The LDES Council estimates that up to 8 terawatts of long-duration energy storage capacity will be needed globally by 2040, potentially unlocking $540 billion in annual grid savings. Against that projection, the technology pool capable of delivering economically viable storage beyond four hours remains narrow and largely unproven at commercial scale. The announcement by Victoria’s State Electricity Commission that it will deploy a 20 MW, 200 MWh compressed CO2 battery at the site of the decommissioned Hazelwood power station in the Latrobe Valley is therefore more than a single infrastructure commitment. It is the first commercial deployment of this technology in Australia and only the second 20 MW-scale installation of Energy Dome’s CO2 Battery anywhere in the world, following the Sardinia unit that came into full operation in July 2025.
The project specifications, ten hours of continuous discharge duration, position it well above the two-to-four hour range that characterises virtually all of the battery storage deployed in Australia to date. The SEC’s framing of the project is explicit on this point: the state has built substantial shorter-duration battery capacity but lacks any facility capable of bridging multi-hour or multi-day renewable generation gaps. With Victoria’s coal and gas fleet being progressively retired and its 2030 clean energy target requiring an increasingly wind- and solar-dominated generation mix, the absence of firm long-duration storage is a structural vulnerability rather than a planning gap.
How the CO2 Battery Works and What Distinguishes It
Energy Dome’s system stores energy thermodynamically rather than electrochemically. During charging, grid electricity compresses CO2 gas into liquid form and stores it in standard pressure vessels at ambient temperature, a characteristic that differentiates the technology from conventional compressed air energy storage, which requires either underground caverns or cryogenic temperatures. The compression process generates heat that is captured and stored separately. During discharge, the liquid CO2 is re-expanded through a turbine, with the stored heat used to improve expansion efficiency, generating electricity that is returned to the grid. The CO2 itself is not consumed but circulates in a closed loop, with a single 200 MWh unit requiring approximately 2,000 tonnes of the gas.
The company claims a round-trip efficiency above 75% with no degradation over a 30-year-plus lifetime, a contrast with lithium-ion systems, which typically degrade measurably over a cycle life of 10 to 12 years. The 75% round-trip efficiency figure was achieved at the Sardinia demonstration plant and has been independently cited in regulatory submissions to the UK Parliament. Alliant Energy, which is deploying a 20 MW, 200 MWh CO2 Battery at the Columbia Energy Centre in Wisconsin with a groundbreaking target of 2026 and completion in late 2027, estimated the total project cost at between $60 million and $90 million, reflecting a capital cost range of $300 to $450 per kWh at this scale. Energy Dome claims its capital expenditure is 1.7 times cheaper than lithium-ion at comparable durations, a claim that is broadly consistent with the cost dynamics of longer-duration storage comparisons but requires qualification by discharge duration: at four hours or less, lithium-ion remains cost-competitive; the CO2 battery’s economic case strengthens as duration extends beyond that threshold.
The Critical Minerals Argument and Its Limits
Energy Dome markets its technology’s independence from lithium, cobalt, nickel, and other critical minerals as a central differentiation. The CO2 battery uses steel, water, and CO2, all of which are available from multiple global suppliers with no material supply chain concentration risk. For a jurisdiction like Victoria that is simultaneously scaling renewable generation and competing for battery supply chains that are heavily concentrated in China, the supply chain argument has genuine policy resonance. The Hazelwood announcement notes explicitly that the technology avoids critical mineral supply chain exposure, language that reflects both the SEC’s awareness of lithium supply chain risk and the broader Australian government interest in reducing dependence on Chinese-controlled battery supply chains.
The counterargument is that CO2 itself must be sourced, transported, and maintained within the system. A 200 MWh unit contains 2,000 tonnes of CO2, and the risk of a major release, while not a safety hazard at toxic concentrations, does create a localised displacement risk. In the event of a dome puncture, the 2,000 tonnes would enter the atmosphere and require a 70-metre exclusion zone until the air cleared. Energy Dome’s CEO, Claudio Spadacini, has characterised this as a negligible atmospheric impact, equivalent to approximately 15 transatlantic return flights on a large aircraft, and the comparison holds in purely volumetric terms. The operational and permitting implications for urban-adjacent sites are a more complex question that the Hazelwood location partially addresses by providing a large, already-industrial site with an established infrastructure footprint.
The Hazelwood Site as an Enabling Factor
The choice of the former Hazelwood power station site is operationally and symbolically significant. Hazelwood operated one of the most carbon-intensive coal plants in the developed world before closing in 2017, and the site has been undergoing a managed rehabilitation process since. The SEC’s 143-hectare energy innovation precinct adjacent to the plant provides flat terrain, existing grid connection infrastructure, and a medium-voltage connection capability that Energy Dome’s standard 200 MWh unit requires. The land footprint of approximately 5 hectares per standard unit fits comfortably within the precinct boundary.
The grid connection point at a former large coal plant is particularly valuable for long-duration storage deployment. Transmission infrastructure built to carry hundreds of megawatts of coal generation can accommodate storage assets and new renewable connections without requiring the costly upgrades that greenfield grid connection projects in regional areas frequently encounter. The SEC’s indication that additional projects are planned for the SEC Energy Works precinct suggests it views the site as a platform for progressive LDES and new energy technology deployment rather than a single demonstration commitment.
Where CO2 Battery Technology Sits in the Commercial Landscape
Energy Dome’s global pipeline exceeds 30 GWh across projects in Italy, the United States, Ireland, India, and now Australia. Google has partnered with the company on a multi-continent storage buildout, with the first bilateral project underway in Ireland. The LDES Council’s abatement cost analysis for comparable long-duration storage options estimated a median abatement cost in 2023 of approximately £106.83 per tonne of CO2, 83% lower than battery-based alternatives for the same long-duration role, declining to £97.13 per tonne in 2030 as batteries gain more operational opportunities in cleaner systems. That gap narrows but does not close, which provides a basis for continued investment in non-lithium long-duration technologies rather than assuming cost and performance convergence.
The Sardinia 20 MW plant’s July 2025 commissioning provides the first operational data at commercial scale from which the Victoria project’s performance projections can be derived. One full year of operation in a Mediterranean climate with variable renewable generation provides meaningful but not fully representative data for an Australian application, and the Latrobe Valley’s weather and grid conditions will produce a different operational profile. The SEC’s description of the project as part of an innovation precinct rather than a committed grid infrastructure programme implies that real-world performance data from the Hazelwood installation will inform subsequent deployment decisions, which is the appropriate framing for technology at this stage of its commercial trajectory.
