The renewable energy revolution has a storage problem. Wind and solar energy are variable, meaning that, unlike fossil fuels, they don’t produce according to demand. Instead, they are reliant on the weather, the time of day, and the season of the year, meaning that energy production will wax and wane according to patterns far outside of human control. What’s more, these patterns are often in direct opposition to energy consumption patterns – we all turn our lights on when the sun goes down, forcing solar panels to clock out for the day. Finding effective, efficient, and long-term energy storage solutions that don’t break the bank or create geopolitical tensions has proven to be a challenge, but the sector is bursting with new innovations that could reshape the energy industry as we know it.
At present, the renewable energy industry is largely dependent on lithium-ion battery storage. This presents some significant issues because these batteries can only hold onto energy for a matter of hours, while the fluctuation of renewable energy production will require storage for whole seasons. What’s more, lithium-ion batteries require finite, non-renewable rare Earth elements which are going to become increasingly scarce in the future. This presents major potential geopolitical pitfalls, as China has a chokehold on many rare Earth element supply chains, including lithium.
Developing long-term energy storage that doesn’t rely on lithium is therefore a crucial step along the path to the green energy transition. In fact, a net-zero energy future will require a whopping 6TWh of energy storage. A report released in October of last year projects that the global off-grid energy storage system market is expected to grow by USD $6.22 billion during the 5 years between 2022-2026 alone, at an acceleration rate of 7%.
However, the long-term energy storage sector is still nascent, with many projects and ideas still squarely within the research and development stage. It’s not yet immediately clear what ideas will rise to the top, but whichever scientists and developers manage to corner the market are going to be rewarded handsomely for their efforts, as demand for energy storage is going to skyrocket in coming years.
One of the most promising approaches to the long-term energy storage problem is the idea of a gravity battery. The idea itself is quite simple. It’s a system that uses excess energy generated by renewable energy sources when production is high but demand is low to lift a heavy load. When energy is needed, that load drops, generating electricity.
The most common form of gravity batteries is pumped hydro energy storage, in which quantities of water are pumped uphill and then released to spin turbines. However, pumped hydro presents a lot of shortcomings. The dams that are often used in such systems have major negative environmental externalities which can seriously harm the natural habitats of animals and plants, and which can also negatively impact or displace the surrounding communities. Furthermore, as extended droughts and low water levels wreak havoc in hydropower sectors, there are questions about whether depending on water for energy storage is such a great idea going forward.
Due in part to these challenges, other forms of gravity storage are increasingly gaining traction. One of these promising new ideas is the conversion of old, abandoned mine shafts into energy storage elevators. In a newly published paper in the scientific journal Energies, scientists from Austria's International Institute of Applied Systems Analysis (IIASA) proposed one such mine-based Underground Gravity Energy Storage (UGES) system, which would store energy by raising and lowering containers full of sand to create electricity through regenerative braking.
A diagram of the proposed Underground Gravity Energy Storage system from Hunt et al. 2023
The idea is that this innovation would not only make use of the abandoned mining infrastructure that would otherwise be nothing but a hazard and an eyesore, but also replace some of the thousands of jobs lost along with the mine’s closure. What’s more, in the words of the scientific paper’s lead author Julian Hunt, “mines already have the basic infrastructure and are connected to the power grid, which significantly reduces the cost and facilitates the implementation of UGES plants."
By Haley Zaremba for Oilprice.com
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