The function of a power plant air-cooled system is to use air instead of water to condense the exhaust steam from the steam turbine in a thermal power plant, turning the exhaust steam from the low-pressure cylinder of the steam turbine into condensate, thus completing a work cycle and entering the next work cycle.

A power plant air-cooled system refers to a closed-loop system using air as the cooling medium for the turbine's cooling system, with dry cooling towers or mechanically ventilated air-cooled heat exchangers. There are three types of power plant air-cooled systems: direct air-cooled systems, indirect air-cooled systems with hybrid condensers, and indirect air-cooled systems with surface condensers.

Compared with conventional wet cooling systems, air-cooled systems can save more than 3/4 of the water. In some coal-rich and water-scarce areas of the world, large-capacity steam turbine generator sets of 300,000 and 600,000 kW have been equipped with air-cooled systems. Currently, the largest air-cooled units in the world are: for direct air-cooled units, the Martinba Power Plant in South Africa (665,000 kW); for indirect air-cooled units with surface condensers, the Kendal Power Plant in South Africa (686,000 kW); and for indirect air-cooled units with hybrid condensers, Iran (325,000 kW). Before 2002, in China, there were three power plants with eight large indirect air-cooled units in operation: Datong Yungang Power Plant (2 x 220,000 kW), Taiyuan No. 2 Power Plant (2 x 200,000 kW), and Inner Mongolia Fengzhen Power Plant (4 x 200,000 kW). The indirect air-cooled units of Datong and Taiyuan power plants were imported from abroad, while those of Inner Mongolia Fengzhen Power Plant were provided by Harbin Air Conditioning Co., Ltd. After 2002, the large-scale power plant air-cooled market began to fully launch in China. According to preliminary statistics, by September 2005, more than 20 projects with a capacity of over 300,000 kW had been tendered and started, with a total installed capacity exceeding 22 million kW. Harbin Air Conditioning Co., Ltd. undertook 7 projects with a total capacity of 4.2 million kW, while the remaining projects were won by German GEA and SPX. In addition, GEA and SPX hold 60% and 35% of the global air-cooled market share, respectively. Harbin Air Conditioning Co., Ltd., currently the only company in China with the capability to design and manufacture air-cooled systems, had only produced indirect air-cooled systems below 200,000 kW before 2002. However, since then, newly built power plants have generally adopted large-scale units with a single unit capacity of 300,000-600,000 kW and generally use direct air-cooled systems. To accelerate the localization of large-scale power plant air-cooled systems, Vice Premier Zeng Peiyan of the State Council made two endorsements. With the strong coordination and support of relevant departments, China Power Investment Corporation and Huaneng Power International gave full support and trust to the localization of large-scale power plant air-cooled systems. In 2004, Harbin Air Conditioning Co., Ltd. won orders for the 600,000 kW Tongliao Phase III and the 300,000 kW Wulashan units' direct air-cooled systems. Recently, the Wulashan Power Plant's direct air-cooled system has been put into operation. This achievement not only broke the near 70-year monopoly of foreign companies in this field but also made China the third country in the world, after the United States and Germany, to fully master this technology.