Edinburgh firm Gravitricity announced it is developing projects to start providing underground gravity energy storage to deep mine operators in Slovenia, Germany, The Czech Republic and Finland.
Underground energy storage gives end-of-life mine shafts, which otherwise face costly infilling and decommissioning costs, a second life.
According to Gravitricity, its energy storage system, called GraviStore, uses heavy weights – totalling up to 12,000 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.
“The system offers many of the best characteristics of pumped storage hydro and lithium-ion batteries – but unlike batteries, the Gravitricity system can operate for decades without any reduction in performance,” the firm said in a media statement.
Among the company’s clients are the Velenje coal mine in northeastern Slovenia, which is owned and operated by government-owned Premogovnik Velenje; First Quantum Mineral’s Pyhäsalmi mine – Europe’s deepest zinc and copper mine – in central Finland; the former Darkov mine in the Czech Republic, which is being decommissioned by DIAMO, the Czech state enterprise in charge of mitigating the consequences of uranium ore and coal mining; and the Geiger Group’s Grube Teutschenthal mine near Halle, central Germany.
“Gravity energy storage offers a powerful green opportunity to mine operators looking to extend a mine’s life beyond the extraction of materials. As well as being a genuine alternative to decommissioning, new underground energy storage schemes can provide economic and employment opportunities in communities where traditional jobs are in decline,” Gravitricity founder and executive chairman, Martin Wright, said. “Our work with mine operators is underlining the interest in our technology, and we are in dialogue with both mine owners and public sector organizations to turn these studies into operational plans.”
Wright pointed out that Gravitricity has already demonstrated its GraviStore technology with an above-ground 250kW demonstrator, where the company successfully raised and lowered two 25-tonne weights to generate full power and verify the system’s speed of response.
The £1-million, 12-metre-high test rig proved the system can go from zero to full power in less than a second – which can be extremely valuable in the frequency response and backup power markets –, while it also has the ability to vary power output dependent on demand.
