Big batteries flex their muscles as AEMO, ARENA underline “game-changing” role in closing coal

Australia’s rapidly growing fleet of big batteries have continued to flex their muscles this week, taking out record shares of supply at times in the evening peak, as well as reaching record charging levels in the middle of the day.

On Thursday, at 12.45pm, the collecting charging of the nation’s big batteries hit an unprecedented rate of 2.26 gigawatts, nearly 20 per cent higher than the previous peak of 1.83 GW set just two days earlier, according to GPE NEMLog. A year, the charging peak stood at just 875 MW.

This new peak was reached even without the involvement of the nation’s most powerful battery, the partially commissioned 850 MW, 1680 MWh Waratah Super Battery in NSW.

That battery is currently offline for scheduled maintenance, and its path to full commissioning has been derailed at the 11th hour by a catastrophic transformer failure.

Earlier this week, big batteries were also flexing their muscles in the evening peaks, reaching a record 40 per cent share of supply at one stage in South Australia – the country’s most advanced renewable grid – and where gas generators were relegated to a small walk-on part for grid security.

That grid security is important, because it is essential to the running of the grid and keeping the lights on.

And even as big batteries play a greater role in soaking up excess renewables, and injecting them into the grid in the more lucrative evening peaks, two new reports have highlighted their critical role in supporting grid security, and allowing the remaining coal fired generators to close on schedule.

The Australian Renewable Energy Agency, for instance, has highlighted the critical role of grid-forming inverters that are now being rolled out with nearly every new big battery project.

That is largely thanks largely to its ground-breaking funding, which has helped battery projects – such as Western Downs (pictured above), now the biggest such battery in the southern hemisphere, install and in some cases retrofit this new technology.

“These (big batteries) aren’t just storage units soaking up excess solar and wind, they are active players stabilising the grid and rewriting the rules of how modern power systems operate,” ARENA writes in a new report.

“For an industry that has long debated the role of batteries in providing “system strength,” this milestone is significant. It marks the moment batteries stopped being a supporting act and became central to keeping the lights on.”

Transmission companies and the Australian Energy Market Operator often talk about “system strength” being the heartbeat of the grid – providing resilience to the grid in the face of disruptions.

There is still debate among energy experts about the ability of battery grid forming inverters to provide all the system strength qualities delivered by the legacy coal and gas generators, and to what extent synchronous condensers, spinning machines that do not burn fuel, are required.

Battery storage developers such as Tesla argue strongly that they can. See: Tesla says battery inverters can do the job of spinning machines at a fraction of the cost

But the technology is so new that those responsible for delivering it to the grid want more evidence – hence the importance of the accelerated rollout funded by ARENA that has helped solve issues such connection agreements, technology risk and market signals.

“Australia’s grid has traditionally relied on conventional synchronous generators, like coal and gas fired power stations, to provide system strength: the stable voltage waveforms and inertia needed to keep the lights on,” ARENA writes.

“As these facilities retire, the grid becomes more vulnerable to disruption.

“Grid-forming inverters change the game, enabling batteries to maintain a stable and secure frequency and voltage, making them a cornerstone of a renewable-dominated power system.”

“This isn’t just about storage, it’s about resilience. Grid-forming batteries provide the invisible scaffolding for a secure, renewable powered grid,” ARENA says.

But there is still some hesitation.

“Historically, options for replacing system strength have been limited. Synchronous condensers are a well-understood technology, but are costly, inflexible and slow to deploy. Grid-following batteries are cheaper and more flexible, but incapable of providing the same stabilising services.”

This is echoed by AEMO, which like Tesla and ARENA, acknowledges the lower cost of the battery option, but is not yet convinced they can do everything that is required.

AEMO has asked for a series of significant rule changes to underline the urgency of having more grid forming batteries and syncons providing the essential system strength to allow the coal fired generators to retire.

AEMO cites NSW as an example, saying that just meeting minimum fault level requirements from coal plant would require approximately 20 per cent of annual wholesale energy generation.

“Considering plant capacity factors, the share of renewables in the wholesale market when relying on coal plant only for minimum fault levels would be unlikely to exceed 65 per cent of annual generation,” it says.

It says that it already has to issue directions to manage system strength due to unplanned coal plant outages. Without an accelerated rollout of grid forming batteries and syncons, such directions might be required for 30 per cent of the time after the planned closure of Eraring in late 2027.

“Depending on outage scenarios, there may be approximately three days out of the year in NSW where there will be insufficient resources available in the system to meet minimum fault levels and major interventions such as network reconfigurations or de-energisation would be required.”

Such levels were common in South Australia, but now much reduced because of the presence of four syncons, batteries with grid forming inverters, and the first stage of the new transmission link to NSW.

AEMO says that in the two years before synchronous condensers were installed in South Australia, to consumers paid $140 million in directions to maintain system strength, which resulted in $343 million in lost savings from curtailed renewables.

“By contrast, the synchronous condensers procured by ElectraNet came at a net capital cost of $169.4 million.”

The problem is that global demand for syncons is now high, and the wait time is three or four years.

AEMO still insists that syncons are necessary because it is not yet convinced that grid forming battery inverters – despite the insistence of Tesla and others – can provide protection quality fault current.

“Existing synchronous generators can be retrofitted (e.g. with a clutch) to operate in synchronous condenser mode, but this option can have technical and commercial barriers,” it says.

“For new incoming synchronous generators, the addition of clutches can materially affect project design.

“The capability of inverter-based resources to provide minimum protection quality fault current and the operational risks of doing so have not yet been demonstrated and tested with in-field testing,” it adds, although it is writing contracts with some facilities to test their capabilities.

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