In a thermal power plant an air cooled condenser (ACC) is used to condense the turbine exhaust low pressure steam at sub-atmosphere pressure so that it can be pumped back to the feed water system. Sub-atmospheric pressure or vacuum pressure in the ACC enables the turbine to generate more output or electrical energy. The condensed steam is then sent back to the boiler thus completing the power cycle.
As the air-cooled condensers do not require cooling water as in the case of water-cooled condensers or cooling towers. Therefor a power plant with air cooled condensers don’t require a cooling water source and can be installed in locations where water availability is less.
Reduction or elimination of thermal pollution, entrainment, and impingement issues typically associated with once-through and evaporative cooling and elimination of visible plume and drift from the operating cooling system (though clearly not the primary driver) are the other reasons to select the ACC.