Intelligent CIO North America Issue 35 | Page 66


Key steps to optimize data center cooling performance

One of the most important things data center operators can do to reduce energy costs is to make the cooling system as efficient as possible , especially since next to the IT equipment , cooling is the main source of energy usage and potential wasted energy in the data center , says Gordon Johnson , Senior CFD Engineer , Subzero Engineering . temperatures ( cooling optimization ) and lower the airflow to the IT equipment ( airflow optimization ).

In terms of efficiency and energy savings , most experts agree that a 1DF ( 0.55DC ) increase in supply temperature results in approximately a 1.6 to 2 % savings in the overall cost to operate the data center .
Optimizing cooling performance reduces cooling costs and OPEX , this should be on the top of the list for anyone looking to reduce annual energy costs and their carbon footprint .
With today ’ s average rack power density at between 10 to 11 kW , many data centers likely have unused or even wasted cooling capacity in their air-cooled data center , especially if they ’ re not practicing a comprehensive airflow and rack management strategy such as installing containment and practicing good rack hygiene .
After airflow and rack management has been implemented , it ’ s time to raise the
Gordon Johnson , Senior CFD Engineer , Subzero Engineering
There ’ s no reason why everyone should not be operating their supply temperatures as close to ASHRAE ( American Society of Heating , Refrigeration and Air-Conditioning Engineers ) recommendation for server inlets of 80.6 DF ( 27DC ).
Not doing this is simply the biggest overall waste in efficiency and TCO ( Total Cost of Ownership ) for data centers .
And that ’ s not all . Along with raising supply temperatures results , most newer data centers are equipped with air-side or waterside economizers which results in even more energy savings , because the higher set point temperatures increase the amount of time that outdoor air can be used for cooling .
The second step to improve energy efficiency is airflow optimization since we only want to supply the amount of airflow ( CFM / CMH ) that our IT equipment needs , typically we want 10 – 15 % more supply airflow to ensure we maintain positive pressure in our cold aisle ( s ).
This practice will reduce bypass air , which is wasted supply air from the cooling units that is not contributing to the overall cooling of the IT equipment . It ’ s an expensive problem because it costs money to both cool and blow the supply air , so we need to ensure that it ’ s only going to the server inlets in our racks .
To achieve the most savings from airflow optimization , cooling units should be equipped with either VFDs ( Variable Frequency Drives ) or EC fans to maintain the 10 to 15 % higher supply airflow versus demand airflow in the room .
Many new data centers are using the ‘ flooded room ’ design to achieve large savings with airflow optimization . By using perimeter cooling such as CRAHs and fan walls to flood the entire white space , they avoid having to match floor tiles or individual cold aisles to airflow ( CFM / CMH ) requirements for various rack power densities ( kW ).
Major colocation and hyperscale data center operators have long realized the importance of airflow management which starts with containment , because it enables them to achieve large energy and efficiency savings via airflow and cooling optimization .
As rack densities continue to expand this will become even more important if we ’ re going to get more sustainable as an industry .
The best energy saved is the energy we don ’ t consume in the first place – and this has never been truer than in our industry . p
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