Mechanism of CO2 Emission Reduction by Global Energy Interconnection

1 Introduction

The global warming and climate change due to greenhouse gas emissions are becoming a serious challenge that impedes the sustainable development of the human and natural systems.In 2017, the concentration of greenhouse gases has reached 407 ppm, which was the highest level achieved during the past 800,000 years.At the same time,the global average temperature exceeded the pre-industrial level by 1.1 °C, resulting in three hottest years in history[1].It is remarkable that the effects of greenhouse gas emissions and global warming are becoming stronger at an unprecedented rate [1].

As a result, the climate change significantly affected all aspects of the natural and human systems, causing increasingly extreme climate events and disasters with huge economic and human life losses [2-5].A quasi-linear relationship is observed between the cumulative emissions of greenhouse gases and temperature increase.In order to limit the increase in the global average temperature to below 2 °C above the pre-industrial level according to the Paris agreement, the remaining global carbon budget should not exceed 550−1300 Gt CO2 in 2011−2050, and 630−1180 Gt CO2 in 2011−2100 with a 50% probability [6].

Essentially, the use of fossil fuel is the dominant factor of greenhouse gas emissions.It is undisputable that the emissions caused by fossil combustion are the largest contributor to the global warming (especially the CO2 emissions from fossil fuels) [7].Thus, it is critical to reduce the level of CO2 emissions from fossil fuel combustion.One possible approach involves the transition from fossil fuels to low-carbon energy sources on the supply side, and another one is aimed at the reduction of CO2 emissions by various end-use sectors on the demand side.According to the results of the meta-analysis of various 2 °C scenarios [8]published in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), reaching the limit of 2 °C temperature increase requires that the share of the primary low-carbon energy sources increase from 15% in 2010 to about 90% in 2100 with zero emission levels in the enduse sectors [9].On the supply side, these low-carbon energy sources include renewable wind, solar, hydro, and nuclear energies as well as fossil fuel combustion with carbon capture and storage (CCS) and negative carbon energy such as bioenergy with CCS and afforestation.Thus, the first main characteristic of the modern energy system is that it will be dominated by low-carbon energy sources on the supply side in the future.Another main characteristic of the modern energy system is the electrification of the end-use sectors,since electricity is a highly efficient and cost-effective form of energy.Furthermore, most electrical energy will be produced by those low-carbon and zero-carbon energy sources.

The Global Energy Interconnection (GEI) is a modern energy system aimed at promoting the current efforts to meet the global power demand in a clean and green manner.It also involves “clean replacement”, “electricity replacement”, and “grid interconnection” at the global scale[10].GEI provides a foundation platform to implement the majority of the aforementioned techniques and schemes [11].With the development of the grid interconnection, clean replacement, and electricity replacement strategies, GEI will strongly contribute to the global temperature control by limiting the level of CO2 emissions.

The aim of this study is to elucidate the mechanism of CO2 emission reduction by GEI and quantitatively analyze the contributions of various GEI components to achieving the 2 °C temperature increase limit.For this purpose, a plausible mechanism of emission reductions is discussed using an integrated framework, after which the contributions of the clean replacement, electricity replacement, and CCS components are determined.Moreover, the estimated emission reduction contributions are further verified by numerical calculations.The remainder of this paper is organized as follows.In section 2, we introduce a GEI concept, including its clean replacement, electricity replacement, and interconnection components.In section 3, the detailed mechanism and quantitative contribution of GEI-based emission reductions are analyzed using appropriate frameworks and formulations.Numerical analysis is conducted in section 4.Finally, the conclusions of this study are presented in section 5.

2 GEI Concept

2.1 GEI

The GEI concept is based on using smart grids, ultrahigh voltage (UHV) grids, and clean energy [10].With the rapid development of technologies in these three areas, GEI has become a frontier of advanced energy technologies across the world.

Smart grids represent the GEI foundation because their development has dramatically improved the reliability,topological flexibility, efficiency, and sustainability of energy networks during the last few decades [12-13].Studies on microgrids, power transmission, energy storage, smart operation and control, and renewable energy integration [14-19]show that smart grids can adapt to the interconnection and consumption of various centralized and distributed clean energy resources, meet the requirements for the connection and interaction of various types of smart electric equipment, and promote the collaborative development of energy, grid, load and storage, multi-energy complements, and efficient utilization.

The UHV grid is the key GEI component, which realizes the transmission of alternating current (AC) at a voltage of 1000 kV or higher and direct current (DC) at voltages of ±800 kV,±1100 kV, or higher [10,20].The results of recent studies reveal that the security and stability performance of UHV grids meet the general requirements of power systems [21]; hence,these grids represent a cost efficient and environmentally friendly advanced power transmission technology, which possesses significant advantages including long transmission distances, large capacities, high efficiencies, low line losses,limited land usage, and high security [22].They also enable transmission of 10 GW of electricity at distances amounting to thousands of kilometers and realization of transnational and transcontinental grid interconnection.

Clean energy is the highest priority for GEI development,and the related technologies have significantly advanced during the last years.The large-scale integration of clean energy sources such as wind, solar energy, and marine current energy, can potentially exhibit high stability and efficiency [23-24].It is also found that the costs of wind and solar energies are expected to decline dramatically,thus decreasing their prices as compared to those of fossil fuels [25-28].Because of the technological progress and rapid cost reduction of the conversion of hydro, wind, and solar power, such clean energy resources will totally surpass and quickly replace fossil fuels and ultimately become the dominant energy sources of the future.

2.2 Main Characteristics of GEI and Related CO2 Emission Reduction

GEI is characterized by the high level of electrification,large scale of clean energy development, and vast power grids (interconnections) spanning across various regions,countries, and continents.By replacing fossil fuels with clean energy sources, increasing the share of electricity in the final energy consumption, and forming a general pattern of the global interconnection of power grids across regions,countries and continents, GEI can be realized as a modern energy system.In addition, the technological development of the energy supply, transmission, and consumption as well as the utilization of low-carbon energy resources in the enduse sectors and low-carbon awareness in daily lives will accelerate the energy transition due to GEI implementation.

The first characteristic of GEI is a relatively large scale of clean energy development due to clean replacement.This term refers to replacing fossil energy with clean alternatives such as solar energy, wind, and hydropower on the energy production side.The latest report of the International Renewable Energy Agency shows that the share of renewable energy in the total primary energy supply in 2015 is 15%, which will increase by 66% in 2050 [29].Owing to the steep decline of clean energy costs and rapid improvement of power generation and storage of clean energy sources, the share of clean energy in the primary energy supply is expected to exceed that of fossil energy very soon.As a result, the transition of the energy production from fossil fuels to clean energy sources reduces the level of global CO2 emissions from the energy supply.

The second characteristic of GEI is a large fraction of electricity in the final energy consumption due to electricity replacement, which means replacing coal, petroleum, natural gas, and primary biomass energy sources with electricity on the energy consumption side.The results of recent studies show that increasing the share of electricity in the energy consumption is an irreversible trend.For example, in the transport sector, 55% of the new cars sales and 33% of the global fleet will be electric by 2040, which will displace 7.3 million barrels of transportation fuel per day [30].In addition, with the advancement and popularization of electric boilers, cookers, and heating (cooling) devices,as well as the development of zero-carbon buildings,electricity will become the dominant energy source in the final consumption.To achieve the 2 °C temperature increase limit specified by the IPCC, the electricity generation sector must reduce emissions at a faster speed than other sectors.Electricity production is required to reach a zeroemission level around 2050, and the industrial sector must reduce the level of CO2 emissions in 2050 by half of the 2010 level and reach zero emissions in 2100.Further, the building sector is required to reach a zero-emission level in 2100 as well, and the CO2 emissions in the transport sector in 2100 must be twice as low as those of the 2010 level [9].Electricity production can be highly efficient, inexpensive,and free from carbon energy resources in the final energy consumption if it is realized using clean energy generation power plants.The transition of the energy consumption pattern from the utilization of coal, oil, and gas to electricity can accelerate achieving zero emissions in the final sectors and promote the global reduction of CO2 emissions.

The third characteristic of GEI is a vast interconnecting grid utilizing cutting-edge technologies such as ultrahigh voltage alternating current, ultrahigh voltage direct current,high voltage direct current – voltage source converters,and smart grids [10].Clean energy is unevenly distributed across the world; it is also intermittent and volatile and thus has to be integrated into a single macro-power grid for better development on a large scale.By 2017, the number of Chinese UHV projects under construction or in operation has reached 25.By covering a total of 37,000 kilometers of transmission lines and reaching a transmission capacity of more than 210 GW, they have laid a solid foundation for making China the largest country with the integrated power capacities of hydro, wind, and photovoltaic energy sources in the world.In 2017, the 800-kV Belo Monte Hydropower UHV Transmission Project was completed in Brazil, making it possible to transmit the hydropower abundant in the north to various load centers located in the southeastern region[31-32].Hence, these UHV grids play a significant role in the reduction of CO2 emissions through electricity trading across the border and increasing the local potential of the development of large-scale clean energy sources.With the advancement of interconnection technologies, the use of interconnected grids can promote the global production,allocation, and utilization of clean energy resources and global reduction of CO2 emissions.

Fig.1 Integrated framework for reducing CO2 emissions by GEI: mechanism and contributions of its various components.

3 Methods

3.1 Integrated Framework for Reducing CO2 Emissions by GEI

The integrated framework for the reduction of CO2 emissions by GEI that illustrates its mechanism and contributions of various GEI components is shown in Fig.1.The upper part of this diagram describes the reference energy system consisting of the primary energy supply,energy transformation, and final energy consumption.It is essential to determine their contributions to the reduction of CO2 emissions after the clean replacement, electricity replacement, and interconnection stages.Various energy resources are considered here, including coal, oil, natural gas, hydro, wind, solar, biomass, nuclear, geothermal, and ocean power.Using different transformation technologies,primary energy can be either converted to other energy resources or utilized directly in the final energy consumption sectors.Electricity, heat, biomass, coal, coke, crude oil,oil products, natural gas, or hydrogen can be potentially utilized in the final energy consumption sectors including agriculture/forestry, industrial manufacture, transport,residential sector, commercial and public services, and nonenergy use.

By using a scenario analysis method, an interconnection scenario is designed based on the GEI concept (Fig.2, blue line).In addition, the business-as-usual (BAU) scenario is designed as a reference based on the national polices (NPi_V4) developed by the International Institute for Applied Systems Analysis (IIASA; Fig.2, yellow line) [33].The intended nationally determined contributions (NDCs) before 2030 and same efforts committed after 2030 are considered in this scenario.The lower part of Fig.1 describes the analysis framework of GEI’s contributions to reducing CO2 emissions.By estimating sectoral consumptions of fossil fuels in each scenario, multiplying them by CO2 emissions factors, and taking into account the efficiency of the energy system, total CO2 emissions can be calculated.The final energy consumption of the non-energy use sector is subtracted since it does not contribute to the reduction of CO2 emission according to different uses.The stored and unoxidized carbons are considered during the conversion of carbon emission into CO2 emission in accordance with the IPCC guidelines for national greenhouse gas inventories [34].

The total contribution to the reduction of CO2 emissions by GEI can be expressed by the emission difference between the BAU and interconnection scenarios.It consists of the clean replacement, electricity replacement, and CCS components with the interconnection grid.Detailed calculations are provided in sections 3.2–3.4 below.

3.2 Total Contribution of GEI

To quantitatively analyze the emission reduction contribution of GEI, the following relationship is formulated:

where ∆C is the emission reduction contribution calculated from the difference between the cumulative emissions of the BAU and interconnection scenarios; and,, and are the contributions from the clean replacement, CCS development, and electricity replacement development,respectively.

According to the evaluation process and related formulations [35], the cumulative carbon emissions during a specified period in the BAU scenario can be calculated as follows:

where ABAU, BBAU,Λf , and Λp are the BAU matrix of the final fossil fuel consumption with an energy conversion efficiency, fossil fuel consumption for power generation,emission factors in the end use, and emission factors for power generation defined as

where is the i -th(i =1,2,…, M) fossil fuel consumed by the j - th( j =1,2,…, N) final consumption sector at time t based on the BAU scenario;is the power generated by the i -th fossil fuel at time t based on the BAU scenario; Cfi, j(t) is the carbon emission factor of the i -th fossil fuel in the j - th final consumption sector,which is also a function of time t; and is the carbon emission factor of the fossil-based power generation.Here,we consider the cumulative emission reduction from M fossil fuels (coal, oil, gas, etc.) by N sectors (transportation,building, industry, etc.) within a period spanning from the initial time t0 to certain time Tm in the future.In this formulation, by considering the energy loss in the industrial process from the primary energy to the end use (such as transformation and refining),is defined as the energy conversion efficiency of the i -th fossil fuel in the j-th consumption sector at time t.Similarly, the cumulative carbon emissions within a certain period based on interconnection scenario can be derived as follows:

where

whereis the i -th fossil fuel consumed by the j -th consumption sector at time t based on the interconnection scenario; and is the power generated by the i -th fossil fuel at time t based on the interconnection scenario.According to (1) and (2), the difference between the cumulative carbon emissions can be apparently deducted as

Since the fossil fuel consumption for power generation in the BAU scenario is larger than that in the interconnection scenario, the following inequality is obtained:

Due to the electrification of the final consumption departments,more power with high energy efficiency is consumed; therefore,the amount of fossil fuels in the end use will be significantly reduced.Hence, the final consumption of fossil fuels in the interconnection scenario is much smaller than that in the BAU scenario due to electricity replacement.As a result,

Compared to the BAU scenario, the emission reduction contribution in the interconnection scenario is verified according to (3), (4), and (5):

3.3 Contributions of Clean Replacement and Electricity Replacement

Since a larger fraction of renewable energy is utilized for power generation in the interconnection scenario (instead of fossil fuels), it significantly reduces the level of CO2 emissions.In addition, the CCS component helps eliminate partial emissions of fossil-based power generation.Moreover, since the efficiency of fossil fuel utilization is expected to be improved in the future, smaller amounts of fossil fuel are consumed, which naturally reduces the emission amount (this type of improvements is included in the generalized clean replacement as well).Hence,by taking into account the improvement of fossil energy efficiency, the emission reduction contribution from the clean replacement component can be written as

where is the CCS ratio of the i - th fossil fuel at time t based on the BAU scenario, and is the same parameter obtained in the interconnection scenario.The emission reduction contribution from the CCS development can be calculated as

By summing up (11) and (12), the total emission reduction contribution can be expressed as

which is dominated by the difference in the fossil-based power generation between the BAU and interconnection scenarios.

In addition to the clean replacement and CCS development,the electricity replacement also contributes to the emission reduction due to the removal of a significant amount of fossil fuels and high fraction of the electric energy in the final consumption.The emission reduction contribution of the electricity replacement can be expressed as

By summing up (12) and (13), the GEI mitigation contribution equation (6) can be derived.

3.4 Contribution of Grid Interconnection

In this subsection, by analyzing the final consumption side, we determine how the grid interconnection affects the local emissions in a certain region (a city, country,continent, etc.) of the world.By considering the scenario without grid interconnection, the final energy consumption in the k -th region consists of the final fossil consumption Efos, power generated by fossil fuels Epow, fos, and power generated using renewable energy sources Epow, ren:

Note that Epow, fos, k, and Epow, ren, k are locally generated since the grids are not interconnected.Apparently, only the first two terms in (14) related to the use of fossil fuels contribute to CO2 emissions.

After that, analysis can be performed by considering the grid interconnection.In this case, the final energy consumption in a certain region can be expressed as

whereand are the imported or exported power generated by fossil fuels and renewable energy sources, respectively.These terms are positive if the imported power is greater than the exported one and negative in the opposite situation.Assuming the same energy consumption =, the existence of imported/ exported power strongly affects the energy consumption from local resources, such as the final fossil fuel consumption, power generated by fossil fuels and power generated by renewable energy Therefore,the local fossil-related energy consumption variation that contributes to the CO2 emission reduction can be simply expressed as

Due to the grid interconnection, it is highly possible that the imported power, especially the renewable-energy-based power is large enough to reduce the local fossilrelated energy consumption.Hence, the results obtained by (16) can be positive depending on the development of foreign renewable energy sources.

From the global perspective, the reduction in the local fossil-related energy consumption may potentially increase the foreign fossil-related energy consumption.Hence, by considering a number of K interconnected regions, the variation of the fossil-related energy consumption can be expressed as

Equation (17) shows that the global fossil-related energy consumption does not change if the amount of consumed renewable energy is constant.However, the grid interconnection enables the development of largescale renewable energy utilization and power generation,which potentially promotes the clean replacement and electricity replacement.By increasing the grid coverage and outreach, it is possible to optimize the global allocation of renewable energy sources using large power supply bases and interconnections.By addressing the problem of the uneven distribution of renewable resources, the grid interconnection becomes a precondition of the clean replacement and electricity replacement.In addition, it promotes the cost reduction of the renewable energy-based power generation, which further accelerates the worldwide clean replacement and electricity replacement by taking into account economic effects.Thus, the grids interconnection ultimately contributes to the emission reduction of CO2.

4 Results and Discussion

4.1 BAU and Interconnection Scenarios

Assuming the same population and economic development in the SSP2 scenario [36], the interconnection and BAU scenario are considered.The interconnection scenario is designed based on the GEI concept stating that at high level of electrification, large scale of clean energy development, and grid interconnection across various regions, countries, and continents, the clean replacement and electricity replacement will cause a transition towards the modern energy system.The interconnection scenario illustrates the mechanism of the reduction of CO2 emissions through the rapid development of renewable energy sources and utilization of electricity in the final energy consumption sectors.In addition, both the developing and developed countries can benefit from the emission reductions through grid interconnection.The total primary energy supplies,total final energy consumption, and amounts of electricity generated and consumed in the interconnection scenario are listed in Tables 1−3.

Table 1 Total primary energy supplies in the interconnection scenario (Mtce)

2010 2020 2030 2040 2050 2070 2100 TPES 18187214172297024865260352746727702 Coal 4909 5138 4044 2814 1115 741 331 Oil 5735 6363 6041 5137 3227 1931 715 Gas 3908 4582 4388 4167 3230 3023 2791 Nuclear 854 856 945 922 814 834 728 Hydro 976 1268 1644 1934 2143 2299 2123 Other Renewables 1808 3211 5910 9889 155071863921012

Table 2 Total final energy consumption in the interconnection scenario (Mtce)

2010 2020 2030 2040 2050 2070 2100 TFC 12545 14432 158821652416824 17750 19210 Coal 1400 1358 1038 727 553 260 50 Oil 5139 5721 5710 4881 3099 1800 600

continue

2010 2020 2030 2040 2050 2070 2100 Gas 1788 2115 2284 2077 1550 1000 600 Electricity 2200 3044 4463 5932 7416 9890 12560 Heat 392 421 425 477 631 585 432 Bioenergy 1438 1641 1668 1888 2524 2406 1907 Others 31 131 294 543 1051 1809 3062 Industry 4074 5034 5162 5172 5317 4986 5305 Transport 2679 3086 3706 3241 3348 3716 4601 Building 3960 4353 4645 4913 5238 5637 7379 No-energy Use 852 746 1074 1870 1536 2099 640 Others 980 1213 1295 1328 1385 1311 1285

Table 3 Electricity generation and consumption in the interconnection scenario (Mtce)

2010 2020 2030 2040 2050 2070 2100 Coal 2591 2955 2828 1988 554 449 120 Oil 299 317 316 248 127 139 132 Gas 1215 1625 2007 2024 1646 1661 1219 Nuclear 854 856 945 922 814 906 880 Hydro 976 1268 1644 1934 2143 2388 2318 Other Renewables 297 1333 3733 7103 11310 14506 17472 Fossil Fuels with CCS 0 0 258 1065 1163 2249 1471

In the interconnection scenario, the energy production pattern will shift from the fossil energy production to the clean energy production.By around 2025, the global fossil energy production will reach its peak and then begin to decline each year, while the production of clean energy will be expanding on a yearly basis.The share of clean energy in the primary energy will exceed that of fossil energy before 2040 and then grow to 71.6% by 2050.As a result, the energy consumption pattern will also shift from relying on coal, oil, and gas usage to electricity.During the 2015−2050 period, the share of fossil fuels in the end energy uses will drop from 67% to 31%, while the share of electricity in the end energy consumption will significantly increase from 18.6% in 2015 to 44.1% in 2050 and then to 49.2% in 2070.

4.2 CO2 Emission Pathway and Contribution of Interconnection Scenario

The emission reduction pathway proposed in the interconnection scenario is shown in Fig.2.In the numerical analysis, the method formulated in equations (2) and (3) is used to calculate the total CO2 emissions in the BAU and interconnection scenarios.The red and blue curves indicate the integral functions in (2) and (3) respectively, which correspond to the emissions released over in a certain year(here, one year is considered as the integral infinitesimal).In the interconnection scenario represented by the blue region, the total CO2 emissions are expected to reach a peak value around 2025 and then drop rapidly.In 2030, the energy-related CO2 emissions will reach a value of about 25 Gt CO2, which is lower than the NDC emission target level.By 2050, the emissions will be reduced by more than 50% as compared to their level in 1990, and net zero carbon emissions will be achieved by around 2065.The total cumulative emissions in the interconnection scenario are equal to around 1000 Gt CO2, making it a possible pathway to meeting the 2 °C target of the Paris agreement.However, the BAU scenario (denoted by the red curve)indicates that the total emissions will significantly increase if the current policy remains unchanged.In this scenario,the total emissions will reach a level of around 80 Gt CO2 in 2100, and the cumulative emissions will be equal to 4300 Gt CO2 by the same time, leading to a temperature increase of 3.5−4 °C.According to (1), the area of the gap between the red and blue regions indicates the emission reduction contribution of GEI, which is equal to a relatively large value of 3100≈∆C Gt CO2.

The results of numerical analysis of the emission reductions caused by all components of the interconnection scenario are also shown in Fig.2.The values calculated via equations (8), (9), and (11) are denoted by the green, blue,and yellow colors corresponding to the clean replacement,electricity replacement, and CCS development, respectively.The clean replacement contribution with a fraction of 53%is the dominant component of the total contribution, which results in a cumulative CO2 emission reduction of 1600 Gt by 2100.In the interconnection scenario, GEI drives the large-scale development and utilization of clean energy with a share of 66% in the primary energy supply by 2050.

The electricity replacement component also significantly contributes to emission reduction.Since more electricity is used in the final consumption instead of fossil fuels,the implementation of GEI significantly improves the energy efficiency and reduces emission levels in the final consumption sectors.The rate of electricity usage in the final energy consumption will increase by 44% in 2050.As a result, the electricity replacement will reduce the cumulative emissions by about 1300 Gt CO2 in 2100, which is equal to 42% of the total emission reduction (the blue area in Fig.2).

Fig.2 CO2 emission reduction contributions in the interconnection scenario

The CCS development (the yellow area) produces an additional bonus to the emission reduction in the interconnection scenario.Its magnitude is equal to about 170 Gt CO2, which accounts for 5% of the total GEI contribution.

4.3 Contribution of Interconnection Scenario

According to the described mechanisms, the grid interconnection essentially promotes the development of the clean replacement and electricity replacement processes.

In this subsection, we quantitatively compare the BAU and interconnection scenarios by considering the future consumption of clean resources and electrification.According to Fig.3, the consumption of clean energy resources in the interconnection scenario dramatically increases to about 18000 Mtce by 2050, which is 4.5 times greater than that in 2015 and 2 times as high as the level obtained in the BAU scenario.Further, in this scenario,the annual growth of clean energy resources in the primary energy supply amounts to 4.4%.On the contrary, in the BAU scenario, the consumption of clean resources reaches 9100 Mtce in 2050, which is 2.3 times greater than that in 2015 with an annual growth rate of 2.3%.The utilization of clean energy in the BAU scenario is limited due to the randomness and uneven distribution of clean energy resources.

Fig.3 Consumption of clean resources in the BAU and interconnection scenarios

In Fig.4, the electrification rates calculated in the BAU and interconnection scenarios are compared.Similarly,using the data obtained for year 2015 as a reference, the electrification rate can reach a magnitude of about 44%,which is 2.4 times greater than the 2015 level.This large power amount based on the interconnection scenario(especially on the use of renewable energy-based power plants) dramatically increases the supply volume to promote high-efficiency power usage with low emissions.In addition, the interconnected grids located between various regions enable optimal power allocation, which further improves the efficiency of power utilization.However, in the BAU scenario, the fraction of electricity will be about 23% of the total final energy consumption, which is 1.2 times greater than the 2015 level.In this case, to meet the requirements of energy usage on the demand side, large amounts of fossil fuels must be still utilized in the final consumption, which results in harmful CO2 emissions.However, in the interconnection scenario, the electrification rate can reach a value of about 43%, which is 2.4 times higher than the level achieved in 2015.

Fig.4 Electrification rates obtained in the BAU and interconnection scenarios

5 Conclusion

In this work, the CO2 emission reduction via GEI implementation is discussed.First, the reduction mechanism and contributions of various GEI components are qualitatively analyzed using a comprehensive framework.After that,the emission reduction contributions are determined for the clean replacement, electricity replacement, and CCS components via numerical simulations.As compared to the BAU scenario, the interconnection scenario can provide an emission reduction of 3100 Gt CO2 by 2100 with 53%contributed by the clean replacement, 42% by the electricity replacement, and 5% − by CCS.It is concluded that the implementation of grid interconnection promotes the clean energy utilization at an annual growth rate of 4.4% from 2015 to 2050 and increases the electrification rate by a factor of 2.4 from 19% to 44% over the same period.

Acknowledgements

This work was supported by the GEIGC Science and Technology Project in the framework of the “Scenario Analysis of Emission Reduction Pathways and Technical Solutions to Achieving the Paris Agreement Goals” (grant No.52450018000Q) and China’s National R&D Program“Integrated Impact Assessment of Climate Change on Economic System” (grant No.2016YFA0602602).We also thank IIASA for providing the scenario data.