Scottish Energy storage company Gravitricity has revealed plans to add hydrogen and heat storage to their underground gravity energy system.
Gravitricity has submitted a global patent to turn purpose-built shafts into pressurised energy stores, capable of safely accumulating significant quantities of the gas.
“The future hydrogen economy will need to find economic and safe ways to store hydrogen where it’s needed,” says company 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”.
According to Wright, each Gravitricity shaft will serve as a large, sealed pressure vessel. The shaft will be used to hold significant quantities of gas, which will be more economic and safer than above-ground storage pressure vessels. Furthermore, it will increase the storage capacity of the system.
The Gravitricity team plans to build single or multiple shafts and co-locate them with a green hydrogen electrolysis plant. The dual function would be to store excess electricity for use by the electrolysers when needed, and to store the plant’s output as a buffer into the gas grid.
Says Wright: “This will not only smooth the input and output of the green hydrogen plant, but it will improve the economics, bringing down the cost of green H2. The hydrogen store could also be used as a fuelling point, providing low (or zero) carbon hydrogen fuel for heavy goods vehicles, ships or trains, or be used to generate significant additional quantities of electricity if required.”
Wright believes a pilot hydrogen storage system can be in place within a few years.
Company managing director Charlie Blair explains the company’s goal: “The majority of early schemes will be built in existing mine shafts, but we are already in discussion with a major UK concern with plans to build a purpose-built shaft – solely for our gravity system.
“In the decade ahead, we believe that the capacity to sink single or multiple shafts exactly where required could result in the rapid scale-up of our technology. Not just in the UK, but around the world.”
Blair emphasises that below-ground hydrogen storage will ultimately become an extremely valuable revenue stream for Gravitricity projects. “Longer term, we can also build inter-seasonal heat storage into our system to provide a further service making best use of our infrastructure,” Blair concludes.
Gravitricity is currently operating its 250kW demonstrator in Edinburgh and is scaling up to commence work on its first 4-8MW scheme later this year.