Contact

Dr. Sebastian Unger

Head Thermal Energy and Process Technology
s.ungerAthzdr.de
Phone: +49 351 260 3225

Supercritical CO2-power cycles for efficient heat utilization

With the transformation of energy systems taking place worldwide, the further development and expansion of dispatchable generation units and energy storage systems to maintain security of supply and system stability as well as heat supply must be driven forward. Due to the special properties of carbon dioxide above the critical point (31°C, 73.8 bar), there are advantages to using it in thermodynamic cycle processes. These cycle processes achieve higher efficiencies and a significant reduction in the size and complexity of the individual components. This enables the more efficient utilisation of industrial (waste heat), geothermal and solar heat sources as well as thermal energy storage systems. Heat sources that could not previously be utilised economically thus show potential for stable energy supply. However, there are a number of challenges and research requirements before commercialisation can be driven forward. For example, although turbomachines with supercritical CO2 (sCO2) are significantly more compact than water vapour turbines, the temperature remains at a high level and large amounts of heat must be recuperated internally using compact and cost-efficient heat exchangers. Furthermore, due to the high energy density, the aerodynamic optimisation of the turbomachinery is of particular importance. In addition, new types of improved sealing and bearing technologies must be developed or adapted. The high pressure load combined with high process temperatures places increased demands on the construction materials used, which must be qualified for this application. Finally, due to the originality of the sCO2 process, there is hardly any operating experience worldwide with regard to control and instrumentation in such plants.

Foto: Carbosola facility 2025-01 ©Copyright: Dr. Sebastian Unger

CARBOSOLA

Through the development, construction, and operation of this test facility, componen­ts will be tested, and generic experiments will be conducted to obtain data for the modeling and simulation of flows and heat transport in sCO₂.
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Foto: simulation heat exchanger channel ©Copyright: Dr. Sebastian Unger

Development of compact sCO₂ heat exchangers

Diffusion-welded heat exchangers (Printed Circuit Heat Exchanger-PCHE) are a compact solution for recuperators and coolers in the sCO₂ power circuit (hydraulic dia­meters of up to 1 mm) due to the ­very small channels and at the same time achieve an extremely high resistance for the prevailing high-pressure environment.
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Foto: CO2 storage power cycle ©Copyright: Dr. Sebastian Unger

Thermal storage as a heat source for sCO₂ processes

CO₂ based electrothermal energy and geological storage system is a “high-risk/high-reward” concept aiming to bring a high-efficient, cost-effective and scalable energy storage technology by making feasible the integration of transcritical CO₂ cycles with underground energy storage achieved through the simultaneous CO₂ storage and geothermal heat extraction.
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ESCO

The ESCO project aims to generate findings on sCO2 technology and validate them using the CARBOSOLA technology demonstrator. Individual novel components, such as the heat exchangers and the flow measurement technology, are being developed and analysed in the laboratory. Furthermore, suitable materials are validated under CO2 atmosphere and techno-economic analyses are carried out for different overall systems.
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