geo:build

System optimization of geothermal heating and cooling supply for office buildings - reversible heat pumps and free cooling
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Near-surface geothermal energy and the possibility of using the ground as seasonal storage contribute to saving fossil fuels. To ensure that this can also be realized in the future, there is also a need for future research in the field of the interaction of heat input and extraction, the integration into the overall energy concept of the building and the hydraulic and control technology implementation, taking into account the local boundary conditions.

As part of the Geo:build research project, geothermal systems for heat and cold supply are to be analyzed in theory and practice. In addition to optimizing the implementation of geothermal heat and cold storage systems, the aim of the research project is to develop and test a more efficient use of these storage systems.

The research project is divided into six work packages. At the beginning of the project, the coordination and alternating operation between free cooling and chiller in cooling mode will be considered. This is followed by the development of energetically and economically sensible combinations of this technology. One focus of the work packages is the metrological recording of five office buildings with reversible heat pumps and free cooling as well as the analysis of their operating strategies and system functions. In addition, building and system simulations as well as simulations of heat input and extraction into the ground and its thermal behavior are carried out. The knowledge gained from the simulations will then be implemented and tested by means of test runs within a field trial.

Research objectives:
Further develop and evaluate optimized operating strategies and application-oriented storage concepts for expanding the degree of storage utilization, in particular with ground-coupled chillers and the change of operation between chiller and free cooling
Approaches to solutions for controlling and designing the systems with regard to:

Operating and control concepts that enable immediate switching between chiller operation and free cooling operation
Effects and possibilities of probe field splitting,
the regeneration phase between chiller operation and free cooling,
a constant temperature level in the ground as well as the practicable heat extraction and input, the available output to the building and the ratio between heat input and extraction
Furthermore, it should be clarified whether initial reliable estimates for the design can be made at an early planning stage on the basis of building designs (A/V ratio, orientation, thermal insulation standard, ...) and the planned use or operation of ground-coupled systems for heating and cooling.

Gelsenwasser AG
Gelsenwasser
Location: Gelsenkirchen, Germany

Owner: Gelsenwasser AG

Thermally utilized foundation form:
36 geothermal probes, each 150 m long
326 kW heating capacity (HP), 200 kW free cooling,
320 kW cooling capacity (KM)

VGH Regional Head Office Lüneburg
VGH
Location: Lüneburg, Germany

Owner: VGH Versicherungen Hannover

Thermally utilized foundation form:
101 energy piles, each 20 m long
82 kW heating capacity (HP), 80 kW free cooling,
89 kW cooling capacity (KM)
Freundlieb am See office building
Freundlieb am See
Location: Dortmund, Germany

Owner: Freundlieb Bauunternehmung GmbH&Co.KG

Thermally utilized foundation form:
12 geothermal probes, each 144 m long
87.6 kW heating capacity (HP), 60 kW free cooling,
68.4 kW cooling capacity (KM)

Lecture hall and seminar building
Lecture hall building
Location: Salzgitter, Germany

Owner: Braunschweig/Wolfenbüttel University of Applied Sciences

Termally used foundation form:
12 geothermal probes, each 95 m long
60 kW heating capacity (HP), 60 kW free cooling,
45 kW cooling capacity (KM)

• Cooperation partners Ostfalia University - Faculty of Supply Engineering, Wolfenbüttel UBeG GbR, Wetzlar Zent-Frenger GmbH, Heppenheim

• Federal Ministry for Economic Affairs and Energy (BMWi) FKZ:O3ET1024A