Scottish coal mines set to generate electricity again with new ‘pumped storage’ gravity-driven turbines

Charlie Blair at the former Newtongrange coal mine, near Edinburgh
Charlie Blair at the former Newtongrange coal mine, near Edinburgh

Abandoned Scottish coal mines could find a new lease of life with old mine shafts turned into renewable energy stores.

This is the aim of Edinburgh start-up Gravitricity, which has received a £650,000 government grant for its plan to harness the power of gravity to store renewable energy.

Its technology would use a massive weight suspended in mine shafts to capture green power, and then release it in seconds – using the power of gravity of the plummeting weight to drive electricity turbines in the same way that pump-stored hydro power operates.

Gravitricity will sink the cash into building a scale demonstrator later this year and then find a dis-used coal mine shaft in which to install a full-scale prototype by 2020.

Managing director Charlie Blair, explained: “As we increasingly rely on renewable energy, there is an increasing need to find new ways to store that energy – so we can produce quick bursts of power exactly when it is needed.

 “So far there is a lot of focus on batteries, but our idea is quite different.  Unlike batteries, the Gravitricity system can operate for decades without any degradation or reduction in performance.

“We will use a heavy weight – up to 2,000 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 start-up plans to build models from 1 to 20MW, and Blair estimates each Gravitricity energy storage system will last for up to 50 years. 

Of course the idea of using gravity to store energy is not new. Britain already relies on a number of Scottish pumped storage hydro schemes, where water is pumped uphill to be released when required.

Graphic of coal mine gravity-driven turbine generator
Graphic of coal mine gravity-driven turbine generator

Edinburgh-based Gravitricity was set up two years ago, with Martin Wright as chairman – he also chairs the Renewable Energy Association, the largest such industry body in the UK.

Before joining Gravitricity, Charlie Blair was head of marine energy at the Carbon Trust. 

Also on board is technical director Peter Fraenkel, a visiting professor at Edinburgh University and veteran marine energy engineer who was awarded an MBE for these services in 2013.

8 Feb 2018

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