Geothermal Alliance Bavaria 3.0 (GAB) 

Motivation

The Molasse Basin in Bavaria is the hotspot for geothermal utilization in Germany. For this reason, in 2016, three Bavarian universities, the Technical University of Munich (TUM), Friedrich-Alexander University Erlangen-Nuremberg (FAU) and the University of Bayreuth, joined forces under the umbrella of the Geothermal Alliance Bavaria (GAB) to consolidate research efforts and address open scientific questions in deep geothermal energy. Since 2020, Ludwig Maximilian University of Munich (LMU) and Munich University of Applied Sciences have also joined the alliance. In addition to excellent research, the joint project “Geothermal Alliance Bavaria” has created a platform for knowledge and data transfer between academia, industry and policymakers. The need for training qualified new professionals in the field of geothermal energy is met by the joint master’s program „GeoThermie/GeoEnergy“at FAU and TUM. The alliance’s holistic research approach has proven successful, enabling close cooperation between engineers and geoscientists and allowing work that transcends the boundaries of individual subdisciplines. 

At the beginning of 2025, the third funding phase of the Geothermal Alliance Bavaria started and will run until the end of 2028. In the current funding phase, the chair is primarily working on the further development of innovative technologies for electricity, heat and cold production from geothermal energy in the subproject “Plant Engineering and Flexible Operation,” and on increasing the flexibility potential of future geothermal energy systems in the subproject “System Optimization.”

Plant Engineering and Flexible Operation

Geothermal energy provides a nearly constant heat output throughout the year. However, flexible utilization concepts are required due to seasonal demand fluctuations. Within GAB, two central plant concepts are being investigated:

Reversible high-temperature heat pumps / Organic Rankine Cycle (ORC) 

• Investigation of dynamic operation in both directions: high-temperature heat pump and ORC.

• Measurement campaigns and high-fidelity component models to validate a dynamic simulation model (digital twin).

• Objectives: efficiency improvements (e.g., two-phase processes, working fluid and expander optimization, oil management) and near-real-time, data-driven control strategies (predictive control, reinforcement learning). 

Absorption Chiller

• Potential applications for supplying cooling from geothermal heat (particularly in summer).

• Conversion and flexible operating modes: chiller, heat pump or heat transformer.

• Objective: increase utilization rates, broaden the range of applications and replace peak-load boilers in winter months. Measurements and validated simulations are used to evaluate control strategies and plant engineering solutions.