Disused mine shafts in the UK could get a second life as “gravity batteries” — a novel form of energy storage under development by a Scottish engineering company. Like chemical batteries, these could be used to rapidly respond to fluctuating grid demands.
Edinburgh-based startup Gravitricity plans to equip the long-abandoned mine shafts with enormous weights and winches. Surplus power will be drawn from the grid to raise the weights closer to ground level. When the time comes to inject energy back into the grid, the weights can be released for a burst of power generation.
The physics behind the idea is similar to that of pumped hydro — water is driven uphill when energy is cheap and plentiful, then released when demand is high to power generators. Gravitricity highlight a key benefit over pumped hydro, however, an almost instant response to fluctuations as well as a potential degradation-free operational lifespan of 50 years. Innovate UK has awarded the startup a £650,000 grant.
“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.
“So far there is a lot of focus on batteries, but our idea is quite different. Gravitricity uses a heavy weight – up to 2000 tonnes – suspended in a deep shaft by cables attached to winches. 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.”
“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.”
Gravitricity has a target date for a part-scale demonstration model later this year, with a full-scale working prototype planned for 2020.
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