The power grid in eastern Australia could experience strains from too little power demand as soon as next spring unless states speed up actions to cope with surplus generation from solar panels on sunny days, the Australian Energy Market Operator (Aemo) has warned.
In a report released on Monday, Aemo called for an “emergency backstop” mechanism to ensure grid stability when households and other solar photovoltaic (PV) owners export excess electricity.
“South Australia, Victoria, Queensland and New South Wales may be exposed to regional shortfalls in the ability to deliver backstop capability required for management of severe emergency outage conditions” if transmission lines go down, it said. “This means that use of high customer impact mechanisms … may be required in some circumstances.”
While Aemo’s recent issues have involved the risk of electricity demand exceeding generation capability in NSW, the need to cope with insufficient load in the grid has been gaining urgency. Australians may add 3 gigawatts of rooftop solar in 2024 alone, according to the Clean Energy Council.
Michael Gatt, an Aemo executive, said the market operator had flagged the issue of so-called minimum system loads for several years and was aiming to work with state governments and network companies to develop solutions.
“Aemo does not want to directly control people’s rooftop solar,” Gatt said. That said, if actions to secure the grid weren’t enough, it may be necessary on “very rare occasions” to intervene to reduce output from solar systems or even to cut them off.
While several states had some backstop capacity, the ongoing expansion of rooftop PV meant those measures would become inadequate, Aemo said.
However, external interventions, including the use of high voltage levels to remotely control households’ solar inverters, was not without its costs, independent analysts such as Gabrielle Kuiper say.
Kuiper, a director of the Superpower Institute, said there were better alternatives than reducing rooftop solar output on mild days of abundant sunshine when consumers don’t need much power for heating or cooling.
These would become clearer if there was an effort to pass a change to the national electricity rules. This step would require cost-benefit analyses and greater evidence of the risks of grid instability, she said, noting Australia was one of the few nations in the world to move to a “really high proportion of variable renewable generation” in the grid.
One step might be to create a market mirroring the one used to pay big users to cut demand during periods of scant supply. Instead, they could be rewarded for adding load to help soak up solar power.
Batteries, too, could be nudged to charge up during low demand periods. Households’ batteries offer their owners opportunities to participate in so-called virtual power plants, sharing in the rewards of coordinated charging or discharging. Community batteries could also share the benefits.
“You need to put in place everything else that you possibly can to ensure [turning off rooftop solar] is the last resort,” Kuiper said. “We haven’t seen that kind of analysis of the different options and how they all stack up together.”
Electrical engineers say the use of “overvoltage” to turn off households’ inverters may also shorten the life of some appliances.
