Chiller
Beginner
A giant air conditioner that makes cold water for the datacenter.
Novice
A refrigeration machine that cools water using a compressor, then rejects the heat outdoors through a cooling tower or air-cooled condenser. It is usually the biggest energy user in a cooling plant.
Expert
Efficiency is expressed as a coefficient of performance (heat moved ÷ electrical input) or kW/ton; it improves as the chilled-water supply temperature rises, which is why warm-water liquid cooling and economizers reduce chiller energy.