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

9

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

11

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