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Our Center for Energy located in Vienna invites applications for a PhD Thesis position. At the Center for Energy, we develop sustainable solutions for the energy system of the future, taking into account technological, regulatory and economic requirements. Our portfolio of topics focuses on three key systems: cities and the built environment, public energy supply systems, and industrial energy systems.

The PhD project focuses on the development and experimental validation of underground thermal energy storage systems for medium-temperature applications (80–110°C). Among thermal energy storage (TES) technologies, underground thermal energy storage (UTES) systems are of particular interest due to their high storage capacity, low-footprint, and long-term heat storage potential. However, existing UTES solutions are predominantly water-based, for e.g. pit thermal energy storage (PTES),and face temperature, safety, and land-use limitations. To overcome these challenges, this PhD explores a novel concept of underground solid media thermal energy storage to enable higher operating temperatures, improved land-use efficiency, and reduced environmental impact.

• You will carry out laboratory-scale tests to examine the thermo-physical behavior of storage media under controlled charging and discharging cycles.
• You will contribute to the design, construction, and operation of an upscaled SMTES prototype (20-foot container scale) to investigate realistic thermal behavior, temperature stratification, and system dynamics.
• You will evaluate the storage envelope and insulation performance (e.g. glass foam aggregate) from a building-physics perspective, focusing on heat losses, moisture migration, and mechanical stability.
• You will support data acquisition and sensor setup for temperature profiling, model calibration and validation.
• You will apply multi-physical numerical modeling to develop 3D coupled thermo-hydraulic-(mechanical) models and perform system-level simulations to analyse heat and moisture transport within the of the SMTES system and assess its performance under different boundary conditions.

• You will use experimental results to validate models and create a digital twin for real-time operational optimisation.
• Based on your findings, you will establish a design and optimisation framework, including dimensioning and layout principles and correlations between material properties, geometry and operational parameters.
• You will conduct technical performance and environmental analyses, including energy density, thermal efficiency, response time and materials reuse aspects in cooperation with project partners.
• Last but not least, you will evaluate the storage concept and integrate validated models into system-level optimisation, such as coupling with heat pumps or district heating networks.
• You will engage in scientific planning, will publish your findings in international journals and present them at conferences.