Shaping the future of flexible geothermal energy

Project Information

FlexGeo

Grant agreement ID: 101147576

DOI

10.3030/101147576

EC signature date 19 April 2024

Start date 1 June 2024

End date 31 May 2028

Funded under

• Climate, Energy and Mobility

Total cost

€ 5 662 113,75

EU contribution

€ 4 997 041,25

Coordinated by

TECHNISCHE UNIVERSITAET MUENCHEN
Germany

Periodic Reporting for period 1 - FlexGeo (Shaping the future of flexible geothermal energy)

Reporting period: 2024-06-01 to 2025-09-30

Summary of the context and overall objectives of the project

Geothermal energy can provide clean and reliable heat, cold and power throughout the year, yet today most systems operate in a steady and inflexible manner. This limits their contribution to modern energy systems, which require technologies that can react dynamically to changing conditions caused by fluctuating solar and wind energy. At the same time, many promising geothermal regions in Europe remain underused because existing solutions do not offer the flexibility, efficiency and/or economic performance that make an implementation feasible.

FlexGeo was created to address this gap. The project develops and demonstrates a new generation of geothermal energy systems and technologies. Core innovation is the reversible Organic Rankine Cycle technology, meaning one system that can operate as a power plant and high-temperature heat pumps. Depending on the energy systems' need, the plant can switch within very few minutes between power production and power consumption in heat pump mode. Furthermore, advanced geothermal technologies, such as 5GDHC systems and underground thermal storage are assessed and combined with advanced digital control. The goal is to enable geothermal systems to reach a new level of flexibility.

The project objectives reflect this ambition. FlexGeo designs and tests a reversible ORC demonstrator at a TRL7 scale. Furthermore, it develops detailed open source models for geothermal heat pumps, storage systems, district heating networks and advanced closed loop geothermal concepts. It integrates these models into a comprehensive simulation framework to identify optimal system designs and operational strategies for different European settings. It further carries out techno-economic and environmental assessments to quantify costs, benefits, and potential improvements across the full system.

A central part of the project pathway is the active involvement of stakeholders. Through the FlexGeo Observer Board, industry representatives, planners, regulators and research experts contribute practical insights and review early project outputs. This ensures that the developed solutions respond to actual market needs and can be replicated under different regulatory and geological conditions. In summary, the project aims to show that geothermal systems can move from mostly static operation toward a highly flexible and cost-effective role in heating and power supply. By validating key technical innovations and by providing openly accessible models and data, FlexGeo supports future investments, reduces planning risks and promotes wider use of geothermal resources across Europe.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

During the first reporting period FlexGeo sucessfully worked on all scientific and technical work packages and established a solid basis for the development and demonstration of flexible geothermal systems. Although a few tasks experienced minor delays, all milestones and deliverables scheduled for RP1 were ultimately achieved.

In WP2, the two reversible ORC test rigs at TUM and ULiège were completed, commissioned and successfully operated, generating an extensive dataset for heat pump and ORC mode. These data enabled the validation of detailed component models and the development of fast surrogate models that significantly accelerate system optimisation workflows. The experimental findings fed directly into the ongoing detailed engineering of the 200 kWel demonstrator, where WP5 completed the initial integration concept and prepared the ground for component procurement and installation. WP3 delivered the first systematic analysis of technical requirements for providing grid reserve power with geothermal technologies across several countries. Flexibility envelopes for reversible ORC units, district heating networks and storage solutions were derived, forming an essential input for upcoming control strategy development. Parallel to this, first versions of dynamic 4GDHC and 5GDHC network models and an expanding digital twin of the TUM test rig were created, laying the foundation for advanced control tasks in the next reporting period. In WP4, major progress was made on modelling flexible geothermal energy systems. Detailed component models for UTES, district heating networks, and advanced closed-loop systems were developed and validated. ETH and TUW completed a first integrated modelling framework capable of simulating geothermal configurations under realistic operational and market constraints. A comprehensive list of innovative system concepts was compiled and pre-assessed, laying the groundwork for subsequent optimization activities.

WP6 initiated the techno-economic and environmental evaluation of the FlexGeo concepts. A harmonised data structure was created to ensure consistency across CAPEX, OPEX and life cycle inventory inputs. Partner data collection has begun, and the framework is now ready for the first KPI calculations once finalised scenarios become available.Finally WP7 completed a comprehensive regulatory and market analysis across five European countries. This work delivered essential insights into technical requirements, policy conditions and market barriers, which will guide system design, modelling scenarios and later exploitation activities. Taken together these achievements demonstrate that FlexGeo has completed all required scientific and technical groundwork for RP1. The project is now well positioned to enter the next phase, which will focus on detailed optimisation, advanced control development, and the construction and testing of the full-scale demonstrator.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Although most final results will be achieved in later reporting periods, FlexGeo has already delivered several advances that go beyond current practice in geothermal energy systems. The project completed the first reversible ORC prototypes specifically designed for flexible geothermal applications, generating new insights into dual-mode operation under realistic temperature and load conditions. FlexGeo also developed several advanced open modelling tools for geothermal components, district heating networks and high-temperature storage, together with the first structured scenario framework that links these tools to real-world flexibility requirements. The regulatory and market analysis provides a consolidated view of the conditions under which flexible geothermal solutions can be deployed across Europe.

These early achievements confirm that the project is on a good track. To ensure full uptake of the final innovations, continued experimental validation, demonstration at a meaningful scale, refined control strategies, and supportive market and regulatory frameworks will remain essential. The forthcoming work on the 200 kWel demonstrator and the integrated techno-economic and environmental assessments will be key steps toward preparing for future market introduction.