A former BHP executive who began his career at the Port Kembla steelworks is working on a plan to turn abandoned mine shafts, including those in the Illawarra, into a reserve for renewable energy.
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The idea is remarkably simple: A weight and pulley system would be installed in abandoned mine shafts.
When energy is plentiful and cheap during the day, the system lifts the weight to the surface of the mine shaft.
Then, when renewable energy is needed gravity pulls the weight down, turning an axle which drives a motor that creates electricity which is then passed through to the grid.
The man behind this idea, Mark Swinnerton, has publicly launched his company, Green Gravity, based on the networks and knowledge he developed over 20 years in the resources industry.
"When I was coming out of BHP, I'd been thinking about the sustainability of the resources sector, including energy but also lifecycle and rehabilitation, the full life cycle and footprint of the resources sector," he said.
Mr Swinnerton found that there are nearly 100,000 abandoned mines in Australia, with only a small percentage having ever been rehabilitated. In the Illawarra, the Wongawilli Colliery and the Russell Vale mine currently sit in care and maintenance status, making them potential sites for re-use.
"I made it a mission to find what more could we do with these old assets that have already been produced and are now sitting there idle or even causing an environmental impact," he said.
As the renewable energy boom has taken off, the need for reliable energy storage has also increased, making a concept such as Green Gravity viable.
While batteries and pumped hydro have been the focus for energy storage in Australia, Mr Swinnerton said that Green Gravity would be more competitive with these technologies.
"The capital required to build a megawatt hour of capacity will be competitive with [batteries] on the market today. Importantly, our technology will have the life expectancies of pumped hydro, which means when you look at the total cost over the lifecycle, our technology will be more competitive than lithium ion batteries."
Other firms internationally have experimented with the same principles, with one of the most advanced being Swiss start up Energy Vault. However, what sets Green Gravity apart, according to Mr Swinnerton, is the use of existing facilities such as mine shafts, instead of constructing towers or pits for blocks to be raised and lowered.
Mr Swinnerton said he also aims to utilise local industry in the Illawarra to make the business a success, including local engineering firms, sourcing power from projects such as the mooted offshore wind farm and creating weights from iron or steel produced at his former workplace.
Green Gravity is already in talks with a number of mining companies to re-use shafts and has coordinated private funding to start to get the company off the ground. A demonstration plan is planned for the next months.
Mr Swinnerton also suggests that by turning what is currently a liability, disused mines, into an asset, would provide mining companies with the capital earned from energy storage to invest in mine rehabilitation, including in those sites where there are no provisions for rehabilitation.
"By bringing new economic opportunities to that site, we enhance the value creation, and we can divert more resources to rehabilitation earlier," he said.
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