business energy

How Gravitricity turns old coal mines into energy storage

As more and more renewable energy is added to the grid, the role of energy storage grows. Stored energy helps to balance the grid and respond to demand spikes. It also evens out the intermittent nature of renewable energy, capturing it when it is generated and releasing it when it is needed.

There are many forms of energy storage. Some of them rely on highly advanced technology, and others really quite simple. The energy storage technology patented by Gravitricity is one of the simple ones. They haul weights up a shaft while the wind is blowing or the sun is shining, and then lower them again to release the energy into the grid.

This isn’t a new idea. A grandfather clock is powered by a slowly falling weight. But it’s not been done at this kind of size before – a full scale Gravitricity system could be raising and lowering as much as 12,000 tonnes in weight,

The core technology here is a winch – no rare earth metals, no cobalt or un-recyclable elements. It’s designed to run for 50 years. It’s far cheaper than many other storage options, and perhaps my favourite part of it – the best place to put them is old mine shafts. Once a coal mine is closed down, the shafts remain as a hazard more than anything. Using the pits for renewable energy storage re-uses the left-behind remnants of the fossil fuel industry. Double it up with heat harvesting from coal mines, and the legacy infrastructure is redeemed for the future.

Here’s a good video explainer. You can ignore the fundraising bit at the end – the campaign was successful and the company is due to build its demonstration project in Scotland this year.



  1. It will be interesting to see how the economics of Gravitricity can compare with other approaches like ARES (sending lots of rail-truck loads up inclines) or Energy Vault (stacking/un-stacking towers of heavy blocks), or indeed other technologies like Thermo-Photovoltaics (Antora), compressed gas bags (Hydrostor) or liquefying air (Highview). I thought this CNBC article gave quite a nice round-up (one contributor saw lots of different economic niches):
    Some interesting (maybe daunting?) economics figures in this article:

  2. I expect there will be lots of solution variants, all of which could be techically feasible, but probably the most important issue is to understand the landscape of economic niches. I expect Chris Goodall would be excellent on this (he has some involvement in grid stabilisation and maybe storage, but I’m not aware of him doing a systematic review of this area). Maybe a collaboration would be profitable? I could see good complementary strengths between you two.

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