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Subproject 4

Cavern thermal energy storage (CTES)

Novelty of the solution of the subproject 

SP4 introduces a novel approach to STES by developing an innovative insulation system that can be applied to any geometry. This is achieved through integration of advanced laser scanning methods, which capture precise spatial dimensions, and an algorithm that optimizes the arrangement and machining of insulation panels. This approach allows the use of standard insulation materials and ensures their chemical and mechanical resistance up to 95°C for 50+ years.

SP4 also aims to foster the construction of STES cavities in urban underground infrastructure and ensure their long-term use in different geological conditions. This involves developing procedures for the  construction of cavities and measures to ensure their durability over 50 years, particularly in solid rock formations. SP4 leverages expertise in underground construction and combines it with STES know-how to define evaluation parameters and develop an assessment methodology using data-science methods.

Furthermore, SP4 addresses the challenge of high thermal losses and low stratification efficiencies in tunnel geometries. Using a modelling framework, the project will i) identify pathways to keep thermal losses in tunnel STES below 30% and it will ii) develop measures ensuring stable stratification in tunnels. Results are validated through experimental work at SCAUT’s Hagerbach Test Gallery.

Objectives of the subproject 


  • Advanced 3D-scanning: Develop and demonstrate an advanced algorithm capable of  determining the optimal arrangement and machining of thermal insulation elements based on precise 3D scanning data.

  • Robust underground cavities: Advance the understanding of the influence of temperature and pressure on the long-term structural integrity of underground cavities.


  • Decrease investment costs for STES by 30% through reutilization of existing infrastructure.

  • Boost profitability of thermal grids by augmenting the annual heat output, achieved through fulfilling 100% of the heating demand with renewable energy sources.


  • Minimize land footprint of STES by repurposing existing underground infrastructure. Preserves above-ground space for other uses and minimizes visual impact, while reducing strain on land resources.

  • Community Benefits: Improve energy affordability, efficiency, and security for communities through reduced energy costs and sustainable energy solutions.


  • Contribute to full decarbonization of thermal grids

  • Reduce embodied grey energy of STES by 50% compared to conventional STES systems

Research partners

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