Intelligent Data Centres Issue 45 | Page 42

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 ° 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 advantage as it allows for the cooling of the system without activation of the compressor .
The adiabatic technology can additionally improve the efficiency of a chilled water system . In these systems , the ambient air is cooled down by passing through wet pads . The air is then delivered at a lower temperature , achieving a higher freecooling capacity of the chiller and a more efficient operation of the compressor . The core of this solution is the onboard controller of the unit : it enables the use of water whenever strictly needed , according either to redundancy , efficiency or cooling demand needs . The controller has the main responsibility in preventing water from being wasted , improving the WUE ( water usage effectiveness ) of the data centre . The application of water is always a matter of balancing different aspects and constraints .
Further improvements to data centre efficiency can be made through the optimisation of chilled water systems controls . Chilled plant manager technology can co-ordinate the operation of all the units and main components of the chilled water systems . It allows an integration and co-ordination of the working mode between units and the main components , enabling improved efficiencies and performance at partial loads or , in the unlikely event of failure , finding the best way to react and grant cooling continuity to the system .
Combining all the technology optimisations , chilled water systems can significantly reduce the direct and indirect emissions . The following table can summarise an example of the results in London , where the system never fully works in direct expansion mode , thus granting excellent system efficiency and reducing costs .
Scaling with confidence
An example of how chilled water systems can achieve these benefits is in the case of Green Mountain , a Norwegian hydro-powered data centre where the thermal management system plays a big role . Green Mountain gained five megawatts of additional cooling capacity after the installation of Vertiv ’ s chilled water units , demonstrating how these systems , as part of a broader strategy , can facilitate sustainable data centre configurations .
Many hyperscale and colocation providers are now embracing the opportunity chilled water systems present , not only from a cost and speed of deployment perspective , but with sustainability front and centre . This needs to continue as we move into the next phase of the race for expanding capacity and improving the data centre sustainability . With such rapid expansion and increasing pressure to achieve net-zero , data centre providers must rely on new technologies to meet the requirements of both today and tomorrow . �
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
Optimisation of the chilled water system control
1.114 0.000 344 55248 55592 5416 8515
1.100 0.000 344 48493 48837 5416 8678
Improved compressor technology and Low GWP refrigerant
1.094 0.000 1 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
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