Sardinia Demonstration

Executive Overview

The Sardinia Demonstration is a 2.5 MW / 4 MWh CO₂ battery built and operated by Energy Dome at Ottana, Sardinia, Italy — the world's first commercial CO₂ battery long-duration energy storage plant, grid-connected on June 8, 2022. The system uses carbon dioxide in a closed thermodynamic cycle to store and release electricity without combustion, rare materials, or geographic site constraints. The demonstration plant operated continuously for over two years, and a first full-scale 20 MW / 200 MWh plant at the same Ottana site was commissioned in Q4 2024 with ENGIE as offtaker (COD Q3 2025 per contract). Energy Dome was founded in February 2020 and progressed from concept to commercial multi-megawatt demonstration in approximately two years. Investors include 360 Capital, Barclays, Novum Capital Partners, and Third Derivative. Energy Dome won the 2022 BloombergNEF Pioneers competition in the round-the-clock zero-emissions power category.

How It Works & Differentiation

During charging, surplus grid electricity drives compressors that pressurise ambient CO₂ gas; the heat of compression is stored in a packed particle bed Thermal Energy Storage (TES) system with no moving parts, and the CO₂ is condensed to liquid and stored in ambient-temperature carbon-steel pressure vessels — no cryogenics or chillers required. During discharge, liquid CO₂ is evaporated, reheated by the TES, and expanded through a turbine to generate electricity. The full cycle delivers approximately 75% round-trip efficiency with no atmospheric emissions and no site dependency. The 20 MW standard configuration discharges 18 MW for 10 hours and charges at 24 MW for 10 hours. All components are off-the-shelf equipment from the oil and gas industry's global supply chain. System cost is cited as less than half that of an equivalent lithium-ion BESS.

Commercialization & Traction

Following the Sardinia demonstration, Energy Dome signed an agreement with Italian utility A2A for a 20 MW / 5-hour facility and a non-exclusive licence agreement with Ansaldo Energia covering Italy, Germany, the Middle East, and Africa. In the United States, Energy Dome received a DOE contract for up to $30.7 million for the Columbia Energy Storage Project (20 MW / 200 MWh) in Columbia County, Wisconsin, installed on a retiring coal facility, with Notice to Proceed in Q4 2024 and a targeted operational date of 2027 (with 50% DOE cost-share). The NTPC project in Kudgi, Karnataka, India (20 MW / 160 MWh) — the first CO₂ battery in Asia — followed. The giga-scale configuration supports 75 MW / 1,020 MWh, or 150 MW for 9.3 hours.

Scalability & Strategic Context

The Sardinia Demonstration is the global proof-of-concept for CO₂ battery long-duration storage. Its demonstration of ambient-temperature liquid CO₂ storage in standard carbon-steel vessels — eliminating the cryogenic infrastructure required by liquid air energy storage (LAES) — is the key cost differentiation versus competing long-duration storage technologies. At 20 MW / 200 MWh scale, Energy Dome projects LCOS below $100/MWh at scale, competitive with lithium-ion for durations above approximately 8 hours. The combination of Sardinia, Wisconsin, and India deployments across three continents in under three years of commercial operation is the most geographically distributed long-duration storage technology validation in the current generation of novel storage.