Techniques of humidification in data centres

An interesting overview of the recent improvement in data centres humidification techniques.
A major issue in data centres is electrostatic discharge (ESD), because it can damage sensitive electronic components and can cause data loss. To prevent ESD in data centres, humidification is needed.

Standardization: ASHRAE published in September 2016 its Standard 90.4.2016 Energy Standard for Data Centers1, softening slightly the previous guidelines. The following points concern more particularly humidification:

-    Recommended level of relative humidity (RH): 25 to 45% – versus 40% minimum before.
-    Recommended dew-point temperature: 18 to 27°C dry-bulb temperature and 5.5°C dew-point temperature.
-    Recommended temperature window: from 18 to 27°C – versus 20 to 25°C before.
-    Maximum humidity level: 69% RH and 15°C dew point.

Until recently, the techniques used to combat ESD involved high energy consumption humidifying systems, such as electrode boiler steam humidifiers, incorporated in the Computer Room Air Conditioning units (CRAC).

The loosening of the standards involved by the ASHRAE 90.4.2016 standard encourages the use of low energy consumption humidification systems in data centres, such as cold-water humidifier2, or more significantly free air cooling: fresh air bought in from the outside is used instead of an air conditioning system. Those two techniques can be associated: by supplementing free air cooling systems with evaporative cooling from cold-water humidifiers, the use of free air cooling systems can be extended from 70% of the year to 95%.

For further information, please read the article published by HVAC&R online following the link below:

1 See the IIR article
2 In 2008, Fujitsu data centres in London employed spray humidifiers to prevent ESD by preheating the cold, saturated fresh air to 30°C with heat recovery from the data halls. Energy cost saving was around GBP 35 000 a year.