Former mines around the world could soon be enjoying a second lease life thanks to cutting edge technology developed by an Edinburgh startup.
As more and more of the world's power comes from clean, green, renewable sources, there's a growing need to find effective ways to capture and store the kind of intermittent energy produced by wind, sun and water, and release it rapidly again when it's needed. Gravitricity, a Scottish startup, has come up with a simple but effective solution that could also be a source of new jobs for ex-mining communities around the world.
The technology is based on a simple principle: the raising and lowering of a heavy weight in a deep hole underground allows electrical power to be absorbed or generated as needed.
As Charlie Blair, the managing director of the Scottish firm told Mining Technology:
“Gravitricity uses a heavy weight, up to 2,000 tons, suspended in a deep shaft by cables attached to winches. (...) It is a simple case of 'What goes up, must come down'.”
It has the same advantages as pumped-storage systems, as used in the German mining town of Bottrop, where a disused coal mine was filled with water to convert it into a huge renewable energy store - but here there's no need for a nearby lake or reservoir.
All the system requires a cylindrical weight, a system of ropes and winches (for raising and lowering the weight) and a deep hole in the ground - which of course makes disused mineshafts the perfect place. Raising and lowering the cylinder allows energy to be stored or expended and the speed at which it is dropped controls the release.
“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” explained Blair. “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 can generate up to 20 MW of power with an output duration between 15 minutes and 8 hours.
The technology is designed to last for 50 years, has 80 to 90 per cent efficiency, and because it makes use of existing infrastructure (i.e. pre-existing mine shafts) it's cost-effective too. Unlike other renewable energy storage solutions, such as lithium ion batteries, there's no issue of disposal or degradation, and the implementation of this kind of technology would also mean increased investment and new jobs in ex-mining communities.
And things are looking good for the company. Innovate UK, the government innovation agency, just granted Gravitricity 650,000 GBP to continue its research and the company is aiming to trial their first full-scale prototype at a disused mine in the UK by 2020.
You can check out Gravitricity's elevator pitch in the video below.