The photo is sourced from Gravitricity
The storage will be set up in a 6-metre-wide and 365-metre-deep underground shaft lined with steel. The shaft will be able to store 100 tons of hydrogen at a time under a pressure of 220 bar. This volume will be sufficient to power more than 1,000 freight trucks and provide the vehicle fleet of 500 fuel cell buses with fuel for a week. Gravitricity estimates that one storage will be able to power an electrolysis unit combined with a 460-megawatt (MW) wind power plant for hydrogen production.
The project will make it possible to expand the range of applications of the gravity energy storage technology. Earlier, Gravitricity built a demo above-ground facility for electricity storage in the port of Edinburgh resembling a 15-metre elevator shaft, in which the elevator cabin is replaced by two loads weighing 50 tons in total. In charging mode, the system uses electricity to lift the load from the lowest point to the highest point, accumulating potential energy in the load. When the energy needs to be converted into electricity, the load descends under the action of gravity while electric motors switch to generator mode and supply electricity to the consumer. Therefore, the amount of electricity, which can be generated by the storage depends on the weight of the load and the height (or depth) of the shaft.
Gravitricity’s initiative offers an alternative to the solution for storing hydrogen in hollowed out salt caverns, which is going to be piloted by the engineering company Bilfinger and the gas transmission company Gasunie. In 2022, the two companies announced their intention to set up four salt caverns – round-shaped underground cavities – in the Netherlands province of Groningen for an underground storage of hydrogen with an overall capacity of a little over 300 mln m3. The storage will be established in several stages: first, a 1,500-metre-deep well will be drilled to inject freshwater into the cavern via a coaxial pipe. The resulting brine will be pumped via a discharge pipe to a salt production enterprise while freshwater will be injected into the salt cavity for three years until it gets full. Finally, at the last stage liquid will be pushed out of the storage via gas. The first cavern will be put into operation in 2026.
