Energy Vault Holdings Inc, a leader in sustainable grid-scale energy storage solutions, and Carbosulcis S.p.A., a coal mining company owned by the Autonomous Region of Sardinia, have announced their plans to develop a 100 MW hybrid gravity energy storage system, a solution designed by Energy Vault for underground mines, pairing modular gravity storage and batteries.
This unique energy storage solution to be deployed within 500-m-deep mine shafts, along with the VaultOS™ proprietary energy management software, is essential for the Sardinia Government’s targeted conversion of the coal mine to a Carbon Free Technology Hub, where the availability of low/zero emissions energy will be a catalyst to attract new industrial and technological activities, Energy Vault says.
This hybrid energy storage solution leverages Energy Vault EV0™ gravity technology through a new water-based, modular pumped hydro application. The proposed system combines long-established pumped hydro energy storage technology with Energy Vault’s gravity energy storage technology, allowing the partners to repurpose the underground features of the site as a retired coal mine. The hybrid energy storage solution is designed to optimise and fully capitalise on the specific topology of the site and the 500-m-deep mine shafts, highlighting the unique proposition of Energy Vault as a fully integrated and diversified provider of tailormade energy storage solutions, the company says.
The parties recently executed a land lease agreement, with installation of the first modular gravity components set to commence in September 2024 with the testing of the underground component of the hybrid energy storage system expected to be completed in 2025.
Carbosulcis’ Nuraxi Figus site, located on the island of Sardinia in Italy, is currently set to be retired by the end of 2026, and the Sardinia Regional Government aims to convert the site into a technology hub with a minimum environmental impact to help the industrial and economic reconversion of an area heavily affected by the exit from coal production. In addition, the hybrid energy storage system will help to stabilise the island’s power grid, with plans to dispatch renewable energy to help meet the high demand during peak load hours while encouraging further local use of renewable generation in Sardinia. The proposed site would be wholly owned and operated by Energy Vault.
Francesco Lippi, Chief Executive Officer (Amministratore Unico), Carbosulcis, said: “We are very excited about the innovative energy storage combined solution proposed by Energy Vault, including underground gravity energy storage technology, that we are testing together and that can become one of the solutions to support our project to convert our mine into a new technology hub. This project will maximise the local use of renewable energy and, at the same time, provide services that will improve the stability of the power grid in Sardinia. We are deeply appreciative of the partnership that Energy Vault has demonstrated thus far, and their customer-centric approach to the design of energy storage solutions has already proved extremely valuable. Energy storage is a critical component to better utilising renewable energy around-the-clock on the island of Sardinia. We see this important collaboration with Energy Vault as a vital step in the development of the technology hub, which is intended to promote innovation, by recovering a former mining site and strengthening the concept of “smart transition” to renewable energy in an area like the Sulcis Inglesientes heavily affected by the exit from fossil fuels, like coal.”
Marco Terruzin, Chief Commercial and Product Officer, Energy Vault, said: “We are proud to collaborate with Carbosulcis for such an important project. The conversion of the coal mine in Nuraxi Figus to a technology hub powered by renewable energy will help the Sardinia region to economically revitalise one of its areas most affected by the exit from fossil fuels. We believe that this exciting application of our energy storage solutions, including a new use for our gravity energy storage technology – deploying it underground – could hold vast potential for future applications. Discovering and researching new uses of our technology demonstrates the broad versatility and potential of our unique and innovative portfolio of energy storage solutions. We see a future where our technology helps power the world with renewables.”
EV0 is part of Energy Vault’s G-VAULT™ Gravity Energy Storage System portfolio and was announced in May 2024 along with other new gravity storage system products. The new design is a water and vessel-based “modular pumped hydro” solution that is uniquely addressing applications for underground deep mine shafts, in this case a 500-m-deep shaft at one of the largest coal mines in Italy, which is now under closure, the company explains. The mine with reserves amounting to 2.5 billion tonnes of sub-bituminous coal, used to be one of the largest coal mines of its kind in Europe and the world.
This is the second deployment of a hybrid energy storage system by Energy Vault after the Calistoga PG&E project in northern California, USA, the largest green microgrid in the world, which pairs green hydrogen with lithium-ion batteries, Energy Vault says.