In data center terminology, free cooling is the phrase used to describe a strategy for reducing energy consumption by leveraging the natural low air temperatures and cooler climates in some geographical regions. In this process, naturally occurring cold outside air is used inside the data center to aid the cooling process.
Leveraging cooler outside air uses less power than other cooling methods and can reduce or replace parts of mechanical refrigeration that requires high energy consumption to operate.
The free cooling process typically uses a mixture of outside air and air recirculation systems to cool air temperatures inside the data center by replacing or eliminating the compressor operation in air conditioning units or can be used to reduce the chiller operation for chilled water systems.
Data centers using free cooling systems use an economizer system -- fluid and air economizers -- to lower cooling system energy usage.