ZHANG Chao 

Associate Professor, School of Economics and Management, Tongji University

Associate Dean of the Department of Public Administration 

· Bachelor—Ph.D of Engineering，School of Environment,   Tsinghua University

· Postdoctorate，Kennedy School of Government, Harvard University 

Research fields include energy and environmental systems analysis, industrial ecology and ecological economics, etc. 

In recent years, a large number of studies have been carried out on issues of sustainability assessment and collaborative management of the water-energy coupled system, environmental footprint analysis, and resource efficiency evaluation from the perspective of social metabolism, etc., with results which are mainly published in international high-level academic journals such as Environmental Science & Technology, Applied Energy, Journal of Cleaner Production and Ecological Economics. 

The water resource pressure brought by thermoelectric power generation in the water-short area—northwest of China has increased significantly, where a measure of  "total quantity control of water. " should be implemented in the development of coal and electricity base. "Decoupling between water use and thermoelectric power generation growth in China" was published online on September 10 in the form of a cover article by Nature Energy, an international authoritative academic journal. This paper, for the first time, establishes a high-resolution geological information database of water use for thermoelectric power generation in China with long time series, reveals the evolution process of space-time pattern of water intake, water consumption and water resource pressure from thermoelectric power generation between 2000 and 2015, and quantitatively evaluates the contribution of various influencing factors to the improvement of water use efficiency of thermoelectric power generation. This study has a great reference significance for China in policy formulation relating reasonable water resource management and power industry development.

Evolution of spatial distribution of water resources pressure caused by thermal power extraction 

Both globally and in China, thermoelectric power is the second-largest sector for water usage after agricultural irrigation. The growing demand for electricity continues to spur and drive capacity expansion in the thermoelectric power industry, creating increasing competition for water resources. At present, water resource risk has become one of the major risks affecting global sustainable development, and water resource has also become another important environmental challenge faced by the power industry following air pollution emission and greenhouse gas emission.Taking the traditional circulating cooling coal-fired power plant as an example, about two liters of water are consumed per kilowatt-hour, of which about 80% is evaporated in the condenser cooling process, and the rest is mainly used for flue gas desulfurization, ash scum removal and boiler water replenishment. Although the dc cooling power plant isn’t water consuming as much as cooling tower’s evaporation, it relies on continuous through-flow cooling water source. The small and medium-sized units with low thermal efficiency consume more than 100 liters of water per kilowatt-hour，meanwhile, discharge warming drainage which is the main source of thermal pollution in water.

China has the world's largest installed thermoelectric power generation capacity, with a total of 1.14 billion kilowatt (including nuclear power) in 2017, about 35% higher than the United States. China's thermoelectric power industry not only rapidly grows in scale, but also significantly changes in the spatial distribution of power production. In recent years, with the promotion of the "west-east power transmission project", the construction of large coal power bases in northwest China has made rapid progress, and most of the new thermoelectric power production capacity has been transferred to the water shortage area in northwest China. The influence of the westward shift of thermoelectric power capacity on local water resources and water environment has attracted wide attention.

The research firstly built a complete geographic information database of time series generator set covering about 99% of the thermoelectric power installed capacity, and established a water withdrawal intensity multivariate regression model according to the sampling data of China water generator set, on the basis of which calculated the water withdrawal and consumption list of thermoelectric power containing detailed geographical information. The study found that the thermoelectric power generation of the high water pressure zone (where water pressure exponent is greater than 0.4, the index reflects the ratio of withdrawals and available water resources in certain basin) across the country grew from 0.64 trillion kwh in 2000 (accounting for 58.5% of the total national thermal power that year) to 2.89 trillion kwh in 2015 (accounting for 66.5%), increasing by 3.5 times.Among the ten first-level water resources regions in China, the northwestern river basins covering Xinjiang, western Inner Mongolia and other regions increased by nearly 14 times, which is the first-level region with the fastest expansion of thermoelectric power production capacity since the new millennium among which the thermoelectric power generation in arid regions dominated by desert and gobi landforms grew from less than 5 billion kwh to nearly 100 billion kwh. 

In order to cope with the risk of water resources caused by the production capacity surge and spatial distribution change, China has issued a series of management policies to promote the improvement of water efficiency of power industry. For example, new units replacing water cooling with air cooling technology in water-scarce areas in north China are being built, seawater cooling replacing fresh water in coastal areas is being promoted, access standards are being raised to realize the upsizing of units, water intake quota standards for thermal power generation are being raised to promote the application of water-saving technology, and old units with low efficiency of energy and water resources are being eliminated in a rapid pace.It is found that thanks to the combined action of various policies, the technical structure of China's thermoelectric power generation has changed greatly and the technical efficiency has been improved continuously. The total amount of fresh water intake for thermoelectric power generation reached a peak of 67.3 billion cubic meters in 2011, accounting for about 11% of the total amount of water intake in the country that year, and it continually decline realizing the decoupling between water use and thermoelectric power generation.At the same time, the increase in total water consumption has slowed down significantly. Among various influencing factors, the change of cooling technology structure contributes more than 70% to the "decoupling" of total water intake which reflects most obviously in the northwestern river basin. Air cooling technology started in northwest China from 2007, while had accounted for 69% of the total thermoelectric power generation in the northwestern river basin by 2015. It can be said that under the constraint of mandatory technical policy, most new power plants in northwest China adopt this water-saving technology. 

Although China's thermoelectric power industry has achieved remarkable water-saving effect on the whole, due to the extremely uneven spatial distribution of water resources in China, the pressure on water resources in energy development hot spots will continue, and the potential water risks should not be ignored. The study found that, from 2000 to 2015, the pressure index of thermoelectric power water resources in most areas of Haihe river basin decreased significantly, while the catchment area where large coal power bases located in northwest China increased significantly, especially the coal power bases such as east Junggar , Yili and Hami increased the most. The amount of thermoelectric power generation in individual catchment areas has exceeded the local average amount of surface water resources available for ages, presenting a severe contradiction between energy development and sustainable water resource use. It is the fundamental way that promoting the coordinated planning and management of energy and water resources system to relieve the pressure of thermoelectric power water resources.

First and corresponding author of this article – Chao Zhang, associate professor of department of economics and management in Tongji University, interdisciplinary professor of the UN environment programme – school of environment and sustainable development of Tongji University, said that the future development of power industry in China will face increasing resources and environment constraints. At present, the atmospheric pollutant emission and carbon emissions has caused full attention, while water resource problems in power industry haven’t been taken into account until recent years. Risk warning on the coal power planning and construction in 2021 issued by the National Energy Administration in May 2018 shows that resource constraints on coal power development in Xinjiang, Inner Mongolia, Ningxia and other northwestern regions are all green. Although the document points out that the index takes into account factors such as the emission of air pollutants, water resources, total coal consumption, etc., it cannot accurately reflect the information of water resources and water environment carrying capacity of the region where the coal power base is located due to the lack of factor evaluation conclusion.On the other hand, if we consider the problem from the perspective of building water supply projects to guarantee the water demand of energy projects, we may easily fall into the department-based mindset. In the future planning and management, attention should be paid to the overall impact of the development of power industry on the water circulation in river basins and regions, and more stringent measures such as the total water intake control should be taken with the help of better water measurement methods in extremely water-deficient areas, thus to promote the refinement and systematization of water resource management.

The joint author of this paper, Dr. Lijin Zhong, the former director of China Water Project in World Resources Institute said that the energy department's related research and staff had always been looking forward that water saving technical reconstruction or air cooling technology innovation can solve the problem of local competition with water in the face of the impact on the local water resources in the development of thermoelectric power. Water saving work of electric power industry in China has made significant effect after a series of policies since 2000, however, through the introduction of more microscopic and detailed spatial analysis methods, this study found that in the past water resource management of China's power industry, the systematic water pressure and water resource risk recognition were lacking, and furthermore, the spatial characteristics of water resource were neglected. The research not only shows that the technical progress at the micro scale may bring the "rebound effect" at the macro scale, but also reveals the importance and urgency of establishing the cross-elemental and cross-sectoral coordination mechanism of energy and water resource management, so as to avoid the risk transfer caused by scale growth and improper layout. 

Regarding the development trend of water impact on electric power industry, another co-author of this paper,  Dr. Jiao Wang, a researcher of the China Water Project in World Resources Institute, said that considering coal plants growth slowing, technical structure optimization, and renewable energy substitution effect, the research conclusion that total water use in power industry in China has been over the peak is reliable. However,  due to the changes in the spatial distribution of power installation, the water consumption and water resource pressure in key development areas are likely to increase further.In the longer term, the impact of large-scale development of low-carbon electricity on water resources depends on the choice of development path. Wind power and solar photovoltaic power generation have obvious water-saving synergies, while solar concentrated power generation, fossil fuel power plants equipped with carbon capture and storage facilities (CCS), inland nuclear power plants and other low-carbon power technologies tend to use more water than current advanced coal-fired power stations.