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XV EUROPEAN CONFERENCE MILANO 7th-8thJUNE 2013 CSGLatest Technology in Refrigeration and Air ConditioningUnder the Auspices of the PRESIDENCY OF THE COUNCIL OF MINISTERSOptimization of combined heating andcooling in SupermarketsTorben Funder-KristensenHead of Public Industry AffairsTFK@danfoss.com
Content Introduction Balancing demands The heat recovery concept Why CO2 ? CO2 compared to R404A The Case of Heat RecoveryHeat balanceCOSP and COPTEWICOST ConclusionSubcriticalCO2Transcritical & SubcriticalCO2Transcritical& Subcritical CO2SubcriticalCO2Efficiency Limits ofTranscritical CO2SubcriticalCO2Transcritical & SubcriticalCO2Transcritical& Subcritical CO2SubcriticalCO2SubcriticalCO2Transcritical & SubcriticalCO2Transcritical& Subcritical CO2SubcriticalCO2EfficiencyLimits ofTranscritical CO2
Balancing the triangleof demands• Ensure safe solutions• Ensure energy efficientsolutions• Ensure low direct emission• Ensure affordable solutions• The good thing is that it ispossible with CO2 asrefrigerantTEWI SafetyAffordabillityLeak tight ToxicityCOPGWPFlammabillityCostService
Hot water for sanitary purposes Cooling for conservation ofperishable foodsHeating for comfortIntroduction - a Super Market Needsthe scene is set for heat recovery…………..
The Heat RecoveryConcept Utilise the fact that coolingcreates heat! Design a system where thedischarge gas is utilised to serveheating needs Select the most suitablerefrigerant Ensure Cooling obligations Optimise COSPHeat lost toambientHeat usedfor heatingCooling ofproducts is aHeat sourceCOSP : Coefficient of System Performance
Why CO2? Mature status as refrigerant forrefrigeration – more than 2000 systemsrunning in the EU Temperature regulation within largetemperature band of discharge gas Efficiency less dependent on dischargetemperature Efficiency most dependent on returnwater temperature Transcritical phase invites for highefficient counter flow heat exchangers
CO2 compared to R404A• Many refrigerants are good at low Heat Recovery rates• CO2 is significantly superior at high temperatures
The Heat Balance The Heat recovery factor showsthe potential for heat recovery In this case during wintercondition HRF = 2.6 at thesufficient cooling capacity If the full Cooling capacity wereutilised i.e. by utilising externalevaporators the heating factorcould be increased even moreCOP : Coefficient of Cooling Performance• Numbers are in kW• COP is set to average during day• Ventilation loss (Qvent ) is net zero due todehumidification
System set up in the case fromSouthern Denmark
Case results COP is nearly constant COSP fluctuates with the heating demand and increases with decreasingtemperature – howver strongly influenced by other heating sources in thestore More than sufficient Heat available.
Case : TEWI comparisonbetween systems Heat recovery will increasecompressor power consumption byclose to 10 % due to temporary peakheating tasks TEWI decreases significantly usingCO2 and heat recovery. More than30 % improvements was achievedcompared to a conventional systemwith high direct emission Minor TEWI decrease based on heatrecovery aloneR404AsystemCO2BoosterCO2 Boosterwith heatrecoveryElectricity : ½ kg CO2/kWHGas: 2 kg CO2 / M3Leakage rate 10%Charge: 200kg R404A (GWP =3922)372 Tons CO2 per Year-27%-34%
Case : Energy runningcost comparison betweensystems The CO2 booster system with heatrecovery decreases overall energycost with more than 20 % Savings in running costs for toppingup on refrigerants leaks are notconsidered The CO2 system with Heat recoveryincreases Electricity cost up to 10%compared to systems without heatrecovery.Electricity : 0,14 € / kWhGas : 1,40 € / m3R404AsystemCO2BoosterCO2 Boosterwith heatrecovery95.000 € per Year-7%-28%
Conclusion• Supermarket applications are very suitable forimproving overall system performance of CO2systems using heat recovery• The traditional CO2 weaknesses as hightemperatures and pressures is turned intoadvantages using heat recovery• TEWI can be reduced by 5-10 % using heatrecovery• Running cost can be reduced by more than20% by introducing heat recovery and removingconventional heating sources• Pay back has been proven to be very short onexcess investments