a) Temperature conditions. In severely cold regions, direct air cooling systems should be prioritized. Severely cold regions refer to areas where the average temperature of the coldest month over many years is below -10℃. After comprehensive comparison, if an indirect air cooling system is indeed required, especially in extremely cold regions, anti-freezing measures need to be thoroughly studied.

b) Wind field and wind speed conditions. In areas with relatively stable wind field flow patterns, direct air cooling systems are preferable; when the prevailing wind direction is unclear or the wind direction is extremely unsuitable for the overall layout of direct air cooling, indirect air cooling systems should be used. When the ambient wind speed is high, both types of air cooling systems can be used. Due to the higher basic wind pressure, the investment in indirect cooling towers will be higher. The type of air cooling system should be determined after comparing the investment with direct air cooling systems that have wind protection measures. Generally, since indirect air cooling systems are less affected by wind than direct air cooling systems, indirect air cooling systems are recommended. A stable wind field refers to a clear and high-frequency prevailing wind direction throughout the year or summer over many years. Considering only the wind direction data, it is very suitable to use direct air cooling. However, this does not mean that indirect air cooling systems cannot be used; other conditions need to be comprehensively analyzed.

c) Site conditions. When the site conditions of the power plant are limited and a large indirect cooling tower cannot be installed, a direct air cooling system should be used. When only a direct air cooling system can be used, if the wind direction and wind speed significantly affect the air cooling system, measures to prevent environmental wind should be thoroughly studied.

d) Noise conditions. When the surrounding environmental conditions are limited (e.g., close to residential areas), the noise standards are very high, and if the cost of noise reduction measures for direct air cooling systems is high, economically unreasonable, or simply cannot meet the requirements, an indirect air cooling system should be used.

e) Coal price conditions. After technical and economic comparison, when the coal price is higher than the critical coal price where the economic efficiency of direct cooling and indirect cooling is equivalent, an indirect air cooling system should be used.

f) Unit summer operation conditions. Since direct air cooling is more affected by environmental wind than indirect air cooling, the load fluctuation is larger during high wind and high temperature, and it may cause unit tripping. If the owner has strict requirements for the future summer operation of the unit, indirect air cooling systems should be prioritized.

g) Urgent and slow conditions of power plant construction. Since the construction period of large cooling towers for indirect air cooling systems is longer, if the project requires a faster construction speed for units to quickly solve the power shortage, direct air cooling systems should be prioritized.