I. Necessity and Significance of Constructing Large Air-Cooled Power Plants

As we all know, water is a limited resource. Freshwater resources are decreasing year by year worldwide, and the per capita water resources in China are about one-fourth of the world average. The severe shortage of water resources has seriously threatened the human living environment, so saving water has become a global trend.

How to implement the national policy of optimizing resource allocation and accelerating the development of central and western China under the condition of limited water resources is a major policy issue. In addition to consuming a large amount of fuel, thermal power generation also requires a large amount of water. A 200MW power plant, if using open cooling, requires a total water replenishment of 21000m3/h. Even with a wet cooling tower, the water replenishment is as high as 1000m3/h. China's freshwater resources are very scarce, with per capita freshwater resources only 1/4 of the world average. More than 80% of China's freshwater is concentrated in the south, while coal bases are in the north. Pit-head power plants face the severe situation of competing for water with farmland and livestock, while air-cooled units do not consume circulating water in principle. Therefore, the development of air-cooled units is the only way for power construction in coal-rich and water-scarce areas. The governance of desertification, restoration of vegetation, and protection of the ecological environment in northern China all require extremely scarce and precious water. Unified planning and rational use of water resources are important guarantees for coordinating economic development and the ecological environment. Power plant water consumption will inevitably be subject to certain restrictions. Therefore, in coal-rich and water-expensive pit-head areas, it is particularly suitable to develop water-saving, efficient, and low-emission air-cooled power plants.

The average water consumption rate of China's operating thermal power units is 1m3/GW*s, and that of units with a capacity of 300MW or more is 0.9m3/GW*s, which is much higher than the 0.7m3/GW*s level of developed countries. In addition to adopting dry ash removal, comprehensive reuse of water resources, and strengthening management with the idea of "water is as precious as oil," saving the circulating water cooling tower water, which accounts for 2/3 of the total water consumption of the plant, that is, using air-cooled units to reduce evaporation and wind losses from cooling towers, is a better choice for the coal-rich and water-scarce northern regions.

If air-cooling technology is combined with dry ash removal, supplemented by a rainwater harvesting system and a drainage recovery and reuse system, the "water bottleneck" in the power development of northern China will be overcome.

The air-cooled unit cooling system itself can save more than 97% of water, and the total plant water saving is about 65%. Generally, 1m3/s of water can be used to build a 1 million kW wet-cooled unit, while only 0.35m3/s of water is needed to build a 1 million kW air-cooled unit. Therefore, the same amount of water can build an air-cooled unit three times larger than a wet-cooled unit, which fully demonstrates the superiority of air-cooling technology in water saving and its broad prospects for promotion and use.

Although the initial investment of a power plant using air-cooling technology is higher than that of a wet-cooled unit, it greatly saves limited water resources and saves a large amount of water fees in the long-term operation. Constructing air-cooled power plants in coal-rich and water-scarce areas saves water resources on a macro level and creates conditions for sustainable development. For investors, it can fully utilize the advantages of coal and water resource combinations, increase the installed capacity under certain water resource conditions, and make the project comply with national industrial license policies for smooth implementation. Therefore, the construction of large air-cooled power plants has profound strategic significance.

II. Current Status of Water Resources in China

China is extremely poor in water resources, with per capita freshwater resources of only 2300 cubic meters, only one-fourth of the world average, and the distribution of water resources is extremely uneven. The total amount of water resources in the north over many years averages only 12% of the national total, while the population accounts for 37% of the national total, and the land accounts for 45%. The "South-to-North Water Diversion" project is still unknown when it will start. Experts have analyzed that in another 10 years, China will enter a period of severe water shortage. Since the beginning of spring this year, China has experienced the most severe drought in 10 years, and the drought has made the long-accumulated contradictions in China's water resources even more apparent. More than 200 million mu of crops were affected, more than 20 million people had difficulty drinking water, and more than 10 million livestock were also affected. More than 20 provinces, autonomous regions, and municipalities directly under the Central Government, with a population of more than 200 million, were affected by water shortages to varying degrees. More than 400 cities experienced water shortages, and the water prices in many cities have risen by 10% to 50%, and are priced according to use. Some cities have begun to limit or even shut down water use in certain industries, and the excess water will be charged at a multiple price.

Most of the northwest region has a dry climate, with low rainfall and high evaporation. Surface water and groundwater resources are relatively scarce. For example, in the Urumqi area of Xinjiang, the annual rainfall is less than 200 mm, while the annual evaporation is about 20000 mm. The main water source comes from the melting of snow and ice in the Tianshan Mountains. According to reports, the average total water resources in the northwest region are about 232 billion cubic meters, accounting for only about 8% of the national total, and the distribution is severely uneven. The drinking water problem for a considerable part of the population has not yet been solved, while infrastructure construction, key development zones for agriculture and animal husbandry, and ecological environment construction all require water. Due to the uneven distribution of water resources, the difficulty of development and utilization is high, and many projects require large-scale water diversion from tens or even hundreds of kilometers. Some projects have complex terrain, increasing construction investment and operating costs. The total water resources in Shaanxi Province are 42.2 billion cubic meters, averaging 1290 cubic meters and 850 cubic meters per capita and per hectare of cultivated land, respectively, which is 50% and 40% of the national average. The annual water shortage is 3.9 billion cubic meters, resulting in a grain reduction of more than 10 billion kilograms, affecting people's daily life water use, and causing industrial losses of nearly 10 billion yuan. Since the founding of the People's Republic of China, with the continuous increase in industrial and agricultural water use, the groundwater level in the Hexi Corridor of Gansu Province has dropped sharply, with the groundwater level in Jiayuguan City dropping by more than 60 meters and that in Zhangye City dropping by nearly 100 meters. In the 1950s, the area of Caohu Lake was about 326 square kilometers. Due to excessive groundwater extraction by nearby cities and enterprises, coupled with blind land reclamation, the lake has disappeared. In northern Shaanxi, western Inner Mongolia, and Xinjiang, coal resources are abundant, but water resources are often scarce near coal mines. With the full implementation of the Western Development Strategy, the contradiction between water supply and demand will become increasingly acute. Only by rationally utilizing and saving water and entering a virtuous cycle of sustainable development and utilization of water resources can we serve economic construction and social development and maintain the momentum of sustainable development in the northwest region.