Rio Tinto Advances 360 MWh Thermal Storage at Yarwun Refinery

Rio Tinto has teamed with California‑based Rondo Energy to evaluate a 30 MW/360 MWh heat‑storage system at its Yarwun alumina refinery near Gladstone, Queensland. The project would mark one of the first big‑scale demonstrations of stored renewable heat for industrial steam and a first for the alumina sector.

How the thermal battery works at Yarwun

Rondo’s system uses electricity to heat refractory bricks that can tolerate very high temperatures. The bricks hold the energy as heat, which is later released to generate steam for the plant’s existing steam network. Charging occurs when grid power is cheap and abundant — typically midday when solar output peaks — while the stored heat is dispatched continuously, allowing the refinery to operate after sunset. The proposed unit would store 360 MWh of thermal energy, deliver up to 30 MW of heat, and accept electricity at a rate of 78 MW, meaning it can absorb power faster than it discharges heat. The technology claims a round‑trip efficiency above 98 % and can supply steam or hot air up to 1,000 °C. Because the battery connects directly to the current steam infrastructure, the refinery’s processes remain unchanged; only the heat source shifts from fossil fuels to low‑cost electricity.

Expected emissions impact

Rio Tinto estimates the battery could cover roughly 5 % of Yarwun’s steam demand and reduce the site’s direct carbon dioxide emissions by about 67,000 tonnes per year. Alumina refining is a notoriously difficult sector to decarbonize; worldwide, the aluminum industry’s refining step accounts for approximately 175 million tonnes of CO₂ equivalent annually. Replacing a portion of the coal and natural gas used for steam generation would represent a meaningful step toward cleaner production.

Funding and timeline

The Australian Renewable Energy Agency (ARENA) has committed an initial AUD 3.6 million (about US $2.5 million) for the front‑end engineering and design study, which is slated to last roughly 12 months. Rio Tinto will match that amount. Should the study prove the concept technically and economically viable, ARENA would provide up to AUD 38 million for construction and commissioning, plus up to AUD 33.3 million in conditional contingency support. Rio Tinto has indicated its total spend over the project’s life would exceed ARENA’s contribution if deployment proceeds.

Significance for industrial heat decarbonization

Industrial process heat is one of the toughest emissions sources to address because demand is continuous, while renewable generation is intermittent. Thermal storage offers a way to use inexpensive renewable electricity for round‑the‑clock heat without redesigning factory equipment. The Yarwun feasibility work will test whether the integration can deliver reliable high‑pressure steam at a competitive cost. Successful demonstration would give other heavy‑industry players confidence to pursue similar solutions, extending the project’s value well beyond a single refinery.