Can coal be used to make energy storage batteries

Old coal mines can be converted into "gravity batteries" by retrofitting them with equipment that raises and lowers giant piles of sand. Underground Gravity Energy Storage system: A schematic of different system sections. ( Credit: JD Hunt et al., Energies, 2023)

Using a project called the Global Coal Mine Tracker, which holds data on 3,760 coal mines worldwide, the researchers at IIASA estimate that UGES has the global potential to store as much as 70 terawatt hours of energy – enough to power the UK for three months.

A deeper mine would not only produce and store more energy, but would also be more cost effective. Energy storage costs vary from $1 to $10 per kilowatt-hour for UGES, the authors calculate, downright cheap compared to lithium-ion batteries, which currently cost about $150/kWh. Battery prices continue to fall as chemistries improve, however.

Fascinated by the considerable chemical properties and interlayer distances, carbon materials have been widely applied in energy storage systems (ESSs). As the richest mineral, coal is always used as the fuel, accompanying with inferior values.

Scientists recently proposed repurposing old mine shafts to generate electricity by lowering containers of sand and storing electricity by raising the sand back up again. While the method cannot generate as much power for the grid as batteries or pumped hydro, it can cheaply store energy for months or years with no loss.

While batteries are an effective solution for daily energy storage, we still lack a cost-effective solution for storage over longer periods. But now, researchers at the International Institute for Applied Systems Analysis (IIASA) think they've found one in the form of old mine shafts. All that's needed is 40 million tonnes of sand.