Pumped Storage Hydro

Gravity energy storage planned for coal mine in Sardinia

On the Italian island of Sardinia, Energy Vault is planning to develop a 100 MW hybrid gravity energy storage system within a 500-m-deep coal mine shaft.

Gravity energy storage planned for coal mine in Sardinia
Energy Vault and Carbosulcis announce 100MW gravity energy storage project at coal mining site in Sardinia (Photo: Business Wire)

On the Italian island of Sardinia, Energy Vault plans to develop a 100 MW hybrid gravity energy storage system within a 500-meter-deep coal mine shaft. The project is planned for the Nuraxi Figus coal mine, which is owned by Carbosulcis S.p.A and is set to be retired by the end of 2026.

The Sardinia Regional Government aims to convert the site into a green technology hub to restore the area damaged by mining activities, as well as to encourage new industrial activities.

Together with VaultOS energy management software, energy storage developer Energy Vault will deploy the EV0 gravity technology at the mine, which includes a water-based, modular pumped hydro application. The system combines pumped hydro energy storage technology with Energy Vault’s gravity energy storage technology, allowing the underground features of the retired coal mine to be repurposed.

“We are very excited about the innovative energy storage combined solution…that can become one of the solutions to support our project to convert our mine into a new Technology Hub,” said Francesco Lippi, chief executive officer of Carbosulcis. “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.”

Lippi added that energy storage will play a critical role in ensuring renewable energy can be used around the clock on the island and will promote the energy transition in areas heavily affected by coal mining.

Installation of the first modular gravity components is set to begin in September 2024, with the testing of the system expected to be completed in 2025.

“The conversion of the coal mine in Nuraxi Figus to a Technology Hub powered by renewable energy will help the Sardinia region to economically revitalize one of its areas most affected by the exit from fossil fuels,” said Marco Terruzin, chief commercial and product officer at Energy Vault. “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.”

According to Energy Vault, the hybrid energy storage system will help balance Sardinia’s grid and will boost the use of renewable energy to meet peak load demand.

The proposed site would be wholly owned and operated by Energy Vault, demonstrating the company’s commitment to serving as a long-term partner in the region.

The Nuraxi Figus coal mine has reserves amounting to 2.5 billion tons of sub-bituminous coal and used to be one of the largest coal mines of its kind in Europe. The mining concession for the cultivation of coal is the only one still active in Italy and includes the Eocene Sulcis Carbon Basin, extending over a surface of about 400 km2 along the mainland and on the same amount toward the sea, beyond the coast.

This is the second deployment of a hybrid energy storage system by Energy Vault after the Calistoga PG&E project in northern California, which pairs green hydrogen with lithium-ion batteries.

This article was originally published on Power Engineering International.