Records continue to tumble across Australia’s main grids as the spring weather boosts the output of wind and solar and mild weather moderates demand, but none are as spectacular as those being set in South Australia.
The state’s unique end-of-the-line grid already leads the country, and arguably the globe, in the integration of variable wind and solar, with an average of more than 70 per cent of its demand over the last year and a world-first target of 100 per cent net renewables by 2027.
On Sunday, at 9.35 am, the state set a new milestone, setting a new record share of wind and solar (as a percentage of state electricity demand) of 150.7 per cent, beating a record set on Christmas Day last year, when – for obvious reasons – there was little electricity demand.
As Geoff Eldridge, from GPE NEMLog, notes, this means that the rooftop PV, along with large scale wind and solar farms, were generating 50.7 per cent more power than the state’s total electricity demand at the time.
The scale of excess output was further crystallised later in the day with a new minimum record for instantaneous residual demand, which hit minus 927 megawatts at 12.35pm.
Eldridge says residual demand is what’s left for other generators to supply after wind and solar have met a share of the demand. A negative residual demand means wind and solar were producing more electricity than SA needed, resulting in excess renewable generation which can be managed by exporting and battery charging. The remainder is curtailed.
Of the surplus 927 MW, the state was exporting 685 MW to Victoria, while another 163 MW was being soaked up by the state’s growing fleet of battery storage projects, and 730 MW of output was curtailed. Prices at the time were minus $47/MWh, a good opportunity for batteries to charge.
A further 84 MW was being produced by a couple of gas generators – not because their power output was needed, but because the state, at least for the moment, relies on them for essential grid services such as system strength and fault current.
That will be reduced considerably when the new link to NSW is completed in a few years, and it will allow the state to both export more, and import more when needs be.
“Balancing the system with such high renewable penetration is challenging but necessary as the energy transition progresses,” Eldridge says. “Managing excess generation through exports, storage, and curtailment is critical to keeping the grid stable and efficient.”
It wasn’t the only record to fall over the weekend. In Queensland, the country’s most coal dependent state in terms of annual share of demand and generation, large scale solar hit a record share of 34 per cent, and coal output – in megawatt terms – hit a record low of 2,882 MW.
The Queensland coal fleet capacity is more than 8,000 MW, so that is about as low as it can run until more units are closed down.
In Victoria on Saturday, just before the AFL grand final, rooftop solar also hit a new record output of 3,164 MW – although it did not push operational demand down low enough for the market operator to enact Minimum System Load protocols and possibly switch off some rooftop solar panels to maintain grid stability.
It had flagged a potential MSL event on Friday but cancelled it in the morning. Those events will likely occur at other times in spring and over the summer holidays, although the market operator is now working on new rules for big batteries to avoid a potentially unpopular and unwieldy solar switch off.
