1. XV EUROPEAN CONFERENCE MILANO 7th
-8th
JUNE 2013 CSG
Latest Technology in Refrigeration and Air Conditioning
Under the Auspices of the PRESIDENCY OF THE COUNCIL OF MINISTERS
Optimization of combined heating and
cooling in Supermarkets
Torben Funder-Kristensen
Head of Public Industry Affairs
TFK@danfoss.com

2. Content
 Introduction
 Balancing demands
 The heat recovery concept
 Why CO2 ?
 CO2 compared to R404A
 The Case of Heat Recovery
Heat balance
COSP and COP
TEWI
COST
 Conclusion
SubcriticalCO2
Transcritical & SubcriticalCO2
Transcritical& Subcritical CO2
SubcriticalCO2
Efficiency Limits of
Transcritical CO2
SubcriticalCO2
Transcritical & SubcriticalCO2
Transcritical& Subcritical CO2
SubcriticalCO2
SubcriticalCO2
Transcritical & SubcriticalCO2
Transcritical& Subcritical CO2
SubcriticalCO2
EfficiencyLimits of
Transcritical CO2

3. Balancing the triangle
of demands
• Ensure safe solutions
• Ensure energy efficient
solutions
• Ensure low direct emission
• Ensure affordable solutions
• The good thing is that it is
possible with CO2 as
refrigerant
TEWI Safety
Affordabillity
Leak tight Toxicity
COP
GWP
Flammabillity
Cost
Service

4. Hot water for sanitary purposes Cooling for conservation of
perishable foods
Heating for comfort
Introduction - a Super Market Needs
the scene is set for heat recovery…………..

5. The Heat Recovery
Concept
 Utilise the fact that cooling
creates heat!
 Design a system where the
discharge gas is utilised to serve
heating needs
 Select the most suitable
refrigerant
 Ensure Cooling obligations
 Optimise COSP
Heat lost to
ambient
Heat used
for heating
Cooling of
products is a
Heat source
COSP : Coefficient of System Performance

6. Why CO2?
 Mature status as refrigerant for
refrigeration – more than 2000 systems
running in the EU
 Temperature regulation within large
temperature band of discharge gas
 Efficiency less dependent on discharge
temperature
 Efficiency most dependent on return
water temperature
 Transcritical phase invites for high
efficient counter flow heat exchangers

7. CO2 compared to R404A
• Many refrigerants are good at low Heat Recovery rates
• CO2 is significantly superior at high temperatures

8. Heat Reclaim Case
 Southern Denmark
 Area: 1000 m2
from 2010
 Compressors: 5 MT (1 VS), 4 LT
 Cooling Capacity: 160 kW
 Online COP calculation
 Heating :
 Sanitary water (1800 l tank (65 o
C )
 Floor heating/low temp coils (35 o
C )
 Heating investments (add on) is less
than 7000 €
MT Pack LT Pack
Performance of
refrigeration system (COP)

9. The Heat Balance
 The Heat recovery factor shows
the potential for heat recovery
 In this case during winter
condition HRF = 2.6 at the
sufficient cooling capacity
 If the full Cooling capacity were
utilised i.e. by utilising external
evaporators the heating factor
could be increased even more
COP : Coefficient of Cooling Performance
• Numbers are in kW
• COP is set to average during day
• Ventilation loss (Qvent ) is net zero due to
dehumidification

10. System set up in the case from
Southern Denmark

11. Case results
 COP is nearly constant
 COSP fluctuates with the heating demand and increases with decreasing
temperature – howver strongly influenced by other heating sources in the
store
 More than sufficient Heat available.

12. Case : TEWI comparison
between systems
 Heat recovery will increase
compressor power consumption by
close to 10 % due to temporary peak
heating tasks
 TEWI decreases significantly using
CO2 and heat recovery. More than
30 % improvements was achieved
compared to a conventional system
with high direct emission
 Minor TEWI decrease based on heat
recovery alone
R404A
system
CO2
Booster
CO2 Booster
with heat
recovery
Electricity : ½ kg CO2/kWH
Gas: 2 kg CO2 / M3
Leakage rate 10%
Charge: 200kg R404A (GWP =3922)
372 Tons CO2 per Year
-27%
-34%

13. Case : Energy running
cost comparison between
systems
 The CO2 booster system with heat
recovery decreases overall energy
cost with more than 20 %
 Savings in running costs for topping
up on refrigerants leaks are not
considered
 The CO2 system with Heat recovery
increases Electricity cost up to 10%
compared to systems without heat
recovery.
Electricity : 0,14 € / kWh
Gas : 1,40 € / m3
R404A
system
CO2
Booster
CO2 Booster
with heat
recovery
95.000 € per Year
-7%
-28%

14. Conclusion
• Supermarket applications are very suitable for
improving overall system performance of CO2
systems using heat recovery
• The traditional CO2 weaknesses as high
temperatures and pressures is turned into
advantages using heat recovery
• TEWI can be reduced by 5-10 % using heat
recovery
• Running cost can be reduced by more than
20% by introducing heat recovery and removing
conventional heating sources
• Pay back has been proven to be very short on
excess investments

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