Rio Tinto wants to put Australia’s cheap midday electricity to work at its Yarwun alumina refinery – by storing it in hot bricks and using that heat battery to make steam after the sun sets.

The global mining giant and California-based Rondo Energy have started engineering and design work on a huge heat battery near Gladstone, Queensland. Rondo calls it Australia’s largest planned thermal energy storage project and says it would be a first for the alumina industry.

Alumina is a hard white powder made of aluminum and oxygen that’s used to make aluminum metal, sandpaper, and strong ceramics. Globally, aluminum sector refining accounts for roughly 175 million tonnes of carbon dioxide equivalent annually.

It’s still at the study stage, but the potential payoff is substantial. Rio Tinto estimates the battery could supply around 5% of Yarwun’s steam needs and cut the refinery’s direct emissions by about 67,000 metric tons of carbon dioxide annually. It would replace some of the coal and natural gas used to generate steam.

Rondo’s heat battery uses electricity to heat refractory bricks, which can withstand high temperatures. The bricks hold that energy as heat, which is then used to produce steam for the refinery’s existing steam network.

That matters because industrial heat demand doesn’t stop when solar production drops. Rondo’s heat battery charges during hours when electricity is cheap and plentiful, then delivers heat continuously so factories can keep running.

The proposed Yarwun system would have 360 megawatt-hours (MWh) of thermal storage and deliver up to 30 megawatts MW of heat.

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