The Australian Energy Market Operator has issued a series of new decrees about the operating environment for South Australia, as it seeks to navigate the renewables-dominated state grid through two weeks as an effective energy “island”, but with the power hungry Portland aluminium smelter now attached to the end of its elongated network.
AEMO, as RenewEconomy reported earlier this week, has effectively taken control of the state’s three big batteries – Hornsdale, Lake Bonney and Dalrymple North – because it values their fast response and versatility and sees them as key to responding in any unexpected outages or trips.
It is boosting the amount of gas generation it normally requires to operate in South Australia to ensure that it has enough “system strength” in the absence of the main link to Victoria, which was cut when a storm or tornado tore down six large transmission towers last Friday.
Now it has issued new operating guidelines, warning that the imports from Victoria via the remaining Murraylink connector will be constrained to zero, and 23 different wind, solar and gas generators could be constrained to zero output if South Australia’s minimum demand falls below 800MW.
That is most likely to happen on a weekend with good sunshine, and with rooftop solar meeting a lot of demand. But it also highlights the fact that rooftop solar is largely uncontrolled by AEMO, and so it is the large scale renewable installations that have to make way.
In this situation, it is causing a headache for the grid operator, and it underlines why AEMO has been pushing for new measures and mechanisms that allows it to have some sort of control over the output of rooftop solar, now totalling more than 10GW in Australia on more than 2.2 million rooftops.
Managing the S.A. grid for the two weeks it will take to build a temporary line to link back into Victoria is further complicated by the fact that Victoria’s huge Portland aluminium smelter is also now attached to the South Australia grid, because the collapsed towers happened to the east (in grid terms) of the smelter and left it isolated from the rest of Victori’s grid.
Portland’s load requirements of near 500MW are being met by the newly repaired gas units at Origin Energy’s Mortlake gas generator, which is also on the South Australia side of the damaged transmission lines. Both Portland and Mortlake are synchronised with the S.A. grid but it is not entirely clear what happens if one of the Mortlake units runs into problems.
AEMO, meanwhile, has also issued a revised and increased technical guidance on which gas units need to be running at any one time in South Australia to ensure enough “synchronous generation” is available should the need arise.
But the startling outcome of the review of the S.A. grid’s operations is the number of plants – wind, solar and gas – that would be constrained down to zero if minimum demand falls below 800MW.
These include the Angaston, Barker Inlet, Dry Creek, Hallett, Londsdale, Montaro, Port Lincoln, Port Stanvac, Quarantine, and Snuggery gas and diesel generators, along with the Bungala 1 and 2 solar farms, the Tailem Bend solar farm, and the Hornsdale, Lincoln Gap, Cathedral Rocks, Mt Millar, Starfish Hill and Wattle Point wind farms.
Four wind farms – Lake Bonney and Canunda in South Australia, and Macarthur and Portland in Victoria, have been constrained to zero as a result of the tornado that tore down the transmission lines.
The gas and diesel units would be unlikely to run anyway, given that the wholesale price would likely be too low. But it would be a deflating result for the wind and solar farms, particularly those that would likely otherwise run because of fixed price contracts.
The jostling for position in the South Australia grid, with only limited exports to Victoria via the underground Murray Link line, has seen average prices in South Australia stay below zero since the tornadoes hit last Friday. According to AEMO data, they have averaged minus $1.68 until midnight on Wednesday.
The share of renewables in the state’s grid has averaged 50 per cent since it became an energy “island”, with rooftop solar providing much of daytime demand, and wind energy playing its role at night time. Prices have been volatile, it’s been negative more than positive.
That has created more problems, however. AEMO has had to intervene to prevent an “excess of negative pricing residues” flowing between South Australia and Victoria, and causing price settlement issues in both states. It has also had to impose a price limit on the frequency and ancillary services market, after the various FCAS markets pushed the price to the market cap for several days running.
This is the result of the few gas generators capable of delivering FCAS in South Australia having no competition from interstate, due to the failed Heywood interconnector, and the lack of competition from local batteries otherwise seconded by AEMO.