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© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
OCHSNER Borehole heat exchangers with CO2
Dr. Gerald Lutz
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Contents:
Benefit of using CO2 as heat transfer medium
Functionality of a CO2 - tube
Installation example of a CO2-tube
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Classification of renewable energy sources
Quelle: EHPA (European Heat Pump Association) classification of ambient heat
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Different variants for the energetic use of ambient heat from the ground
Quelle: Ehrbar, M. ;Peterlunger, A.: Pumpenlose Erdwärmesonde: Schlussbericht Potenzialabschätzung, Machbarkeitsstudie energetisch und wirtschaftlich, Interstaatliche Hochschule für Technik Buchs, (o.J.) Buchs, S.8f.
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
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Quelle: Ehrbar, M. ;Peterlunger, A.: Pumpenlose Erdwärmesonde: Schlussbericht Potenzialabschätzung, Machbarkeitsstudie energetisch und wirtschaftlich, Interstaatliche Hochschule für Technik Buchs, (o.J.) Buchs, S.8f.
Heating of air by leading it through a gravel zone
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Different variants for the energetic use of ambient heat from the ground
Quelle: Ehrbar, M. ;Peterlunger, A.: Pumpenlose Erdwärmesonde: Schlussbericht Potenzialabschätzung, Machbarkeitsstudie energetisch und wirtschaftlich, Interstaatliche Hochschule für Technik Buchs, (o.J.) Buchs, S.8f.
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
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Quelle: Ochsner
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.
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Different variants for the energetic use of ambient heat from the ground
Quelle: Ehrbar, M. ;Peterlunger, A.: Pumpenlose Erdwärmesonde: Schlussbericht Potenzialabschätzung, Machbarkeitsstudie energetisch und wirtschaftlich, Interstaatliche Hochschule für Technik Buchs, (o.J.) Buchs, S.8f.
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
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Quelle: Ochsner
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
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Different variants for the energetic use of ambient heat from the ground
Quelle: Ehrbar, M. ;Peterlunger, A.: Pumpenlose Erdwärmesonde: Schlussbericht Potenzialabschätzung, Machbarkeitsstudie energetisch und wirtschaftlich, Interstaatliche Hochschule für Technik Buchs, (o.J.) Buchs, S.8f.
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
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Quelle: Ochsner
Glykol- and water- heat pipes
The brine circulates in earth taps around 100 m deep
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Different variants for the energetic use of ambient heat from the ground
Quelle: Ehrbar, M. ;Peterlunger, A.: Pumpenlose Erdwärmesonde: Schlussbericht Potenzialabschätzung, Machbarkeitsstudie energetisch und wirtschaftlich, Interstaatliche Hochschule für Technik Buchs, (o.J.) Buchs, S.8f.
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
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
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
Benefit of using CO2-tubes
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Disadvantages of conventional working fluids(Prophylen,- oder Ethylenglykol)
Very exact definition of the glykol concentration
missing addition of inhibitors is resulting in corrosions
Benefit of using CO2-tubes
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
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
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Transcritical CO2-process (Lorentzen Prozess)
Rieberer, R; Halozan,H.: CO2 als Kältemittel, Institut für Wärmetechnik TU-Graz (2004)
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Comparison of CO2 with other refrigerants
Refrigerant ODP GWP Critical temperature[°C]
criticalpressure [bar]
R744 (CO2) 0 1 31,1 73,8
R134a 0 1300 101 40,7
R407C 0 1525 86,7 46
R410a 0 1725 72,1 49,2
Potential to ozon layer destruction and greenhouse effect
Critical temperature and critical pressure
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Functionality of CO2- tube
Prinzip des Wärmerohres (Vgl.Ochsner)
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
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
CO2-tube coupled with as direct expansion heat pump
Kältekreis einer Direkterwärmungs- Wärmepumpe gekoppelt mit einer CO2-Sonde. Ochsner Wärmepumpen GmbH
Refrigerant circulates in the cooling head and evaporates there
highest performance
largest working reliability
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Single tube system/ double tube system
Einrohrsonde/Zweirohrsonde. Vgl. Ehrbar, M.)
Danger of interruption
liquid und CO2-steam
If diameter is to large
Separation of liquid and gas phase
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
CO2-tube high-grade steel pipe: Maximum capacity and length – dependency on tube dimension
FKW Hannover Prof.H. Kruse
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
4,5
5,0
6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40Rohrinnendurchmesser [mm]
Th
eore
tis
che
ma
x. E
ntz
ug
slei
stu
ng
[kW
]
0
10
20
30
40
50
60
70
80
90
100
Fil
mlä
ng
e [m
]
1 Rohr
2 Rohre4 Rohre
8 Rohre
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Quelle: Objektdaten und Anlagenart des Installations-Beispiels
Installation-example: object data
Objektdaten
Heated area 160 m²
Construction method
Low energy house
Heat demand ~ 33 W/m²
Number of persons 3
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Quelle: Objektdaten und Anlagenart des Installations-Beispiels
Heating system
Heat pump OCHSNER Golf GMDW 7
Heating capacity(E0/W35)
6,4 kW
Heat source Ground source direct expansion, 1 CO2-tube
Heating mode monovalent
Distribution system Floor – and wall heating system
Flow temperature max. 35°
hydr. decoupling 300 Liter buffer vessel
Hot water supply OCHSNER Europa 303
heating system
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Drilling
Quelle: Errichtung einer Bohrung für die Einbringung einer CO2-Wellrohrsonde (Ochsner GmbH)
borehole with depth of 100 m
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Tube
Quelle: CO2-high-grade steel pipe (Ochsner GmbH)
100 m
ambient heat 15 C
developing pressure 50 bar
pressure resistant, flexible high-grade
steel pipe
CO2 diffuses by conv. PE tubes
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
CO2-tube – installation tunnel
Quelle: Ochsner
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Bringing in of the tube
Quelle: Einbringung der CO2-Wellrohrsonde (Ochsner GmbH)
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Connection of the CO2-tube
Quelle: CO2-Erdwärmesonde (Ochsner GmbH)
Distance CO2-tube – heat
pump not more than 25 meters.
Refrigerant leading pipes and cooling head have to be isolated
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Seasonal Performance Figure
Quelle: Monthly performance figure and seasonal performance for heating season 2006/2007 (Ochsner GmbH)
4,8
4,13,9 3,9 4 3,9 4,1 4,1
0
0,5
1
1,5
2
2,5
3
3,5
4
4,5
5
Performance Figures
Oct. 06 Nov. 06 Dec. 06 Jan. 07 Feb. 07 Mar. 07 Apr. 07 SPF
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
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
Advantages of the CO2-tube
© Dr. Gerald Lutz The Geothermal Heat Pumps market in Central & Eastern Europe Bratislava, 12. Nov. 2007
OCHSNER Borehole heat exchangers with CO2
Thank you for your interest!