World’s most isolated grid wants big batteries to last longer to fill gaps as last coal shuts down

• The default storage setting for big batteries in Australia’s biggest state is about to be lifted to six hours duration – or even more – as grid authorities prepare for the closure of its last coal fired power station at the end of the decade.

Western Australia – host to the world’s biggest isolated grid, with no connections to other states or countries – has become one of the hotspots for battery storage in the last couple of years as it seeks to soak up its extraordinary amounts of rooftop solar and provide grid support in the evening peaks.

Its first big battery – at Kwinana – only began production two years ago, but within the next two months it will finalise commissioning of what will be the two biggest batteries in the country – Neoen’s 560 MW, 2,240 MWh battery and Synergy’s 500 MW, 2,000 MWh, both located in the coal town of Collie.

There are at least another half a dozen big batteries under construction or which have won government contracts and will be built soon. And, from a standing start, W.A. has led the way in the development of four-hour battery projects, with total capacity of 1.3 GW and 5.2 GWh.

Now it’s about to take that to the next stage, potentially targeting six hour batteries, after local energy authorities identified a new “duration gap” that is starting to emerge, partly because the state has no – and little prospect of having any – pumped hydro facilities.

W.A. is currently the only state in Australia with a so-called “capacity market”, that provides payments for capacity to be available at certain times, usually in the evening peaks.

Since 2021, the Reserve Capacity Mechanism (RCM) – which pays generators, including batteries, to make capacity available so the state has enough to meet the 1-in-10 year peak demand – has rewarded 4-hour batteries.

The W.A. government body, Energy Policy W.A., has reviewed the Availability Duration Gap (ADG) forecasts prepared by the Australian Energy Market Operator, looking at several 1-in-10 peak forecast demand curves and determining how long the battery fleet duration needs to be to make sure the demand curve is met.

Its initial conclusion is that four-hour batteries will leave the state’s main grid with “unmet capacity”, and it has modelled a range of outcome using 4 hour, 5-hour, 5.5 hour and six hour batteries.

A final decision is not likely to be made until after AEMO releases its latest Electricity Statement of Opportunities for the W.A. Grid on June 24, which will include crucial demand forecasts.

“We don’t have pumped hydro, and this approach simply reflects the needs of the system – in that at some point you have enough 4-hour batteries and need to factor in future MWh being used over a longer duration,” says Jai Thomas, the convenor of energy at Energy Policy W.A.

“In the end, the outcome is likely to be that future batteries will have their revenue (via capacity credits) spread across a longer duration – which will reduce the incentive.

“However, with the capacity credit price likely to stay high, and battery costs reducing, this should allow for sufficient revenues but deliver the longer duration needed to support the power system through transition.”

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