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OCHSNER Borehole heat exchangers with CO 2 Dr. Gerald Lutz

OCHSNER Borehole heat exchangers with CO 2 Dr. Gerald Lutz. Contents:. Benefit of using CO 2 as heat transfer medium Functionality of a CO 2 - tube Installation example of a CO 2 -tube. Classification of renewable energy sources.

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OCHSNER Borehole heat exchangers with CO 2 Dr. Gerald Lutz

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  1. OCHSNER Borehole heat exchangers with CO2 Dr. Gerald Lutz

  2. Contents: • Benefit of using CO2 as heat transfer medium • Functionality of a CO2 - tube • Installation example of a CO2-tube

  3. Classification of renewable energy sources Quelle:EHPA (European Heat Pump Association) classification of ambient heat

  4. Different variants for the energetic use of ambient heat from the ground • Heating of air by leading it through a gravel zone • Groundwater as a heat source • Direct expansion/flat collectors • Glykol- and water- heat pipes • Heat pipes without circulation pumps Quelle: Ehrbar, M. ;Peterlunger, A.: Pumpenlose Erdwärmesonde: Schlussbericht Potenzialabschätzung, Machbarkeitsstudie energetisch und wirtschaftlich, Interstaatliche Hochschule für Technik Buchs, (o.J.) Buchs, S.8f.

  5. Heating of air by leading it through a gravel zone Quelle: Ehrbar, M. ;Peterlunger, A.: Pumpenlose Erdwärmesonde: Schlussbericht Potenzialabschätzung, Machbarkeitsstudie energetisch und wirtschaftlich, Interstaatliche Hochschule für Technik Buchs, (o.J.) Buchs, S.8f.

  6. Different variants for the energetic use of ambient heat from the ground • Heating of air by leading it through a gravel zone • Groundwater as a heat source • Direct expansion/flat collectors • Glykol- and water- heat pipes • Heat pipes without circulation pumps Quelle: Ehrbar, M. ;Peterlunger, A.: Pumpenlose Erdwärmesonde: Schlussbericht Potenzialabschätzung, Machbarkeitsstudie energetisch und wirtschaftlich, Interstaatliche Hochschule für Technik Buchs, (o.J.) Buchs, S.8f.

  7. Groundwater as a heat source • highest COP. • A constant temperature from + 8 °C to + 12 °C • The groundwater is pumped from the delivery well to the heat pump and from there 15 meters to the sink well. Quelle: Ochsner

  8. Different variants for the energetic use of ambient heat from the ground • Heating of air by leading it through a gravel zone • Groundwater as a heat source • Direct expansion/flat collectors • Glykol- and water- heat pipes • Heat pipes without circulation pumps Quelle: Ehrbar, M. ;Peterlunger, A.: Pumpenlose Erdwärmesonde: Schlussbericht Potenzialabschätzung, Machbarkeitsstudie energetisch und wirtschaftlich, Interstaatliche Hochschule für Technik Buchs, (o.J.) Buchs, S.8f.

  9. Direct expansion/flat collectors • refrigerant cycle of the heat pump is used directly • no heat exchangers from brine to R 407C needed • Also no brine cirulating pump is needed • With the brine system the brine circulates • in horizontal collector tubes, or • in trenches Quelle: Ochsner

  10. Different variants for the energetic use of ambient heat from the ground • Heating of air by leading it through a gravel zone • Groundwater as a heat source • Direct expansion/flat collectors • Glykol- and water- heat pipes • Heat pipes without circulation pumps Quelle: Ehrbar, M. ;Peterlunger, A.: Pumpenlose Erdwärmesonde: Schlussbericht Potenzialabschätzung, Machbarkeitsstudie energetisch und wirtschaftlich, Interstaatliche Hochschule für Technik Buchs, (o.J.) Buchs, S.8f.

  11. Glykol- and water- heat pipes • The brine circulates in earth taps around 100 m deep Quelle: Ochsner

  12. Different variants for the energetic use of ambient heat from the ground • Heating of air by leading it through a gravel zone • Groundwater as a heat source • Direct expansion/flat collectors • Glykol- and water- heat pipes • Heat pipes without circulation pumps using CO2 Quelle: Ehrbar, M. ;Peterlunger, A.: Pumpenlose Erdwärmesonde: Schlussbericht Potenzialabschätzung, Machbarkeitsstudie energetisch und wirtschaftlich, Interstaatliche Hochschule für Technik Buchs, (o.J.) Buchs, S.8f.

  13. Benefit of using CO2-tubes Benefit of CO2 as a heat transfer medium • CO2 is non-toxic • not flammable • Greenhouse relevance is neclectable (compared to other refrigerants !) (GWP=1) • Ozon deplating potential (ODP=0) • not water endangering • cheap • no special regulations for its disposal

  14. Benefit of using CO2-tubes Disadvantages of conventional working fluids (Prophylen,- oder Ethylenglykol) • Very exact definition of the glykol concentration • missing addition of inhibitors is resulting in corrosions

  15. Thermodynamic characteristics of CO2- subcritical and transcritical cyclic process • high volumetric cooling capacity (6 – 8 times higher as f.e. R407C, R717) small volumetric flow rates smaller pressure losses smaller tube profiles • low critical temperature 31,1°C, and a high critical pressure 73,8 bar. • Difficult to use within the refrigerant cycle because of flow temp. of >35˚C. • Changing of steam pressure with 1 bar/K. • Pressure of more than 100 bar with flow-temp. of >30˚C

  16. Transcritical CO2-process (Lorentzen Prozess) Rieberer, R; Halozan,H.:CO2 als Kältemittel, Institut für Wärmetechnik TU-Graz (2004)

  17. Comparison of CO2 with other refrigerants • Potential to ozon layer destruction and greenhouse effect • Critical temperature and critical pressure

  18. Functionality of CO2- tube • Principle of a heat pipe: • heat pipe transports warmth between heat source and a heat consumer • heat transfer medium is CO2) • The heat transfer medium takes up heat energy – ascends as steam inside the pipe (Thermosyphonprinzip) • delivers the energy in the heat exchanger • condensation of CO2 • CO2 descends Prinzip des Wärmerohres (Vgl.Ochsner)

  19. CO2-tube coupled with as direct expansion heat pump • Refrigerant circulates in the cooling head and evaporates there • highest performance • largest working reliability Kältekreis einer Direkterwärmungs- Wärmepumpe gekoppelt mit einer CO2-Sonde. Ochsner Wärmepumpen GmbH

  20. Single tube system/ double tube system Danger of interruption liquid  und CO2-steam  If diameter is to large Separation of liquid and gas phase Einrohrsonde/Zweirohrsonde. Vgl. Ehrbar, M.)

  21. CO2-tube high-grade steel pipe: Maximum capacity and length – dependency on tube dimension FKW Hannover Prof.H. Kruse

  22. Installation-example: object data Quelle: Objektdaten und Anlagenart des Installations-Beispiels

  23. heating system Quelle: Objektdaten und Anlagenart des Installations-Beispiels

  24. Drilling • borehole with depth of 100 m Quelle: Errichtung einer Bohrung für die Einbringung einer CO2-Wellrohrsonde (Ochsner GmbH)

  25. Tube • 100 m • ambient heat 15 C • developing pressure 50 bar • pressure resistant, flexible high-grade steel pipe • CO2 diffuses by conv. PE tubes Quelle: CO2-high-grade steel pipe (Ochsner GmbH)

  26. CO2-tube – installation tunnel Quelle: Ochsner

  27. Bringing in of the tube Quelle: Einbringung derCO2-Wellrohrsonde (Ochsner GmbH)

  28. Connection of the CO2-tube Distance CO2-tube – heat pump not more than 25 meters. Refrigerant leading pipes and cooling head have to be isolated Quelle: CO2-Erdwärmesonde (Ochsner GmbH)

  29. Seasonal Performance Figure Quelle: Monthly performance figure and seasonal performance for heating season 2006/2007 (Ochsner GmbH)

  30. Advantages of the CO2-tube • Advantages of CO2-as a heat transfer medium • no circulating pumps: higher SPF than conventional earth tubes (conventional pumps have a running capacity of 200 W with SFH ~ 360 kWh 15-20% higher JAZ) • environmental friendlyness: lower CO2-emissions because of higher working reliability by closed cycle without mobile parts • lower investment costs

  31. Thank you for your interest!

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