Explained | Europe’s deepest base metal mine to be turned into ‘gravity energy’ store

As the world shifts to renewable energy and discards or reduces its reliance on fossil fuels, mining has gone down. With this, mines across the globe have to be decommissioned, recycled or discarded. The process of decommissioning a mine that is no longer in use is expensive and time-consuming, and requires a huge number of resources. In India, the average cost as per EE Power stands at a staggering $58 million, while in the United States, it reaches approximately $117 million.

To make better use of these mines, a United Kingdom-based firm has come up with a unique solution: an underground energy store. The firm, Gravitricity, is now turning a disused mine in Finland into its first full-scale prototype gravity energy store. Here's all you need to know.

Europe's deepest mine turns energy store

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Pyhäsalmi Mine, which happens to be Europe's deepest base metal mine, is located in the small Finland town called Pyhäjärvi. The mine, which has a depth of 4,738 feet (1,444.14 metre) is now being transformed into an underground energy store that will use gravity to retain excess power.

The mine was opened in 1962 and over its lifetime; it was the source of more than 60 million tonnes of ore. Once a treasure trove of zinc and copper, it was decommissioned in August 2022.

Now, it is being given a new lease on life with what the Scottish company Gravitricity says are "some of the best characteristics of lithium-ion batteries and pumped hydro storage".

How will the battery work?

The battery, as per Euro News, will store excess power, for example, from wind turbines on a windy day.

GraviStore, as the underground battery is called, raises and lowers heavy weights in underground shafts.

Imagine weights being hoisted up the towering 530-metre auxiliary shaft of the Pyhäsalmi mine when surplus power is available. Then, when needed, these weights are released, activating the winches, which now function as generators, producing electricity either in short bursts or a steady stream, depending on demand.

This innovative energy system boasts a capacity to store a whopping 2MW of power, seamlessly integrating into the local energy grid.

Why decommissioned mines?

As per the report, a recent study by a team of international researchers found that gravity batteries in decommissioned mines could be a cost-effective, long-term solution for storing energy.

This, as per scientists from the International Institute for Applied Systems Analysis (IIASA) is especially true as we transition to renewable power.

As per their estimates, abandoned mine shafts could serve as storage for around 70TWh of power, or roughly how much the daily global consumption is. This discovery underscores the untapped potential of repurposing old mining infrastructure for sustainable energy initiatives.

Local community

With the decommissioning of the Pyhäsalmi Mine, several hundred people lost their jobs and their livelihoods. Now, in Pyhäjärvi, the local community is embracing this opportunity for revitalisation. They have set up a development company andsigned a contract with Gravitricity to transform the old mine shaft.

As per the report, Martin Wright, the executive chairman of Gravitricity, envisions this project not only as a technological milestone but also as a catalyst for economic regeneration.

"This project will demonstrate at full scale how our technology can offer reliable long-life energy storage that can capture and store energy during periods of low demand and release it rapidly when required," said Wright.

"This full-scale project will provide a pathway to other commercial projects and allow our solution to be embedded into mine decommissioning activities, offering a potential future for mines approaching the end of their original service life," he added.

By providing "low carbon jobs" in an area grappling with the fallout from the closure of mining operations, the project seeks to breathe new life into the community.

The dangers of abandoned mines

As per EE Power, in 2024, experts predict a meagre 466 million tonnes of coal extraction, marking a historic low since 1962. While this is good for the planet, it comes with its own set of problems.

Idle or abandoned mines are not mere inactive plots but rather ticking time bombs of decay and deterioration if left unattended.

Shockingly, millions of Americans reside within a mile of these abandoned coal mines, according to estimates from the US Department of the Interior.

Experts warn that there are approximately 159,735 abandoned metal mines, each of which presents its own set of environmental hazards.

These neglected mines pose grave risks to local water sources. Mines associated with precious metals can leach mercury, contaminating sediments and seeping lead into the soil. Meanwhile, sulphide mines contribute to acidic mine drainage, further exacerbating environmental woes. Furthermore, records show hundreds of fatalities and injuries from accidents involving collapsing mine structures.