Free Cooling Mode uses available outdoor air or water resources to cool buildings without mechanical refrigeration system operation, eliminating compressor energy consumption. This passive cooling approach leverages naturally cool sources when outdoor or water temperatures support adequate cooling capacity.
Cooling Sources and Methods
Free cooling can utilize outdoor air through economizers, groundwater or cooling towers through waterside free cooling heat exchangers, or night-flushed thermal mass. Outdoor air free cooling works when temperatures fall below 55°F; waterside free cooling operates year-round in temperate climates. Systems automatically bypass compressors and divert flow through free cooling coils when these conditions are met, maintaining setpoint temperatures without refrigeration.
Applications
Free cooling is most effective in data centers and server rooms requiring continuous 65-72°F conditioning, where 40-60% of annual cooling can be provided passively. Office buildings in northern climates benefit from 5-6 months of economizer operation. Hybrid cooling towers combining mechanical and evaporative cooling enable year-round free cooling in many climates.
Implementation
Free cooling requires sophisticated controls, temperature sensors at multiple points, and properly sized heat exchangers. Annual energy savings can reach 30-50% for facilities with significant cooling loads in favorable climates.