From pv magazine Australia
Green Gravity draws on the ancient cornerstone of Australia’s wealth, coal mining, to remove the final hurdle to a fully renewable electricity system. It proposes lifting and releasing ultra-heavy weights down the shafts of legacy mines, in a reimagining of how the universal force of attraction, gravity, can be used to store renewable energy.
While the much-hyped Swiss company Energy Vault has recently hit some rough waters, Green Gravity CEO Mark Swinnerton insists his company has merits of its own, many of which stem from the fact that its concept is based on the reuse of abandoned but very abundant infrastructures. In recent weeks, Green Gravity has raised AU$1.4 million in its first formal fundraising round with a number of private investors, “with huge excess interest,” Swinnerton told The Associated Press. pv magazine Australia. “We are working towards higher revenues in a few months when we finalize the capital cost of the demo plant.”
Swinnerton added that he has contacted larger funds and received great interest. Notably, Energy Vault attracted investment from Leonardo DiCaprio, among other big names.
The new Green Gravity team has also launched studies on its supply chain and manufacturing footprint. This is something that Swinnerton, who spent nearly two decades at mining giant BHP, insists will be much easier than with other storage solutions.
“We don’t have to go extract the lithium, or process it with new systems, we don’t have to recycle the chemicals because we don’t have chemicals,” Swinnerton said. “People sometimes ask, ‘Why can you suddenly find something so simple and yet it’s an open market?’ and my answer is: ‘actually it’s because it’s never been needed before’. The only reason it’s needed now is because renewables penetration has passed a tipping point where all of a sudden natural cover doesn’t work in the market, more storage assets are needed.”
Green Gravity’s technology is flexible in two key ways, according to Swinnerton.
“The first is that the power of the system is associated with the speed at which we move the weights through the mine shafts. Of course, a motor can go at different speeds, so we can choose to change the duration and power dynamically, if we need to,” he said. “Which is unusual: most power systems can’t change their duration dynamically.”
The company plans to do this through advanced software and artificial intelligence (AI).
“What we are going to do is move multiple objects without being able to see them. So AI is going to be able to help improve the responsiveness of detection systems, to be able to learn how to optimize movement, and how to better respond to the needs of the power grid in real time to be able to learn how to make our system adapts to and supports the network,” Swinnerton said. “We are studying models that can potentially provide inertia, we are studying models that can certainly play into the stability of the network and the variety of frequency and voltage markets. We are also designed to have multiple durations and we believe that these deep mine shafts [que pueden tener el doble de la altura de la torre de Sydney en profundidad] they have a real opportunity for medium or long-term storage.”
Ultimately, Green Gravity intends to bring a series of storage products to market. The former, Swinnerton said, will offer between two and three hours of playtime, but says there is potential for a shorter playtime that focuses on network support, as well as a full-length model. The second area where Green Gravity can offer flexibility, Swinnerton says, goes back to the infrastructure it will use.
“Because we can use the infrastructure that already exists, we can achieve a very low-cost footprint,” he said. “We can couple capacity with unit costs similar to pumped hydro, but with much less capital. So you don’t have to pay 700 million Australian dollars like some of the big pumping projects. Just say, “Well, we’ll pay A$30 million.” You will get less energy, but you will have a unit cost result similar to that of pumped hydro, and there are many”.
In other words, Green Gravity does not intend to carry out a large project, but rather many smaller ones, a model that reduces risks and allows greater financing flexibility. Which brings us to another important facet of the proposal: Australia is full of mine shafts. “Australia’s mining history is everywhere,” Swinnerton said.
The company has discovered at least 3 GWh of potential storage capacity in the 175 sites that it has evaluated and deemed suitable. “I can unequivocally guarantee you that there is more than that available, and that is only in Australia. There are so many gigawatt-hours available in the rest of the world that Australia should be aware of,” Swinnerton said.
He added that, in his opinion, the Green Gravity concept will also offer legacy mining operations a valuable trade-off, providing them with an income stream to finance their rehabilitation.
Again, it’s a fairly simple concept: Green Gravity would go in and reuse the ore shafts and possibly other infrastructure, providing mines that no longer sell product with a steady trickle of money to restore ore bodies. This would be especially useful in the case of government-owned mines, where taxpayers have to foot the bill for rehabilitation.
According to Swinnerton, recent federal elections in Australia, coupled with the scramble for battery materials, have boosted Green Gravity’s prospects. “I think there is a real chance to speed up the process and I am very interested in working with the incoming government in this regard,” he said.
The company is now in the final stages of negotiating a major operating partnership, expected to be announced in the coming weeks.
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