Optimized Layout of Large-Scale Coal-Fired Power Plant CCUS Projects under Water Resource Constraints in China

Abstract

Carbon capture, utilization, and storage (CCUS) technologies are an integral part of the carbon-neutral technology portfolio at the present phase. However, large-scale implementation of CCUS technologies may increase urban water consumption and raise urban water security issues. In this paper, 596 large-scale coal-fired power plants were investigated in terms of water withdrawal and water consumption. To minimize total water withdrawal and total water consumption, a source-sink matching model for CCUS projects under water resource constraints was established to optimize the layout of CCUS projects in China. The results show that there is a mismatch between the distribution of coal-fired power plants in a spatial location and water resources. The annual increase in water withdrawal of about 27.6 billion tons and water consumption of about 2.4 billion tons is needed to achieve the 2 °C target, which will aggravate the water scarcity in the north-central cities. Implementation of CO₂-enhanced water recovery (CO₂-EWR) technology can offset some of the increase in urban water consumption owing to CCUS deployment. This study can provide data support for site selection in the large-scale deployment of CCUS technology and provide the theoretical basis for decision-makers to lay out CCUS projects.

1. Introduction

CCUS technology, which is an indispensable part of the carbon neutral technology cluster, is the key technical means and the bottom-up technical guarantee to achieve the temperature control target of the Paris Agreement, and it is also the only technology that can realize the large-scale low-carbon utilization of fossil energy at the present stage. To achieve carbon neutrality, China needs to increase the size of its CCUS projects to 10 million tons [1,2]. There are four regions that form potential CCUS program cluster areas [3], of which three clusters are located in relatively water-scarce regions north of the Yangtze River. Deploying CCUS in areas where urban water resources are relatively scarce will have an impact on urban water use. This is primarily because the implementation of CCUS technology in power plants increases the amount of water used in coal-fired power plants [4]. The main reason for this is that the heat exchangers and CO₂ compressors which are added to the decarbonization system require cooling water, which increases the total cooling load of the plant [5]. Depending on the difference between power generation and capture technologies, water consumption in power plants is estimated to increase by 33% to 90% after the deployment of CCUS technology [6,7,8]. However, it is considered that China is a water-scarce country, especially for its energy base [9], and the spatial and temporal distribution is uneven, with a multi-year average of 2.81 trillion tons of total surface water resources, a low per capita water resources ownership of less than 25% of the world, and a multi-year average of 6.2 trillion tons of total annual precipitation, which translates into a depth of precipitation of 0.648 m, which is about 20% lower compared to the global average terrestrial precipitation value [4]. Even more seriously, there is a mismatch between Chinese power plants and water resources, with water-rich cities located south of the Yangtze River, while large coal-fired power plants are concentrated in Northern and Northwestern China. Studies have shown that as climate change worsens, the contradiction between increased water use for electricity and the increasing scarcity of water resources will continue to be accentuated [10,11], and annual water withdrawals and consumption will also show a clear increasing trend [12]. In addition, the development and implementation of coal-based carbon capture and storage technologies may exacerbate water scarcity in these areas [13,14]. From the economic point of view of implementing CCUS technology in power plants, coal-fired power plants should be located closer to CO₂ storage sites [15,16]; however, the cities suitable for CO₂ storage generally have scarce water resources and there is a mismatch between the suitable storage sites and the distribution of water resources in China. In other words, there is a mismatch between the distribution of suitable storage sites and water resources in China. This contradiction between the increase in water consumption for electricity and the growing scarcity of water resources may be further exacerbated by the retrofitting of power plants with carbon capture technology [17,18]. Deep carbon reduction and water conservation are two interacting environmental challenges facing China’s power sector [19].

The aim of this study is to investigate the problem of changing the layout of CCUS project source-sink matching under water resource constraints by modeling the source-sink matching under water resource constraints in China. For the first time, it is proposed to identify the cities that prioritize the deployment of CCUS projects under the goal of minimizing urban water withdrawal and consumption, and the increase in water withdrawal and consumption due to the deployment of CCUS. Aiming to indicate the changes in the pressure indices of electricity water withdrawal and water consumption in urban China, and the impacts of water resources on the source-sink matching layout of CCUS projects, this work can provide theoretical support for alleviating the contradiction between water security and carbon emission reduction in China. Because of this, this paper carries out an in-depth study on the impact of water resources on the layout of CCUS projects. The following questions are addressed: (1) How will the source-sink matching layout of CCUS projects in China change under the constraints of urban water resources? (2) Does CO₂-EWR technology improve the mitigation of water consumption in CCUS projects?

2. Material and Methods

Firstly, the amount of water resources of coal-fired power plants and cities where coal-fired power plants are located that are suitable for CCUS retrofit are obtained. The selection of large coal-fired power plants that are suitable for CCUS implementation is based on the applicability criteria for CCUS retrofits. The specific screening methods are as follows: Coal-fired power plants must satisfy the following suitability criteria in the initial screening: (1) the plant was established after 1995; (2) the installed capacity is more than 300 MW; and (3) the plant is within 800 km of the nearest water storage basin. The total number of power plants meeting the suitability criteria is 591, with a total installed capacity of about 664 gigawatts [3,20]. The average multi-year water resources for 236 cities were compiled using 596 power plant cities as the research unit. The urban water resources data were obtained from the water resources bulletins issued by provinces and cities, and the data on 596 coal-fired power plants were obtained from the China Electricity Council (CEC).

Secondly, the cooling method of the coal-fired power plant is determined. Based on the enterprise data of coal-fired power plants provided by CEC, the location is determined in Google Maps, and by determining whether there is a circulating cooling tower for coal-fired, whether there is an inflow of seawater, river water, river water, lake water, etc., and whether there is a heat sink for dry cooling, it is determined whether the plant is circulating-cooled, DC-cooled, or air-cooled, respectively. Then, according to the power generation technology of each power plant, nine types of coal-fired power plants with different water withdrawal and consumption are obtained, such as ultra-supercritical-circulating-cooling, supercritical-circulating-cooling, subcritical-circulating-cooling, ultra-supercritical-direct-cooling, supercritical-direct-cooling, subcritical-direct-cooling, ultra-supercritical-wind-cooling, supercritical-wind-cooling, subcritical-wind-cooling, and so on.

Finally, according to the corresponding cooling methods of different coal-fired power plants, the corresponding water withdrawal and consumption per unit of power generation can be found, as shown in

Table 1. Water withdrawal and consumption per unit of power generation for different power plants before and after CCUS retrofitting (m³/MWh).

Power Generation Technology	Cooling Method	Withdrawal	Consumption	Data Sources
Subcritical power plant	Once-through	116.48	1.24	[4,21,22]
Subcritical power plant with CCUS	Once-through	199.11	1.77	[4,21,22]
Supercritical power plant	Once-through	88.9	0.69	[4,21,22]
Supercritical power plant with CCUS	Once-through	161.49	0.85	[4,21,22]
Ultra-supercritical power plant	Once-through	82.8	0.228	[4,23]
Ultra-supercritical power plant with CCUS	Once-through	143.2	0.344	[4,24]
Subcritical power plant	Recirculating	2.31	2.01	[4,21,22]
Subcritical power plant with CCUS	Recirculating	4.51	3.65	[4,21,22]
Supercritical power plant	Recirculating	2.19	1.61	[4,21,22]
Supercritical power plant with CCUS	Recirculating	4.14	3.06	[4,21,22]
Ultra-supercritical power plant	Recirculating	1.58	1.26	[4,21,22]
Ultra-supercritical power plant with CCUS	Recirculating	3.44	2.53	[4,21,22]
Subcritical power plant	Dry	0.23	0.2	[4,21,22]
Subcritical power plant with CCUS	Dry	0.45	0.36	[4,21,22]
Supercritical power plant	Dry	0.21	0.16	[4,21,22]
Supercritical power plant with CCUS	Dry	0.41	0.31	[4,21,22]
Ultra-supercritical power plant	Dry	0.15	0.12	[4,21,22]
Ultra-supercritical power plant with CCUS	Dry	0.34	0.25	[4,21,22]

. Based on the power generation capacity and the technology of the power plant, the first step is to calculate the annual water withdrawal and water consumption of each power plant without a carbon capture system and with a carbon capture system. In the second step, the annual emissions of CO₂ from each power plant are calculated. The amount of water withdrawn per year for each power plant is compared to the amount of CO₂ emissions per year for each power plant to obtain the amount of water withdrawn and consumed per ton of CO₂ emitted with and without CCUS.

(1)

Minimum water withdrawal

In the full CCUS process, the main water-related aspects include three aspects. The first is the increased water withdrawal (water consumption) in the capture section due to the addition of carbon capture technology. Second, in the CO₂ transport stage, 0.05 tons of softened water per ton of CO₂ is required for compression and liquefaction due to the need to pressurize the CO₂ [25]. Third, in the CO₂ sequestration stage, salty water is obtained using CO₂-EWR technology. The obtained brackish water is converted into fresh water. The total target volume of water withdrawal is equal to the volume of water withdrawn from the capture stage minus the volume of freshwater obtained from the sequestration stage and the desalination and treatment stage.

$${\mathrm{minQ}}_w={\displaystyle \sum _{i=1}^m{\displaystyle \sum _{j=1}^n\left[\left(W{Q}_i+TR{Q}_{ij}\times D_{ij}-EW{R}_j\right)\times x_{ij}\right]}}$$

(1)

where ${\mathrm{Q}}_w$ is the total water withdrawal from coal-fired power plants after the implementation of CCUS during the planning period, $W{Q}_i$ is the corresponding withdrawal from different power plants in tons of water/tons of CO₂, and $EW{R}_j$ is the amount of freshwater obtained by sequestering 1 ton of CO₂. $TR{Q}_{ij}$ is the water consumed per unit of transportation between sources and sinks, which is generally due to the softened water consumed in the CO₂ pressurization chain, as shown in Equation (1). The optimization model refers to the literature [3,26].

(2)

Minimum water consumption

According to the different cooling methods of power plants, coal-fired power plants can generally be divided into once-through cooling and circulation cooling. For once-through cooling, there is generally a large amount of water withdrawal, but the water consumption is small. For circulation cooling, the difference between water withdrawal and water consumption is small. Once-through cooling is commonly found in China’s coastal areas, along rivers and rivers with abundant water resources. Recirculation cooling is often found in areas of Northwest and North China where freshwater resources are less abundant. Therefore, the optimization with minimum water consumption better reflects the consumption of water resources in the whole CCUS process. It is more conducive to the optimal layout of CCUS with minimum water resources, as shown in Equation (2).

$${\mathrm{minQ}}_c={\displaystyle \sum _{i=1}^m{\displaystyle \sum _{j=1}^n\left[\left(C{Q}_i+TR{Q}_{ij}\times D_{ij}-EW{R}_j\right)\times x_{ij}\right]}}$$

(2)

where ${\mathrm{Q}}_c$ is the total water consumption of coal-fired power plants in the planning period after the implementation of CCUS, and $CQ$ is the corresponding water consumption of different power plants in tons of water/tons of CO₂.

(3)

The constraint

The constraints for the objective functions (1) and (2) are basically the same, and both need to fulfill the target amount of source-sink matching.

(1) The actual capture amount of each carbon source is less than or equal to the theoretical maximum capture amount, as shown in Equation (3).

$${\displaystyle \sum _{i=1}^n{x}_{ij}\le {\eta }_i}\times E_i \forall i\in S,\forall j\in R$$

(3)

where ${\eta }_i$ denotes the maximum capture rate of carbon source $i$, and $E_i$ denotes the emissions of carbon source $i$.

(2) The sum of point source capture from coal-fired power plants is more than or equal to the total amount of CCUS plant capture that needs to be accounted for in order to achieve the 2 °C target. $RR{C}_{power}$ is the amount of CO₂ capture needed by coal-fired power plants to achieve the 2 °C target, as shown in Equation (4).

$${\displaystyle \sum _{i=1}^m{\displaystyle \sum _{j=1}^n{x}_{ij}\ge RR{C}_{power}}} \forall i\in S,\forall j\in R$$

(4)

(3) The actual sequestration amount of the individual carbon sink $j$ is less than or equal to its effective sequestration amount. $Q_j$ is the maximum effective storage potential of each storage site, as shown in Equation (5).

$${\displaystyle \sum _{j=1}^n{x}_{ij}\le Q_j} \forall i\in S,\forall j\in R$$

(5)

(4) Water resource constraints at CO₂ capture sites. $H_i^s$ is the water resource modulus (the amount of water in an area compared to the area of that area, i.e., the amount of water per unit area) for the location of each sequestration source. $H_{average}^s$ is the national average water resource modulus, as shown in Equation (6).

$$H_i^s\le H_{average}^s \forall i\in R$$

(6)

(5) Non-negative constraints, as shown in Equation (7).

$$x_{ij}\ge 0$$

(7)

(4)

Water stress index

Available studies have already started to address water withdrawal and consumption by power plants in China [27,28,29,30,31]. The water stress index is the ratio of water use in a region to the total water resources in that region, also known as the water stress index, or critical ratio. In this paper, the power water stress coefficient is shown in Equation (8). In order to better reflect the degree of change in water stress before and after the implementation of CCUS in power plants, we highlighted the difference between the urban water stress coefficient after CCUS implementation and the urban water stress index without CCUS implementation to bring out the extent of change in urban water usage, as shown in Equation (9). The results are divided into four levels. When the difference value is under 0.01, it is considered that there is no impact on the urban water stress. When the value is between 0.01~0.05, it is considered to have no impact on the urban water stress. When the value is between 0.01~0.05, it is considered to have no impact on the urban water stress. A value of 0.05 is considered to have a low impact on urban water stress. A value between 0.05 and 0.1 is considered to have a moderate impact on urban water use. A value between 0.1 and 0.2 will have a large impact on urban water use. Finally, a value which is greater than 0.2 will have a serious impact on urban water use, as shown in Equations (8) and (9).

$$WT{A}_{n,k}={\displaystyle \frac{{\displaystyle \sum _i{TWE}_{n,k,i}}}{A{W}_{n,k}}}$$

(8)

$$WTA{C}_{n,k}=WT{A}_{n,k}-WT{A}_{n,0}$$

(9)

$WT{A}_{n,k}$ represents the electricity-water stress index under the $k$th technology scenario in the $n$th city; ${\mathrm{AW}}_{n,k}$ represents the multi-year average water availability under the $k$th condition in the $n$th city; ${\displaystyle \sum _i{TWE}_{n,k,i}}$ represents the sum of the water consumption of individual power plants in the $n$th city under the $k$th technology scenario; $i$ represents the number of power plants suitable for CCUS implementation in a particular city; $WTA{C}_{n,k}$ represents the change in the water stress index under the $k$th technology scenario in the $n$th city; and $WT{A}_{n,0}$ represents the electricity water stress index of the power plants in the $n$th city without the implementation of CCUS.

(5)

The CO₂-EWR

Under the constraints of carbon neutrality goals, CO₂ has been extensively applied in geological developments [32], e.g., CO₂-based polymer fracturing fluids for enhanced oil recovery [33], CO₂ as a substitute for methane [34], and CO₂-enhanced water recovery (EWR). The CO₂-EWR has become a research focus in the field of CCUS [5,35], and it is used to estimate the amount of saline water obtained through EWR at a supercritical CO₂ density of 0.60 tons/m³. Assuming that each ton of carbon dioxide injected into a brackish water aquifer replaces the same volume of water, i.e., the ratio of CO₂ to the brackish water mass displacement is 0.6:1 [36],the salty water is not available for direct utilization, therefore, the resulting salty water needs to be desalted, which is generally carried out by reverse osmosis. In this paper, in regard to the existing data [37,38,39], the driven brackish water is converted into blue water in the ratio of 1:0.5, and the final quality of the blue water obtained is equal to the quality of the sequestered CO₂, i.e., the amount of CO₂ sequestered is approximately equal to the amount of blue water obtained by CO₂-EWR. It is also assumed that all of the city’s water obtained through CO₂-EWR is allocated to coal-fired power plants implementing the CCUS.

3. Results and Discussion

(1)

Layout of CCUS source and sink matches for minimum water withdrawals

Figure 1 shows the distribution of urban water consumption pressure indices at the time of minimum water withdrawal. In terms of the magnitude of the water withdrawal stress index, cities with an urban water modulus (amount of water per unit area) of less than 0.1 tons/km² will not participate in source-sink matching due to the added water constraint. This makes the overall water-abundant cities more involved in carbon capture. The average value of the national level power abstraction stress index is 0.02, compared to the national average of 0.02 when the cost is at its lowest. In particular, the power abstraction stress index of cities participating in the CCUS program is less than 0.1. The total number of cities with abstraction stress indices ranging from 0.01 to 0.05 is 17, mainly located in Henan (Luoyang City, Henan Province) and Henan Province (Luoyang City, Henan Province). These cities are located in Henan (Luoyang, Pingdingshan, Xuchang, Zhengzhou, Hebi, and Jiyuan), Hebei (Shijiazhuang and Langfang), Shanxi (Jincheng), Shandong (Dezhou, Jining, Zaozhuang, Weihai, and Zibo), Anhui (Huaibei), Xinjiang (Urumqi), and Tianjin. The water withdrawal pressure index is the largest in the city of Henan Province, Jiyuan City, with a value of 0.1 under the constraints of water resources, and the layout of the national CCUS project is mainly concentrated in the Yangtze River Delta region, as well as Tianjin and Qinhuangdao and other areas of the Beijing-Tianjin-Hebei region.

The reasons for the above are as follows: Firstly, it is related to the way of water withdrawal. The power plants with large water withdrawals often adopt once-through cooling, which requires the construction of power plants in rivers, lakes, and seashores, and these regions and cities meet the conditions. Secondly, there are suitable geological conditions for CO₂ storage around, which are especially suitable for the area of CO₂-EWR, and according to the existing research, large amounts of these areas are in the North Jiangsu Basin and Bohai Basin, respectively.

Figure 2 shows the distribution of the increase in urban water consumption due to the CCUS retrofitting. In terms of water withdrawals from power plants, accomplishing a 2 °C emissions reduction under water resource constraints would require an increase in water withdrawals of about 27.6 billion tons per year, which is 20.3 billion tons per year less than when carbon capture is implemented at the lowest cost, involving 166 cities. This is because CO₂ would be used entirely for EWR at the time of the lowest water withdrawal target, which increases the number of water resources. Of these cities, the increase in water withdrawals due to the implementation of carbon capture averages about 0.5 billion tons per year per city. There are 14 cities with an increase in urban electricity withdrawals of more than 100 million tons per year, of which the increase in withdrawals is between 100 and 200 million tons per year. From lowest to highest, these are Chengmai (101 million tons), Jiaxing (102 million tons), Dongfang (106 million tons), Tongling (111 million tons), Qinhuangdao (112 million tons), Tianjin (135 million tons), Zhenjiang (145 million tons), Ma’anshan (145 million tons), Ma’anshan (154 million tons), (145 million tons), Maanshan (162 million tons), Nanjing (174 million tons), and Shantou (185 million tons). In the Yangtze River Delta Economic Zone, because of the huge scale of electricity consumption and the abundance of water resources in the region, most of the coal-fired power plants employ once-through cooling, and the amount of water withdrawn by the power plants has increased significantly after the implementation of carbon capture. Cities that have increased their water withdrawals by more than 200 million tons per year due to CCUS implementation include Wuxi (204 million tons), Yangzhou (325 million tons), Suzhou (651 million tons), and Shanghai (687 million tons). Although some coal-fired power plants in Suzhou and Shanghai use seawater for cooling, they still need to desalinate seawater, and this part of the desalinated water resource also requires a certain economic cost, so the desalination of seawater is included in the local urban water resources in this study.

(2)

Layout of CCUS source and sink match for minimum water consumption

Figure 3 shows the distribution of the water stress index for the city with the minimum amount of water consumption. In terms of water consumption, under the water constraints, accomplishing a 2 °C emissions reduction would require the water consumption of about 2.4 billion tons per year, with an average increase of about 520 million tons per year over not implementing CCUS, involving 165 cities. The increase in water consumption due to the implementation of carbon capture in each of these cities averages 3.2 million tons per year. Of these cities, 13 increased water consumption for urban electricity by more than 100,000 tons per year. The cities with an increase in water consumption of 100,000 to 150,000 tons per year, from lowest to highest, are Jincheng (102,000 tons), Jiyuan (109,000 tons), Liupanshui (110,000 tons), Chongqing (114,000 tons), Bijie (118,000 tons), Huainan (138,000 tons), Pingdingshan (141,000 tons), Luoyang (142,000 tons), Qujing (147,000 tons), Xuzhou (148,000 tons), and Jining (149,000 tons). The cities of Tianjin and Shijiazhuang will increase their water consumption by more than 150,000 tons due to the implementation of the CCUS project, with 161,000 tons and 179,000 tons, respectively. The total water resources of these two cities are currently lower than the national average water resources of cities, with a population size of more than 10 million, and even under the constraints of water resources, water consumption is still high, which is closely related to the city’s coal-fired power plants with large installed capacity.

Figure 4 shows the distribution of the increase in urban water consumption due to the implementation of CCUS. In terms of the amount of the water consumption stress index, cities with an urban water modulus (amount of water per unit area) of less than 0.1 tons/km² will not participate in source-sink matching due to the added water constraint. This makes it clear that overall water-abundant cities will be more involved in carbon capture and the national-level electricity water consumption stress index, which averages out at 92% lower than the national average water consumption electricity stress index at the lowest cost. Specifically, all cities participating in the CCUS project have an electricity water stress index of less than 0.1, and there are 17 cities with a water stress index between 0.01 and 0.05, mainly in Henan (Luoyang City, Pingdingshan City, Xuchang City, Zhengzhou City, Hebi City, and Jiyuan City), Hebei (Shijiazhuang City and Langfang City), Shanxi (Jincheng City), Shandong (Dezhou City, Jining City, Zaozhuang City, Weihai City, and Jining City), Shandong (Jining City, Zaozhuang City, Weihai City, and Jining City), Shandong (Dezhou, Jining, Zaozhuang, Weihai, and Zibo), Anhui (Huaibei), Xinjiang (Urumqi), and Tianjin. The city with the largest water consumption pressure index is Jiyuan City in Henan Province at 0.1. Under the constraints of water resources, the layout of CCUS projects across the country has been shifted to the south, but as the distribution of coal-fired power plants is concentrated in the provinces of Hebei, Henan, and Shandong, in order to fulfill the 2 °C emission reduction target, the above five provinces still need to deploy CCUS projects on a large scale, which has increased the pressure on the consumption of water in this part of the city significantly.

(3)

Impact of implementing CO₂-EWR technology on urban water consumption

Under the constraint of the 2 °C target to achieve the lowest water consumption, 166 cities are involved, as shown in Figure 5, with 59 cities increasing their water consumption by more than 10 million tons per year through CO₂-EWR, and 15 cities, mainly Shijiazhuang, Tianjin, and Jining, with more than 30 million tons. These cities are mainly those with a high proportion of recycled cooling. The number of cities that can make up for the additional water consumption through CO₂-EWR is 82, accounting for about 49% of the total number of cities. The proportion of cities that can compensate for the additional water consumption through water resources obtained from CO₂-EWR is significantly higher compared to the lowest cost and the lowest amount of water withdrawal. 84 cities cannot compensate for the increased water consumption due to the deployment of CCUS in power plants by CO₂-EWR, and about 82% of these cities are found in water-scarce areas north of the Yangtze River. Other parts of the cities are distributed south of the Yangtze River, mainly in the Yunnan-Guizhou region, such as Guiyang City and Qujing City, which have more coal-fired power plants but have fewer basins suitable for storage, and therefore, have fewer amounts of CO₂ to match to when matching sources and sinks and less water added by CO₂-EWR.

4. Conclusions

The coal-fired power plants implementing carbon capture are severely constrained by water resources when deploying CCUS projects. This paper establishes databases of Chinese urban water resources and the urban power water stress index. To minimize total water withdrawal and minimize total water consumption, it establishes a source-sink matching model for CCUS projects under water resource constraints, optimizes the layout of CCUS projects in China, and mainly obtains the following conclusions:

(1)

There is a mismatch between coal-fired power plants and the spatial distribution of water resources. From the perspective of power plant cooling methods, by accounting for the water usage of coal-fired power plants in various cities, it can be obtained that the total water usage of power plants without CCUS retrofitting is about 4.6 billion tons. It is divided into four categories: once-through cooling, circulating tower cooling, air cooling, and seawater. Once-through cooling, among which the power plants using circulating tower cooling have the highest water consumption, is 86.4% of the total water consumption.

(2)

In terms of distribution, suitable coal-fired power plants are mainly concentrated in water-scarce cities in North and Northwest China, with an average annual water resource of less than 5 billion tons. The cooling method of power plants is based on circulating tower cooling, with a high water-consumption rate per unit; the power generation technology is based on subcritical power plants, with a high water-consumption rate per unit. In the cities of North and Northwest China, where power plant cooling is based on circulating towers, the deployment of CCUS will further increase the water consumption of power plants and exacerbate the water scarcity in the cities in the north-central part of the country.

(3)

Urban water resource differences will change the layout of CCUS source-sink matching in China. Under the water source constraint, cities with scarce water resources will not participate in CCUS construction. This makes the overall CCUS program move southward, and the total water intake and consumption will decrease significantly. The development of CO₂-EWR will alleviate the CCUS water consumption problem to a certain extent, especially in cities with a high proportion of dry cooling and direct current cooling in power plants, but it will not fundamentally compensate for the increase in water consumption and water withdrawals due to the implementation of carbon capture technology.