Advancing Multiphysics Simulation for Next-Generation Thermal Energy Storage
From 29–31 October 2025, INTERSTORES was strongly represented at the COMSOL Conference 2025 in Amsterdam, one of the world’s leading events for multiphysics simulation, numerical modelling, and advanced engineering design. Held at the Meervaart Theater, the conference brought together more than 280 researchers, engineers, software developers, and industry leaders to exchange the latest advancements in simulation-driven innovation across energy, geoscience, and industrial systems.
INTERSTORES partner Dr. Abdulrahman Dahash (AIT Austrian Institute of Technology) participated as both a panellist in the session “Simulation for Underground Energy Storage” and as lead author of two scientific papers, each demonstrating how advanced computational tools can accelerate the development and optimisation of seasonal Thermal Energy Storage (sTES) technologies.
Panel Contribution: Simulation for Underground Energy Storage
Panelists: Dr. Abdulrahman Dahash, Scientist, AIT Austrian Intitute of technology; Prof.habil. Dr.-Ing. Dipl.Math. Ekkehard Holzbecher, GUtech/Freie University Berlin; Sven Friedel, Managing Director, COMSOL Multiphysics GmbH
Moderator: Phillip Oberdorfer, Technology Communication Manager, COMSOL Multiphysics GmbH
In the dedicated panel on underground energy storage modelling, Dr. Dahash highlighted how simulation-based design supports the safe and efficient integration of underground thermal energy storage (UTES) into future district heating systems. The discussion underscored the importance of computational tools, particularly COMSOL Multiphysics®, in predicting thermal performance, evaluating long-term behaviour, and reducing design risks for both cavern-based and shallow subsurface storage systems.
His contribution strengthened INTERSTORES’ visibility among the international simulation community and emphasized the project’s role in pioneering digital frameworks for sustainable heating solutions.
Visibility, Outreach, and Impact
With over 100 attendees in the UTES panel audience and more than 280 total conference participants, the event provided a significant platform for knowledge exchange and stakeholder engagement.
These contributions highlight INTERSTORES’ leadership in integrating advanced simulation methods into the design of safe, efficient, and replicable thermal energy storage technologies.
As Europe accelerates its transition to climate-neutral energy systems, multiphysics modelling is proving to be a key enabler for innovation, and INTERSTORES remains at the forefront of this transformation.
Paper 1
Design Optimization of World’s Largest Cavern Thermal Energy Storage (VARANTO)
The first paper, “Simulation-based design of world’s largest cavern thermal energy storage: Optimization of VARANTO,” write by:
- Abdulrahman Dahash (AIT),
- Fabrizia Giordano (AIT),
- Kimmo Korhonen (GTK),
- Sami Vallin (GTK),
- Kahti Ahlqvist (GTK) and
- Markku Hagström (GTK),
presents a comprehensive thermo-hydro-mechanical (THM) modelling workflow for the VARANTO CTES (Cavern Thermal Energy Storage) system, which is being realised in Vantaa, Finland.
Using COMSOL Multiphysics®, the team developed a thermo-hydraulic-mechanical (THM) model to simulate charging/discharging, stratification, heat losses, groundwater interactions, and rock stability, enabling optimized cavern geometry and layout.
As authors state in their publication, the approach using multiphysics modeling enabled the optimisation of cavern geometry and configuration, leading to the development of the improved VARANTO II design, which increased predicted storage efficiency from 63% to 67%, while ensuring long-term stability and safety.
This research offers a replicable framework for the next generation of large-scale cavern storage systems, directly supporting INTERSTORES’ mission to demonstrate and replicate TES solutions across Europe.
Repository links
Paper 2
Optimizing Heat Exchanger Design for Water-Gravel TES (incampus site)
The second paper, “Toward High Thermal-Hydraulic Performance of Heat Exchangers for Water-Gravel Thermal Energy Storage” written by:
- Abdulrahman Dahash (AIT),
- Fabrizia Giordano (AIT),
- Ahmed Serageldin (AIT),
- Emre Bas (PGM), and
- Rainer Strobel (PGM),
focuses on the incampus demo site in Ingolstadt, Germany, one of INTERSTORES’ key large-scale water‑gravel seasonal thermal energy storage (WGTES – Reno-sTES) demonstration sites.
Using COMSOL Multiphysics, the authors developed a coupled thermos-hydraulic model to evaluate and optimise heat exchanger layout, flow conditions, and thermal-to-hydraulic performance at the INTERSTORES incampus demo site.
As authors state in their conclusions, of all tested configurations, the single-sided Tichelmann design (H3) emerged as the most effective, striking the right balance between thermal output and hydraulic demand, therefore, its selection for the incampus storage system. The analyses also revealed how strongly insulation affects system performance, with EPS/XPS demonstrating the greatest ability to minimise heat losses and maximise usable energy capacity.
This research demonstrates how simulation supports real-world engineering decisions and helps optimise the performance of sTES systems before construction, saving both time and investment costs.
Repository links