Canadian company Hydrostor is bringing a new compressed-air energy storage project to Broken Hill. 

Hydrostor has partnered with the operator of Broken Hill's zinc, lead, and silver mine to construct a 200-megawatt plant with a claimed eight hours of continuous power storage, located in a disused cavity near the historic mining town.

Hydrostor's technology harnesses surplus wind and solar energy from the grid during off-peak hours to operate an air compressor. 

The compressed air is then stored 600 metres below the surface at Perilya's Broken Hill Potosi mine site. When energy demand arises, the compressed air is released to drive a turbine, generating electricity for grid stabilisation, local consumption, or sale in the National Electricity Market at premium prices during times of scarcity.

Hydrostor's system has been described as “pneumatic pumped hydro storage”, and is valued for its compactness and versatility compared to conventional pumped hydro storage. Notably, it requires just one-twentieth of the water volume per megawatt-hour of energy storage and can be located virtually anywhere.

The latest project, known as the Silver City Energy Storage Centre, may only be the beginning of Hydrostor's activities.

The company says it envisions four additional projects across New South Wales, Victoria, and South Australia, each boasting 500-megawatt plants with eight hours of storage capacity, totaling a massive 4000 megawatt hours.

As coal power exits the stage, the need for long-duration energy storage becomes increasingly pressing. 

Most large batteries currently offer only a few hours of storage, while other long-duration options like pumped hydro face delays in development.

Broken Hill often faces unreliable power supply, so the project has been designed to provide 50 MW of standby power to TransGrid. When standby power is not needed, the entire 200 MW capacity will be available for sale to the grid, offering both energy and stability services.

The $560 million price tag for the Silver City Energy Storage project is currently under review, with a final investment decision anticipated by the end of 2024.

More details are accessible here.