A disused cavern in the famed Broken Hill silver, lead and zinc mine is to play host to what will be the world’s biggest renewable-powered compressed air storage facility in the world, potentially offering a new form of long duration storage to support wind and solar.
Canadian start-up Hydrostor has signed a deal with Australian mining company Perilya to use a disused cavern at the Potosi mine to support the Silver City Energy Storage project, which will feature compressed air energy storage technology with a facility rated at 200MW and eight hours of storage, or 1600MWh.
The technology is one of a number of newly emerging competitors to pumped hydro to provide long duration storage, including various “gravity” storage technologies, and new variations of solar thermal technology such as RayGen’s newly commissioned plant at Mildura.
The Broken Hill project has been a long time in the making. It was first proposed in 2020, but as RenewEconomy reported in 2021, it was almost sidelined by Australia’s regulatory madness which nearly forced transmission group Transgrid to instead choose new diesel generators to replace the town’s ageing back-up generation.
In the end, the innovative clean energy alternative won out, but it does represent a bit of a punt, considering that Hydrostor abandoned an ARENA-funded project in a South Australia zinc mine because of its lack of scale, and only has a small 2MW, 10MWh facility in Ontario that has been operating since 2019 as proof it works.
If the Broken Hill project is successful, it will be a showcase for the technology for the world.
Hydrostor says the Potosi mine has several key features, including very hard and impermeable metamorphic rock, an existing underground mine and infrastructure, and ideal depth (about 600 metres below ground).
Hydrostor will get access to property, mine infrastructure, and construction support services, which will enable it to fast-track the process and reduce set up costs.
And the deal is obviously delivering more value to the mine owners Perilya, which itself is now owned by Shenzhen Zhongjin Lingnan Nonfemet, one of China’s largest zinc producers.
The Silver City project will be used by Transgrid to provide backup power for Broken Hill and the far west region of NSW, and is expected to provide reliable backup power for the town, as well as existing and new mining activities in the region.
The storage facility will set aside 250MWh of its 1600MWh capacity to back-up power under a contract with Transgrid, and use the remaining capacity to trade on the market on a daily basis – pumping and compressing air in the cavern when prices are low, and discharging when prices and demand are high.
CAES technology is not new, and there are large projects in Germany and the US, but these mostly use gas turbines to deliver the power to compress and heat the air, which is then stored in caverns, before being released and re-heated and expanded to drive more turbines.
Hydrostor’s technology differs from the others in that it is emissions free and uses a method known as hydrostatic compensation, where a head of water in the surface reservoir is used to maintain pressure.
It claims a round-trip efficiency of more than 60 per cent, which is significantly less than pumped hydro (70-80 per cent), and battery storage (more than 90 per cent).
Renewable power is expected to be provided by the existing 200MW Silverton wind farm and the 53MW Broken Hill solar farm, both of which are often heavily constrained because of the lack of local demand and limits on the link to other consumers.
AGL is also building a 50 MW/50 MWh lithium ion battery at Broken Hill to support its operations there.
The Silver City project has been backed by by the NSW Government under the Emerging Energy Program and by the federal government via a new $45 million grant from ARENA under its support program for long duration storage.
Construction is expected to start in the middle of 2024 and be complete in 2027. The project is expected to provide 750 direct and indirect jobs during construction, and 70 ongoing jobs in operation, and is expected to contribute more than $1 billion to the regional economy.
