Australian technology may help generate power from defunct gold mines in Kolar Gold Fields

An Australian renewable-energy company’s unique scheme to generate electricity may resuscitate the fortunes of one of India’s iconic but defunct gold mines, namely the Kolar Gold Fields (KGF), in Karnataka.

An Australian renewable-energy company’s unique scheme to generate electricity may resuscitate the fortunes of one of India’s iconic but defunct gold mines, namely the Kolar Gold Fields (KGF), in Karnataka.

A hiccup that makes renewable energy unreliable, from solar or wind power, is that there is no power during nights or windless days. Charging a battery to use as a backup during this downtime hikes power prices. While the common approach to addressing this challenge is to design them better, find more efficient conducting materials and install large battery farms to store power, Green Gravity’s idea is to rely on low-tech gravity.

Their plan is to find defunct mines, which often go hundreds or even thousands of metres deep, and haul a ‘weighted block’ — this could be as much as 40 tonnes — up to the top of the mine shaft using renewable power during the day when such power is available. When backup power is required, the heavy block will fall, under gravity, and the ensuing momentum will power a generator via a connected shaft (or rotor). The depth to which the block can slip can be determined via a braking system, thus giving control on the amount of power that can be produced.

The same principle underlies the so-called ‘pumped hydropower’ storage, a well-established approach where water from the ground is pumped upstream electrically into a reservoir. From here, when needed, water is released downhill to move a turbine and produce electricity, like in a hydroelectric plant.

Pumped hydropower, or even Green Gravity’s approach, may use more energy than produced but when accounting for being able to make renewable energy available at off-peak hours, can mean less reliance on coal-produced power and access to reliable power. Currently, India has installed about 4,746 MW of pumped-storage, according to figures from India’s Central Electricity Authority.

Using weighted blocks instead of water means that decommissioned mines can be put to use and the environmental costs and challenges of moving water up can be avoided, Mark Swinnerton, Founder and CEO, Green Gravity told The Hindu. “By using gravity as the fuel, we dispense with consuming the critical water, land, and chemicals which other storage technologies rely on.”

“At mines such as at Kolar, you can produce up to 100 or even thousands of megawatt-hours of power,” Mr. Swinnerton said. Some of the KGF’s deepest mines run nearly 3,000 metres. Operational for almost two centuries, the KGF mines — the world’s second deepest — has reportedly yielded nearly 800 tonnes of gold for 51 million tonnes of mined rock.