COMPRESSED AIR ENERGY STORAGE (CAES) SYSTEM IN ARTIFICIAL UNDERGROUND CAVERNS WITHIN THE ROCK SALT FORMATION OF MONOLITHI, IOANNINA, GREECE

19th WORLD CONFERENCE OF THE ASSOCIATED RESEARCH CENTRES FOR THE URBAN UNDERGROUND SPACE, Belgrade, Serbia, November 4-7, 2025. (Paper No: 7.5.219,  pp. 956-969)

 

АУТОР(И) / AUTHOR(S): Konstantinos Bampousis, Ioannis Vlachogiannis, Andreas Benardos

 

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DOI:  10.46793/ACUUS2025.7.5.219

САЖЕТАК / ABSTRACT:

Compressed Air Energy Storage (CAES) is emerging as a strategic solution to address the increasing need for scalable, long-duration energy storage in systems with high renewable penetration. As Greece transitions toward decarbonized electricity networks, the Monolithi site in Ioannina offers a unique opportunity to develop the country’s first underground CAES system using naturally sealed salt formations. This study evaluates the feasibility, design optimization, and long-term geomechanical stability of artificial spherical storage caverns within the halite deposit, which lies at a depth of approximately 150 m and exhibits high cohesion and low permeability.

The geological and geotechnical assessment was conducted using historical data from Hellenic Survey of Geology & Mineral Exploration (HSGME), followed by 2D and 3D numerical analyses to assess the optimal design of the complex and to evaluate its performance in the construction and operation phase, in terms of stability. This optimization in the design started from a simplistic layout of 2 main caverns and finally progressed in the suggestion of a 3-cavern layout that allowed for an increased capacity, ensuring the feasibility of the project. At the same time the analysis verified the stability of the cavern structures at all construction and operating conditions, with limited plastic zone development and displacements. More particularly, the 3D numerical analyses confirmed the optimal caverns’ spatial configuration and insights were attained for all important effects, such as surface uplift and stress redistribution near cavern boundaries, validating the benefits of internal pressurization. The system remained structurally stable with all strength factors exceeding safety thresholds – even under a full cyclic pressure range (0-6-0 MPa).

Thermodynamic calculations estimate an energy potential of 150 MWh per cycle, translating to up to 30 GWh/year under modern round-trip efficiency assumptions (70%) and 300 annual cycles. The initial CAPEX is estimated between 19,5–29,3 million EUR, indicating that the Monolithi CAES system could represent a cost-effective, spatially flexible alternative to pumped hydro storage. This research demonstrates the critical role of 3D numerical modeling in design validation and highlights the strategic importance of such infrastructure in supporting Greece’s renewable integration and compliance with EU decarbonization objectives.

КЉУЧНЕ РЕЧИ / KEYWORDS:

CAES, Salt Caverns, 3D Numerical Modeling, Energy Storage, Greece Energy Transition

ПРОЈЕКАТ / ACKNOWLEDGEMENT:

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