Push-It gathers at Bochum for General Assembly
Last week, the Push-IT consortium came together for 2.5 energising and inspiring days at the Fraunhofer Institute in Bochum, Germany. It was fantastic to reconnect face-to-face with partners from across Europe and realign around our shared mission of driving innovation and impact. A highlight of the General Assembly was the interactive poster sessions — a welcome new format that sparked great conversations and deeper understanding across work packages. Each site had a presentation together with all the technologies of Work Package 3 and Tessel Grubben.
Site updates
Darmstadt (Germany): BTES + DHN Integration
Project Goals:
The Darmstadt initiative is piloting the connection of three boreholes for seasonal thermal storage, with a focus on charging during summer and discharging in winter. Additional aims include evaluating performance, testing a novel PE pipe-based construction method, and calibrating a site-specific co-simulation model.
Status:
- Detailed design and tenders for the hydraulic container and connection lines are complete.
- Heat pump tender is ongoing.
Next Steps:
- Installation of the hydraulic container and connection line.
- Begin thermal cycling operations.
- Evaluate overall system performance.
Challenges:
- Potential delays due to supply chain and personnel shortages.
- Risk of delayed heat pump delivery affecting schedules.
Bochum (Germany): Mine Thermal Storage (MTES) at RUB
Project goals:
Bochum explores using a flooded colliery beneath Ruhr University Bochum (RUB) to store waste heat from refrigeration processes. The system aims to balance seasonal heating and cooling demands via co-simulation with RUB’s thermal grid.
Progress:
- Drilling into the flooded mine began in September 2024.
- Development of an integrated co-simulation model is in progress.
Next steps:
- Conduct tracer tests to assess hydrodynamic behavior.
- Launch educational outreach efforts, including geothermal trail signage and a children’s book on thermal energy.
Berlin (Germany): HT-ATES in Adlershof
Project goals:
This urban project aims to store 30 GWh of excess heat from a wood-fired plant using a high-temperature aquifer system. A sidetrack well has been developed for the Hot Push-Pull Test (HPPT) and detailed subsurface characterization.
Status:
- Sidetrack well completed in September 2024.
- High salinity (39 g/L) and nitrogen concentration observed.
- Risk identified for carbonate scaling under elevated temperatures.
Next Steps:
- Field installation of HPPT equipment (scheduled June 23, 2025).
- Microbiological and chemical analyses (by BRGM).
- Stakeholder engagement and authority consultations (by BGS).
- Possible sensor-integrated pump testing.
United Downs (UK): MTES Feasibility in Cornwall
Project goals:
This feasibility study evaluates using historic mine shafts near a geothermal plant for high-temperature MTES. The work includes numerical modeling, regulatory assessments, and community engagement.
Progress:
- Great Consolidated Mines site selected over United Mines.
- Modeling has focused on upper shaft zones due to limited data on deeper workings.
- Subsurface models are under development, with early regulatory dialogue initiated.
Challenges:
- GPS and data limitations affecting hydrological modeling.
- Shaft obstructions impede deeper cross-flow assessments.
Delft (Netherlands): HT-ATES with Advanced Monitoring
Project goals:
Located on the TU Delft campus, this project combines high-temperature ATES with innovative drilling, casing, and real-time monitoring technologies. It will support TU Delft’s district heating network.
Monitoring Innovations:
- Fiber-optic sensors for DTS, DSS, and DAS.
- Active heating loop to calibrate thermal measurements.
- Monitoring of microbial and geochemical dynamics.
Status:
- System concept finalized; design underway.
- Procurement of long-lead equipment in progress.
Challenges:
- Delays in Water Permit (WPC) processing.
- Technical risks associated with deep drilling and integration.
Next Milestone:
- HPPT to begin in early 2026, testing ambient, 45°C, and 80°C injection cycles.
Litoměřice (Czechia): BTES
Project Goals:
The goal is to store heat from diverse surface energy sources — such as solar thermal panels, photovoltaics, and waste heat from a hydrogen electrolyser — in the subsurface down to approximately 500 metres. In the long term, this stored heat will be used to supply the district heating system of the town of Litoměřice.
Status:
- Drilling of the hydrogeological monitoring wells finished
- Both wells were logged to analyze their structure and verticality, with final reports on the logging results expected soon.
Next Steps:
- Aquifer evaluation through pumping tests, resistivity surveys, and groundwater sampling
- Thermo-hydraulic testing on rock core samples
- Data processing and interpretation to support future design decisions
Work Package 3 updates
Co-Simulation: Cross-Site Digital Twin Development
Objective:
To bridge UTES systems (BTES, ATES, MTES) with DHNs through dynamic co-simulation environments that support controller testing, optimization, and scenario planning.
Progress:
- Thermo-hydraulic models implemented in Modelica.
- Subsurface models completed in FEFLOW and SPRING.
- Functional interfaces in place for model integration.
Next Phases:
- Optimize smart controller behavior.
- Launch virtual site environments.
- Develop surrogate models for faster MTES simulations.
Future Vision:
- A reusable co-simulation library and flexible digital twins that can be deployed across new locations.
HPPT (Hot Push-Pull Test): A Shared Methodology
Objective:
The HPPT method injects hot water into a well and extracts it later to analyze hydraulic, thermal, microbial, and geochemical responses of subsurface formations.
Focus Areas:
- Hydraulic: Transmissivity, dispersivity, groundwater velocity.
- Thermal: Heat retention and recovery efficiency.
- Microbiological: Population shifts, biofilm risk.
- Geochemical: Mineral precipitation, potential contamination.
Site Updates:
- Berlin: Sidetrack and test prep complete; testing begins June 2025.
- Delft: Long-term, multi-temperature HPPT cycles planned for early 2026.
First Mine water samples have been taken and analyzed in 2025.
Water Quality
Objective:
Investigate common pitfalls related to water chemistry and microbial activity. We provide recommendations to anticipate and deal with water quality issues for future sites.
Progress:
- Developing and establishing monitoring systems
- In Bochum several tests have been performed, results have still to be analyzed
Smart District Heating Controller
Objective:
Implement Model-Based Predictive Control (MPC) for managing heating and cooling in smart district heating systems. The controller uses a model of the system to:
- Optimize charging/discharging of seasonal thermal storage systems
- Schedule heating/cooling sources efficiently
- Maximize output from geothermal wells
- Minimize peak energy demand (reduce reliance on expensive/polluting peak boilers)
- Lower supply and return temperatures for improved energy efficiency
- Ensure thermal comfort for users
The approach uses a receding horizon control strategy: only the first optimal action from a limited future horizon is applied, then recalculated in the next time step.
Status:
The smart controller will be tested in both virtual and real-world demonstrations at the sites of Delft, Bochum and Darmstadt. At the moment we are defining the scope of the controllers for each of the three demo sites. Next to that, the virtual demonstrators are under development.
Challenges:
- Seasonal Storage Dynamics: PUSH-IT systems store energy from summer to winter, requiring longer prediction horizons than typical MPC setups.
- Measurements & Predictions: Accurate state estimation (e.g., state of charge) is difficult, especially in large, underground storage systems.
Research update
Tessel Grubben (Netherlands): Borehole Stability Study
Challenge Addressed:
How can stable, enlarged boreholes be reliably constructed in unconsolidated sandy formations for deep groundwater access?
Study Insights:
- Stability is linked to increased shear strength from dilation during unloading.
- Experimental data fit using a Modified Cam Clay model.
- FEM simulations support findings.
Next Steps:
- Use Discrete Element Method (DEM) to simulate borehole collapse mechanisms.
- Apply insights to improve performance and reduce costs of Expanded Diameter Gravel Wells (EDGW).
We are very happy with the progress that has been made and the succes of the General Assembly. In the coming weeks, extended updates from the sites will be uploaded to our website, so keep an eye out for that!
PUSH-IT is a project funded by the European Union’s Horizon Europe research and innovation programme under grant agreement No 101096566.
Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union. Neither the European Union nor the granting authority can be held responsible for them.
