Inter-regional Transmission Research Articles

Research on adjustable load dividend transmission strategy under aggregate operation mode

In recent years, the scale of inter-provincial and inter-regional power transmission keeps growing, the proportion of new energy keeps rising, and the complexity of power grid structure increases the risk of its operation control. Under the aggregation operation mode, the adjustable load has great electricity elasticity. Guiding its electricity consumption behavior and making it participate in the power grid regulation operation can greatly improve the safety of operation, promote the absorption of new energy and realize the optimal allocation of power resources. This paper studies the form of adjustable load participation in grid regulation in different scenarios under the aggregate operation mode, analyzes the cost and benefit of adjustable load participation in electricity market transactions, and then combines the evaluation method based on the contribution of adjustable load users in different scenarios to propose a dividend transmission strategy of adjustable load in the aggregate operation mode.

Environmental sustainability improvement in chloromethanes production based on life cycle assessment

Chloromethanes (CMS), as major chlorine-consuming products and upstream raw material for emerging industries, play an irreplaceable role in the chemical industry and impose non-negligible environmental pressure during production. This study adopted the cradle-to-gate life cycle assessment approach to quantify the environmental performance of CMS production in China by using integrated data from five CMS enterprises, which underpin approximately 21 % of China's total CMS production capacity. An integrated and regionalized life cycle impact assessment method was employed to suit Chinese conditions and avoid spatial differences. The results indicate that fossil depletion is the dominant impact category, which was ascribed mainly to methanol production (37.0 %), electricity generation (27.3 %), and steam production (23.4 %). The coke oven gas-to-methanol process shows superiority in mitigating fossil consumption and CO 2 emission compared with the traditional coal-to-methanol process, with reduction ratios of 80.3 % and 83.2 %, respectively. Renewable energy power generation and pollution transfer in inter-regional power transmission also deserve attention. Green methanol, waste heat reuse, and advanced heat recovery technologies are recommended for further alleviation of the environmental burden. In addition, CMS-related industrial chains can improve industrial concentration and promote integrated development to achieve high-efficiency utilization of raw materials and energy.

Has the Inter-Regional Power Transmission Promoted Economic Development? A Quantitative Assessment in China

As one of the largest energy consumers in the world, China’s total electricity consumption has increased by 416.33% during the sample years of 2001 to 2019. In 2019, the top five provinces in terms of power use were all located on the eastern coast. They have contributed 38.39% of the total consumption, causing a power shortage of 594.5 billion kWh in the provinces, while the power generation in the central and western regions have far exceeded their electricity consumption. In order to alleviate the problem of the mismatch between the power resource centers and the load centers in China, ultra-high voltage (UHV) projects, as one of the most important projects in recent years, have bridged the resource gap between the regions and have improved the allocation efficiency of the power resources. Although the cross-provincial transmission of electricity opens the pathway for the consumption of resources, the causal effects of the project on the regions along the line have not been accurately analyzed. Firstly, by constructing a quasi-natural experiment, this paper uses county-level panel data during the period of 2000 to 2019 to analyze the economic benefits that are generated by the inter-regional power transmission project. Secondly, the pathways of the economic effects of UHV are also verified. Finally, this paper also analyzes the heterogeneous effect of power-resource-rich provinces in the construction of the project. Through the pathways of local enterprise dynamics, employment level, and industrial structure, the findings prove that cross-regional power transmission has significantly enhanced the economic growth of the related regions and has played an especially positive role for the power exporting provinces. This paper provides empirical evidence for the effect of optimal resource allocation and the infrastructure development of developing countries and supplies a policy reference for developing countries’ resource allocation optimization strategies.

Who shapes the embodied carbon dioxide emissions of interconnected power grids in China? A seasonal perspective

With the rapid development of interregional power transmission, the redistribution of fossil and renewable energy resources has changed sharply, and its complexity poses a challenge to the evaluation of power carbon emission responsibility. This study constructs an interprovincial power transmission framework to measure the seasonal carbon emissions embodied in regional electricity consumption over the period of 2008–2015 based on quarterly data. Then, a structural decomposition approach was developed to identify the influential factors of carbon emissions embodied in provincial electricity consumption from a seasonal perspective. The results show that the assessment for embodied emissions of power consumption based on different levels of data may vary by as much as 20%, and the carbon emissions and carbon intensity of power consumption exhibit significant seasonal characteristics. Furthermore, it is revealed that the economic scale in the fourth quarter makes the most significant contribution to the emissions increment, especially in underdeveloped provinces, while the change in energy efficiency of power generation reduces more carbon emissions in the first and second quarters. In addition, the impact of the power transmission scale is more significant in the third and fourth quarters, and it has been close to or even more than the impact of traditional factors in some quarters. Finally, the impact of economic scale, power generation energy intensity, power generation mix and electricity utilization efficiency on the emissions of regional power grids shows a relatively stable increasing trend, but this trend of directional stability is not reflected in the effect of the power transmission structure and transmission scale. This study contributes to the identification of the impact of the power transmission structure and transmission scale. Moreover, this study highlights the importance of considering seasonal characteristics when estimating the carbon emissions of power consumption and formulating specific emission reduction policies. Additionally, it provides a more accurate evaluation of carbon emissions and proposes several prominent recommendations for policy makers.

Assessing the integration effect of inter-regional transmission on variable power generation under renewable energy consumption policy in China

Integrating a high share of variable renewable energy into multi-region power systems is essential and requires an interconnected transmission grid to coordinate regional power system operations. This paper proposes a multi-region power system optimization model to evaluate the role of interconnection in China's power sector for economic benefit, variable renewable energy power generation and allocation, transmission line efficiency and carbon emission transfer in the context of renewable energy consumption policy. The results show that inter-regional power transmission coupled with flexibility technology can facilitate renewable power generation and delivery. The renewable energy consumption policy would intensify this effect, although it leads to a slight drop in economic efficiency. Improving the compatibility of transmission network with variable power is crucial because wind and solar power are expected to make up 60% of the total inter-regional power transmission, particularly the share in the outward transmission lines from the northwest region reaching 91%. Renewable energy integration policy targets in northwest, north, Inner-Mongolia and northeast regions can be improved to 37.5%, 31.5%, 35.3%, and 36.9%, respectively.

Using temperature sensitivity to estimate shiftable electricity demand

SummaryThe growth of intermittent renewable energy and climate change makes it increasingly difficult to manage electricity demand variability. Centralized storage can help but is costly. An alternative is to shift demand. Cooling and heating demands are substantial and can be economically shifted using thermal storage. To estimate what thermal storage, employed at a scale, might due to reshape electricity loads, we pair fine-scale weather data with hourly electricity use to estimate the share of temperature-sensitive demand across 31 regions that span the continental United States. We then show how much variability can be reduced by shifting temperature-sensitive loads, with and without improved transmission between regions. We find that approximately three-quarters of within-day, within-region demand variability can be eliminated by shifting just half of temperature-sensitive demand. The variability-reducing benefits of shifting temperature-sensitive demand complement those gained from the improved interregional transmission, and greatly mitigate the challenge of serving higher peaks under climate change.

Enabling a low-carbon electricity system for Southern Africa

<h2>Summary</h2> Southern Africa faces the dual challenge of providing affordable energy to meet rapidly growing electricity demand while limiting carbon emissions and socio-environmental impacts. We combined open-source geospatial, hydrological, and electricity grid-investment models to develop cost-optimal low-carbon electricity pathways for Southern Africa. If technology and fuel prices continue to follow current trends, wind and solar technologies can become the dominant sources of electricity in the region by 2040. Importantly, no new coal capacity is built in any scenario except when inter-regional transmission is constrained. Furthermore, despite the abundant hydropower potential in the region, nearly half of the planned hydropower capacity is not cost competitive, thus supporting freshwater conservation efforts. An 80% clean energy target can halve annual greenhouse gas emissions by 2040, as compared with 2020, with only a modest 6% cost premium. Alternatively, retiring coal plants 20 years earlier could result in even greater emission reductions but could incur 12% higher annual costs.

Molecular epidemiology of HIV-1 in Oryol Oblast, Russia.

The HIV/AIDS epidemic in Russia is growing, with approximately 100,000 people infected annually. Molecular epidemiology can provide insight into the structure and dynamics of the epidemic. However, its applicability in Russia is limited by the weakness of genetic surveillance, as viral genetic data are only available for <1 per cent of cases. Here, we provide a detailed description of the HIV-1 epidemic for one geographic region of Russia, Oryol Oblast, by collecting and sequencing viral samples from about a third of its known HIV-positive population (768 out of 2,157 patients). We identify multiple introductions of HIV-1 into Oryol Oblast, resulting in eighty-two transmission lineages that together comprise 66 per cent of the samples. Most introductions are of subtype A (315/332), the predominant HIV-1 subtype in Russia, followed by CRF63 and subtype B. Bayesian analysis estimates the effective reproduction number Re for subtype A at 2.8 [1.7–4.4], in line with a growing epidemic. The frequency of CRF63 has been growing more rapidly, with the median Re of 11.8 [4.6–28.7], in agreement with recent reports of this variant rising in frequency in some regions of Russia. In contrast to the patterns described previously in European and North American countries, we see no overrepresentation of males in transmission lineages; meanwhile, injecting drug users are overrepresented in transmission lineages. This likely reflects the structure of the HIV-1 epidemic in Russia dominated by heterosexual and, to a smaller extent, people who inject drugs transmission. Samples attributed to men who have sex with men (MSM) transmission are associated with subtype B and are less prevalent than expected from the male-to-female ratio for this subtype, suggesting underreporting of the MSM transmission route. Together, our results provide a high-resolution description of the HIV-1 epidemic in Oryol Oblast, Russia, characterized by frequent interregional transmission, rapid growth of the epidemic, and rapid displacement of subtype A with the recombinant CRF63 variant.

Regional power system transitions towards carbon neutrality: The case of North China

China has announced its goal of reaching carbon neutrality by 2060, which will have a profound impact on its energy and economic systems. During this process, the power sector will play a key role in helping the country on its road towards carbon neutrality. This study develops a multi-regional power dispatch and capacity expansion model to combine long-term capacity expansion with short-term power dispatch. The model is built to optimise the carbon-neutral transition pathway from the perspective of economics, focussing on power system stability and reliability under high penetrations of renewables. Using the case study of North China, the cost-effective methods for power system transitions under the targets of reaching peak emissions by 2030 and achieving carbon neutrality by 2060 are discussed under different scenarios. We find that the future power supply system will rely heavily on renewable energy which will account for more than 89% of power generation. Inner Mongolia will produce more than 84% of power in the North China region. The inter-regional power transmission capacity will be five times higher than its current level. Policy choices will lead to different transition pathways as the early-stage installation decisions will have a lock-in effect on the following carbon emission reduction strategies and determine the importance of technologies adopted in achieving carbon neutrality. Although the transition to a low-carbon economy will result in an increase in cost by 17–19%, it will bring huge climate benefits to the world.

Regional disparity of flexibility options for integrating variable renewable energy

Integrating massive variable renewable energy requires sufficient flexibility to maintain stability of power systems. Incorporating flexibility options could provide insights into the system operation optimization for fully integrating wind and solar power. In order to find regional disparity in flexibility options under various system configurations and power demands, we quantify the flexibility requirement by residual load curve and formulate the flexibility provision by an integrated optimization model to present flexibility solutions and distributions in power system operations. The model integrates the interactions of demand side response, energy storage and interregional interconnection. A case study of China is conducted. The results indicate that demand flexibility enables cost-efficient integration of variable renewables in coal-based and load-centred areas. Regions with abundant renewables prefer to adopt the integration option of demand side response and energy storage to meet the dramatically fluctuating flexibility requirement. Interregional transmission provides a necessary solution for areas with imbalanced power supply capability and electricity demand.

The potential of green ammonia production to reduce renewable power curtailment and encourage the energy transition in China

The pursuing of inter-regional power transmission to address renewable power curtailment in China has resulted in disappointing gains. This paper evaluates the case of local green ammonia production to address this issue. An improved optimization-based simulation model is applied to simulate lifetime green manufacturing, and the impacts of main institutional incentives and oxygen synergy on investment are analysed. Levelized cost of ammonia is estimated at around 820 USD/t, which is about twice the present price. The operating rate, ammonia price, the electrical efficiency of electrolysers and the electricity price are found to be the key factors in green ammonia investment. Carbon pricing and value-added tax exemption exert obvious influences on the energy transition in China. A subsidy of approximately 450 USD/t will be required according to the present price; however, this can be reduced by 100 USD/t through oxygen synergy. Compared to inter-regional power transmission, green ammonia production shows both economic and environmental advantages. Therefore, we propose an appropriate combination of both options to address renewable power curtailment and the integration of oxygen manufacturing into hydrogen production. We consider the findings and policy implications will contribute to addressing renewable power curtailment and boosting the hydrogen economy in China.

Has the inter-regional transmission expansion promoted the low-carbon transition of China’s power sector?

China is facing unprecedented pressure to reduce carbon emissions than ever before. Significant differences do exist among regions in resource endowment, emission potential and environmental capacity. The introduction of inter-regional transmission lines is of great significance in alleviating environmental pressure and regulating the power mix. However, it is uncertain whether and to what extent the electricity sector has been locked into fossil fuel, as well as the regional differences in low-carbon transition. This study investigates whether the transmission grid expansion represented by more ultra-high voltage (UHV) lines construction will mitigate carbon emissions through a mixed complementarity problems equilibrium analysis. Through simulating the influence of various carbon emission caps on inter-regional transmission lines, it explores the regional differences in low-carbon transition in the power sector, and investigates the regions’ reliance on fossil-fuel from the perspective of carbon lock-in. We propose the following suggestions: (1) Mitigating the reliance on fossil fuel-fired power may relieve the low-carbon transition pressures of the central, eastern, and southern regions; (2) The inter-regional transmission lines help to regulate the distribution of carbon emissions by adjusting emission cost; and (3) The effect of the inter-regional transmission lines on mitigating the carbon lock-in of regional power sector will be weakened when facing a tight carbon emission cap.

THE DISTRIBUTIONAL EFFECT OF INTER-REGIONAL TRANSMISSION GRID EXPANSION ON CHINA’S POWER INDUSTRY

China suffers significant heterogeneities in resource endowments and geological conditions across the regions. Ultra-high voltage (UHV) line construction is a project put forward by the government to boost the inter-regional transmission grid expansion, benefiting economic development by reducing pollutant emissions and absorbing more clean energy. This study investigates the extent to which this giant infrastructure has distributional effects on China’s power industry. We estimate the distributional effect of UHV lines from the perspective of power deployment, carbon emissions, and producer surplus by simulating an equilibrium model of the national electricity market through the mixed complementarity problems (MCPs) method. Furthermore, the Lorenz curve is also employed to investigate the distributional effect of UHV introduction. The results indicate that: (1) the distributional effect of introducing UHV lines is regressive considering its limited contributions to the equalization of environmental and economic welfare; (2) the emission reduction effect of the UHV lines has been improved between 2015 and 2018; (3) power plants with a large installation capacity could seek more economic profits while emitting more pollution; (4) the deployment of clean power in the resource-abundant regions is far below its potential. Meanwhile, we propose improving the structure and technology of the power mix, which can accelerate China’s market-oriented reform of the power system by equally distributing the benefits.

Climate change and CCS increase the water vulnerability of China's thermoelectric power fleet

Large numbers of China's thermal power plants are in water-stressed regions. Changes in the availability of water resources due to climate change may impact the vulnerability of regional and national electricity generation. Here we explore this vulnerability for coal-fired power units (CPUs) as the generation-type most exposed to climate risk. We find many plants are already experiencing water scarcity and 120–176 GW of capacity will be exposed to water scarcity for at least one additional month per year in the 2030s. In the absence of carbon capture and storage (CCS) the national useable capacity of CPUs will increase slightly, mainly due to an increase in water availability for power plants in northern China under all climate scenarios except RCP8.5. However, CCS systems have been identified as essential in China's national roadmap for carbon neutrality and their use represents high water requirements. The addition of CCS significantly exacerbates water vulnerability, leading to further useable-capacity reductions of 7.4–7.7%. We assess several adaptations and find that early retirement of power plants is most effective, with interregional power transmission also playing an important mitigating role. Our work highlights the need for improved awareness of water resources in electricity planning.

China's flexibility challenge in achieving carbon neutrality by 2060

China, with a heavy dependence on coal power, has announced a clear goal of carbon neutrality by 2060. Electrification of final energy use and high penetration of renewable energy are essential to achieve this. The resulting growth of intermittent renewables and changes in demand curve profiles require greater flexibility in the power system for real-time balancing – greater ability of generators and consumers to ramp up and down. However, the plan and market system with regulated prices makes this challenging. We discuss the options to improve flexibility, including 1) increasing supply-side flexibility, through retrofitting existing power plants to boost their responsiveness; 2) promoting flexibility from power grids, through building an efficient power grid with inter-provincial and inter-regional transmission capacity to balance spatial mismatch, given that China has a vast territory; 3) encouraging demand flexibility, through demand-response measures to enable demand shifting over time and space to address fluctuations in renewable energy generation; and 4) providing flexibility from energy storage. We consider policies to achieve this, in particular, power market reforms to unlock the flexibility potential of these sources. Regulated electricity prices and lack of auxiliary services markets are major obstacles and we discuss how markets in other countries provide lessons in providing incentives for a more flexible system.

Negligible Carbon Costs of Inter-Regional Transmission Grid in Comparing to its Carbon Reduction Benefits Involving Renewable Power Delivery

Negligible Carbon Costs of Inter-Regional Transmission Grid in Comparing to its Carbon Reduction Benefits Involving Renewable Power Delivery

Adaptive Grid Partitioning Considering Power Supply and Load Distribution

Renewable energy such as wind power, hydro-power and photovoltaic are connected to the power system as distributed power sources will increase the instability of power system operation. To ensure the stable operation of the power system after renewable energy and load access, it is necessary to properly partition the power grid. A grid partition method considering renewable energy access and load fluctuation is proposed. First, cluster analysis was carried out on the operation scenarios of renewable energy and load by using the improved K-means algorithm, and several operation scenarios of power system were obtained. The three operation scenarios with the highest probability were selected as the three normal operation states of power system. Then, the power system is partitioned, and the comprehensive flexibility evaluation indexes are proposed from the perspectives of regional supply and demand balance and inter-regional transmission capacity. The flexibility evaluation indexes from these two perspectives are calculated under three operating states, and the two flexibility evaluation indexes are weighted to evaluate the comprehensive flexibility of the power system after the partition. The comprehensive flexibility index of the power system is different under different partition strategies. The partition strategy with the best evaluation of the comprehensive flexibility index is chosen as the final partition strategy. Finally, according to the historical data of renewable energy and load in a certain region, the IEEE 39-bus system with renewable energy access and load fluctuation is partitioned under different partitioning strategies, and the comprehensive flexibility of the partitioned power system is evaluated, and the final partitioning strategy is determined according to the comprehensive flexibility index of the power system.

Does it pay to develop a ground source heat pump system? Evidence from China

The application potential and environmental benefits of ground source heat pump (GSHP) systems have become the focal points of decarbonization in the building sector. Synchronized and scientific analysis of GSHP systems' environmental and economic performance, however, remains lacking. This study analyzes the application prospects of GSHP systems via a life cycle assessment-based life cycle costing method, and considers China's actual status quo. The internal and external annual costs of a GSHP system per square meter are $ 4.05 and $ 1.37, respectively. Electricity generation and steel production are key processes to improve the environmental performance of a GSHP system further. Compared with coal-based heating, a GSHP system can mitigate 65%–95% of the environmental impact and 85% of external costs, except for the metal depletion impact which is 1.5 times higher than that of coal-based heating. In Shandong Province, promoting GSHP systems can substitute up to 69.4% of the district heating area, which implies reductions in fossil depletion, greenhouse gas emissions, human health impact, ecosystem quality impact, and external costs by up to 2.37 × 1010 kg oil eq, 1.08 × 1011 kg CO2 eq, 3.87 × 105 DALY, 1.18 × 103 Species. year, and $ 2.51 × 1010, respectively. In consideration of environmental and economic aspects, a GSHP system can exhibit benefits compared with coal-based heating after 2.34 years of operation. To improve the economic and environmental performance of GSHP systems, a series of recommendations on financial subsidies, renewable energy development, inter-regional power transmission, steel scrap utilization, and hydrogen reduction steelmaking is provided.

A random-walk-based epidemiological model

Random walkers on a two-dimensional square lattice are used to explore the spatio-temporal growth of an epidemic. We have found that a simple random-walk system generates non-trivial dynamics compared with traditional well-mixed models. Phase diagrams characterizing the long-term behaviors of the epidemics are calculated numerically. The functional dependence of the basic reproductive number R_{0} on the model’s defining parameters reveals the role of spatial fluctuations and leads to a novel expression for R_{0}. Special attention is given to simulations of inter-regional transmission of the contagion. The scaling of the epidemic with respect to space and time scales is studied in detail in the critical region, which is shown to be compatible with the directed-percolation universality class.

Pneumonia Patients Caused by Co-infection With SARS-CoV-2 and Human Adenovirus in China.

Objectives: To data, no patients with obvious epidemiological relationship co-infected with SARS-CoV-2 and other pathogens have been reported. Here, we investigated 10 patients caused by co-infection with SARS-CoV-2 and human adenovirus (HAdV), resulting in third-generation transmission.Materials and Methods: From Jan 15, 2020, we enrolled 10 patients with pneumonia in Hunan Province, China. Epidemiological, clinical, and laboratory investigation results from these patients were analyzed. An epidemiological investigation was performed to assess whether patient infections were linked using conventional methods and metagenomic sequencing.Results: The presence of co-infection with SARS-CoV-2 and HAdV was determined via RT-PCR and metagenomic sequencing. Phylogenetic analysis revealed that SARS-CoV-2 and HAdV genomes clustered together, with similar genetic relationships. The first patient likely became co-infected during meetings or travel in Wuhan. The patient transmitted the virus via dinners and meetings, which resulted in four second-generation cases. Then, a second-generation case transmitted the virus to her family members or relatives via presymptomatic transmission.Conclusions: This study described an example of co-infection with SARS-CoV-2 and HAdV in pneumonia patients, which caused third-generation cases and inter-regional transmission via meetings, household interactions, and dinner parties. We also observed the persistent and presymptomatic transmission of co-infection, which has the potential to make the continued control of the COVID-19 pandemic challenging. Continuous surveillance is needed to monitor the prevalence, infectivity, transmissibility, and pathogenicity of SARS-CoV-2 co-infection with other pathogens to evaluate its real risk.