An ancient rock formation that is older than the dinosaurs is being explored as a solution to one of Australia’s biggest green energy problems.
Geoscience Australia has identified a thick salt deposit in outback Queensland’s Adavale Basin as a potential underground hydrogen battery.
With the potential to power millions of homes across eastern Australia, the project could help address the looming renewable energy storage gap.
The Adavale Basin sits below the towns of Quilpie, Blackall and Charleville, and the largest underground freshwater reservoir in the world — the Great Artesian Basin (GAB).
As Geoscience Australia’s $31 million drilling project wrapped up, the question residents wanted answered was whether their only reliable water source would be at risk.
An ‘on-demand’ underground battery
First discovered in 1958, geologists consider the Adavale Basin to be “under-explored” and notoriously difficult to study.
The Adavale Basin is difficult to access, located underneath the Great Artesian Basin and Galilee Basin in Queensland. (Supplied: Geoscience Australia)
Buried underneath the Eromanga and Galilee Basins — two other large rock formations that are part of the broader GAB — there is no evidence of the Adavale Basin on the surface.
It also contains the only layer of rock salt discovered anywhere in eastern Australia that is potentially thick enough to store hydrogen energy deep in the Earth’s crust.
Known as the Boree Salt deposit, Geoscience Australia head of advice, investment, attraction and analysis Mitchell Bouma said it could be used to create artificial battery-like containers.
“You can dissolve that rock salt out and you can store things within that dissolved cavern, like hydrogen gas or compressed air,”
he said.
“You can produce these things [hydrogen gas] out there, pump them into the cavern, and it’s basically this on-demand battery that’s under the ground.”
Storing hydrogen gas in underground salt caverns has been used overseas for decades, with the first site at Teesside in the UK in operation since 1971.
Geoscience Australia has gathered rock core samples from the Adavale Basin. (Supplied: Geoscience Australia)
Independent energy geoscientist Mark Bunch from the University of Adelaide said this kind of storage had “enormous potential”.
“You go underground because of the scale,”
he said.
“We can store all kinds of industrial gases and other chemical products at the surface in huge tanks, but you can do it at a much vaster scale [hundreds of cubic kilometres] if you go underground.”
In the United States, the Advanced Clean Energy Storage hub being developed in Delta, Utah will use two salt caverns to store 5,500 metric tonnes of working capacity each.
A joint venture between oil giant Chevron and Mitsubishi Power, the company estimated it would take more than 40,000 shipping containerss worth of lithium-ion batteries to produce the equivalent megawatt-hours of one cavern.
An outback site near Blackall is being touted for its potential to store hydrogen energy underground. (ABC News: Chris Gillette)
Dr Bunch said just a handful of artificial caverns within the Adavale Basin would be enough to power 20 million homes a day, based on Brisbane’s average household demand.
Depth perception
To assess the potential of storing hydrogen in Adavale Basin salt caverns, geologists drilled a 3-kilometre deep borehole into the Boree Salt deposit in November, breaking Geoscience Australia’s depth record.
They collected a 976-metre solid rock core, more than 500 rock chips and several groundwater samples.
Hydrogen gas could potentially be stored in caverns made by partially dissolving a salt deposit. (Supplied: Geoscience Australia)
Mr Bouma, who managed the project, said underground energy storage was significantly cheaper than above-ground alternatives because it did not have the same “surface infrastructure costs”.
A single cavern could potentially store about 6,000 tonnes of hydrogen or about 100 gigawatt hours of energy, equivalent to about 50 of Australia’s largest super batteries.
While Geoscience Australia conducts research, any development of the Adavale Basin will be up to industry. (Supplied: Geoscience Australia)
But some residents living above the caverns are less enthusiastic about their energy potential and more concerned about the potential for disaster.
Blackall-Tambo Shire Mayor Andrew Martin represents about 1,900 residents and said he was wary of anything that might jeopardise the region’s only constant source of water.
“It’s the precautionary principle,”
he said.
“If you get one increase in pressure in the Great Artesian Basin, or one movement of the subterranean plates, or some catastrophe somewhere, somehow, it just beggars belief.”
Quilpie, Blackall and Charleville are directly above the Adavale Basin. (Supplied: Geoscience Australia)
But Dr Bunch said pumping hydrogen gas into underground salt caverns was unlikely to damage the basin, because of how salt and gas interact.
The key to safe gas storage is maintaining the correct pressure; in tanks, too little pressure can create a dangerous vacuum, while too much pressure can lead to explosions.
But underground, Dr Bunch said even in a “worst-case scenario” of a fault in the rock caused by the wrong pressure, the salt would become a “toothpaste-like substance” that naturally adjusts to pressure changes and prevents rock moving.
“This shouldn’t ever be much of an issue because salt is free to move,”
he said.
“In the scenario [of a fault], the salt would move to fill the space, shrink and be pulled in.”
Dr Bunch said that movement would spread the effect and prevent further damage to other rocks, and noted this would be happening about 2km below the groundwater used for drinking water and agriculture.
Agriculture is one of the industries that relies on the Great Artesian Basin as its primary water source. (ABC News: Chris Gillette)
“I just don’t see it as a scenario that would play out,” he said.
“It’s a different scenario to storing gases in other rock types that might be more brittle.”
Geoscience Australia said it would use the samples to analyse the region’s mineral and groundwater resources, with the first findings expected to be delivered mid-year.
But Cr Martin said he wanted to see more evidence to ensure any future exploration of the Adavale Basin was in the best interest of his community.
“You cannot guarantee that this is absolutely fail-safe for time immemorial,”
he said.
“Take the community with you, otherwise you’re going to have a constant set of worry beads going on about what the bloody hell are they doing to our lifeblood?”
