Britain’s cheapest “virtual battery” could be made by hoisting and dropping 12,000-tonne weights – half the mass of the Statue of Liberty – down unused mine shafts, according to Imperial College London. The surprising new origin of “gravity energy” is being made by Gravitricity, an Edinburgh-based startup, which wishes to use Britain’s old mines to make better use of clean electricity at half the price of lithium-ion batteries.
Gravitricity explained its system stores energy by using electric cranes to plant the weights to the top of the shaft when there is plenty of renewable energy, then dropping the weights down to vertical shafts to generate electricity when required. The plan mimics hydropower projects, which have played an essential part in assisting in balancing the electricity grid since the mid-1970s. Charlie Blair, Gravitricity’s managing director, stated: “The beauty of this is that this can be done numerous times a day for years, without any waste of a performance. This makes it a competition to other forms of energy storage –like lithium-ion batteries.”
A full-scale plan would drop 24 weights making 12,000 tonnes to a height of 800 meters to generate enough electricity to power 63,000 houses for more than an hour. By carefully controlling the winches, Gravitricity said it could extend this time by allowing the weights to fall slowly and release electricity over a longer time.
Oliver Schmidt, the lead author of Imperial’s report, said Gravitricity’s model is the biggest price competition energy storage option as it has a relatively low initial cost and a lifespan of more than 25 years.