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Air Conditioningand
Computer Centre Power Efficiency
The Reality
Christophe MartelTony Cass
2
Data Centre Cooling Options
• Outside Air• Cooled Air
– Central distribution– Local distribution– Very local distribution
• Direct Water Cooling
3
Basic Housekeeping is essential!
Nice background for a ballerina...
... and a nice way to preheat the inlet airfor the servers behind!
A muchbetterdesign.
4
Basic Housekeeping is essential!
Mind the gaps!
5
Basic Housekeeping is essential!
Hot is cool!
But not too hot: Vendors now accept that their systems will run at higher temperatures, but there are reports that server energy efficiency starts to drop above a certain temperature.
5.0 10.6 16.1 21.7 27.2 32.80
500
1000
1500
2000
2500
3000
3500
GenevaNew York
Indoor conditions from 20°C to 27°C
Classicalfree cooling
Outdoor Temperature[°C]
Nb of hours/ year
ExtraFree
coolingCOOLING
6
High density starts at 6KW/rack
Hot corridor
Hot corridor
Cold corridor
0 < low density < 2kW/m2 < high density Central air cooling < 2kW/m2 < Local air cooling
30% of the area for racks
2,0 m
0,6 m
Area1,2 m2
Area0,36 m2
Basic data
Standard air velocity: max 0.25 m/s
Temperature in/out IT : 8°C
Area equivalence:1 rack front side = 3.33 floor
tiles
Typical rackTypical room
Air Air flow Coolingspeed rate power[m/s] [m3/h] [W]0.25 1080 29380.5 2160 5875
0.25 324 8810.5 648 1763
Rack front side (1.2m2)
Floor tile (0.36m2)
7
Reducing air speed
False floor. False ceiling for return air. Cold aisle closed. Hot aisle open.
Cold aisle closed
8
Reducing air speed
No false floor. False ceiling for return air. Cold aisle open. Hot aisle closed.
Wall side or peripheral air distribution
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How do you make cold air?
• Via heat exchange with something else which rejects heat to the environment
– something else is usually water• Heat wheel is one alternative
– But closer in spirit to complete fresh air cooling: supplemental cold air generation will be required if peak temperatures approach the desired set point for machine room temperature.
10
How do you make cold water?
Air cooled chillers
dry coolers
Towers
COOLING PRODUCTION COOLING DISTRIBUTION
PipesPumps
PipesPumps
Screw or Compressor type
Absorption type
Water cooled chillers Water cooled rack
Air handling units
Horizontal / vertical
In row cooling
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Optimising Chilled Water Generation• Fans, pipes: size optimisation -> pressure drop of the
system• Fan/pump motors:
– Preferably variable speed drive (30%); if not then Eff1 class(10%)
• High efficiency exchangers• Filter selection and period maintenance• Regulation optimisation via significant indicators • And, most importantly, the chillers…
Dry cooleror
Cooling tower
Chiller
Fan Computer
FilterFan
Filter
Pump
Pump
12
Annual Electricity Consumption
Efficient Data Centre — PUE=1.3
0.2 0.3 0.1 0.8 19.1
2.8
0.5
76.3
Lighting
Heating
Offices
Ahu
Chillers
Pumps
Cooling units
IT process
0.8 1.2 0.33.4
80.5
11.72.1
Lighting
Heating
Offices
Ahu
Chillers
Pumps
Cooling units
13
Take time for chiller selection• Eurovent Certification certifies the
performance ratings of air-conditioning and refrigeration products according to European and international standards. Energy efficiency Ratio (EER)Ratio of the cooling capacity to the power input of the unit.European Seasonal Energy efficiency Ratio (ESEER)ESEER = A.EER100% + B.EER75% + C.EER50% + D.EER25%
• Recent Chiller Optimisations• Free cooling option for air cooled chiller• Oversizing with variable speed drives (EER up to
10!)• Adiabatic coolers• Smartcools systems
• EER between 3.16 to 3.63 (delta 15%)
• ESEER between 3.86 to 4.31 (delta 20%)
14
Chiller size selectionData centers are easy to design compare to other
buildings!
CoolingPower
[kW]
Time[Days]
Classical CoolingPowerdemand
Coolingpowerinstalled+30%
Typical buildingData
Centre
Coolingpowerinstalled+15%
Chiller 1
Chiller 2
Chiller 3
15
Conclusion
Dry cooleror
Cooling tower
Chiller
Fan Computer
FilterFan
Filter
Pump
Pump
• Optimise...• ... everywhere!
Dry cooleror
Cooling tower
Chiller
Fan Computer
FilterFan
Filter
Pump
Pump