Gleaning insights from German energy transition and large-scale underground energy storage for China’s carbon neutrality

The global energy transition is a widespread phenomenon that requires international exchange of experiences and mutual learning.Germany’s success in its first phase of energy transition can be attributed to its adoption of smart energy technology and implementation of electricity futures and spot marketization,which enabled the achievement of multiple energy spatial–temporal complementarities and overall grid balance through energy conversion and reconversion technologies.While China can draw from Germany’s experience to inform its own energy transition efforts,its 11-fold higher annual electricity consumption requires a distinct approach.We recommend a clean energy system based on smart sector coupling(ENSYSCO)as a suitable pathway for achieving sustainable energy in China,given that renewable energy is expected to guarantee 85%of China’s energy production by 2060,requiring significant future electricity storage capacity.Nonetheless,renewable energy storage remains a significant challenge.We propose four large-scale underground energy storage methods based on ENSYSCO to address this challenge,while considering China’s national conditions.These proposals have culminated in pilot projects for large-scale underground energy storage in China,which we believe is a necessary choice for achieving carbon neutrality in China and enabling efficient and safe grid integration of renewable energy within the framework of ENSYSCO.

Battery Technologies for Grid-Level Large-Scale Electrical Energy Storage

Grid-level large-scale electrical energy storage(GLEES) is an essential approach for balancing the supply–demand of electricity generation, distribution, and usage. Compared with conventional energy storage methods, battery technologies are desirable energy storage devices for GLEES due to their easy modularization, rapid response, flexible installation, and short construction cycles. In general, battery energy storage technologies are expected to meet the requirements of GLEES such as peak shaving and load leveling, voltage and frequency regulation, and emergency response, which are highlighted in this perspective. Furthermore, several types of battery technologies, including lead–acid, nickel–cadmium, nickel–metal hydride, sodium–sulfur, lithium-ion, and flow batteries, are discussed in detail for the application of GLEES. Moreover, some possible developing directions to facilitate efforts in this area are presented to establish a perspective on battery technology, provide a road map for guiding future studies, and promote the commercial application of batteries for GLEES.

Transmission line fault-cause identification method for large-scale new energy grid connection scenarios

The accurate fault-cause identification for overhead transmission lines supports the operation and maintenance personnel in formulating targeted maintenance strategies and shortening the time of inspecting faulty lines.With the goal of achieving“carbon peak and carbon neutrality”,the schemes for clean energy generation have rapidly developed.Moreover,new energy-consuming equipment has been widely connected to the power grid,and the operating characteristics of the power system have significantly changed.Consequently,these have impacted traditional fault identification methods.Based on the time-frequency characteristics of the fault waveform,new energy-related parameters,and deep learning model,this study proposes a fault identification method suitable for scenarios where a high proportion of new energy is connected to the power grid.Ten parameters related to the causes of transmission line fault and new energy connection scenarios are selected as model characteristic parameters.Further,a fault identification model based on adaptive deep belief networks was constructed,and its effect was verified by field data.

Application research on large-scale battery energy storage system under Global Energy Interconnection framework

In the context of constructing Global Energy Interconnection(GEI), energy storage technology, as one of the important basic supporting technologies in power system, will play an important role in the energy configuration and optimization. Based on the most promising battery energy storage technology, this paper introduces the current status of the grid technology, the application of large-scale energy storage technology and the supporting role of battery energy storage for GEI. Based on several key technologies of large-scale battery energy storage system, preliminary analysis of the standard system construction of energy storage system is made, and the future prospect is put forward.

China's INDC and non-fossil energy development

Global climate change promotes the energy system reform. Achieving a high proportion of renewable energy becomes the major countries＇ energy strategy. As proposed in its Intended Nationally Determined Contributions （INDC）, China intends to raise the proportion of non-fossil energy in primary energy consumption to about 20% by 2030. That ambitious goal means the non-fossil energy supplies by 2030 will be 7-8 times that of 2005, and the annual increase rate is more than 8% within the 25 years. Besides, the capacity of wind power, solar power, hy- dropower and nuclear power reaches 400 GW, 350 GW, 450 GW, and 150 GW respectively, and China＇s non-fossil power capacity is even greater than the U.S.＇s total power capacity. In addition, the scale of natural gas increases. Consequently, by 2030, the proportion of coal falls from the current 70% to below 50%, and the CO2 intensity of energy consumption decreases by 20% compared with the level of 2005, which play important roles in significantly reducing the CO2 intensity of GDE Since China has confirmed to achieve the CO2 emissions peak around 2030, at that time, the newly added energy demand will be satisfied by non-fossil energy, and the consumption of fossil fuel will stop growing. By 2030, non-fossil energy accounts for 20%, and the large scale and sound momentum of new and renewable energy industry will support the growth of total energy demand, which plays a key role in CO2 emissions peaking and beginning to decline, and lays the foundation for establishing a new energy system dominated by new and renewable energy in the second half of the 21 st century as well as finally achieving the CO2 zero-emission.

Numerical experimental study on the potential climatic impacts oflarge-scale wind farms in China

Wind energy has been rapidly developed in China during the past decades and the installed capacity has been the largest in the world. In the future, utilization of wind power is still expected to carry out in China mainly with a large-scale centralized layout. Here, we examine the potential climatic impacts of large-scale windfarms associated with deployment scale in China using numerical experiments, in which four deployment scenarios were designed. These four scenarios represented relatively small- (484 GW), medium- (2165 GW) and large-scale (3490 GW and 5412 GW) installed wind power capacities, respectively. Results showed that turbulent kinetic energy, wind velocity, and air temperature varied consistently within those windfarms with the largest changes in turbine hub heights. Moreover, the above relatively large- scale windfarms could induce regional wanning with a maximum of above 0.8 °C in North China. This regional warming may be linked to an anomalous circulation pattern with a negative pressure anomaly center in Northeast China and a positive pressure anomaly center in the middle and lower reaches of the Yangtze-Huaihe River Basin.

An Integrated Framework for Geothermal Energy Storage with CO_(2)Sequestration and Utilization

Subsurface geothermal energy storage has greater potential than other energy storage strategies in terms of capacity scale and time duration.Carbon dioxide(CO_(2))is regarded as a potential medium for energy storage due to its superior thermal properties.Moreover,the use of CO_(2)plumes for geothermal energy storage mitigates the greenhouse effect by storing CO_(2)in geological bodies.In this work,an integrated framework is proposed for synergistic geothermal energy storage and CO_(2)sequestration and utilization.Within this framework,CO_(2)is first injected into geothermal layers for energy accumulation.The resultant high-energy CO_(2)is then introduced into a target oil reservoir for CO_(2)utilization and geothermal energy storage.As a result,CO_(2)is sequestrated in the geological oil reservoir body.The results show that,as high-energy CO_(2)is injected,the average temperature of the whole target reservoir is greatly increased.With the assistance of geothermal energy,the geological utilization efficiency of CO_(2)is higher,resulting in a 10.1%increase in oil displacement efficiency.According to a storage-potential assessment of the simulated CO_(2)site,110 years after the CO_(2)injection,the utilization efficiency of the geological body will be as high as 91.2%,and the final injection quantity of the CO_(2)in the site will be as high as 9.529×10^(8)t.After 1000 years sequestration,the supercritical phase dominates in CO_(2)sequestration,followed by the liquid phase and then the mineralized phase.In addition,CO_(2)sequestration accounting for dissolution trapping increases significantly due to the presence of residual oil.More importantly,CO_(2)exhibits excellent performance in storing geothermal energy on a large scale;for example,the total energy stored in the studied geological body can provide the yearly energy supply for over 3.5×10^(7) normal households.Application of this integrated approach holds great significance for large-scale geothermal energy storage and the achievement of carbon neutrality.

Industrial Arrangement of Large-scale,Non-grid-connected Wind Power Industrial Zones in Coastal Areas of China

Constructing an industrial system for a large-scale,non-grid-connected wind power industry is a key step towards the diverse utilization of wind power.However,wind power exploitation is not only a technical challenge but an industrial problem as well.The objective of this study is to introduce a concept of large-scale,non-grid-connected wind power(LSNGCWP) industrial zones and establish an evaluation model to assess their industrial arrangement.The data of wind energy,industry,nature resources and socio-economy were collected in this study.Using spatial overlay analysis of geographic information system,this study proposes a spatial arrangement of the LSNGCWP indus-trial zones in the coastal areas of China,which could be summarized as the 'one line and three circles' structure,which will contribute to the optimization of the industrial structure,advance the wind power technology,coordinate the multi-industrial cooperation,and upgrade the industrial transformation of China's coastal areas.

A Study of Holographic Dark Energy Models with Configuration Entropy

The holographic dark energy models provide an alternative description of dark energy.These models are motivated by the possible application of the holographic principle to the dark energy problem.In this work,we present a theoretical study of the one parameter Li holographic dark energy and the two parameter Barrow holographic dark energy models using configuration entropy of the matter distribution in the universe.The configuration entropy rate exhibits a distinct minimum at a specific scale factor that corresponds to the epoch,beyond which dark energy takes a driving role in the accelerated expansion of the universe.We find that the location of the minimum and magnitude of the entropy rate at the minimum are sensitive to the parameters of the models.We find the best fit relations between these quantities and the parameters of each model.We propose that these relations can be used to constrain the parameters of the holographic dark energy models from future observations such as the SKA.Our study suggests that the signature of a large quantum gravitational effect on the future event horizon can be detected from measurements of the configuration entropy of the matter distribution at multiple redshifts.

An overview of application-oriented multifunctional large-scale stationary battery and hydrogen hybrid energy storage system

The imperative to address traditional energy crises and environmental concerns has accelerated the need for energy structure transformation.However,the variable nature of renewable energy poses challenges in meeting complex practical energy requirements.To address this issue,the construction of a multifunctional large-scale stationary energy storage system is considered an effective solution.This paper critically examines the battery and hydrogen hybrid energy storage systems.Both technologies face limitations hindering them from fully meeting future energy storage needs,such as large storage capacity in limited space,frequent storage with rapid response,and continuous storage without loss.Batteries,with their rapid response(<1 s)and high efficiency(>90%),excel in frequent short-duration energy storage.However,limitations such as a self-discharge rate(>1%)and capacity loss(~20%)restrict their use for long-duration energy storage.Hydrogen,as a potential energy carrier,is suitable for large-scale,long-duration energy storage due to its high energy density,steady state,and low loss.Nevertheless,it is less efficient for frequent energy storage due to its low storage efficiency(~50%).Ongoing research suggests that a battery and hydrogen hybrid energy storage system could combine the strengths of both technologies to meet the growing demand for large-scale,long-duration energy storage.To assess their applied potentials,this paper provides a detailed analysis of the research status of both energy storage technologies using proposed key performance indices.Additionally,application-oriented future directions and challenges of the battery and hydrogen hybrid energy storage system are outlined from multiple perspectives,offering guidance for the development of advanced energy storage systems.

Review of the development of power system out-of-step splitting control and some thoughts on the impact of large-scale access of renewable energy

Out-of-step oscillation is a very destructive physical phenomenon in power system, which could directly cause big blackout accompanied by serious sociology-economic impacts. Out-of-step splitting control is an indispensable means, which could protect the system from major shocks of out-of-step oscillation. After years of development, it has achieved certain amount of research results. Have the existing methods been able to meet the requirements of out-of-step splitting? What improvements are needed? Under this background, this review is written. It combs the development of out-of-step splitting control technologies and analyzes the technical routes and characteristics of different methods. It points out the contradiction between rapidity and optimality is the biggest technical problem, existing in both the traditional local measurement based out-of-step splitting protection and the wide-area information based out-of-step splitting protection. It further points out that the advantages of the two types of protections can be combined with the unique physical characteristics of the out-of-step center to form a more advantageous splitting strategy. Besides, facing the fact of large-scale renewable energy access to power grid in recent years, this review also analyzes the challenges brought by it and provides some corresponding suggestions. It is hoped to provide some guidance for the subsequent research work.

Comparative techno-economic analysis of large-scale renewable energy storage technologies

Energy storage is an effective way to address the instability of renewable energy generation modes,such as wind and solar,which are projected to play an important role in the sustainable and low-carbon society.Economics and carbon emissions are important indicators that should be thoroughly considered for evaluating the feasibility of energy storage technologies(ESTs).In this study,we study two promising routes for large-scale renewable energy storage,electrochemical energy storage(EES)and hydrogen energy storage(HES),via technical analysis of the ESTs.The levelized cost of storage(LCOS),carbon emissions and uncertainty assessments for EESs and HESs over the life cycle are conducted with full consideration of the critical links for these routes.In order to reduce the evaluation error,we use the Monte Carlo method to derive a large number of data for estimating the economy and carbon emission level of ESTs based on the collected data.The results show that lithium ion(Li-ion)batteries show the lowest LCOS and carbon emissions,at 0.314 US$kWh-1 and 72.76 g CO_(2) e kWh^(-1),compared with other batteries for EES.Different HES routes,meaning different combinations of hydrogen production,delivery and refueling methods,show substantial differences in economics,and the lowest LCOS and carbon emissions,at 0.227 US$kWh^(-1) and 61.63 gCO_(2) e kWh^(-1),are achieved using HES routes that involve hydrogen production by alkaline electrolyzer(AE),delivery by hydrogen pipeline and corresponding refueling.The findings of this study suggest that HES and EES have comparable levels of economics and carbon emissions that should be both considered for large-scale renewable energy storage to achieve future decarbonization goals.

Many-objective Optimization Method Based on Dimension Reduction for Operation of Large-scale Cooling Energy Systems

Large-scale cooling energy system has developed well in the past decade.However,its optimization is still a problem to be tackled due to the nonlinearity and large scale of existing systems.Reducing the scale of problems without oversimplifying the actual system model is a big challenge nowadays.This paper proposes a dimension reduction-based many-objective optimization(DRMO)method to solve an accurate nonlinear model of a practical large-scale cooling energy system.In the first stage,many-objective and many-variable of the large system are pre-processed to reduce the overall scale of the optimization problem.The relationships between many objectives are analyzed to find a few representative objectives.Key control variables are extracted to reduce the dimension of variables and the number of equality constraints.In the second stage,the manyobjective group search optimization(GSO)method is used to solve the low-dimensional nonlinear model,and a Pareto-front is obtained.In the final stage,candidate solutions along the Paretofront are graded on many-objective levels of system operators.The candidate solution with the highest average utility value is selected as the best running mode.Simulations are carried out on a 619-node-614-branch cooling system,and results show the ability of the proposed method in solving large-scale system operation problems.

Contingency Reserve Evaluation for Fast Frequency Response of Multiple Battery Energy Storage Systems in a Large-scale Power Grid

Recently,the fast frequency response(FFR)service by large-scale battery energy storage systems(BESSs)has been successfully proved to arrest the frequency excursion during an unexpected power outage.However,adequate frequency response relies on proper evaluation of the contingency reserve of BESSs.The BESS FFR reserve is commonly managed under fixed contracts,ignoring various response characteristics of different BESSs and their coexisting interactions.This paper proposes a new methodology based on dynamic grid response and various BESS response characteristics to optimise the FFR reserves and prevent the frequency from breaching the under-frequency load shedding(UFLS)thresholds.The superiority of the proposed method is demonstrated to manage three large-scale BESSs operating simultaneously in an Australian power grid under high renewable penetration scenarios.Further,the proposed method can identify remaining battery power and energy reserve to be safely utilised for other grid services(e.g.,energy arbitrage).The results can provide valuable insights for integrating FFR into conventional ancillary services and techno-effective management of multiple BESSs.

Main Energy Paths and Energy Cascade Processes of the Two Types of Persistent Heavy Rainfall Events over the Yangtze River–Huaihe River Basin

Two types of persistent heavy rainfall events （PHREs） over the Yangtze River-Huaihe River Basin were determined in a recent statistical study： type A, whose precipitation is mainly located to the south of the Yangtze River; and type B, whose precipitation is mainly located to the north of the river. The present study investigated these two PHRE types using a newly derived set of energy equations to show the scale interaction and main energy paths contributing to the persistence of the precipitation. The main results were as follows. The available potential energy （APE） and kinetic energy （KE） associated with both PHRE types generally increased upward in the troposphere, with the energy of the type-A PHREs stronger than that of the type-B PHREs （except for in the middle troposphere）. There were two main common and universal energy paths of the two PHRE types： （1） the baroclinic energy conversion from APE to KE was the dominant energy source for the evolution of large-scale background circulations; and （2） the downscaled energy cascade processes of KE and APE were vital for sustaining the eddy flow, which directly caused the PHREs. The significant differences between the two PHRE types mainly appeared in the lower troposphere, where the baroclinic energy conversion associated with the eddy flow in type-A PHREs was from KE to APE, which reduced the intensity of the precipitation-related eddy flow; whereas, the conversion in type-B PHREs was from APE to KE, which enhanced the eddy flow.

Research Progress on Energy Plants in Piggery Wastewater Treatment

Large-scale pig-raising can discharge a great deal of wastewater,which contains high content of organic matter,ammonia nitrogen and suspended solids.The improper treatment of the piggery wastewater can lead to serious environmental problems. As a liquid fertilizer,piggery wastewater is relatively low in fertilizer efficiency and high in transportation cost,so it is very necessary to treat it in situ. Energy plants have the advantages of rapid growth,large biomass,strong tillering ability and developed root system. Therefore,energy plants can be used to absorb and transform the pollutants( like nitrogen and phosphorus) in piggery wastewater into the components of plants,as well as form the rhizosphere environment which is conducive to microbial growth,so as to enhance the effects of nitrogen and phosphorus removal. The obtained energy plants can be recycled as the raw materials for biogas to increase the production of biogas,which brings economic benefits while solving the environmental problems caused by piggery wastewater.

Discussion on Natural Gas＇s Key Role in China＇s Energy-mix Transition

The evolution history of energy utilization around the world shows that a clean and low-carbon utilization of energy is the inevitable approach for dealing with climate change and for constructing a harmonious ecosystem.This paper focuses on the strategy options in China's energy-mix transition period based on an analysis of the global energy development trend.It is proved that using clean energy forms is critical to the realization of an energy transition in the country.As a result,natural gas is a practical choice,and structural reforms may help to bring its potential into full play.

Development of High Areal Capacity Electrolytic MnO_(2)-Zn Battery via an Iodine Mediator

The commercialization of electrolytic MnO_(2)-Zn batteries is highly applauded owing to the advantages of cost-effectiveness,high safety,high energy density,and durable working performance.However,due to the low reversibility of the cathode MnO_(2)/Mn^(2+)chemistry at high areal capacities and the severe Zn anode corrosion,the practical application of MnO_(2)-Zn batteries is hampered by inadequate lifespan.Leveraging the full advantage of an iodine redox mediator,here we design a highly rechargeable electrolytic MnO_(2)-Zn battery with a high areal capacity.The MnO_(2)-Zn battery coupled with an iodine mediator in a mild electrolyte shows a high discharge voltage of 1.85 V and a robust areal capacity of 10 mAh cm^(-2)under a substantial discharge current density of 160 mA cm^(-2).The MnO_(2)/I_(2)-Zn battery with an areal capacity of 10 mAh cm^(-2)exhibits prolonged stability of over 950 cycles under a high-capacity retention of~94%.The scaled-up MnO_(2)/I_(2)-Zn battery reveals a stable cycle life under a cell capacity of~600 mAh.Moreover,our constructed MnO_(2)/I_(2)-Zn battery demonstrates a practical energy density of~37 Wh kg^(-1)and a competitive energy cost of<18 US$kWh^(-1)by taking into account the cathode,anode,and electrolyte.The MnO_(2)/I_(2)-Zn battery,with its remarkable reversibility and reasonable energy density,enlightens a new arena of large-scale energy storage devices.

2D Materials Boost Advanced Zn Anodes:Principles,Advances,and Challenges

Aqueous zinc-ion battery(ZIB)featuring with high safety,low cost,environmentally friendly,and high energy density is one of the most promising systems for large-scale energy storage application.Despite extensive research progress made in developing high-performance cathodes,the Zn anode issues,such as Zn dendrites,corrosion,and hydrogen evolution,have been observed to shorten ZIB’s lifespan seriously,thus restricting their practical application.Engineering advanced Zn anodes based on two-dimensional(2D)materials are widely investigated to address these issues.With atomic thickness,2D materials possess ultrahigh specific surface area,much exposed active sites,superior mechanical strength and flexibility,and unique electrical properties,which confirm to be a promising alternative anode material for ZIBs.This review aims to boost rational design strategies of 2D materials for practical application of ZIB by combining the fundamental principle and research progress.Firstly,the fundamental principles of 2D materials against the drawbacks of Zn anode are introduced.Then,the designed strategies of several typical 2D materials for stable Zn anodes are comprehensively summarized.Finally,perspectives on the future development of advanced Zn anodes by taking advantage of these unique properties of 2D materials are proposed.

Energy Security Planning for Hydrogen Fuel Cell Vehicles in Large-Scale Events:A Case Study of Beijing 2022 Winter Olympics

Energy security planning is fundamental to safeguarding the traffic operation in large-scale events.To guarantee the promo-tion of green,zero-carbon,and environmental-friendly hydrogen fuel cell vehicles(HFCVs)in large-scale events,a five-stage planning method is proposed considering the demand and supply potential of hydrogen energy.Specifically,to meet the requirements of the large-scale events’demand,a new calculation approach is proposed to calculate the hydrogen amount and the distribution of hydrogen stations.In addition,energy supply is guaranteed from four aspects,namely hydrogen produc-tion,hydrogen storage,hydrogen delivery,and hydrogen refueling.The emergency plan is established based on the overall support plan,which can realize multi-dimensional energy security.Furthermore,the planning method is demonstrative as it powers the Beijing 2022 Winter Olympics as the first“green”Olympic,providing both theoretical and practical evidence for the energy security planning of large-scale events.This study provides suggestions about ensuring the energy demand after the race,broadening the application scenarios,and accelerating the application of HFCVs.