At 1.30pm on December 31 last year, distributed solar – mostly PV mounted on rooftops – achieved a remarkable milestone in the state of South Australia: It produced enough electricity to meet the demand needs of the entire state.
It was only for a short period of time, but significant all the same. A decade ago most energy experts will have told you this was not possible. Some political pundits will tell you it is still not. But the lights didn’t just stay on, they shone a path to the future of a grid that soon could be running with no fossil fuels at all.
The Australian Energy Market Operator says that on New Year’s Eve rooftop solar reached 101.7 per cent of demand in South Australia (see graph below), with the excess 26 MW among a whole bunch of electricity – mostly sourced from wind and solar and a little bit of gas – that was exported to Victoria.
AEMO says it is a world-first for a grid of its size, and the occasion is featured in the updated engineering roadmap that is has released this week, outlining its plan to solve all the technical challenges that will allow such events to occur more often – as it surely will – and without the need to keep fossil fuels burning in the background.
“South Australia’s world leading contribution from rooftop solar systems has been made possible through the installation of power system equipment to keep the grid secure, advances in the connection between rooftop solar and the grid, and the implementation of policies which protect consumers from unwanted disruptions,” says AEMO chief executive Daniel Westerman.
“These initiatives are part of a broader effort to support the continuous increase of renewables in the energy mix, while ensuring a secure and reliable supply of electricity for consumers.”
Another statistic highlighted in the report is the new peak for “available” renewables, which reached 99.7 per cent in early October and will surely reach levels of more than 100 per cent as more wind and solar generation is rolled out across the grid.
Much of that potential output was curtailed, due to economic reasons (prices below zero) and because of grid constraints. And the record on Australia’s main grid for instantaneous renewables remains at just 72.1 per cent, and 84 per cent on the separate and isolated Western Australia grid.
But if the federal government’s target of 82 per cent renewables share is to be met in 2030, there will have to be large periods when the share of renewables is significantly higher, in the mid to high 90s, and even at or close to 100 per cent if the market operator is confident it can switch off coal and gas and keep the grid secure.
“AEMO must be ready to operate the power system under all foreseeable conditions, including during periods of world-leading contribution from rooftop solar and grid-scale renewable energy,” Westerman says.
Most of the challenges for a 100 per cent renewables grid are focused around grid protocols and ensuring that all the essential grid services – such as inertia and system strength – can be delivered by new inverter based technologies.
A lot of work has already been done – mostly on trials and specifications of “grid-forming” inverters and running entire systems on inverter-based technologies, and on standards for technologies such as EVs and home batteries that will play a significant role in a future grid.
But AEMO says a “scale up in effort is required to enable Australia to keep breaking new ground and accelerate the energy transition towards 100% renewables.”
The new engineering roadmap identifies 37 new priority actions for the 2025 fiscal year, much of them focused on distributed energy, the management of rooftop PV, the flexibility of loads and introducing “emergency backstops” to enable the operator to retain control of the grid.
It also plans more work on “synthetic inertia”, and making sure inverter makers understand the performance requirements of grid-forming inverters, and mark out a series of “transition points” that includes the reduction in the number of synchronous generators online, the retirement of coal, and the growth of consumer generation.
To put this into a global context, AEMO notes that Australia has few peers in terms of grids of its size that are also effectively isolated.
Australia is one of the world’s leading grids in managing high rates of wind and solar penetration, although no other grid on this scale has the same levels of rooftop solar.
“Australia finds itself at the edge of current global capability of power system management in several aspects, including DPV penetration and the maximum instantaneous contribution of variable renewables in large, GW scale power systems,” it notes.
One of the priorities this year is the gap in performance standards in what it calls “mid-scale” DER, meaning solar farms and batteries bigger than 200 kW but smaller than 5 MW, which have mostly been exempt from close scrutiny. It says new requirements have been drafter and will be released soon for consultation.
It also wants to extend a more formal “emergency backstop” protocol for distributed energy systems, mostly rooftop solar, to Queensland, NSW and Victoria.
These protocols has already been used to good effect in South Australia, particularly when that grid was “islanded” from the rest of the system in November, 2022, and was able to continue to operate with a high renewable share.
Interestingly, AEMO was also keen to point out that the delay in new connections and commissioning was largely outside its remit.
Whilst AEMO approved 12GW of connection applications in FY2024, the time taken for developers, construction providers and OEMs to physically deliver these projects has increased substantially (with 75% of projects taking up to 21 months to be constructed and ready for market registration).
It said key challenges include project financing, the volume and complexity of contractual arrangements, workforce resourcing, and supply chain constraints, which meant only 2.4GW of projects had been registered and 2.2 GW had achieved full output in FY2024.
“These are challenges that fall outside of AEMO’s direct remit and instead require broad whole-of-sector efforts to address, without which there will be difficulties in realising the 2024 ISP Optimal Development Path,” it noted.
