Wind farms and rooftop solar installations could be switched off in the coming days to protect South Australia's energy grid, with experts warning of the risk of more blackouts following the weekend's extreme weather.
The state remains cut off from the national electricity market after key infrastructure was toppled in the state's east.
Transmission company ElectraNet is aiming to have a temporary fix in place for its crumpled giant pylon along the SA-Victoria interconnector by Sunday night, but has warned of potential stability issues in the meantime as SA continues to generate power without the capacity to export the surplus.
In a scene reminiscent of the 2016 statewide blackout, wild weather ripped down the transmission tower just south of Tailem Bend about 5pm on Saturday, isolating South Australia from the rest of the national grid.
That has created the risk of what some experts call a "solar spill", in which too much electricity from renewables is generated during periods of low demand and threatens to overload the system.
ElectraNet chief executive Simon Emms said the "highest risk" of that occurring would be on Thursday because of sunny weather conditions forecast for Adelaide.
He said the problem was unique to South Australia because of its high reliance on renewables.
"There's no risk of not having enough electricity, the risk is we have too much electricity for the demand on the system at that point in time," he said.
"It's only going to happen in South Australia because South Australia's renewables penetration I think is north of 60, almost 70, per cent. The other states are in the 20 or 30 per cent [range].
"On Thursday, we'll work with the Australian Energy Market Operator and SA Power Networks. The first step, they'll turn off wind farms and commercial solar farms to hopefully minimise the impact on the rooftop solar."
Mr Emms said construction of a new pylon would "probably take many months", but that crews were currently working to safely remove the collapsed pylon and replace it with temporary towers.
"We're currently aiming to have the interconnector back on by the end of the weekend," he said.
"The interconnector to Victoria was built in the 1980s so the towers are approximately 30 or 40 years old, they're about 50-metres tall, and it obviously takes a very localised severe event to cause that sort of damage to such a significant piece of infrastructure.
"With the interconnector out of service, we're not connected to Victoria so that means we can't export any surplus power.
"To maintain system security we need a certain number of gas-fired units on, and that requires the dialling down of renewable generation during the peak periods of sun."
South Australians could face further blackouts
South Australia's energy supply has been back in the spotlight in recent days, after 163,000 homes and businesses had supply cut as a result of Saturday's storms.
Professor Bruce Mountain from Victoria University’s Victoria Energy Policy Centre said the state remained vulnerable while the interconnector was down.
"The risk to the system would be in South Australia some level of load shedding," Professor Mountain said.
"It is possible that suburbs and areas could be switched off for at least some period.
"In those sorts of events ... there's a shutdown order, there's a sequenced approach, there's a way to determine which areas are better to switch off than the other."
But Professor Mountain said it would be a much more manageable process than the blackouts caused by the weekend storms.
"Because they can anticipate a lot of this, it wouldn't be a systemic regional wide breakdown," he said.
Professor Mountain said while creating another interconnector to NSW would help SA in the future, more battery storage should be the immediate priority.
"That storage brings on clean supply, it insulates you against these supply risks, it decreases the demand for gas, it has all sorts of benefits across the electricity sector and across the gas sector," he said.
"I encourage the South Australian government to establish a storage target, as other states have, so that they have got a policy focus on it and ensures that they bring in that storage quickly.
"For some reason, the South Australian government in recent years has dropped this off its list and has had all its eyes on interconnection.
"There's no substitute for storage and building up that storage should be done. That should be South Australia's first focus."
The authority to remotely turn off household solar panels to protect the grid was granted to SA Power Networks two years ago, but has been used only sporadically and sparingly since then.
ElectraNet chief executive Simon Emms said the likelihood of an imminent solar and wind switch-off depended on the "supply-and-demand balance on the day", but said the risk of similar events in future would be attenuated by a second interconnector between SA and New South Wales, which is still being built.
"Obviously, the sunnier it is, the more rooftop solar there will be," he said.
"Customers being asked to dial down their solar is a rare event and it's only driven by the fact that the interconnector's out of service. When the interconnector to New South Wales is built, it will be even less likely."
