Cooling Economizers

"Free cooling" is the process of extracting heat from the data center floor without using compressors to eject that heat to the outside. Turning compressors off greatly reduces the power draw required to remove heat. This is typically accomplished using relatively cold outside air to absorb heat directly from the data center space, the chilled water loop, or the refrigerant loop.

The type of economizer system to use depends on several criteria and is highly dependent on geography (average outside air temperature, altitude, humidity, etc). From an equipment design perspective, economizer efficiency has to do with approach temperature of the coil(s) and the maximum outside air temperature required in order to attain the desired temperature on the data center floor with the compressors turned off.