength issues have resulted in some new wind and solar farms to be told they have to add in expensive synchronous condensers.
But in yet another sign that regulatory regime has not kept up with the pace of transformation, the rules have caused these syncons to be installed in a random and haphazard fashion, to the point where Transgrid recently complained it was likely causing more problems and instability for the grid than they were solving.
Most of these new syncons have never been switched on, and may never be. That contrasts with the four new syncons planned for South Australia which are expected to have a significant benefit – mainly because they have been properly planned and are designed to relieve the need to have gas plants operating when the power those gas plants generate is not needed. And that in turn will allow the vast amounts of wind and solar to produce their power unabated, and with a stable and reliable grid.