Transition scenarios of power generation in China under global 2 ℃ and 1.5 ℃ targets

1 Background

The Paris Agreement implemented targets for 2100 specifying that global temperature increases are maintained well below 2 °C, with an ambitious target of 1.5 °C.China signed the agreement supporting these global targets, and retained the option to “strengthen the long-term global goal on the basis of best available scientific knowledge,including in relation to a global average temperature rise of 2 °C and 1.5 °C”.Moreover, the IPCC 5th Assessment Report (AR5) recommended that research communities model the emission pathways and feasibilities of the global targets.Recently, several global emission scenario studies have presented energy and emission scenarios focusing on the 2 °C target, which requires that global emissions peak before 2020.However, studies on the 1.5 °C target remain very limited.In order to determine whether this target is possible,the IPCC, according to a requirement of United Nations Framework Convention on Climate Change (UNFCCC),launched the process to publish a Special Report on the 1.5 °C target by 2018.Recent modeling research on global emission pathways required to achieve the 1.5 °C target suggested that global emissions would need to reach zero between 2050 and 2060, becoming negative thereafter [1-5].Achieving these targets is a substantial challenge requiring further efforts from individual countries.It is therefore crucial to conduct further analysis at the country scale to ascertain the possibility of mitigating CO2 emissions through the 2 °C and 1.5 °C target pathways.This paper presents modeling results of the IPAC modeling team at the Energy Research Institute (ERI) analyzing China’s energy and emission scenarios in the power generation sector against the background of global 2 °C and 1.5 °C targets.

2 Research methodology and key assumptions

2.1 Methodology framework

In this study, we use the linked Integrated Policy Assessment Model of China (IPAC) to perform a quantitative analysis, covering both global scenarios and China’s national emission scenario.IPAC is an integrated model developed by Energy Research Institute (ERI)to analyze global, national, and regional energy and environment policies.ERI has been conducting long-term research into developing and utilizing energy models since 1992[6-13].

In order to analyze global and national emission scenarios, we use three models including the IPACEmission global model and two national models: the IPAC-CGE model and IPAC-AIM/technology model.The relationships among the three models are shown in Fig.1;they are currently soft-linked, which means that the output of one model is used as the input of another model.In the IPAC-Emission model, each model is hard-linked.

The IPAC-Emission model is a global model of the IPAC family, which currently covers nine regions and is being extended to 22 regions.Because this model focuses on energy and land use activities, in order to simulate other gas emissions, the model was revised to include HFC,PHC, SF6, CH4, and N2O analysis.The Energy Modeling Forum (EMF)-21 results of [7]were used here.Data for the abatement curve for HFC, PFC, and SF6 emissions from industrial processes and other sources were used in the IPAC model.IPAC-AIM/technology is the main component of the IPAC model [6].The IPAC-AIM/technology model employs a cost-minimization principle; i.e., technologies with the lowest costs are selected to provide the energy service.The current version of the IPAC-AIM/technology model includes 42 sectors and their products and almost 600 technologies, including existing and potential technologies.

Fig.1 Links between the different models used in this research

IPAC-SGM (Second Generation Model) is a general equilibrium model (CGE model) for China.It is mainly responsible for analyzing the economic impacts of different energy and environmental policies and can analyze both mid-and long-term energy and environment scenarios.IPAC-SGM divides the entire economic system into household, government, agriculture, energy, and other production sectors.Currently, there are 42 sectors in the IPAC-SGM model.Scenario selection for China is based on relevant studies on GDP, population, sector outputs,etc., but the IPAC modeling team also conducts its own research on these parameters using the IPAC-SGM and its own population model.Economic activities are becoming a key research topic in IPAC modeling studies due to large potential changes in economic development.Sector development trends are a crucial factor for energy and emission scenarios in modeling studies.Energy intensive sectors, such as ferrous metal manufacture, non-ferrous metal manufacture, building material manufacture, and the chemical industry, accounts for 50% of total final energy use in China.Future changes in these sectors are very important for scenario analysis.By using the IPAC modeling framework, we generate scenarios for these economic activities.Moreover, the physical unit output in energy intensive sectors is determined using the CGE model and input-output analysis.

2.2 Scenarios

The IPAC team developed and published different emission scenarios for China [6-13].These scenarios include the baseline scenario, low carbon scenario, enhanced low carbon scenario, 2 °C scenario, and the recently completed 1.5 °C scenario.Recent studies from the IPAC modeling team predominantly focus on the 2 °C and 1.5 °C scenarios.This study also uses these two scenarios and focuses on the power generation sector.

2.3 Key assumptions

This section presents the key parameters used in the IPAC modeling analysis of the two scenarios, where population and macro-economy parameters are kept constant.These parameters have been documented in previous publications.Table 1 presents the population scenario.The GDP growth used here was revised using previous IPAC studies and recent development trends in China.GDP growth and structure changes were calculated using the IPAC-SGM model, which is a CGE model.Fig.2 presents the GDP assumption in the IPAC model, and presents structural changes in the secondary sector [9][14].

Table 1 IPAC population scenario

Unit 2005 2010 2020 2030 2040 2050 Population million 1308 1360 1440 1470 1470 1440 Urbanization rate 43% 49% 63% 70% 74% 79%Urban population million 562 666 907 1029 1088 1138 Person per household 2.96 2.88 2.80 2.75 2.70 2.65 Urban household million 190 231 324 374 403 429 Rural population million 745 694 533 441 382 302 Person per household 4.08 3.80 3.50 3.40 3.20 3.00 Rural household million 183 183 152 130 119 101

Fig.2 GDP growth in China (with a constant price in 2010)

Indicates that future GDP growth will mainly come from the tertiary sector and non-energy intensive industries,such as electronic product manufacture and light industry manufacture.A study into the demand for energy intensive products revealed that many energy intensive products will peak between 2020 and 2025, assuming that future exports of energy intensive products will not increase significantly as it is already a major part of the global output.[14]presents the outputs of major energy intensive sector products, derived from a demand analysis of these energy intensive products conducted by a physical unit I/O table,with consideration of future infrastructure and consumption development.For example, in one scenario, building floor space was set as 89 billion m2 in 2050, when China will be well developed and personal income will be high, with per capita floor space of 64 m2.In this case, the number of newly built buildings per year will reach a peak before 2020 then start to decrease.Because more than 55% and 70% of China’s steel and cement are used in building construction,respectively, and many other energy intensive products are also closely linked with building construction, we can assume that the demand for many energy intensive products will also reach a peak at this point.Moreover, the outputs of many consumer goods in China represent more than half of the global output, leaving little room for future increases.The share of value added for the energy intensive industry in GDP is predicted to decrease from 11% in 2010 to less than 6% in 2050.

Energy intensive products consume almost 50% of energy in China, so the lack of a significant increase in energy intensive production, with much lower growth than the GDP, will also limit the energy use related to these energy intensive products.This can contribute to decreasing energy intensity per GDP as well as CO2 intensity.Table 3 presents the key parameters in urban households in China.The data is given based on population growth, size of household, and personal income.By 2030, due to their high income, urban households in China will have similar living quality to developed countries from the aspect of electronic appliances, space heating, space cooling etc.Data for households in developed countries were also analyzed and compared.

Table 2 Energy intensive product output scenario in IPAC

Unit 2005 2010 2014 2020 2030 2040 2050 Crude Steel million ton 355 627 813 710 570 440 360 Cement million ton 1060 1868 2490 2950 1600 1200 900 Glass million cases 399 580 831 740 690 670 580 Copper million ton 2.6 4.79 7.95 7.6 7 6.5 4.6 Aluminum million ton 8.51 16.95 24.38 25 17 15 12 Lead and zinc million ton 5.1 8.9-10.05 10 7 6.5 5.5 Sodium carbonate million ton 14.67 20.34 25.25 25 24.5 23.5 22 Caustic soda million ton 12.6 22.28 30.63 30 25 25 24

continue

Unit 2005 2010 2014 2020 2030 2040 2050 Paper and paperboardmillion ton 62.05 92.7 117.85 110 110 105 100 Chemical fertilizer million ton 52.2 63.38 68.76 64 59 56 53 Ethylene million ton 7.56 14.12 16.96 24 23 23 23 Ammonia million ton 46.3 49.65 56.99 52 50 50 45 Calcium carbide million ton 8.5 14.7 25.2 22 16 11 7

Table 3 IPAC urban household parameters

Service 2020 2030 2050 Household million 288 336 380 Share of HH with space heating 42% 44% 48%Index of space heating intensity 2000=1 1.35 1.5 1.6 Service Unit Index of space heating time 2000=1 1.33 1.36 1.4 Share of building with 50%efficiency standard % 20 45 65 Ownership of air conditioner per 100 households(HH)130 180 260 Index of air conditioner intensity 2000=1 1.3 1.4 1.6 Index of air conditioner utilization time 2000=1 1.6 1.8 2.2 Ownership of refrigerator per 100 HH 100 120 130 Average space of refrigerator L 250 310 390 Efficiency of refrigerator kWh/day 0.8 0.8 0.7 Ownership of washing machine per 100 HH 100 100 100 Duration of washing machine use per week h 5.4 8 8 Ownership of TV per 100 HH 180 220 290 Average capacity of TV W 320 300 280 Hours of TV per day h 3.5 3.2 2.9 Penetration rate of CFL % 100% 100% 100%Light per HH 14 21 27 Ownership of water heater per 100 HH 100 100 100 Ownership of solar heater per 100 HH 18 25 33 Ownership of electric cooker per 100 HH 130 140 260

continue

Service 2020 2030 2050 Hours per day of electric cooking min 12 30 50 Service Unit Capacity of other electric appliances W 1500 1800 2300 Hours of other electric appliances min 50 80 100

3 Emission, energy, and power generation transition scenarios

Fig.3 to Fig.5 present the scenario results of the IPAC modeling analysis.China’s emission budgets under the global 2 °C and 1.5 °C targets were adopted based on related studies [2][4].By following the carbon budget for China,we linked China’s CO2 emissions with global emissions for these targets.In order to support the global 2 °C target, CO2 emissions must peak before 2025 (around 2020 to 2022)then reduce to 2.94 billion ton by 2050, representing a 70%emission reduction.As for the 1.5 °C target, CO2 emissions must peak before or around 2020, then start to decrease sharply to 325 million ton by 2050.The energy transition in these two scenarios reveals the pathway enabling low carbon energy to dominate the energy mix by 2050 (Fig.4 and Fig.5).

Fig.3 CO2 emissions in China

Fig.4 Primary energy demand in China under the 2 °C scenario

Fig.5 Primary energy demand in China under the 1.5 °C scenario

Power generation transitions under both scenarios are shown in Fig.6 and Fig.8.In both scenarios, power generation transitions toward clean power generation are significant.In the 2 °C scenario, renewable energy is much more dominant; power generation from renewable energy could reach 48% of total power generation, leaving only 17% for coal-fired power generation.The installed capacity for wind, solar, and hydro is 930, 1040, and 520 GW by 2050, respectively (Fig.7).Nuclear power will also play an important role in the clean power transition.In this study,the nuclear power scenario was adopted from a study by the Chinese Academy of Engineering [15].430 GW of nuclear power could be installed by 2050, with power generation of approximately 3290 TWh, accounting for 28% of total power generation in 2050.

The power generation sector is crucial in the 1.5 °C scenario as this sector should achieve zero or negative emissions by 2050, prompting significantly more electricity use in the end use sector.As a result, power generation will increase to more than 14000 TWh by 2050, with a per capita value of 10320 kWh (Fig.8).Among the power generation sector, renewable and nuclear energy will generate 80% of the total power generation, in which wind power accounts for 21%, solar 16.6%, hydro 14%, biomass 7.6%, and nuclear power 28% in 2050.Their respective contributions in 2015 were 3.3%, 0.7%, 17.7%, 0.3%, and 3%.Coal-fired power and natural gas-fired power will account for 5.3%and 7.1% in 2050, a change from 71% and 3% in 2015.This is a significant transition in 35 years.Considering that the life span of these fossil fuel-fired power plants is typically greater than 35 years, the decision to make this transition must be made immediately.Fig.9 shows that the installed power capacity for wind will increase from 129 GW in 2015 to 1486 GW by 2050, solar from 43 GW to 2246 GW,hydro from 319 GW to 640 GW, biomass power from 11 GW to 250GW, and nuclear from 26GW to 554GW.The average increase in power capacity from 2015 to 2050 will be 36.9 GW for wind power, 52.5 GW for solar power, 9.3 GW for hydro, 6.85 GW for biomass power, and 14 GW for nuclear power; coal-fired power will have to reduce by 20 GW each year.

Fossil fuel power generation must employ CCS in order to reduce emissions by as much as possible.By 2050,100% of coal-fired power and natural gas-fired power will be equipped with CCS (Fig.3), with potential removal rates of 94% and 90%, respectively.Biomass energy with carbon capture and storage (BECCS) is a key option for low emission scenarios in the power generation sector.By 2050, the installed capacity for biomass will be 250 GW and equipped with CCS.Biomass for power generation will mainly come from the firewood of planted trees.Total biomass demand will be 420 Mtce, with a power generation efficiency of 32% with CCS.Altogether, CO2 emissions from power generation will be -414 million ton in 2050,including negative emissions from BECCS (Fig.4).

4 Discussion

In both scenarios, renewable and nuclear energy represent a major share of power generation in 2050.This should be implemented immediately with a significant increase in their newly installed capacity.To achieve this energy transition, reductions in the cost of wind, solar,and nuclear power generation are crucial, together with support from grid and electricity storage.Recent progress in solar PVs and wind power has increased the likelihood of achieving the 2 °C target.The newly installed capacity for solar PV was 55 GW in 2017, which was maintained in 2018; this capacity is actually larger than that required to achieve the 2 °C scenario by 2020.China must use CCS for fossil fuel-fired power generation and other sectors in order to achieve emission targets after 2030, despite CCS not yet being available on the commercial market and being very costly.However, based on the IPAC team’s study on CCS implementation in China, future CCS development will be promoted by reduced costs.Fig.10 presents the CCS used in the 2 °C scenario.

Fig.6 Power generation under the 2 °C scenario

Fig.7 Installed power capacity under the 2 °C scenario

Fig.8 Power generation under the 1.5 °C scenario

Fig.9 Installed power capacity under the 1.5 °C scenario

Key factors for pathways consistent with the 1.5 °C scenario include large-scale use of BECCS to achieve negative emissions in the power generation sector by 2050,a very high share of electricity in end use sectors, highly energy efficient end use technologies, large-scale use of renewable energy and nuclear power, and new industrial processes to change from fossil fuel use to electricitybased processes.Therefore, questions arise regarding the possibility of ensuring a stable large-scale biomass supply by planting energy farms, the water demand for rapidly growing energy farms, the social impact of rapid changes to the energy mix and related costs, and the progress of key technologies including energy supply technology and end use energy technology.In order to understand the costs and benefits of attempting the 1.5 °C target, we must also understand the impacts of temperature increases.These are research tasks for future studies.

In the 1.5 °C scenario, after CO2 emissions reach a peak around 2020, there will be a rapid reduction by 2030,then a transition to negative emissions in 2050.Net CO2 emissions will be 10.13 Gt in 2020, 6.12 Gt in 2030,and -0.59 Gt in 2050 (Fig.13).After 2020, CO2 will be reduced by 483 million ton each year, corresponding to a reduction in coal and oil of almost 220 million ton per year.The power generation sector is the key sector for leading emission reductions.CO2 emissions peaked in 2015, and will experience a rapid reduction after 2020 to -18.6 million ton in 2040 and -1537 million ton in 2050 (Fig.12).BECCS plays a key role in this reduction; after 2030, it will capture more than 1.5 billion ton CO2 per year by 2050 (Fig.14).

Fig.15 presents the annual investment required in the power generation sector, which was US$157 billion in 2015 and will be US$291 billion in 2030 and US$382 billion in 2050;these values are 16% and 39.8% higher than that specified by the 2 °C scenario for 2030 and 2050, respectively.Considering the predicted GDP of China for 2030 and 2050,this is a relatively small investment [14].

Fig.16 illustrates the change in installed capacity per year.The number of coal-fired power plants must be reduced quickly to maintain the same hours of utilization.After 2020, approximately 40.7 GW of capacity should be shut down each year, which constitutes a very rapid change.From 2030 to 2050, coal-fired power plant capacity must be reduced to 23–28 GW per year; this drastic change could be made easier by reducing utilization hours.If utilization hours were reduced to approximately 2500 per year from 2025 to 2030, the shutdown capacity would be only 8 GW per year, and if utilization hours were reduced to 3400 per year, the shutdown capacity for coal-fired power plants would be as little as 4 GW per year.In comparison,utilization hours for coal-fired power plants are 1900 per year in Germany.Reducing utilization hours for coal-fired power plants would also aid the rapid development of wind and solar power.Moreover, biomass could be mixed with coal for use in coal-fired power plants, increasing the usage of biomass and providing lower cost options for biomass power generation.

Fig.10 CO2 removed by CCS in the power generation sector under the 2 °C scenario

Fig.11 Installed capacity with CCS in the power generation sector

Fig.12 CO2 emissionsin the power sector under the 1.5 °C scenario

Fig.13 Net CO2 emissions in China under the 1.5 °C scenario

Fig.14 CO2 emission reduction by CCS

Fig.15 Investment required in the power generation sector

Fig.16 Changes in the power capacity per year

Wind and solar power will increase rapidly in the future.From 2025, their newly installed capacity will be more than 60 GW per year, increasing to more than 75 GW per year after 2030, compared with a newly installed capacity of 34 GW in 2016.Wind power will also need to grow quickly,with a newly installed capacity of more than 40 GW per year, compared to 32 GW in 2015 in China.Biomass power generation should be 10 GW per year after 2025 to ensure long-term BECCS.All newly installed biomass power plants must incorporate CCS or be CCS ready.

Transitions in the power generation sector for both scenarios are rapid and significant.China is the fastestgrowing country for new and renewable energy and is concerned with protecting the ecological basis, orderly development of hydropower, active development of nuclear power, and the encouragement and support of rural,remote, and other suitable areas for developing biomass,solar, geothermal, wind, and other new renewable energy sources.Since 2010, China has been the leading country for renewable energy development.Since 2016, the newly installed capacity in China for renewable energy has been more than 70 WG annually.In 2017, the newly installed capacity for solar PV was 55 GW, which accounts for 53%of the global solar installed capacity [16].

The renewable energy requirements under the 2 °C scenario are possible because of recent progress in renewable energy development in China.The cost-leaning curve for wind and solar for 2010 was much stronger than that used by the model (Fig.6).This progress significantly reduced the cost of wind and solar power within 2 years.Now, the power generation costs for some wind farms can already compete with those of coal-fired power plants.Moreover, the rapid GDP growth rate provides strong support for low carbon development in China.In the last two decades, the annual GDP growth rate remained high at 8.9%.It is expected that the GDP in China will reach 100 trillion Yuan (in current value) by 2020.The investment requirements proposed by this modeling study are very small part of those of GDP at typically less than 2–4%.New and renewable energy is a key sector for promotion by government policies and planning; thus, considerably more investment is expected in this sector in the future.Nonetheless, China already boasts the largest renewable energy investment in the world since 2010, which accounts for 24% of global renewable energy investment [16].

5 Conclusions

In both 2 °C and 1.5 °C scenarios, power generation transitions toward clean power generation are significant and renewable and nuclear energy represent the major share of power generation in 2050.To accomplish this,an immediate and significant increase of newly installed capacity is required; therefore, reductions in the cost of wind, solar, and nuclear power generation are crucial,together with support from grid and electricity storage.In the 2 °C degree scenario, renewable energy is much more significant and power generation from renewable energy could reach 48% of total power generation, leaving only 17% for coal-fired power generation.The installed capacity for wind, solar, and hydro power should be 930 GW, 1040 GW,and 520 GW, respectively, by 2050.Nuclear power will also play an important role in this clean power transition.In this study, the nuclear power scenario was adopted from the Chinese Academy of Engineering [15]; 430 GW of nuclear power could be installed by 2050, with power generation of approximately 3290 TWh, accounting for 28% of total power generation in 2050.In the 1.5 °C scenario, the installed capacity for nuclear should be more than 500 GW by 2050.

The key goal of the 1.5 °C scenario is to achieve zero or negative emissions from power generation by 2050,promoting substantially more electricity use in the end use sector.Among all types of power generation, renewable and nuclear energy should generate 80% of the total power generation.Wind power would account for 21% in 2050,solar 16.6%, hydro 14%, biomass 7.6%, and nuclear power 28%.In contrast, their respective 2015 values were 3.3%,0.7%, 17.7%, 0.3%, and 3%.In 2050, coal-fired power would account for 5.3% and natural gas-fired power for 7.1%; these values were 71% and 3% in 2015, which is a significant transition in 35 years.By considering that the life span of these fossil fuel-fired power plants is typically more than 35 years, it is imperative to act immediately to ensure a successful power generation transition.

Acknowledgements

This work was supported by National Key Basic Research Program of China (973 Program) under Grant 2014CB441301; National Key Basic Research Program of China (No.2017YFA0603804).