Technology is not new
The idea of such storage is not new. The first such facility in Teesside, UK, opened in 1971.
In the United States, Advanced Clean Energy Storage is being built in Millard County, Utah, where two salt caverns will each hold 5,500 tons of hydrogen. With a megawatt-hour capacity, such a cavern is comparable to a lithium-ion battery that could fill more than 40,000 shipping containers.
Bunch estimates that just a few man-made caves in the Adavale basin could power 20 million homes a day (based on average consumption in Brisbane).
In November, geologists drilled a three-kilometre hole into the salt block, setting a new depth record for the Australian Geological Survey. They recovered a 976-meter hard rock core, more than 500 cuttings (rock fragments), and several groundwater samples.
According to Mitchell Bouma, the project leader, underground energy storage is significantly cheaper than above-ground energy storage due to the lack of costs for associated surface infrastructure. Such a cave would be capable of storing around 6,000 tonnes of hydrogen, equivalent to around 100 gigawatt hours of energy – around 50 of Australia's largest super batteries.
Local people panicked
However, the residents themselves living above these caves are less concerned about the energy potential than about the possible risks. They have legitimate concerns that large-scale work on their home could threaten the area's only stable water source.
However, Bunch says that injecting hydrogen into underground salt caverns is unlikely to harm the pool because of the way the salt and gas interact. The key to safe gas storage is maintaining the correct pressure. In a float tank, too low a pressure can create a dangerous vacuum, and too high a pressure can cause an explosion. And underground, even in the worst case, if the wrong pressure causes the rock to break, according to the geophysicist, the salt will act like a “toothpaste analogue”: it will naturally adapt to the pressure change and stop the rock from moving.
“Salt is mobile so there is no big problem here. If a crack appears, the salt will fill the space, shrink and close,” he asserted.
This move will minimize any impact and prevent further damage to other rocks, especially since it lies about two kilometers below an aquifer used for drinking and agriculture.
“I don't see any scenario that is likely to happen. This is unlike gas storage in other more fragile rocks,” Bunch concluded.
The Australian Geological Survey added that the samples collected will be used to analyze the area's mineral and water resources. The first results are expected mid-year.
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