The document discusses rational use of energy in cooling systems. It introduces different types of cooling technologies including dry cooling, evaporative cooling, and compression cooling. It explains that compression cooling, which uses chillers, accounts for 90% of cooling applications. The document then provides details on each type of cooling and gives examples of how energy can be saved through various measures like optimizing temperatures, avoiding oversizing, using variable speed drives, implementing free cooling, recovering waste heat, and improving controls. Specific case studies show energy savings of up to 50% are possible through these kinds of efficiency improvements.

1. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 1
13/07/2006
RATIONAL USE OF ENERGY
in cooling
© LABORELEC

2. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 2
Introduction
Introduction to cooling
Different types of cooling
Dry Cooling
Evaporative Cooling
Compression Cooling (chiller)
Energy savings potential on cooling
installations
Examples
Conclusions

3. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 3
Why cooling?
Cooling of spaces (persons, products,…)
Removing waste heat (process cooling)
INTRODUCTION

4. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 4
Introduction
Cooling towers
(Twater ≈ 20 °C)
Chilled water
(Twater ≈ 5 °C)
Cold rooms, etc.
(Tair ≈ -10 … - 30 °C)

5. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 5
Expensive form of energy
More expensive as required T° drops
⇒ Produce with the most efficient method
INTRODUCTION
=

6. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 6
Dry cooling
Wet cooling (by evaporation)
Compression cooling
(Absorption cooling)
(Gas expansion)
(Thermo-electric cooling)
TYPES OF COOLING
90% of
applications

7. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 7
TYPES OF COOLING
40
35
25
20
T (°C)
EVAPORATIVE COOLING
(open, closed, hybrid,…)
DRY COOLING
COMPRESSION COOLING
(CHILLER)
(aircooled, watercooled)

8. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 8
Outside air is used to cool the medium
Limited by outside air temperature
Advantages
No water treatment necessary
No additional costs for water consumption
Less maintenance costs
DRY COOLING

9. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 9
Advantages
Reduced ground area (higher thermal
power/m²)
More efficient heat exchange
Less electrical consumption
Limits set by wet bulb temperature
Disadvantages
Substantial water consumption
Water treatment may be necessary
EVAPORATIVE COOLING

10. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 10
Types of cooling towers
Open cooling tower
Closed cooling tower
Evaporative condenser
Hybrid cooling tower (combination of dry and
wet cooling principles)
EVAPORATIVE COOLING

11. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 11
Open cooling
tower
EVAPORATIVE COOLING

12. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 12
Closed cooling tower and
Evaporative condensor
EVAPORATIVE COOLING

13. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 13
Hybrid cooling tower
Dry mode (as much as possible)
Adiabatic mode (dry air temperature too high for dry cooling)
Combined dry/wet mode (max power)
Advantages
No water use when in dry mode, so savings on water cost
In combined dry/wet mode there is no visible plume
Disadvantages
High initial cost
No energy savings on electricity
EVAPORATIVE COOLING

14. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 14
expansion
valve
evaporator
compressor
condensor
High Pressure
Liquid Gas
Low pressure
COMPRESSION COOLING
4 main components

15. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 15
Increase efficiency: T1 , T2
Performance of a cooling machine : COP
c
evcd
ev
electrical
evaporator
TT
T
W
Qf
P
P
COP η×
−
===
With:
Qf : thermal power at evaporator (kWth)
W: electrical power at compressor (kW)
Tev : evaporating temperature (K)
Tcd: condensing temperature (K)
ηc : rendement of Carnot
Example:
Tev = -5 °C (=> 268 K)
Tcd = 35 °C (=> 308 K)
ηc = 0,5
COP = 3,35
COMPRESSION COOLING

16. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 16
ENERGY SAVINGS - 1
Optimise condensing and evaporating
temperatures
Condensing temperature as low as possible
Evaporating temperature as high as possible
c
evcd
ev
electrical
evaporator
TT
T
W
Qf
P
P
COP η×
−
===

17. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 17
ENERGY SAVINGS - 2
No exaggerated overdimensioning
Why?
• To cope with reduced efficiency throughout the years
• To much reserve taken in design point
Consequences:
• Installation working under nominal working point
• Reduced efficiency

18. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 18
ENERGY SAVINGS - 3
Use of frequency drives
Most of the time the drives have a reduced load
Applicable on pumps, compressors, fans
Advantages:
Energy savings on electricity
Better regulation off required process value (more
stable)

19. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 19
ENERGY SAVINGS - 4
Higher COP with direct cooling
Direct cooling is the method where the evaporation
is present in the medium to be cooled (for
example: evaporator in cold storage rooms).
No secundary fluids if possible
EVAPORATOR
HEAT
EXCHANGER
-10°C
- 5°C
-5°C
0°C
Primary circuit (refrigerant)
Secundary circuit (glycol-water)

20. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 20
ENERGY SAVINGS - 5
Central systems often consume less energy
Base load is likely to be more stable, so frequent
regime changes are avoided
Sometimes less efficient due to large losses in the
conduits resulting from important distances
between user and cold production.

21. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 21
ENERGY SAVINGS - 6
Use of “free cooling” if
possible
Use of cooling towers
during periods with lower
outside temperatures.
Especially interesting if
cooling temperature is
above 15°C
Proces
Chiller
Cooling
Tower
TsetpointOnly when outside Twb < T setpoint

22. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 22
ENERGY SAVINGS - 7
Heat recovery (where possible)
In cooling a lot of heat is pumped from one place to
another (mostly to the environment)
If there are other processes which need (pre-)
heating, the cooling and heating process can be
combined.
Example: slaughterhouse
• cooling is required to cool the animal carcasses
• heating of water for cleaning purposes.
Energy savings through heat recuperation:
• Electrical savings as condenser load diminishes
• Gas bill is smaller due to less heat required for heating

23. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 23
ENERGY SAVINGS - 8
Intelligent defrosting systems
Defrosting is necessary when there is ice buildup on
the evaporator (for example in cold rooms on the
evaporators). Ice insulates and ice buildup thus
quickly reduces efficiency
2 Types
Clock regulated
defrosting with set
duration
Intelligent systems which
determines moment and
duration of defrost cycle

24. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 24
ENERGY SAVING EXAMPLES - 1
Changing setpoint of cooling towers
Cooling
towers
Process Process
20°C
Process
Initial situationInitial situation
Cooling
towers
Process Process
24°C
Process
New situationNew situation
Energy savings dependingEnergy savings depending
on size and design ofon size and design of
cooling tower!cooling tower!
(40% in this particular case)

25. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 25
ENERGY SAVING EXAMPLES - 2
Frequency regulation on fans of cooling tower
Cooling
towers
Process Process
22°C
Process
Initial situationInitial situation
Regulation on/off
Cooling
towers
Process Process
22°C
Process
New situationNew situation
Frequency regulation
Energy savings, dependingEnergy savings, depending
on load profile, of up to 50%on load profile, of up to 50%

26. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 26
ENERGY SAVING EXAMPLES - 3
Centralised regulation of chiller compressors
Compressor load = 61 % (7 CP)Compressor load = 61 % (7 CP)
All pumps ON (7 pumps)All pumps ON (7 pumps)
1
Process ProcessProcess Process
CH1 CH2 CH3 CH4 CH5 CH6 CH7
Initial situationInitial situation
1
Process ProcessProcess Process
CH1 CH2 CH3 CH4 CH5 CH6 CH7
Compressor load = 100 % (5 CP)Compressor load = 100 % (5 CP)
Only 5 pumps ONOnly 5 pumps ON
New situationNew situation
Energy savings, dependingEnergy savings, depending
on initial load profile, of up to 10%on initial load profile, of up to 10%

27. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 27
ENERGY SAVING EXAMPLES - 4
“Floating” condensing pressure
HP = fixed
Minimised kWh fans.
Maximum kWh Compressor
HP = floating
Maximised kWh fans
Minimum kWh Compressor
Energy savings of up to 30%Energy savings of up to 30%

28. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 28
Conclusions
Important to choose the best setpoints to
control the installation
Not all regulation techniques have the same
energetical impact
Modification to current circuit can sometimes
bring up significant energy savings
=> In general, the ways to optimise cooling
installations are numerous

29. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 29
Thank you for your attention!

30. LABORELEC
Rational use of energy in cooling @ LABORELEC – 13 July 2006 – 30
Questions?