Pyhäsalmi Mine, located 450 kilometers north of Helsinki in Finland, runs deep into the Earth – 1,444 meters, or around 0.9 miles, to be precise. With its copper and zinc deposits depleted, Pyhäsalmi has a lot of vertical space sitting unused that's perfect for capturing the energy of heavy weights being dropped down a shaft, which is precisely what Scottish energy storage tech firm Gravitricity plans to use it for.
First reported by Glaswegian news outlet The Herald, Gravitricity's intent for the Finnish mine isn't, sadly, a mile-high gravity battery, but a smaller one in a 530-meter (1,738 ft) auxiliary shaft. Once complete, the battery will apparently be able to achieve two megawatt-hours of storage capacity.
"This project will demonstrate at full scale how our technology can offer reliable long-life energy storage that can capture and store energy during periods of low demand and release it rapidly when required," Gravitricity executive chairman Martin Wright told The Herald.
A gravity battery is just what it sounds like: Excess energy generated by power plants is used to move a material upward – in Gravitricity's case it's heavy weights in a mine shaft raised by winches – and when there's an energy shortage the load is dropped and the energy is harvested.