Research on carbon emission reduction benefit of wind power project based on life cycle assessment theory

Renewable Energy 155 (2020) 456e468

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Renewable Energy journal homepage: www.elsevier.com/locate/renene

Research on carbon emission reduction benefit of wind power project based on life cycle assessment theory Jinying Li a, Sisi Li a, Fan Wu b, * a b

Department of Economics and Management, North China Electric Power University, Baoding, Hebei, 071003, China Power China Huadong Engineering Corporation Limited, Hangzhou, Zhejiang, 311122, China

a r t i c l e i n f o

a b s t r a c t

Article history: Received 1 June 2019 Received in revised form 4 December 2019 Accepted 23 March 2020 Available online 2 April 2020

With the global energy crisis and the increasing severity of environmental pollution, promoting the exploitation of clean energy, especially the renewable energy, has become an effective way to reduce the consumption of fossil fuels and the emissions of carbon dioxide. Based on the facts above, this paper carries out a comprehensive analysis of the carbon emissions during the whole life cycle of wind power project according to the life-cycle assessment theory, and both the construction of wind farm project and the corresponding networking project are taken into consideration. Then, the Life cycle inventory of wind power project is delivered to carry out the calculation of carbon emissions during the project’s whole life cycle. Finally, the 49.5 MW wind power project in Shi-san-jian-fang area of Xinjiang is employed for empirical analysis to discuss the project’s carbon intensity and the potential of emission reductions. The result shows that the carbon intensity of this wind power project is 4.429 g/kWh and the potential for emission reductions throughout its life cycle reaches 2.0416 million tons in theory, which means wind power project owes huge potential for emission reductions compared with general coalfired stations. © 2020 Elsevier Ltd. All rights reserved.

Keywords: Wind power project Life cycle assessment (LCA) Carbon emissions Emission reductions

1. Introduction As an important support for national economic development, the energy industry is the driving force for the rapid, efficient and sound development of national and regional modernization. At present, the global energy industry is faced with an important challenge: exploring clean environment-friendly energy and improving the efficiency of energy conversion, thereby promoting the optimization and upgrading of energy production structure and consumption structure. In addition, developing and utilizing clean electricity and increasing the proportion of clean electricity will be a major mission for China’s power industry and even the global power industry for a long period of time [1]. With the transformation of development concepts and energy consumption habits, clean power generation methods, such as wind power and solar power generation, are gradually replacing the traditional thermal power generation mode, which will have a significant positive impact on the reduction of fossil resource

* Corresponding author. E-mail addresses: [email protected] (J. Li), [email protected] (S. Li), hdjgwf@ 163.com (F. Wu). https://doi.org/10.1016/j.renene.2020.03.133 0960-1481/© 2020 Elsevier Ltd. All rights reserved.

consumption and carbon dioxide emissions. Also the consequent economic, social and environmental benefits are gradually emerging [2]. Compared with the same period of developed countries, China’s total carbon emissions and carbon intensity are at a higher level, Fig. 1 shows the carbon emissions of energy industry in China, the United States and other energy consumption countries in recent years [3].Therefore, the research on carbon emission reduction benefit of wind power project is of great significance to a series of production practice activities, such as the formulation of new energy policies among governments, the gridconnection planning of wind power enterprises, and the feasibility demonstration of wind power projects. As one of the world’s major renewable energy, wind power plays a key role in solving the energy supply problems of many countries [4e6]. Converting the kinetic energy of wind directly into electricity will not result in any form of pollution or carbon emissions, but if the whole life cycle of wind farm is taken into account, wind turbine manufacturing, transportation and recovery and disposal do have quantitative environmental effects [7,8]. Therefore, it is necessary to analyze and evaluate the whole life cycle of wind power in order to assess the real potential of wind energy to mitigate climate change.

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Fig. 1. Area graph of total carbon emissions trends of the energy industry in China, the United States and other countries (unit: million tons).

To date, the Life Cycle Assessment (LCA) has become pretty mature, with clear standards, a mature system, and a variety of practical methodologies. It can also address the dual needs of environmental assessment and more systematic management and planning [9,10]. Since this method can provide a framework for identifying and evaluating environmental burdens associated with the life cycles of wind power technology in a “cradle” to “grave” approach, and is beneficial to avoid partial-optimization when only a few processes are evaluated, it is suitable for solving the problems raised in this study [11,12]. The LCA method takes into account the carbon emissions in the whole life cycle of the wind power project in a comprehensive manner, so the calculated carbon emissions are more accurate. In addition, the introduction of life cycle assessment provides an exhaustive and general evaluation for the comprehensive benefits of wind power technology, which is more objective than other methods. Life cycle assessment (LCA) is an effective method to quantify the impact of energy technology on the environment [13,14]. It has been widely applied to assess the life cycle impacts of wind power plants, wind turbines or certain power system components on the environment. Existing LCA studies have studied the environmental impact of onshore and offshore wind farm systems. Since wind power generation originated in Europe, European researchers have carried out numerous researches on wind farms. Schleisner [15] first studied the greenhouse gas (GHG) emissions and pollutant emissions of offshore and onshore wind farms in Denmark from the perspective of life cycle, and found that GHG emissions intensity of offshore and onshore wind power projects were 16.5 and 9.7 g CO2-eq/kWh, respectively. Subsequently, Ardente et al. [16] conducted research on wind farms in Italy, and the results showed that the life cycle energy of wind farm was 0.14e0.25 MJ/kWh, with emission intensities of 8.8e18.5 g CO2-eq/ kWh for GHG. Amponsah et al. [17] delivered a detailed review concerning GHG emissions of 14 onshore wind farms and 5 offshore wind farms in order to provide a comparative evaluation between them. Similarly, studies for offshore and onshore wind farms were conducted in Ref. [18e22].

With the popularization and application of wind power technology, relevant researches have been carried out in various countries around the world. More recently, scholars have evaluated the life cycle energy performance and greenhouse gas emissions of wind power projects in the United States [23], Mexico [24], Jordan [25], Brazil [26], Turkey [27], Japan [28] and Libya [29]. Chinese scholars have also begun to evaluate wind farms in China. In Ref. [30,31], it was concluded that the energy consumption and greenhouse gas emission per unit power generation of onshore wind farms in China are about 1/56 and 1/108 of those of thermal power plants. Yang et al. [32] adopted a hybrid life cycle assessment method to calculate the energy consumption and greenhouse gas emissions of China ‘s first offshore wind farm, and compared the results with typical onshore wind farms and other types of renewable energy. In Ref. [33], the environmental impact and benefits of wind power systems have been evaluated and compared with those of other forms of renewable energy by using the LCA method. More similar studies can be found in Refs. [34e38]. From the current research status, numerous studies are devoted to the carbon emission calculation of power industry projects, mainly focusing on the carbon emission reduction benefits of power generation. However, there are still few researches on the carbon emission reduction benefits brought by the construction of power transmission i.e. power network engineering project. Based on the facts above, this paper carries out a comprehensive analysis of the carbon emissions during the entire life cycle of wind power project according to the LCA theory, and both the construction of wind farm project and the corresponding networking project are taken into consideration. The carbon emissions in different life phases of the wind power project, including production, transportation, construction, operation and the end-of-life cycle phase, are analyzed respectively from a systematic perspective. Then, the Life cycle inventory (LCI) of the wind power project is delivered to carry out the calculation of carbon emissions during the project’s whole life cycle, and the true potential of wind energy to mitigate climate change can also be evaluated. This study thus aims at

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providing some reference and recommendations for decision makers of energy sector and power enterprises from the perspective of carbon emission reduction effect and emission reduction potential, when setting emission reduction targets for wind power industry, and formulating wind power development plans. Therefore, the main contributions of this research include the following three aspects: (i) the study has compiled a comprehensive data inventory of the wind power project including the wind farm project and corresponding networking project. Compared with the traditional research on wind farm stations, this paper quantitatively analyzes the whole-life-cycle carbon emission reduction benefits of the wind power project, including power generation (wind farm) and transmission (power to regional grid), from a more systematic and comprehensive perspective analyzing carbon emission reduction potential of the wind power project. (ii) the whole life cycle carbon emission calculation and emission source identification of the wind power project are realized, which provides robust and reliable data support for the analysis of emission reduction potential and emission path control of the projects. (iii) the results of the study will be conductive to energy sector to evaluate the energy and emissions benefits associated with future wind power projects, thus providing certain reference and compliance for wind power development planning and emission reduction target setting. The remaining parts of this paper are organized as follows: Section 2 introduces the technical route and the method theory adopted by this paper; the carbon emission LCA model and data inventory associated with the wind power project are put forward in Section 3; Section 4 presents and discusses the carbon intensity of the wind power project based on the data inventory of the model proposed in this paper, and uses the scenario analysis technology to further analyze the emission reduction potential; this paper finally draws conclusions in Section 5. 2. Method 2.1. Technical route Based on the ISO 14040 and 14044 standards, the calculation of carbon emissions in the whole life cycle of the wind power project

involves the following main research procedures [39,40], as shown in Fig. 2: 1 Goal and scope definition: Defining the goal and intended use of the LCA, and scopes the assessment concerning system. 2 Inventory analysis: Collecting data on inputs (resources and intermediate products) and outputs (emissions, wastes) for all the processes in the system. 3 Impact assessment: Evaluating potential environmental and resource consumption impacts associated with the inputs and outputs. 4 Interpretation: Combining the findings of inventory analysis and impact assessment with the defined goal and scope to reach conclusions.

2.2. Wind power project LCA three-dimensional system Combined with the idea of life cycle phase division, the threedimensional system diagram of LCA on wind power project is constructed from three dimensions: project phase, technical route and method theory [41]. In the LCA three-dimensional system diagram of the wind power project, the x axis is the life cycle of project, representing the five stages of the life cycle of the wind power project; the y axis is the technical route, which stands for the procedures and steps for the whole LCA of the carbon emission reduction analysis of the project; the z axis is the method theory, including LCA theory, scenario analysis and sensitivity analysis, which is the theoretical basis for the whole project, as shown in Fig. 3. 2.3. Wind power project carbon emission LCA model 2.3.1. Goal and scope definition Goal and scope definition, as the first LCA phase, the boundaries of the system and the functionality of the product should be specified [42,43]. The object of the research mainly consists of two parts: wind farm construction project and corresponding networking project. The goal of this study is to assess the benefit of carbon emission reduction in the whole life cycle of the wind power project. And both the construction of wind farm project and the corresponding networking project are taken into consideration, mainly for the following two reasons: First, the inclusion of corresponding networking projects in the research scope is the need of production practice; the second point is to improve the rationality and scientific nature of the research. Fig. 4 shows the system boundaries of the wind power project in this study. 2.3.2. Life cycle inventory calculations In order to effectively identify the emission sources and emission paths, this paper divides the life cycle of the wind power project into five stages: component production, material transportation, project construction, operation, and disposal and recycling, which is different from the life cycle theory of construction project management [44]. The carbon emissions in different life stages of the wind power project are analyzed respectively from a systematic perspective, then the comprehensive calculation model of the entire life cycle carbon emissions (CE) can be obtained, as shown in the following formula:

LCACE ¼ CEP þ CET þ CEC þ CEO þ CED

Fig. 2. The framework of LCA (ISO14040, ISO14044).

(1)

where LCACE denotes the total amount of carbon dioxide emitted during the entire life cycle of the wind power project; CEP refers to the carbon emissions generated from the production of

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Fig. 3. LCA three-dimensional system diagram of wind power project.

Fig. 4. Schematic diagram of scope boundary of wind power project.

components; CET represents the carbon emissions produced by transportation; CEC stands for the carbon emissions from the construction of the project; CEO means the carbon emissions from the operation phase; CED represents the total amount of carbon emissions generated during the disposal and recycling process; In this formula, each unit is kg. Meanwhile, the schematic diagram of the wind power project’s LCA system is shown in Fig. 5. 2.3.2.1. Production of components. Production of system components forms a natural part of any wind power LCA [45]. The main source of carbon emissions in the production phase is the carbon dioxide generated during the production of major equipment materials. Take the wind turbine, the most important equipment in the wind power project, as an example, which mainly includes blade (also known as impeller and rotor), nacelle and tower. Therefore, the carbon emissions during the production phase of the wind

turbine is mainly concerned with the emissions generated from the production of the blades, the nacelle and the tower, from the raw material input to the product output [46]. The calculation model of carbon emissions in the production phase of the wind power project can be further obtained as follows:

CEP ¼ CEP1 þ CEP2 CEP1 ¼

n X i¼1

CEP2 ¼

n X i¼1

(2)

wi  hij  Ij ð1  bi Þ

(3)

wi  hij  Ij ð1  bi Þ

(4)

where CEP expresses the carbon emissions from the production phase of the wind power project (kg); CEP1 illustrates the carbon

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Fig. 5. Schematic diagram of the wind power project’s LCA system.

emissions emitted by the production of various components in the wind farm project (kg); CEP2 demonstrates the carbon emissions produced by the production of each component involved in the corresponding networking project (kg); i represents equipment or components, i ¼ 1, 2, …, n; j indicates the constituent elements of the equipment, j ¼ 1,2, …, m; wi defines the quality of the equipment or component (kg); bi describes the loss rate of equipment or materials (%); hij expresses the proportion of elements j in equipment i (%); Ij stands for the carbon emission factor of element j. 2.3.2.2. Material transportation. Since China is a country with great potential for wind power and owns a large amount of land, the transport-related emissions involved in the utilization of wind power can be significant and thus deserve careful analysis [47]. The carbon emissions during the material transportation phase mainly derive from emissions from fuel or energy consumption (such as diesel, gasoline, electricity) in the course of material transportation. The material transportation phase, as the preliminary activity of the project construction, is an important part of bringing together various materials in the project site. In the process of transportation, a large amount of fuel consumption resulting in the generation of carbon dioxide, which is a major source of carbon emissions in the life cycle of a wind power project. The carbon emissions calculation model for the transportation phase is as follows:

CET ¼

n X i¼1

wi  Di  lK ð1  bi Þ

(5)

Where CET represents the total carbon emissions generated in the

material transportation phase of the wind power project (kg); i defines equipment or components, i ¼ 1,2, …, n; K stands for the mode of transportation, K ¼ 1,2, …, r; wi defines the quality of equipment or material (t); bi describes the loss rate of equipment or materials (%); Di refers to the transport distance of equipment or materials (km); lK indicates the carbon emission factor of a certain mode of transport (kg/(t*km)). 2.3.2.3. Project construction. The construction phase of the wind power project studied in this paper mainly includes two parts: the construction of wind farm project and the corresponding networking project. According to the source of carbon emissions during the construction phase of the project, it is divided into two parts: the consumption of construction materials and the operation of machinery equipment. In order to facilitate the calculation and analysis of carbon emissions during the construction phase of the wind power project, current study will establish the emission model from the perspective of carbon emission sources.

CEC ¼ CECM þ CECE

(6)

Where CEC indicates the carbon emissions emitted during the construction phase of the wind power project (kg); CECM represents the emissions from construction materials consumed in the construction of the wind power project (kg); CECE shows the emissions generated by the consumption of fuel resources during the use of various machinery equipment in the construction stage (kg). Furthermore, the calculation source of CECM includes the production and transportation of various construction materials (such as concrete, stone, sand, etc.), and its calculation model can be expressed as follows:

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CECM ¼ CECMP þ CECMT ¼

n X

Wi  Ii þ

i¼1

n X

Wi  Di  lK

(7)

i¼1

Where CECMP illustrates the emissions emitted by the production of various construction materials (kg); CECMT describes the emissions from the transportation phase of construction materials (kg); i refers to construction materials (concrete, sand, etc.), i ¼ 1,2, …, n; K stands for the mode of transportation, K ¼ 1,2, …, r; Wi expresses the quality of the construction material consumed during the construction phase of the project (kg); Ii demonstrates the carbon emission factors of different construction materials (kg/kg); Di represents the transport distance of construction materials (km); lK describes the carbon emission factor of a certain mode of transportation (kg/(t*km)).

CECE ¼

q X

QL  TL  CLk  Ik

(8)

L¼1

CECE represents the carbon emissions produced by the fuel consumption of various machinery equipment during the construction phase of the project (kg); L refers to construction tools or equipment; L ¼ 1,2, …, q; k stands for different types of energy resources; QL illustrates the number of machinery equipment; TL indicates the number of shifts of machinery; CLk shows the energy consumption level the machinery equipment; Ik demonstrates the carbon emission factor of a certain kind of energy resource (kg/kg). 2.3.2.4. Project operation. The sources of carbon emissions during the operation phase of the wind power project mainly consist of reconditioning and renewal of the components and the consumption of energy resources in the operation process. The replacement of materials in wind farm projects such as wires, cables and blades often involves the production and transportation of a series of new equipment materials. Hence, the operation of the wind power project needs to consider the carbon emissions generated during the production and transportation of the updated equipment materials. Another source of emissions in the operation phase is the carbon emissions generated by the input of various resources during the operation of the project. Therefore, the calculation model of carbon emissions in the operation of the wind power project can be expressed as follows:

CEO ¼ CEreplaceP þ CEreplaceT þ

n X

wi  Ii

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caused by the re-production of resources, and therefore the emissions of this part are negative. The specific accounting model is shown as follows:

CED ¼ CED1 þ CED2 ¼

n X i¼1

0 wi  fZ þ @ 

m X

1 Wj  Ij  4j A

(10)

j¼1

Where CED is the total amount of carbon emissions generated in the disposal and recycling phase of the wind power project (kg); CED1 refers to the emissions generated by the waste disposal process (kg); CED2 defines the amount of emission reduction produced by the recovery process and its value is negative (kg); i denotes the waste to be disposed of, i ¼ 1,2, …, n; Z represents the waste disposal mode; j indicates the recyclable material, j ¼ 1,2, …, m; wi expresses the quality of the waste to be processed (kg); fZ demonstrates the carbon emission factor of waste disposal mode (kg/ kg); Wj illustrates the amount of input of different recyclable materials (kg); Ij stands for the carbon emission factor of the recyclable material (kg/kg); 4j denotes the recovery coefficient of the recyclable material (%). 2.3.3. Impact assessment This phase converts inventory data on inputs and outputs into indicators about the system’s potential impacts on the environment. It mainly assesses and analyzes the potential environmental impacts, resource use and energy consumption of the model system, and explains the relative importance of the environmental and energy impacts at each stage and the environmental and energy impacts of each component of each production stage [49]. 2.3.4. Interpretation Life cycle interpretation is the process of identifying, quantifying, verifying and evaluating information from impact assessments and inventory analysis conclusions, and interpreting them according to the goal of the study. By analyzing the contribution of different life cycle stages, it identifies the elements that contribute the most to the results of LCA, so as to determine whether the information collected and the results provided meet the goal and scope of the study. Additionally, it explains limitations, offers recommendations and describes the environmental effects of each phase of the life cycle, so a relationship can be derived at between the environmental impacts and the thresholds or the safety limits [50].

(9)

i¼1

Where CEO refers to the emissions generated by the operation of the wind power project (kg); CEreplaceP indicates the emissions of the replaced or updated materials at the production stage, and its specific calculation model is the same as that of the production stage (kg); CEreplaceT represents the emissions produced by the transportation of the updated or replaced material or equipment, and the specific calculation model is the same as that of the transportation stage (kg); i stands for the resources consumed in the operation phase of the wind power project (lubricating oil, hydraulic oil, etc.), i ¼ 1,2, …, n; wi is the quality of the resource consumed (kg); Ii illustrates the carbon emission factor of the input resources (kg/kg). 2.3.2.5. Disposal and recycling. The calculation of carbon emissions during the disposal and recycling phase of the wind power project is comprised of the carbon emissions from waste disposal and the reduction of emissions from resource recovery [48]. Among them, the recycling and reuse of resources can reduce the emissions

3. Case study In this study, the 49.5 MW wind power project in Shi-san-jianfang area of Xinjiang was employed for empirical analysis to discuss the emission sources and emission paths in the whole life cycle of the wind power project, and to study the project’s carbon intensity and the potential of emission reduction, using the calculation models and the LCI established in this paper [51]. 3.1. Basic information In this paper, the feasibility study report of the 49.5 MW wind power project in Shi-san-jian-fang area of Xinjiang was taken as the main data source to carry out relevant research. In the Shi-san-jianfang wind farm project, 33 wind turbines with a single unit capacity of 1.54 MW were adopted, with a total installed capacity of 49.5 MW. An additional 110 KV main transformer was added for the expansion of the booster station, and 9 km transmission line was built to realize the wind farm station networking access. The basic parameters of the wind power project are shown in Table 1.

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Table 1 Basic parameters of 49.5 MW wind power project of Shi-san-jian-fang wind farm.

Wind farm project

Power network project

Items

Specification model

Quantity

Wind turbine Box transformer Grounding grid

1.5 MW S11-1600/35 40  4 Galvanized flat iron f50  3:5 Galvanized steel 35 KV,LGJ-240/40 8-core single mode fiber Reinforced concrete tapered pole Anti-corrosion coat/petroleum pitch SZ11-50000/110 S11-315/35 KYN61e40.5(z)-011 Rectangular copper bus Copper core cable LGJ-240/40 OPGW-24B1-100 ZS-35/4 Fog Glass Insulators Linear Tensile

33 33 3465 990 15 16 188 5733 1 1 6 40 4.11 9 9 50 200 24 4

Internal overhead line Communication cable Internal transmission tower Anti-corrosion Main transformer Distribution transformer Switch cabinet Bus Power cable overhead line Earth wire Post insulator Insulator string Transmission tower

3.2. Functional unit As a major criterion for the relationship between the object to be studied and the research topic, the functional unit of LCA is an important starting point and foothold for the conclusion of LCA research and the analysis of LCA results [52]. The core of this article is to calculate and analyze the carbon emissions in the whole life cycle of the wind power project based on LCA theory, and to further study the emission sources and emission reduction potential of the project. Therefore, on the basis of the existing research achievements in relevant fields at home and abroad, the functional unit (FU), which reflects the primary function of the system and is the basis of the LCA, was defined as ‘CO2 emissions per kWh of electricity’. Thus ensuring the horizontal comparison of carbon emission intensities between the wind power project and other electricity generation alternatives in subsequent studies. The calculation method is shown as follows:

UnitLCA ¼

LCACE Twp

(11)

Where UnitLCA represents the LCA functional unit of the subject, which means the carbon emissions per unit of wind power generation, and its unit is g/kWh; LCACE denotes the total carbon emissions in the life cycle of the wind power project, and the unit is g; Twp indicates the total power generation during the life cycle of the project, and the unit is kWh. 3.3. Life cycle inventory The aim of this section is to calculate and analyze the carbon emissions during the life cycle of the wind power project, such as production, transportation, construction, operation and disposal and recycling, and to establish the carbon emission life cycle data inventory for each stage [53].

m m km km m2

m km km km

part of the wind turbine are shown in Table 2. Through statistical analysis of various wind power equipment materials involved in the wind power project, the LCA data inventory of the project in the material production stage can be obtained, as shown in Table 3. 3.3.2. Transportation The carbon emissions generated by the transportation of various wind power equipment and materials at this stage were taken into account. Considering the geographical location and transportation conditions of the wind power station, the transportation mode of all materials in this wind power project was unified as “highway transportation” for the calculation of relevant parameters in the transportation process. The basic data and the LCA data inventory for the transportation phase of the project are shown in Tables 4 and 5. 3.3.3. Construction LCA basic data sources in the construction phase of the project mainly encompass the consumption of infrastructure construction materials and the energy and resource consumption generated by the operation of various machinery equipment. The consumption of infrastructure construction materials for the project mainly considers five aspects: concrete, steel, sand, stone and water resources. The carbon emissions generated in the operation of machinery equipment are mainly from the consumption of diesel, gasoline,

Table 2 Components of 66/1500 KW wind turbine. Component

Material

Total mass

Unit

Blade (impeller and rotor)

Fiberglass Resin Iron Steel Iron Steel Silica Copper Fiberglass Resin Steel Copper Iron Steel

7461.05 11183.65 8221.41 3294.90 4956.25 5782.29 99.12 939.62 9.29 13.42 12074.57 21612.07 9913.36 126375.00

kg kg kg kg kg kg kg kg kg kg kg kg kg kg

Nacelle

3.3.1. Production The basic data in the component production phase mainly concerned with the components or equipment involved in the project, such as wind turbines, transformers, wires, cables, etc. Taking the wind turbine as an example, the installed capacity of a 66/1500 KW wind turbine is 1.5 MW, which mainly consists of four parts: blade, nacelle, tower and generator. The components of each

unit

Generator

Tower

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Table 3 LCA data inventory of carbon emissions during the production phase. Equipment

Material

Wind turbine (Blade,Tower, Nacelle,Generator)

Transformer

Grounding grid overhead line (Aluminium cable steel reinforced) Bus Power cable Communication cable

Earth wire (OPGW)

Switch cabinet Tower (Reinforced concrete tapered pole) Tower (steel structure) Post insulator Insulator string Anticorrosive material

Steel Iron Copper Silica Fiberglass Resin Silica Steel Copper Iron Transformer oil Galvanized steel pipe Galvanized flat iron Steel Aluminium Copper Copper Resin Silica Resin Steel Silica Aluminium Steel Galvanized steel Steel bar (Tower) Concrete Steel Ceramic Glass Anti-corrosion coat Pitch

Carbon emission factor

Quantity

Value

Unit

value

unit

1.45 1.27 0.632 0.904 1.54 2.72 0.904 1.45 0.632 1.27 0.0405 2.34 1.81 1.45 4.62 0.632 0.632 2.72 0.904 2.72 1.45 0.904 4.62 1.45 2.34 1 0.283 1.45 0.904 0.743 0.308 2.956

kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/m3 kg/kg kg/kg kg/kg kg/m2 kg/kg

4904627 852439 744205.8 3271.124 328592.7 492523.5 642.2367 84927.2 47279.81 58404.31 80813 4667.85 5020.785 10000.92 17101.6 369.6008 35663.59 4917.47 206.4162 1156.491 953.8112 171.0177 471.4486 4325.429 10800 43604.72 65.048 56377.6 704.0816 1314.286 5733 20724.8

kg kg kg kg kg kg kg kg kg kg kg kg kg kg kg kg kg kg kg kg kg kg kg kg kg kg m3 kg kg kg m2 kg

Table 4 Basic parameters of material transportation for the wind power project. Material

Transportation mode

Transportation distance(km)

Electric power equipment Building material 12 m Concrete tapered pole

Highway transportation Highway transportation Highway transportation

222 235 210

Table 5 LCA data inventory of carbon emissions in the transportation phase. Material

Electric power equipment Building material Transmission tower

Table 6 Material loss rate during the construction phase of the project.

Carbon emission factor

Quantity

Value

Unit

Value

Unit

0.0615 0.0615 0.0615

kg/(t*km) kg/(t*km) kg/(t*km)

1708417 19513528 21009.95

t*km t*km t*km

electricity and other resources. In addition, the loss of some materials or components during the construction phase as an inevitable phenomenon in the process of project construction. This part of the project was also included in the scope of the research for calculation, thus LCA data inventory of carbon emissions in this stage can be obtained, as shown in Tables 6 and 7. 3.3.4. Operation The operation phase of wind power project is the longest phase in the whole life cycle of the project, and its emission sources mainly include reconditioning and renewal of the components and the consumption of energy and resources in the operation process. The water consumption in the operation phase was calculated

Material

Loss rate(%)

Power cable Overhead line Communication cable Bus Insulator

1.0 1.8 1.5 2.3 2.0

Table 7 LCA data inventory of carbon emissions during the construction phase. Material

Carbon emission factor

Quantity

Value

Unit

Value

Unit

Concrete Steel Sand Stone Diesel Gasoline Electricity Water resources

0.283 1 0.00234 0.0131 3.246 3.136 0.0136 0.00619

kg/m3 kg/kg kg/kg kg/kg kg/kg kg/kg kg/kWh kg/L

18317.6 1377140 13563000 24100000 65297.32 4256.95 71589.6 36500000

m3 kg kg kg kg kg kWh L

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according to 5.25m3/day; the exchange cycle of lubricating oil was three years, and the oil changing amount was 549kg/unit [54]. The changing period of hydraulic oil was two years, and the oil changing amount was measured by 14.85kg/unit; the antifreeze replacement cycle was one year, and the consumption was measured at 45kg/ unit. Then, the carbon emission LCA data inventory for the operation phase can be obtained, as shown in the Table 8. 3.3.5. Disposal and recycling The carbon emissions from the disposal and recycling phase of the project mainly consider the carbon dioxide produced by waste disposal and the emissions reduced by the recovery and utilization of resources. At the stage of waste disposal, the high-molecular material such as the resin and the construction materials such as concrete and sand are not high in the recycling and utilization value at the end of the life cycle, and therefore, the landfill treatment method was adopted. The recovery and utilization rate of the metal materials such as steel, iron and copper is relatively high at the end of the life cycle. Theoretically, the recovery rate of these materials can reach 90% and above [55]. The life cycle of the project is usually 20 years or more, taking into account the corrosion and loss in the long life cycle of the project, the recovery utilization rate of the metal material in the wind power project was set to be 50%. The processing mode of each resource in the recovery processing stage and the LCA data inventory of carbon emission in this stage are shown in Tables 9 and 10. 4. Result and discussion 4.1. Analysis of carbon emission intensity Based on the carbon emission calculation model and the comprehensive LCA data inventory of the project, the carbon emissions of each stage of the 49.5 MW wind power project in Xinjiang can be measured. The final result reveals that the total life cycle carbon emissions of the 49.5 MW wind power project is 10490.83 tons. On account of the wind farm’s theoretical annual generating capacity of 11.843 million kWh and the operating cycle of 20 years, it can be obtained that the carbon emission per unit of wind power generation during the whole life cycle of the wind farm is 4.429 g/kWh (theoretical value). The calculation results are in line with the recommended range of wind power carbon emission intensity 2e81 g/kWh given by IPCC [56,57]. The carbon emissions generated during the life cycle of the 49.5 MW wind power project are shown in Fig. 6, in which the material production phase contributes the most to emissions in the life cycle. The production phase discharges 11,123 tCO2, accounting for 70.61% of the total carbon emissions. Followed is the construction phase of the project, where the carbon emissions are 2,182 tons, occupying 13.85% of the total carbon emissions. In contrast, the emissions in the transportation phase and operation phase are significantly less than those in the first two phases, with 1,306 tCO2 and 276 tCO2 respectively. The emission source of the recycling process consists of two parts. On the one hand, the landfill

Table 9 The processing methods in the recycling phase of the project. Material

Processing mode

Proportion

High-molecular material (Resin,PE, etc.) Construction materials(Concrete) Metal materials(Iron, Copper, Steel, etc)

Landfill Landfill Recycling

100% 100% 50%

of waste, decomposition and other treatment produce 865 tCO2, and on the other hand, the carbon emissions from recycling of resources such as steel and copper have been reduced by 5261 tons. The carbon emission proportion of each phase in the life cycle of this project is shown in Fig. 7. In addition, based on the LCA data inventory of the wind power project, the carbon footprint of the 49.5 MW wind farm project can be obtained by decomposing and analyzing the carbon emissions of the wind power project [58]. The carbon emissions in the production phase are regarded to be generated in the 0th year, the emissions in the transportation and construction phase are emitted in 1st year, and the 2nd-21st year is the operation phase of the wind power project. The disposal and recycling phase of the wind power project generates carbon emissions in the 22 nd year, as shown in Fig. 8. 4.2. Scenario-based emission reduction potential analysis 4.2.1. Baseline scenario analysis From the LCA data inventory and calculation results of the wind power project, it can be found that the two main variables affecting the emission reduction potential of the wind power project are the annual on-grid energy and the recycling level of the recyclable resources. Therefore, the annual wind power curtailment ratio (i.e. the proportion of wind power loss in total wind power generation) of the wind farm is set as 12% under the baseline scenario (the value refers to the overall wind power curtailment ratio of the China’s wind power industry in 2017); the recycling level of the recoverable resources is set at 50%, and the carbon emission intensity of the wind farm under the baseline scenario is 5.033 g/kWh. In this paper, coal-fired power generation is selected as the comparison object, and the emission reduction potential of the project is analyzed. The carbon emission intensity is based on the average carbon emission standard of China’s thermal power industry, with a value of 866.3 g/kWh [59]. In conclusion, the emission reduction potential of the wind power project in the whole life cycle under the baseline scenario can be obtained, as shown in the Table 11. 4.2.2. Multiple scenarios analysis Similarly, the variable factors of wind power curtailment ratio and recycling level are still taken into consideration to set multiple Table 10 LCA data inventory of carbon emissions in the recycling phase of the project. Phase

Material

Recycling

Steel Iron Copper Aluminium Galvanized steel pipe Galvanized flat iron Galvanized steel Steel Landfill(PE) Landfill(others) Waste disposal

Table 8 LCA data inventory of carbon emissions in the operation phase. Material

Lubricating oil Hydraulic oil Antifreeze Water

Carbon emission factor

Quantity

Value

Unit

Value

Unit

0.182 0.0582 0.511 0.00619

kg/kg kg/kg kg/kg kg/L

126819 4900.5 29700 38325000

kg kg kg L

Waste disposal

Carbon emission factor

Quantity

Value

Unit

Value

Unit

1.45 1.27 0.632 4.62 2.34 1.81 2.34 1 0.061 0.018 0.0127

kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg kg/kg

2530606 455421.7 413759.4 8786.525 2333.925 2510.393 5400 688570 498597.4 347916.7 18382.65

kg kg kg kg kg kg kg kg kg kg kg

J. Li et al. / Renewable Energy 155 (2020) 456e468

Fig. 6. Carbon emissions in each phase of the 49.5 MW wind power project(t).

Fig. 7. Carbon emission proportion in each life phase of the wind power project.

Fig. 8. The carbon footprint of the wind power project’s whole life cycle.

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Table 11 Emission reduction potential of 49.5 MW wind power project under baseline scenario. Scenario setting

Parameter

Unit

Wind power curtailment ratio Recycling level Carbon intensity Carbon emission reduction

12 50 5.033 179.53

% % g/kWh million tons

Fig. 9. Multiple scenarios of the wind power project.

scenarios, and the carbon emission situation and corresponding emission reduction potential of the wind power project in multiple scenarios can be obtained. In terms of scenario setting, the factor of “wind power curtailment ratio” is divided into three categories: high (24%), medium (12%) and low (5%), and “recycling level” is divided into three types: positive (90%), ordinary (50%) and negative (30%). Nine different scenarios for the wind power project can be further obtained, as shown in Fig. 9. S3 is the ideal scenario, in which the wind farm has a low wind power curtailment ratio and a high recycling and reuse level, while S7 is a negative scenario, in which the wind farm station has a high wind power curtailment ratio and a low recycling and reuse level. Combined with the LCA data inventory and the carbon emission calculation model for each phase of the wind power project, the carbon emission intensity and emission reduction potential under multiple scenarios can be obtained as Fig. 10.

5. Conclusions This study carries out a whole life cycle carbon emission calculation model and LCA comprehensive data inventory according to the life-cycle assessment theory, and both the construction of wind farm project and the corresponding networking project are taken into consideration. And the 49.5 MW wind power project in Shi-san-jian-fang area of Xinjiang is also employed for empirical analysis. On the basis of the LCA theory, the emission sources and emission paths in each phase of the life cycle of the project are identified and analyzed by defining the system boundaries of the research. Then, the theoretical carbon emissions per unit of wind power generation of the wind power plant is calculated to be 4.429 g, that is, the theoretical value of carbon emission intensity of the wind farm is 4.429 g/kWh. What’s more, according to scenario analysis, this paper further brings the two main variables of “wind power curtailment ratio” and “recycling level” into the research scope, and compares the carbon emission intensity and emission reduction potential of the wind power project under different scenarios. It can be found that, compared with the thermal power generation, the carbon emission intensity of the wind power project is obviously lower and the emission reduction potential in the whole life cycle can be enormous. Therefore, the development and utilization of wind power is of great significance for optimizing regional power structure, improving energy consumption habits and ways, and realizing low carbon and green development of power industry. The practical significance of this paper lies in the identification and calculation of the sources of carbon emissions in each stage of the life cycle of the wind power project, so as to achieve a more systematic and comprehensive analysis of the carbon emission situation and emission reduction potential of the wind power project from the perspective of LCA framework. Furthermore, the research on emission reduction benefit of wind power project provides some reference and decision support for clean energy policy making, emission reduction index setting, power grid planning and feasibility demonstration of renewable energy projects. Author contributions section Jinying Li: Conceptualization, Validation, Supervision, Project administration, Funding acquisition. Sisi Li: Formal analysis, Data

Fig. 10. Comparative analysis of CO2 emission intensity (g/kWh) and emission reduction (million tons) under multiple scenarios.

J. Li et al. / Renewable Energy 155 (2020) 456e468

curation, Writing- Original draft, Writing-Reviewing and Editing preparation, Visualization. Fan Wu: Methodology, Software, Investigation, Resources. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

[19]

[20]

[21]

[22]

CRediT authorship contribution statement [23]

Jinying Li: Conceptualization, Validation, Supervision, Project administration, Funding acquisition. Sisi Li: Formal analysis, Data curation, Writing - original draft, Writing - review & editing, Visualization. Fan Wu: Methodology, Software, Investigation, Resources.

[24]

[25]

Acknowledgments

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This work was supported by Humanities and Social Science Fund of Ministry of Education of China (Grant No.15YJC630058) and Beijing Social Science Fund (Grant No. 18GLB023).

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