Gravitricity has been awarded £650,000 of government funding to test an innovative energy storage system.
Energy will be stored by lifting a giant cylindrical “clock weight” up a disused mineshaft using a winch, and then released by lowering the weight back down.
The funding from Innovate UK’s Infrastructure Systems Innovation competition will be used to design and build a 250kW prototype, ready for testing in late 2018.
Over the course of the year, Gravitricity will also develop a design for a full-scale prototype which is scheduled for deployment in a UK mineshaft in 2019/20.
It claims the technology will have a 50-year lifespan, with no cycle limit or degradation, and a full-cycle efficiency of between 80 and 90 per cent. It will have a rapid response time, going from zero to full power in less than a second, but will also be versatile, with the ability to vary its output by altering the speed at which it operates.
“As we rely more and more on renewable energy, there is an increasing need to find ways to store that energy so we can produce quick bursts of power exactly when it is needed,” said Gravitricity managing director Charlie Blair.
“When there is excess electricity, for example on a windy day, the weight is winched to the top of the shaft ready to generate power,” he explained. “This weight can then be released when required – in less than a second – and the winches become generators, producing either a large burst of electricity quickly, or releasing it more slowly depending on what is needed.”
Blair said the technology is based on the same principle as pumped hydro storage but uses weights instead of water: “It’s a simple case of ‘what goes up, must come down’. The difference is we don’t need a mountain with a loch or lake at the top, and we can react much faster.”
Digging new holes would represent the biggest single cost of deployment, hence why the company is initially testing the technology using existing mineshafts. The company hopes that falling technology costs will eventually make it economically viable to dig new shafts.
The final product will be offered with a power output of 1MW to 20MW and an output duration of 15 minutes to eight hours. Shaft depths will range from 150 metres for new shafts to 1,500 metres for existing mines.
Gravitricity is now raising seed funding to match the grant from Innovate UK.