Rio Tinto and Rondo Start Design of a 360 MWh Heat Battery at Yarwun Refinery

Rio Tinto and Rondo Energy have started front-end engineering and design for a 30 MW, 360 MWh heat battery at Rio Tinto's Yarwun alumina refinery near Gladstone, Queensland, the companies announced on October 20, 2026.

The Rondo release calls it Australia's largest thermal energy storage project and says the unit would deliver heat of up to 1,000°C, mainly as steam into Yarwun's existing steam network, if the project proceeds. pv magazine Australia adds that it would be a world first for the alumina industry. Nothing has been approved for construction: the current stage is a study.

The 360 MWh and 30 MW arithmetic

Divide 360 MWh by 30 MW and the battery runs for 12 hours at full discharge. The release says the unit charges at midday from surplus solar power and discharges continuously, to supply process heat around the clock, and that Australia has about 4 to 6 hours of surplus midday solar a day.

The number that matters here is not the 30 MW discharge but the charging power it implies. Filling 360 MWh in 6 hours takes at least 60 MW of electrical input; in 4 hours, at least 90 MW, before any losses. That is our arithmetic, not a figure from either company, and it means the grid connection and the midday power supply matter as much as the bricks. Neither source gives a charging rating, a cost or a build timeline.

Item	Figure	Source
Storage	360 MWh	Rondo release
Discharge	30 MW	Rondo release
Full-discharge duration	12 hours	The Terminal's arithmetic
Heat output	Up to 1,000°C	Rondo release
Round-trip efficiency	Above 98%	Rondo, via pv magazine

The efficiency figure is Rondo's own and no independent test is cited in the coverage.

Who is paying for the study

The Australian Renewable Energy Agency (ARENA) is providing $3.6 million for the engineering study, per the release, which does not name the currency. A further $38 million is available for deployment after a successful study, and up to $33.3 million of conditional contingency support covers defined risks such as cost overruns and electricity costs.

1. Engineering study (committed)3.6 $ million
2. Deployment (after study)38 $ million
3. Contingency (conditional)33.3 $ million

Source: Rondo Energy release via PR Newswire, Oct. 20, 2026

Only the first line is committed. The other two depend on the study succeeding and on named risks materialising. The release does not state the total project cost, so the share ARENA would cover cannot be worked out from what was published.

What the companies say

Armando Torres, Rio Tinto Pacific Operations Managing Director, said the study will determine whether thermal storage is "a technically and economically viable alternative to fossil fuels" for part of Yarwun's steam requirements, according to pv magazine. Kira Rundel, Rondo's head of Australia, said in the release: "This project shows how Australia's abundant energy can become a competitive advantage for industry." Darren Miller, ARENA's chief executive, said demonstrations like this will help build the evidence industry needs for future investment decisions.

pv magazine reports the project would cut about 67,000 tonnes of carbon dioxide a year from on-site emissions if it goes ahead. That figure appears in one of the two sources we read and not in the release, so treat it as reported rather than confirmed. Neither source says what share of Yarwun's steam the battery would replace; both say only "part".

The next concrete marker is the end of the engineering study, which would unlock the $38 million deployment tranche. Neither company has said how long it will take. For other hardware where an announced capacity has yet to be matched by disclosed numbers, see our coverage of Tenstorrent's Series E and the AGCO Digit pilot.