- Email: [email protected]
Water–energy Nexus in China's Electric Power System
Available online at www.sciencedirect.com
ScienceDirect Energy Procedia 105 (2017) 3972 – 3977
The 8th International Conference on Applied Energy – ICAE2016
Water–energy nexus in China’s electric power system Saige Wanga, Tao Caoa, Bin Chena* a
State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, P.R. China
Abstract The electric power system is water–intensive, which aggravates the water scarcity of China. Deeper understanding of the role of electric transmission systems coupling with virtual water flows is critical for sustainable development of China. In this study, the flux and direction of virtual water within power system were firstly analyzed. Water scarcity index (WSI) was also incorporated to evaluate the virtual scarce water flows. Then, we calculated the hybrid electricity flux by multiplying electricity flux with its proportion of total electricity consumption to elucidate the significance of flux on the node’s electricity supply. Finally, we studied the virtual scarce water flow network and hybrid electricity flux network via throughflow analysis to shed light on the nexus within the power system. The results show that electricity inflows bring in 27.99 GL of virtual scarce water concurrent with 10.865 TW h of electricity, and 47.47 GL of virtual scarce water concurrent with 15.072 TW h of electricity into the north and central regions of China. It can be concluded that a large volume of virtual scarce water (16.3 GL) is transferred via the electric power system, mainly from inland areas to coastal areas, which is roughly the opposite of the distribution of China’s water resources. By doing this, we aim to evaluate the energy–water nexus rate in the electricity power system to balance the tradeoff between electricity supply and the regional inequity of water resources. © 2017 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
© 2016 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Selection and/or peer–review under responsibility of ICAE Peer-review under responsibility of the scientific committee of the 8th International Conference on Applied Energy. Key words: virtual water, virtual scarce water, electric power system, electricity supply
1. Introduction
* Corresponding author. Tel/fax.: +86 10 58807368. E-mail address: [email protected] (Bin Chen)
1876-6102 © 2017 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the 8th International Conference on Applied Energy. doi:10.1016/j.egypro.2017.03.828
Saige Wang et al. / Energy Procedia 105 (2017) 3972 – 3977
Nomenclature Abbreviation WSI
the water stress index
TCWI
transmission–consumption water intensity
GWI
generation water intensity
VSW
virtual scarce water flow
HEF
hybrid electricity flux
The electric power system is a water–intensive sector, which is one of the largest water consumers in China apart from agriculture [1–2]. Indeed, 79% of total freshwater withdrawal and 47% of water consumption of energy production in China 2007 were attributed to the electricity generation [3]. The electricity sector has been a contributor to water scarcity, particularly in Northern China [4]. Substantial increases in power generation capacity will further exacerbate the current water shortage [5–6]. There will be a large increase in water use for the electric power sector, which could have serious consequences for water–scarce locations of the country [7–8]. In terms of water scarcity, existing power plants have to either shutdown due to lack of water, or continue to operate and risk exacerbating water shortages [4, 6, 7, 9]. Several studies have investigated the water–energy nexus in the electricity power sector by accounting the water demand for electricity system. For example, Liu et. al. estimated future state–level electricity generation and consumption and associated water withdrawals and consumption under a set of seven scenarios [9]. Feeley et. al. outlined the freshwater withdrawal and consumption rates for various thermoelectric power generating types and then estimated the potential benefits of Innovations for Existing Plants program technologies at both the national and regional levels in the year 2030 [6]. Also, the virtual water embodied in electric power system had been widely studied by analysing the flux and direction of virtual water and virtual scarce water within power system based on transmission– consumption water intensity [3]. The electric transmission systems can optimize the available resources and ensure the reliable and proper operation of the electric power system to guarantee energy supply [10]. By transferring the electricity from energy–rich to the energy–scarce regions, the electric transmission systems are also reallocating the water resources due to virtual water flows embodied in the electricity flux. However, when balancing the uneven distribution of regional energy resources, the regional inequity of water resources may be exacerbated [7]. Especially, it can exacerbate the water inequity by transferring the virtual water from water–scarce to water–rich regions. Thus, in–depth understanding of the water use coupled with power transmission is essential to improve water resource management in various areas of China [9]. In this paper, we address the water–energy nexus for electric power system in China, focusing on “water for energy”, “virtual water” and “virtual scarce water”. TCWI in the electric power system was defined to transform electricity flows into virtual water flows. Then, we evaluated the significance of electricity flux on energy supply system based on the proportion of electricity flux in the total electricity consumption. Finally, we tried to balance the energy and water in the electricity flux by balancing virtual scarce water and energy supply.
3973
3974
Saige Wang et al. / Energy Procedia 105 (2017) 3972 – 3977
2. Methodology When combusting coal, oil, natural gas, biomass, and waste to produce electricity, the power plants withdraw and consume large amount of water as well. These plants withdraw water from rivers, lakes, and streams to cool equipment before returning it to its source, and consume water (often through evaporative loss) that does not return to the local water circle. For this study, the term virtual water embodied in the electricity flux is meant to encompass both water withdraws and consumption together for electricity production [11–13]. Detailed descriptions and quantitative analyses of water use in various cooling systems show that water use varies widely among different systems [4, 6]. Meanwhile, upstream water use plays a significant role in renewable energy generation without cooling systems, such as wind farm [9]. The water consumption of the k th power plant can be calculated by [14]
DGk Gk
wGk
(1)
DGk
where represents the GWI (the water consumption per unit of electricity generated) of the k th power plant, Gk represents the power generation of the k th power plant ( k 1, 2,3..., K ).
D
The transmission water intensity of the m th line, Tm , is defined as the ratio of its virtual water flux to the electricity flux that flows into it. Thus, the virtual water flux of the m th line can be calculated by [15]
DTm eLIm
wLm
(2) Consequently, the nodal TCWI can be represented as
D
1
ª I ( Eˆin )1 Ain Eˆ Lin B º ( Eˆin )1 WG ¬ ¼
(3)
Similarly, the regional total scarce water consumption vector, WSLoad , can be calculated as
WSI WG A WSL
WSLoad
(4)
Regional hybrid electricity flux vector can be calculated by
Eh L
E Lin B P
(5)
where P represents the proportions of electricity flux for the total amount of regional electricity consumption.
Saige Wang et al. / Energy Procedia 105 (2017) 3972 – 3977
3. Results and Conclusions Fig.1 shows regional electricity generation and flux among six grids, from which we can conclude that there are two virtual scarce water exporters (northeast and northwest), two virtual scarce water importers (east and south), and two virtual scarce water hubs (north and central). The northwest is the largest exporter with 55.51 GL of virtual scarce water, while the east is the largest importer with 75.40 GL of virtual scarce water.
Fig.1. Electricity generation and flux among six grids in China
Fig.2 shows virtual scarce water flux among six regions. Combined with the electricity flux results in Fig.1, we can see that electricity inflows bring in 27.99 GL of virtual scarce water concurrent with 10.87 TW h of electricity, and 47.47 GL of virtual scarce water concurrent with 15.07 TW h of electricity into the north and central regions. Meanwhile, the two electricity outflows remove 63.38 GL of virtual scarce water concurrent with 19.23 TW h of electricity, and 33.06 GL of virtual scarce water concurrent with 63.54 TW h of electricity from the north and central regions. It is found that virtual scarce water is transferred from inland areas to coastal areas, which is roughly the opposite of the distribution of China’s water resources.
3975
3976
Saige Wang et al. / Energy Procedia 105 (2017) 3972 – 3977
Fig.2. Virtual scarce water flux among six regions in China Note: S, south; C, central; E, east; N, north; NE, northeast; NW, northwest.
This study was conducted to investigate the water–energy issues of electric power system in China, particular the electric transmission systems, with the nexus perspective on regional electricity supply and water resource reallocation. Regardless of WSIs, the central region as a virtual water exporter may help other regions alleviate the water shortage. However, incorporating the WSIs, the central region becomes a virtual scarce water importer that would further exacerbate water shortage in other regions. It can be seen that a much different perspective for energy–water nexus can be obtained through incorporating the WSI and virtual scarce water flow concept. 4. Copyright Authors keep full copyright over papers published in Energy Procedia Acknowledgement This work was supported by the National Key Research & Development Program (2016YFA0602304), National Natural Science Foundation of China (No. 71573021, 71628301), Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20130003110027), and China–EU Joint Project from Ministry of Science and Technology of China (No. SQ2013ZOA000022).
Saige Wang et al. / Energy Procedia 105 (2017) 3972 – 3977
References [1] [2] [3] [4] [5] [6] [7] [8] [9]
[10] [11] [12] [13] [14] [15]
Zhang XD, Vesselinov VV. Energy–water nexus: Balancing the tradeoffs between two–level decision makers. Applied Energy. 2016; 183: 77–87. Vishnu N, Antolínez IV. A competitive Markov decision process model for the energy–water–climate change nexus. Applied Energy. 2013; 111: 186–198. Feng KS, Hubacek K, Siu Y L, Li X. The energy and water nexus in Chinese electricity production: A hybrid life cycle analysis. Renewable and Sustainable Energy Reviews. 2014; 39: 342–355. DeNooyer T, Peschel J, Zhang ZX, Ashlynn S. Integrating water resources and power generation: The energy–water nexus in Illinois. Applied Energy. 2016; 162: 363–371. Abrell J, Rausch S. Cross–country electricity trade, renewable energy and European transmission infrastructure policy. Journal of Environmental Economics & Management. 2016; 79: 87–113. Thomas J. Feeley III, Skone TJ, Stiegel GJ, McNemar A, Michael Nemeth, Brian SJ. Murphy, Lynn M. Water: A critical resource in the thermoelectric power industry. Energy. 2008; 33: 1–11. Ackerman F, Fisher J. Is there a water–energy nexus in electricity generation? Long–term scenarios for the western United States. Energy Policy. 2013; 59: 235–241. Mekonnen M, Gerbens PW, Arjen YH. Future electricity: The challenge of reducing both carbon and water footprint. Science of the Total Environment. 2016; 569–570: 1282–1288. Liu L, Hejazi M, Pralit P, Kyle P, Davies E, Zhou YY, Clarke L, Edmonds J. Water demands for electricity generation in the U.S.: Modeling different scenarios for the water–energy nexus. Technological Forecasting & Social Change. 2015; 94: 318– 334. Vilanova MR, Balestieri JA. Exploring the water–energy nexus in Brazil: The electricity use for water supply. Energy. 2015; 85: 415–432. Wang SG, Chen B. Energy–water nexus of urban agglomeration based on multiregional input–output tables and ecological network analysis: A case study of the Beijing–Tianjin–Hebei region. Applied Energy. 2016; 178: 773–783. Chen GQ, Chen B, Zhou H, Dai P. Life cycle carbon emission flow analysis for electricity supply system: A case study of China. Energy Policy. 2013; 61: 1276–1284. Chen B. Energy, ecology and environment: a nexus perspective. Energy, Ecology and Environment. 2016; 1(1):1–2. Zhu XJ, Guo RP, Chen B, Chen B, Zhang J, Tasawar Hayat, Ahmed Alsaedi. Embodiment of virtual water of power generation in the electric power system in China. Applied Energy. 2015; 151: 345–354. Guo RP, Zhu XJ, Chen B, Yue YL. Ecological network analysis of the virtual water network within China’s electric power system during 2007–2012. Applied Energy. 2016; 168: 110–121.
3977
ScienceDirect Energy Procedia 105 (2017) 3972 – 3977
The 8th International Conference on Applied Energy – ICAE2016
Water–energy nexus in China’s electric power system Saige Wanga, Tao Caoa, Bin Chena* a
State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Beijing Normal University, Beijing 100875, P.R. China
Abstract The electric power system is water–intensive, which aggravates the water scarcity of China. Deeper understanding of the role of electric transmission systems coupling with virtual water flows is critical for sustainable development of China. In this study, the flux and direction of virtual water within power system were firstly analyzed. Water scarcity index (WSI) was also incorporated to evaluate the virtual scarce water flows. Then, we calculated the hybrid electricity flux by multiplying electricity flux with its proportion of total electricity consumption to elucidate the significance of flux on the node’s electricity supply. Finally, we studied the virtual scarce water flow network and hybrid electricity flux network via throughflow analysis to shed light on the nexus within the power system. The results show that electricity inflows bring in 27.99 GL of virtual scarce water concurrent with 10.865 TW h of electricity, and 47.47 GL of virtual scarce water concurrent with 15.072 TW h of electricity into the north and central regions of China. It can be concluded that a large volume of virtual scarce water (16.3 GL) is transferred via the electric power system, mainly from inland areas to coastal areas, which is roughly the opposite of the distribution of China’s water resources. By doing this, we aim to evaluate the energy–water nexus rate in the electricity power system to balance the tradeoff between electricity supply and the regional inequity of water resources. © 2017 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
© 2016 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Selection and/or peer–review under responsibility of ICAE Peer-review under responsibility of the scientific committee of the 8th International Conference on Applied Energy. Key words: virtual water, virtual scarce water, electric power system, electricity supply
1. Introduction
* Corresponding author. Tel/fax.: +86 10 58807368. E-mail address: [email protected] (Bin Chen)
1876-6102 © 2017 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the 8th International Conference on Applied Energy. doi:10.1016/j.egypro.2017.03.828
Saige Wang et al. / Energy Procedia 105 (2017) 3972 – 3977
Nomenclature Abbreviation WSI
the water stress index
TCWI
transmission–consumption water intensity
GWI
generation water intensity
VSW
virtual scarce water flow
HEF
hybrid electricity flux
The electric power system is a water–intensive sector, which is one of the largest water consumers in China apart from agriculture [1–2]. Indeed, 79% of total freshwater withdrawal and 47% of water consumption of energy production in China 2007 were attributed to the electricity generation [3]. The electricity sector has been a contributor to water scarcity, particularly in Northern China [4]. Substantial increases in power generation capacity will further exacerbate the current water shortage [5–6]. There will be a large increase in water use for the electric power sector, which could have serious consequences for water–scarce locations of the country [7–8]. In terms of water scarcity, existing power plants have to either shutdown due to lack of water, or continue to operate and risk exacerbating water shortages [4, 6, 7, 9]. Several studies have investigated the water–energy nexus in the electricity power sector by accounting the water demand for electricity system. For example, Liu et. al. estimated future state–level electricity generation and consumption and associated water withdrawals and consumption under a set of seven scenarios [9]. Feeley et. al. outlined the freshwater withdrawal and consumption rates for various thermoelectric power generating types and then estimated the potential benefits of Innovations for Existing Plants program technologies at both the national and regional levels in the year 2030 [6]. Also, the virtual water embodied in electric power system had been widely studied by analysing the flux and direction of virtual water and virtual scarce water within power system based on transmission– consumption water intensity [3]. The electric transmission systems can optimize the available resources and ensure the reliable and proper operation of the electric power system to guarantee energy supply [10]. By transferring the electricity from energy–rich to the energy–scarce regions, the electric transmission systems are also reallocating the water resources due to virtual water flows embodied in the electricity flux. However, when balancing the uneven distribution of regional energy resources, the regional inequity of water resources may be exacerbated [7]. Especially, it can exacerbate the water inequity by transferring the virtual water from water–scarce to water–rich regions. Thus, in–depth understanding of the water use coupled with power transmission is essential to improve water resource management in various areas of China [9]. In this paper, we address the water–energy nexus for electric power system in China, focusing on “water for energy”, “virtual water” and “virtual scarce water”. TCWI in the electric power system was defined to transform electricity flows into virtual water flows. Then, we evaluated the significance of electricity flux on energy supply system based on the proportion of electricity flux in the total electricity consumption. Finally, we tried to balance the energy and water in the electricity flux by balancing virtual scarce water and energy supply.
3973
3974
Saige Wang et al. / Energy Procedia 105 (2017) 3972 – 3977
2. Methodology When combusting coal, oil, natural gas, biomass, and waste to produce electricity, the power plants withdraw and consume large amount of water as well. These plants withdraw water from rivers, lakes, and streams to cool equipment before returning it to its source, and consume water (often through evaporative loss) that does not return to the local water circle. For this study, the term virtual water embodied in the electricity flux is meant to encompass both water withdraws and consumption together for electricity production [11–13]. Detailed descriptions and quantitative analyses of water use in various cooling systems show that water use varies widely among different systems [4, 6]. Meanwhile, upstream water use plays a significant role in renewable energy generation without cooling systems, such as wind farm [9]. The water consumption of the k th power plant can be calculated by [14]
DGk Gk
wGk
(1)
DGk
where represents the GWI (the water consumption per unit of electricity generated) of the k th power plant, Gk represents the power generation of the k th power plant ( k 1, 2,3..., K ).
D
The transmission water intensity of the m th line, Tm , is defined as the ratio of its virtual water flux to the electricity flux that flows into it. Thus, the virtual water flux of the m th line can be calculated by [15]
DTm eLIm
wLm
(2) Consequently, the nodal TCWI can be represented as
D
1
ª I ( Eˆin )1 Ain Eˆ Lin B º ( Eˆin )1 WG ¬ ¼
(3)
Similarly, the regional total scarce water consumption vector, WSLoad , can be calculated as
WSI WG A WSL
WSLoad
(4)
Regional hybrid electricity flux vector can be calculated by
Eh L
E Lin B P
(5)
where P represents the proportions of electricity flux for the total amount of regional electricity consumption.
Saige Wang et al. / Energy Procedia 105 (2017) 3972 – 3977
3. Results and Conclusions Fig.1 shows regional electricity generation and flux among six grids, from which we can conclude that there are two virtual scarce water exporters (northeast and northwest), two virtual scarce water importers (east and south), and two virtual scarce water hubs (north and central). The northwest is the largest exporter with 55.51 GL of virtual scarce water, while the east is the largest importer with 75.40 GL of virtual scarce water.
Fig.1. Electricity generation and flux among six grids in China
Fig.2 shows virtual scarce water flux among six regions. Combined with the electricity flux results in Fig.1, we can see that electricity inflows bring in 27.99 GL of virtual scarce water concurrent with 10.87 TW h of electricity, and 47.47 GL of virtual scarce water concurrent with 15.07 TW h of electricity into the north and central regions. Meanwhile, the two electricity outflows remove 63.38 GL of virtual scarce water concurrent with 19.23 TW h of electricity, and 33.06 GL of virtual scarce water concurrent with 63.54 TW h of electricity from the north and central regions. It is found that virtual scarce water is transferred from inland areas to coastal areas, which is roughly the opposite of the distribution of China’s water resources.
3975
3976
Saige Wang et al. / Energy Procedia 105 (2017) 3972 – 3977
Fig.2. Virtual scarce water flux among six regions in China Note: S, south; C, central; E, east; N, north; NE, northeast; NW, northwest.
This study was conducted to investigate the water–energy issues of electric power system in China, particular the electric transmission systems, with the nexus perspective on regional electricity supply and water resource reallocation. Regardless of WSIs, the central region as a virtual water exporter may help other regions alleviate the water shortage. However, incorporating the WSIs, the central region becomes a virtual scarce water importer that would further exacerbate water shortage in other regions. It can be seen that a much different perspective for energy–water nexus can be obtained through incorporating the WSI and virtual scarce water flow concept. 4. Copyright Authors keep full copyright over papers published in Energy Procedia Acknowledgement This work was supported by the National Key Research & Development Program (2016YFA0602304), National Natural Science Foundation of China (No. 71573021, 71628301), Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20130003110027), and China–EU Joint Project from Ministry of Science and Technology of China (No. SQ2013ZOA000022).
Saige Wang et al. / Energy Procedia 105 (2017) 3972 – 3977
References [1] [2] [3] [4] [5] [6] [7] [8] [9]
[10] [11] [12] [13] [14] [15]
Zhang XD, Vesselinov VV. Energy–water nexus: Balancing the tradeoffs between two–level decision makers. Applied Energy. 2016; 183: 77–87. Vishnu N, Antolínez IV. A competitive Markov decision process model for the energy–water–climate change nexus. Applied Energy. 2013; 111: 186–198. Feng KS, Hubacek K, Siu Y L, Li X. The energy and water nexus in Chinese electricity production: A hybrid life cycle analysis. Renewable and Sustainable Energy Reviews. 2014; 39: 342–355. DeNooyer T, Peschel J, Zhang ZX, Ashlynn S. Integrating water resources and power generation: The energy–water nexus in Illinois. Applied Energy. 2016; 162: 363–371. Abrell J, Rausch S. Cross–country electricity trade, renewable energy and European transmission infrastructure policy. Journal of Environmental Economics & Management. 2016; 79: 87–113. Thomas J. Feeley III, Skone TJ, Stiegel GJ, McNemar A, Michael Nemeth, Brian SJ. Murphy, Lynn M. Water: A critical resource in the thermoelectric power industry. Energy. 2008; 33: 1–11. Ackerman F, Fisher J. Is there a water–energy nexus in electricity generation? Long–term scenarios for the western United States. Energy Policy. 2013; 59: 235–241. Mekonnen M, Gerbens PW, Arjen YH. Future electricity: The challenge of reducing both carbon and water footprint. Science of the Total Environment. 2016; 569–570: 1282–1288. Liu L, Hejazi M, Pralit P, Kyle P, Davies E, Zhou YY, Clarke L, Edmonds J. Water demands for electricity generation in the U.S.: Modeling different scenarios for the water–energy nexus. Technological Forecasting & Social Change. 2015; 94: 318– 334. Vilanova MR, Balestieri JA. Exploring the water–energy nexus in Brazil: The electricity use for water supply. Energy. 2015; 85: 415–432. Wang SG, Chen B. Energy–water nexus of urban agglomeration based on multiregional input–output tables and ecological network analysis: A case study of the Beijing–Tianjin–Hebei region. Applied Energy. 2016; 178: 773–783. Chen GQ, Chen B, Zhou H, Dai P. Life cycle carbon emission flow analysis for electricity supply system: A case study of China. Energy Policy. 2013; 61: 1276–1284. Chen B. Energy, ecology and environment: a nexus perspective. Energy, Ecology and Environment. 2016; 1(1):1–2. Zhu XJ, Guo RP, Chen B, Chen B, Zhang J, Tasawar Hayat, Ahmed Alsaedi. Embodiment of virtual water of power generation in the electric power system in China. Applied Energy. 2015; 151: 345–354. Guo RP, Zhu XJ, Chen B, Yue YL. Ecological network analysis of the virtual water network within China’s electric power system during 2007–2012. Applied Energy. 2016; 168: 110–121.
3977