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Energy efficient and environmental friendly heat pumping system using CO2 as working fluid



The objective of this project is to develop design guidelines for a heat pumping system using the "natural" fluid CO2 as the working fluid. Due to the environmentally friendly behaviour, which is guaranteed by the refrigerant itself, safety aspects and energy efficiency will lead to widespread applications with either an unlimited heat source at constant temperature or a limited heat sink with a large temperature glide.
Technical Approach

The transcritical CO2-cycle, and the components needed to realize it, are different from common technology. Research and technology development work will be carried out to analyze the characteristics of the cycle and to develop new components. This development has to be concentrated on high-pressure equipment, especially compressors, expansion devices and heat exchangers. New control strategies will be developed and tested and special cycle dynamics will be investigated. Due to the high pressure required a detailed safety analysis must be carried out and implemented in the prototype design and construction. Results of theoretical and experimental investigations will be transferred into prototype heat pumps for several applications utilizing the trans-critical CO2-cycle:
hot water heat pumps for residential applications
commercial heat pumps for water heating and heat recovery
heat pumps for space heating for retrofitting existing high-temperature systems
heat pumps for dehumidification and drying processes in residential and commercial applications.

Expected Achievements and Exploitation

The project will provide reports and guidelines on CO2 heat pump characteristics (thermodynamic and transport properties, compressor design and operation, heat exchanger design, control of trans-critical CO2 system, cycle dynamics, design and testing of prototypes, safety and risk of CO2 systems), and a handbook for designing systems. The guidelines will be open to the European heat pumping equipment manufacturers and system planners.

These new heat pumps will lead to energy savings and to a reduction of the emission levels of greenhouse gases compared with usual heat generating systems based on fossil fuels. Advantages over existing heat pumps are that the working fluid CO2 is both safe (not flammable), environmentally benign (no 'ozone depletion potential' nor global warming potential in this application) and applicable even for high outlet temperatures without a significant loss in efficiency.

Call for proposal

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EU contribution
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3,Brahmsplatz 3
1041 WIEN

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Total cost
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Participants (5)