Often when data centre free cooling is discussed, people assume this means direct fresh air cooling. People intuitively assume that direct cooling ismore efficient because there are less components. It’s as simple as opening a window!
However, in many cases this is absolutely incorrect. Indirect systems have unappreciated advantages.
In climates warmer than London, indirect systems are more efficient than direct systems and can allow refrigeration to be eliminated and considerably reduce the electrical plant sizing requirements. The external air can be cooled and used to chill the data centre whilst the humification stays outside.
In order minimise energy consumption, the design should incorporate good data hall air segregation, control to the ASHRAE recommended environmental conditions at the server inlet and adiabatic cooling of outdoor air.
Use of adiabatic evaporative cooling on the outdoor airstream allows free cooling to be achieved for many more hours in the year when there are hot, dry conditions.
In climates such as London, the difference between indirect and direct systems is borderline. However in hotter climates, the difference is notorious.
Further detail on the application for free cooling in data centres is available in our technical papers. (link to a couple Operational Intelligence Whitepapers papers:)
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