Large buildings use machines called chillers to provide cooling. These chillers remove heat from water, and this chilled water is then used to cool and dehumidify the air in a building.
Chillers use two methods to cool the water: vapor compression and absorption refrigeration cycles. Both methods evaporate a refrigerant at a low pressure and condense the refrigerant at a higher pressure.
The vapor compression cycle uses a mechanical compressor to create the pressure difference necessary to circulate refrigerant. The absorption cycle evaporates water to provide the cooling needs to a building, and then absorbs the water with a salt solution. Steam heat can be used to boil off the water in order to start the cycle again.