t cht lk |
|
|
|
London pPUE WUE |
TEWI ( 10y ) – total ton of CO 2
|
Freecooling hours |
Freecooling + Mixed mode |
Data Centre size 12 MW l / kWh Direct Indirect Total h h
Baseline 1.212 0.000 689 102277 102966 0 0
Increasing air and water temperatures 1 . 114 0.000 344 55248 55592 5416 8515
Optimisation of the chilled water system control
1.100 0.000 344 48493 48837 5416 8678
Improved compressor technology and Low GWP refrigerant
1.094 0.000 344 45231 45231 5416 8678
Adiabatic system 1.082 0.162 1 39805 39805 6849 8760
pPUE = partial power usage effectiveness ( attributable to the cooling system ) WUE = Water Usage Effectiveness TEWI = total equivalent warming impact it remains active in the atmosphere , compared to a base of CO 2
. The lower this metric , the lower the atmospheric impact .
The traditional refrigerants can now be replaced by modern HFO ( hydrofluoro-olefin ) refrigerants , which have a lower GWP . It is expected that this will prevent the emissions of up to 105 million tons of equivalent
CO 2 by 2040 . However , most of these new refrigerants are classified by ASHRAE ( American Society of Heating , Refrigerating and Air-Conditioning Engineers ) as mildly flammable therefore requiring a new design for the cooling system , potentially impacting the broader data centre design . cooling technologies to apply low GWP refrigerants in data centre applications and therefore are an example of a valid alternative for reducing direct environmental impacts .
Reduction of the indirect emissions ( cutting energy consumption )
Reducing carbon footprint also means cutting the electricity consumed by a data centre during its operation . This is where chilled water systems can play a big role . In recent years , they have applied a range of cooling system efficiency improvements that allow a reduction of electricity usage .
Chilled water systems offer an excellent solution as the refrigerant is contained within chiller units and , in most applications , these are installed outside of the data centre , thus simplifying the use of flammable fluids . Chilled water systems are one of the first
For example , in a chilled water system , the chiller compressor is the greatest consumer of electricity and the warmer the external climate , the greater the electricity demand of the compressor .
Recently , there has been an increased use of inverter driven compressors which help to achieve higher efficiency levels , especially at partial loads . Chillers equipped with inverter driven screw compressors , or oil free centrifugal compressors , are now available to drastically cut down electricity consumption compared to the previous technology available .
Over the past few years , ASHRAE has increased the recommended operating temperature of data centres equipment up to 27 O C . This has allowed subsequent increases to the water temperatures within chilled water systems and has enabled an extended use of free cooling chillers , even in countries where free cooling was not previously feasible . Free cooling technology has an important
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