OCHSNER CO 2 heat pipes an option for vertical collectors Karl Ochsner Dipl.-Ing. ETH
Content: Benefit of using CO 2 as heat transfer medium Function of a CO 2 heat pipe Exemplary installation of a ground source Heat Pump with CO 2 -heat pipe Classification of Renewable Energy Sources Heat Pumps a Renewable Energy Technology Heat Pump Development in Austria The various Heat Sources
Classification of Renewable Energy Sources Source: EHPA (European Heat Pump Association) classification of ambient heat
Different alternatives for the energetic use of ambient heat Air as a heat source Groundwater as a heat source Ground with Direct Expansion and horizontal collectors Ground source with convenional collectors (wth antifreeze) Ground source with Heat Pipes
Air as heat source Air is led through the evaporator - thereby warmth is withdrawn Compact air/water heat pumps include evaporator and all other components Split-air/water HPs : Evaporator is located outdoors Ochsner Type GMLW heat pump COP A2 / W 35 =4 SPF 3 to 3,5 Souce: Ochsner
Groundwater as a heat source Highest COP A constant temperature from normally + 8 C to + 12 C Groundwater is pumped from the supply well to the heat pump and from there 15 meters to the return well. Souce: Ochsner
Types of ground source systems With Direct expansion system refrigerant circulates and evaporates in coll.pipes no heat exchanger with heat source needed no brine circulating pump is needed Souce: Ochsner With the brine system brine circulates in horizontal collector pipes in parallel or in spiral form in trenches or in vertical collectors
A special alternative: CO 2 heat pipes Heat Source - ground Compressed HPcycle Heating Circulation System self circulating CO 2 -heat pipe Source: Ochsner
Market development heat pumps Austria 2007 Market growth 15 % units 16.000 14.000 12.000 10.000 8.000 6.000 4.000 2.000 0 4.885 5.710 5.880 7.048 8.064 9.900 12.957 swimmingpool dehumidification 90 120 100 113 96 105 79 93 air conditioning heat recovery 80 120 160 221 258 349 421 213 14.968 2000 2001 2002 2003 2004 2005 2006 2007 heating 2.025 2.660 3.200 3.953 4.748 6.193 8.515 10.398 hot water 2.690 2.810 2.420 2.761 2.962 3.253 3.942 4.264 Souce: Faninger, BWP
Installed heat pumps (only heating) Austria 2000-2007 Market growth 22 % 12.000 10.398 10.000 8.515 + 22% units heating only 8.000 6.000 4.000 2.025 2.660 3.200 3.953 4.748 6.193 2.000 0 2000 2001 2002 2003 2004 2005 2006 2007 Souce: Faninger, BWP
Heat pumps: a renewable energy technology i.g. renewable share in Austria Heat Pump SPF: 4 share of renewable electricity: 70% ->total share of renewable: 92,5 %
Benefit of using CO 2 -heat pipes Benefit of CO 2 as a heat transfer medium: CO 2 is chemically neutral not flammable inexpensive no special regulations for its disposal applicable also in water protection area
Benefit of using CO 2 -tubes Evoiding disadvantages of conventional antifreeze ( brine ) (Prophylen,- or Ethylenglycol e.g.): Brine circulating pump needed (power,wear, mixing) Precise definition of flow rate / velocity to ensure turbulent flow Avoiding addition of inhibitors might result in corrosions Precise definition of the concentration necessary
Function of CO 2 - heat pipe Principle of a heat pipe: Heat pipe transports warmth from heat source to heat pump Heat transfer medium is CO 2 The heat transfer medium collects heat energy by evaporating and delivers heat when condensing (Thermosyphon principle) Delivers the heat into the heat exchanger of the Heat Pump (evaporator) while condensing Source: Ochsner, Principle of a heat pipe CO 2 descends as liquid
CO 2 -heat pipe coupled with as direct expansion heat pump System Heat Exchanger acts as evaporator for Heat Pump compression cycle and as condenser for Heat Pipe High system COP / SPF as no brine circulating pump required Compression refrigerant cycle: direct expansion/co 2 -heat pipe Source: Ochsner
Heat Pipe with CO 2 : Maximum heat capacity and length in function of diameter at 50 W/m 5,0 4,5 8 Rohre 8 tubes 100 90 Max. theoretical heat flow [kw] Theoretische max. Entzugsleistung [kw] 4,0 3,5 3,0 2,5 2,0 1,5 1,0 44 Rohre tubes 22 Rohre tubes 11 Rohr tube 80 70 60 50 40 30 20 Liquid CO 2 film lenght [m] Filmlänge [m] 0,5 10 0,0 0 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 Rohrinnendurchmesser [mm] Tube inside-diameter [mm] Source: FKW Hannover Prof.H. Kruse
Installation- example: object data Object data Heated area Construction design Heat demand Number of persons 160 m² Low energy house ~ 33 W/m² 3 Family house Gaffal, Upper Austria Object data and type of heating system Source: Ochsner
Heating system Heat pump Heating capacity (E0/W35) Heat source Heating mode Distribution system Flow temperature hydr. decoupling Hot water supply Heating system OCHSNER Golf GMDW 7 6.4 kw Ground source direct expansion, 1 CO 2 -tube monovalent Floor and wall heating system max. 35 300 Litre buffer tank OCHSNER Europa 303 Object data and type of heating system Source: Ochsner
Drilling borehole with depth of 100 m Source: Drilling of the borehole (Ochsner GmbH)
Heat Pipe Tube 100 m length CO2 pressure at 15 C: 50 bar flexible high-grade steel pipe Source: CO 2 -high-grade steel pipe (Ochsner GmbH)
CO 2 -Heat Pipe installation vault Source: Ochsner
Insertion of the tube Source: Insertion of the CO 2 -tube (Ochsner GmbH)
Connection of the CO 2 -tube to Heat Pump Cycle Distance CO 2 -tube heat pump not more than 25 meters. Refrigerant containing pipes to be insolated Source: (Ochsner GmbH)
Seasonal Performance Figure 5 4,5 4 3,5 4,8 4,1 3,9 3,9 4 3,9 4,1 4,1 Performance Figures 3 2,5 2 1,5 1 0,5 0 Oct. 06 Nov. 06 Dec. 06 Jan. 07 Feb. 07 Mar. 07 Apr. 07 SPF Source: Monthly performance figure and seasonal performance for heating season 2006/2007 (Ochsner GmbH)
Advantages of the CO 2 -Heat Pipe No brine circulating pump: higher SPF than conventional earth taps (conventional pumps for this typical size installation have a power requirement of approx. 200 W x 1800 h 360 kwh results in approx. 10 % difference in SPF) Environmental friendliness and versatile use: Permissible at all locations including water protection area
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