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Cooling the cloud

More mechanical cooling may not be the answer to modern heat loads. Stefano Mozzato

Heat management is a perennial problem for managers of data centers; temperatures build steadily unless tackled by cooling units, almost as power-hungry as the servers they cool. New high-power servers have increased the workload and cooling systems often struggle to keep pace with higher heat loads.

Where heat load exceeds cooling capacity, the effect on reliability can be catastrophic as overheating servers cease to function properly. This, combined with constant pressure to cut cost, rising power rates and environmental concerns, suggests that throwing more mechanical cooling into equation may not be the answer.

Issues with server heat control have conspired to form something of a ‘perfect storm’, Forrester Research acknowledged this in their September 2011 report Power And Cooling Heat Up The Data Center. “Driven by the confluence of rising energy prices, the immense scaling of cloud workloads, and continual pressures on IT budgets -- power and cooling have become even more critical issues than they were several years ago,” the report reads.

Emerson Network Power developed its Liebert PCW cooling system to address these issues. It is an advanced chilled-water floor-mount unit for precision cooling. The company meticulously designed the units interior to improve airflow and added more advanced technology.

One new feature is a redeveloped chassis. Emerson engineers studied airflow within the unit and completely rethought the design of its internal components, including angle of the coil, filters typology and all

Liebert PCW cooling system

elements affecting inner aerodynamics. This aerodynamic design enables reduction in running costs, while Emerson’s EC Fan 2.0 and automotive-like high-efficiency filters minimise noise.

To address cooling energy struggles further, Emerson has developed a roof-mounted freecooling chiller that uses outside air to supplement capacity. The freecooling operates until the outside temperature is in the 20-23C range. Mechanical cooling picks up the slack in warmer weather, while Liebert iCOM control systems adjust settings to match workload, weather and time of day.

While Emerson designed Liebert PCW for medium and large data centers, it is also appropriate for small facilities, as the system can be applied in perimeter-cooling configurations from 30kW to 220kW and above. It is suitable also for facilities where physical redesign is not possible, or where server rooms lack height or raised floor. Liebert PCW is accountable for energy saving from 40 to 70% versus industry best practices.

SEVEN BASIC CONFIGURATIONS For large and medium data centers with at least a 60mm raised floor, the Extended Down configuration can be used. The Extended Up Downflow configuration is for sites with space

constraints at the bottom but without roof- height constraints. Emerson recommends the Extended Up Upflow configuration for data centers without raised floor.

Extended Up frontal air delivery configuration is recommended for users who want to install the unit inside a UPS or a technical room, while Extended Up back air delivery is for data centers where the service corridor is the only space where the floor-mount unit can be installed.

The Downflow configuration is for sites where the floor is raised by at least 600mm, and the ceiling is at least 2.5m high. Finally, the Upflow configuration is for data centers with no raised floor but with ceilings at least 2.5m high.

Liebert PCW comes as part of the SmartAisle cooling solution and can be configured in three different ways. Adjustable legs, fan modules separated from the heat exchange, multiple configurations of water pipes, pluggable electrical connection extend flexibility.

This single engineering project generated seven patents for efficiency, performance and reduced operational cost. It is innovation, rather than more mechanical cooling that is required to cool the Cloud. n


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