Energy Vault, Italian coal miner plan gravity + battery energy storage in old mine shafts

Energy Vault and coal mining company Carbosulcis S.p.A. have announced plans to develop 100 MW hybrid energy storage facilities at the Nuraxi Figus coal mine in Sardinia, Italy's largest former coal mining site.

The planned energy storage system (ESS) will pair a gravity energy storage system (GESS) with a battery. The hybrid ESS (HESS) will be deployed within 500-meter-deep mine shafts, along with Energy Vault's proprietary, VaultOS energy management software, the companies said in a release, adding that the proposed site would be wholly owned and operated by Energy Vault.

The parties disclosed they had recently executed a land lease agreement, and that installation of the first modular gravity components would commence in September 2024 with the testing of the underground component expected to be completed in 2025.

The solution will leverage Energy Vault's EV0 gravity technology through a new water-based, modular pumped hydro application, allowing both partners to repurpose the underground features of the site.

The Sardinia Regional Government, which owns Carbosulcis, expects to retired the Nuraxi Figus site by the end of 2026, and convert it into a Technology Hub.

Francesco Lippi, Chief Executive Officer (Amministratore Unico), Carbosulcis, said in a statement: "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 maximize the local use of renewable energy, and at the same time provide services that will improve the stability of the power grid in Sardinia."

Marco Terruzin, Chief Commercial and Product Officer, Energy Vault, commented: "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."