Ambient air cooling is the use of naturally cool air surrounding a building, such as a data center, to reduce heat inside the facility. The use of ambient air and/or nearby water sources to maintain appropriate ambient temperatures in a data center is sometimes referred to as free cooling because they take advantage of naturally occurring phenomena rather than more heavily technological solutions.
One of the first things to consider for ambient air cooling is location. The prevailing air at many latitudes and elevations can be considerably cooler during certain seasons and times of day than the air that is warmed by data center equipment. By filtering, humidifying and introducing cooler prevailing air directly into the data center, it is possible to reduce or eliminate the use of industrial-grade CRAC systems. Cooling systems that use this approach are sometimes called air-side economizers.
There are two types of ambient air cooling: In air-side free cooling, outside air is brought into the data center directly through filters or indirectly through heat exchangers. In adiabatic free cooling, the air is brought into some sort of chamber and used along with water evaporation to cool the air.
Although ambient air cooling is not actually free of cost because of the technologies involved, savings can be substantial. Other reasons to consider ambient air or water cooling for a data center include the pursuit of a Leadership in Energy and Environmental Design (LEED) certification, the desire for energy savings and an environmentally-aware corporate philosophy.