May 27, 2021: Scottish power generator firm Gravitricity said on May 19 that it was planning to incorporate hydrogen and heat into its underground energy system.
The Edinburgh-based firm signed an agreement to build a 250kW demo at Port Leith, in Scotland, in May last year. This involves using excess electricity from the grid to winch 12,000-tonne steel weights, filled with iron ore, up a 15m-high rig before releasing them down shafts to generate and send electricity to the grid when required.
Testing is halfway through and the technology is operating successfully, says managing director and co-founder Charlie Blair.
Now the firm says it will turn the shafts into pressurised stores for hydrogen, capable of safely accumulating vast quantities of the gas, and capable of storing it as well as dropping the weights.
Blair says a pressure cap will be placed over the top of the shaft to contain the gas, which could be hydrogen or compressed air — “the point is it’s safe underground, contained by the geology of the earth,” he says.
Storing huge amounts of energy storage underground could solve the problem of seasonal storage, of which batteries are simply not capable.
“Seasonal fluctuation are huge,” he says, “and we have to find a way to absorb it and pull it out in the winter. Our technology uses the same space, the same infrastructure, as the weights, and is somewhere between geological storage of hydrogen and above-ground hydrogen, which is expensive.”
“The future hydrogen economy will need to find economic and safe ways to store hydrogen where it’s needed,” said Gravitricity co-founder Martin Wright.
“At present our domestic gas network has vast amounts of storage built in — under the North Sea. The gas grid of the future will be powered by intermittent renewables — and that means we need to find ways to store green hydrogen when energy is plentiful, close to where it’s required.
“Our idea is to make each Gravitricity shaft serve as a very large, sealed pressure vessel, and to use the shaft itself to hold significant quantities of gas.
“We believe this will be far more economic and safer than above-ground storage pressure vessels — and will massively increase the storage capacity of the system.”
He said he envisaged building multiple shafts co-located with a hydrogen electrolysis plant to form a dual function — store excess electricity for the electrolysers to use and the plant’s output as a buffer into the gas grid.
It was unclear how the blocks system would work alongside the hydrogen storage.