Energy access remains a critical challenge in rural South Sudan,with communities heavily relying on expensive and unfriendly environmental energy sources such as diesel generators and biomass.This study addresses the ...Energy access remains a critical challenge in rural South Sudan,with communities heavily relying on expensive and unfriendly environmental energy sources such as diesel generators and biomass.This study addresses the predicament by evaluating the feasibility of renewable energy-based decentralized electrification in the selected village ofDoleibHill,UpperNile,South Sudan.Using a demand assessment and theMulti-Tier Framework(MTF)approach,it categorizes households,public facilities,private sector,Non-GovernmentalOrganizations(NGOs)and business energy needs and designs an optimized hybrid energy system incorporating solar Photovoltaic(PV),wind turbines,batteries,and a generator.The proposed system,simulated in Hybrid Optimization Model Electric Renewable(HOMER)Pro,demonstrates strong economic viability,with a present worth of$292,145,an annual worth of$22,854,a return on investment(ROI)of 36.5%,and an internal rate of return(IRR)of 42.1%.The simple payback period is 2.31 years,and the discounted payback period is 2.62 years.The system achieves a levelized cost of energy(LCOE)of$0.276/kWh and significantly reduces dependence on diesel,producing 798,800 kWh annually fromwind energy.This research provides a replicable model for cost-effective,sustainable rural electrification,offering valuable insights for policymakers and energy planners seeking to expand electricity access in off-grid communities.展开更多
The Hong Kong Observatory(HKO)installed an X-band dual-polarization Phased Array Weather Radar(PAWR)at its wind profiler station at Sha Lo Wan(SLW)in 2021 to monitor high-impact weather in Hong Kong.The PAWR could com...The Hong Kong Observatory(HKO)installed an X-band dual-polarization Phased Array Weather Radar(PAWR)at its wind profiler station at Sha Lo Wan(SLW)in 2021 to monitor high-impact weather in Hong Kong.The PAWR could complete a volume scan in one minute with a spatial resolution of 30 meters.Dual polarimetric variables from the SLW PAWR,including differential reflectivity(ZDR),specific differential phase(KDP),and hydro-classification(HCL)products,were used to diagnose the vertical motion and lightning characteristics of mesoscale convective storms(MCS).Through variational data assimilation,three-dimensional(3-D)wind fields were constructed to validate the SLW PAWR observations.Two MCS events that occurred on 18 September 2022 and 17 June 2023 are central to this study.The findings include(1)negative ZDR serves as a good indicator of the occurrence of intense downdrafts associated with an MCS,a premise further supported by the 3-D wind field analysis results,(2)negative KDP suggested the formation of vertically aligned ice crystals which facilitated cloud electrification,and(3)HCL products indicated the presence of mixed ice crystals and graupel above the 0℃melting layer which promoted active cloud-to-cloud and cloud-to-ground lightning strokes.These results show that the SLW PAWR provides essential observations,which,when coupled with 3-D wind field analysis,can aid in enhancing the understanding of the dynamics and electrification processes within an MCS.展开更多
The triboelectric nanogenerator(TENG)can effectively collect energy based on contact electrification(CE)at diverse interfaces,including solid–solid,liquid–solid,liquid–liquid,gas–solid,and gas–liquid.This enables...The triboelectric nanogenerator(TENG)can effectively collect energy based on contact electrification(CE)at diverse interfaces,including solid–solid,liquid–solid,liquid–liquid,gas–solid,and gas–liquid.This enables energy harvesting from sources such as water,wind,and sound.In this review,we provide an overview of the coexistence of electron and ion transfer in the CE process.We elucidate the diverse dominant mechanisms observed at different interfaces and emphasize the interconnectedness and complementary nature of interface studies.The review also offers a comprehensive summary of the factors influencing charge transfer and the advancements in interfacial modification techniques.Additionally,we highlight the wide range of applications stemming from the distinctive characteristics of charge transfer at various interfaces.Finally,this review elucidates the future opportunities and challenges that interface CE may encounter.We anticipate that this review can offer valuable insights for future research on interface CE and facilitate the continued development and industrialization of TENG.展开更多
In the field of rail transit,the UK Department of Transport stated that it will realize a comprehensive transformation of UK railways by 2050,abandoning traditional diesel trains and upgrading them to new environmenta...In the field of rail transit,the UK Department of Transport stated that it will realize a comprehensive transformation of UK railways by 2050,abandoning traditional diesel trains and upgrading them to new environmentally friendly trains.The current mainstream upgrade methods are electrification and hydrogen fuel cells.Comprehensive upgrades are costly,and choosing the optimal upgrade method for trams and mainline railways is critical.Without a sensitivity analysis,it is difficult for us to determine the influence relationship between each parameter and cost,resulting in a waste of cost when choosing a line reconstruction method.In addition,by analyzing the sensitivity of different parameters to the cost,the primary optimization direction can be determined to reduce the cost.Global higher-order sensitivity analysis enables quantification of parameter interactions,showing non-additive effects between parameters.This paper selects the main parameters that affect the retrofit cost and analyzes the retrofit cost of the two upgrade methods in the case of trams and mainline railways through local and global sensitivity analysis methods.The results of the analysis show that,given the current UK rail system,it is more economical to choose electric trams and hydrogen mainline trains.For trams,the speed at which the train travels has the greatest impact on the final cost.Through the sensitivity analysis,this paper provides an effective data reference for the current railway upgrading and reconstruction plan and provides a theoretical basis for the next step of train parameter optimization.展开更多
A near-term strategy to reduce emissions from rail vehicles,as a path to full electrification for maximal decarbonisation,is to partially electrify a route,with the remainder of the route requiring an additional self-...A near-term strategy to reduce emissions from rail vehicles,as a path to full electrification for maximal decarbonisation,is to partially electrify a route,with the remainder of the route requiring an additional self-powered traction option.These rail vehicles are usually powered by a diesel engine when not operating on electrified track and are referred to as bi-mode vehicles.This paper analyses the benefits of discontinuous electrification compared to continuous electrification using the CO_(2)estimates from a validated high-fidelity bi-mode(diesel-electric)rail vehicle model.This analysis shows that 50%discontinuous electrification provides a maximum of 54%reduction in operational CO_(2)emissions when compared to the same length of continuously electrified track.The highest emissions savings occurred when leaving train stations where vehicles must accelerate quickly to line speed.These results were used to develop a linear regression model for fast estimation of CO_(2)emissions from diesel running and electrification benefits.This model was able to estimate the CO_(2)emissions from a route to within 10%of that given by the high-fidelity model.Finally,additional considerations such as cost and the embodied CO_(2)in electrification infrastructure were analysed to provide a comparison between continuous and discontinuous electrification.Discontinuous electrification can cost up to 56%less per reduction in lifetime emissions than continuous electrification and can save up to 2.3 times more lifetime CO_(2)per distance electrified.展开更多
Owing to increasing environmental concerns and resource scarcity, integrated energy system shave become widely used in communities. Rural energy systems, as one of the important links of the energy network in China, s...Owing to increasing environmental concerns and resource scarcity, integrated energy system shave become widely used in communities. Rural energy systems, as one of the important links of the energy network in China, suffer from low energy efficiency and weak infrastructure. Therefore, it is particularly important to increase the proportion of electricity consumption and build an integrated energy system for rural electrification in China(IESREIC) with a rural distribution network as the core, in line with national conditions. In this study, by analyzing the Chinese regional differences and natural resource endowments, the development characteristics of the IESREIC are summarized. Then, according to the existing rural energy problems, key technologies are proposed for the IESREIC, such as those for planning and operation, value sharing, infrastructure, and a management and control platform. Finally, IESREIC demonstration projects and business models are introduced for agricultural production, rural industrial systems, and rural life. The purpose is to propose research concepts for the IESREIC, provide suggestions for the development of rural energy, and provide a reference for the construction of rural energy systems in countries with characteristics similar to those of China.展开更多
When relative motion occurs between a liquid and a solid, the two phases carry electric charge with opposite signs. The created charge easily accumulates in the liquid, and the amount of the charge carried in an insul...When relative motion occurs between a liquid and a solid, the two phases carry electric charge with opposite signs. The created charge easily accumulates in the liquid, and the amount of the charge carried in an insulated liquid refers to many factors, such as contact area with the solid surface, the contact time, and so forth. However, current theories agree that the amount of charge created during flow electrification is proportional to the contact surface. In this paper, the classical wall current theory is applied to establish an interfacial electrical double-layer model of flow electrification phenomena when an insulated liquid passes over metal pipe surface. Meanwhile, in conjunction with charge relaxation function, the relation between the charge density and flow velocity, the contact time and the contact area is obtained during the liquid flowing process. The experimental result demonstrates that the flowing charge carried in the insulated liquid is not simply proportional to the contact area, but has a non-linear dependence on the contact area and the contact time. Moreover, down flow experimental equipment pipes of different length and diameter, and dielectric hydraulic oil VG46 are used in an experimental study of laminar flow, in order to understand electrification phenomena in dielectric liquid flowing over metal pipes of different length and aperture. If they both increase linearly, charge relaxation will increase exponentially. As a result, the test result verifies related theoretical analysis, and the method given provides a theoretical basis to analyze interracial electrical phenomena.展开更多
In contrast to the conventional direct current railway electrification system(DC-RES),the medium voltage direct current(MVDC)-RES is considered promising for long-distance high-speed corridors.In the MVDC-RES,traction...In contrast to the conventional direct current railway electrification system(DC-RES),the medium voltage direct current(MVDC)-RES is considered promising for long-distance high-speed corridors.In the MVDC-RES,traction substations(TSSs)are placed much farther and train loads are much heavier than in the conventional DC-RES.Hence,the MVDC-RES brings a drastic change in catenary voltage,TSS spacing,and train loading,which affects rail potential and stray current.In this connection,this work performs some significant quantitative analysis of rail potential and stray current in the MVDC-RES environment.An MVDC simulation model is proposed and different grounding schemes are analyzed for a single-train and two TSSs scenario as well as for a multi-train multi-TSS scenario.According to the simulation and analysis,the maximum values of rail potential and stray current at MVDC-RES distances and the maximum safe distance between adjacent TSSs are determined.展开更多
This paper presents a detailed design of a photovoltaic (PV) system for use in the rural electrification of remote settlements that are far off from the electricity grid. Since investment in building transmission line...This paper presents a detailed design of a photovoltaic (PV) system for use in the rural electrification of remote settlements that are far off from the electricity grid. Since investment in building transmission lines from the grid to these localities is not viable, a good solution is <span>an</span><span> installation in these areas of standalone photovoltaic systems. The design process comprises the choice and dimensioning of the solar panels, the battery storage, DC-AC inverter, and mini transmission grid to the different homes. The design is for a 15 kW PV system including an economic evaluation and analysis using Hybrid Optimization of Multiple Energy Resources (HOMER) software. Data on the average monthly solar radiation and temperature w</span><span>ere</span><span> obtained from various sources, including, Photovoltaic Geographical Information System (PVGIS) for Africa. From this data the study area receives a monthly average solar insolation of 6.16 kWh/</span><span>m</span><sup><span style="vertical-align:super;">2</span></sup><span>/day with the worst month </span><span>being </span><span>August with 5.22 kWh/</span><span>m</span><sup><span style="vertical-align:super;">2</span></sup><span>/day. The total daily electrical energy consumption is estimated to be about 72.525 kWh. Simulation results using HOMER software shows that the overall capital cost of the PV system components is $122,337, a replacement cost of $12,889 and an operation and maintenance cost of $29,946 over 10years. A financial analysis of the system showed that the design was both viable and sustainable with low maintenance cost</span><span>.</span>展开更多
Triboelectric nanogenerators(TENGs)based on conjunctive effects of contact electrification(CE)and electrostatic induction are emerging as a new mechanical energy harvesting and sensing technique for promising applicat...Triboelectric nanogenerators(TENGs)based on conjunctive effects of contact electrification(CE)and electrostatic induction are emerging as a new mechanical energy harvesting and sensing technique for promising applications in smart wearables,Internet of Things(IoTs),etc.The surface microstructure of a flexible triboelectric material for the increase of surface area is a common strategy for performance enhancement of TENGs,but the real roles of surface microstructures on their output performance are still not explicit due to the lack of suitable analysis tool and rational experimental design.Taking advantages of the surface-sensitive characteristic of CE effect,this work exploited and developed the electric signal patterns generated by single impact of TENGs as a kind of CE spectrum to analyze and speculate the real roles of surface microstructures of flexible triboelectric materials on the output performance of TENGs.Firstly,four different kinds of surface microstructures,namely planar surface(PS)and three combinations of two basic surface microstructures,i.e.,micro lens arrays(MLAs),fabric textures(FTs),and hierarchical structures of MLAs on FTs(MLA/FTs),were elaborately designed and introduced for an identical triboelectric material(i.e.,silicone elastomer)by a(micro)molding synthesis route.Then they were used for assembly of TENGs based on vertical contact mode to conduct performance evaluation under the same triggering conditions.Through systematic analysis and comparison of their highly repeatable CE spectra by programmed machine,it was found that the surface microstructure for a flexible triboelectric material to maximally enhance the output performance of a TENG shall achieve a positive synergistic effect of increasing triboelectric charge density,effective contact area and contacting/separating velocity,rather than simple increase of its surface area.展开更多
The majority of the population on the African continent is unable to access basic electricity services,this despite the abundance of renewable energy sources(RESs).The inability to adequately tap into these RESs has l...The majority of the population on the African continent is unable to access basic electricity services,this despite the abundance of renewable energy sources(RESs).The inability to adequately tap into these RESs has led to the continued dependence on non-renewable energy sources such as coal for electricity generation,and kerosene for cooking and lighting,the resulting use of which is poor health conditions.The use of Microgrids(MGs)is being extensively researched as a feasible means of tackling the challenge of electrification,especially in rural and remote areas.Recent times have seen an increasing number of research works focusing on Sub-Saharan Africa(SSA),which is one of the regions with the lowest electrification rates in the world.MGs provide the most suitable means to integrate RESs into the electricity generation process,paving the way towards clean energy for the African continent.This paper presents a review of recent literature on the usage of MG technology for rural electrification,with a specific focus on the applicability of MGs in the SSA context.The paper additionally presents the challenges and opportunities to date.Research findings indicate that SSA has already begun the transition towards clean energy via implementation of RES-based MGs.However,two resonating challenges in the literature are adequate support via policy,and proper planning of project implementation.These two major barriers are needed to be overcome in order to fully utilize MGs for rural electrification in SSA.The key methodology derived from this study is that any effort towards rural electrification requires a sufficient amount of investigation,incorporating both the technological and socio-economic aspects into a suitable design for the target location.展开更多
<div style="text-align:left;"> Rural households represent, by far, the greater percentage of dwellings globally without access to the electricity supply. For reasons of low loads, distance from the gri...<div style="text-align:left;"> Rural households represent, by far, the greater percentage of dwellings globally without access to the electricity supply. For reasons of low loads, distance from the grid and speed of deployment, distributed energy systems are now considered viable options for rural electrification. This paper presents the status of solar Photovoltaic (PV) in Nigeria and discusses the way forward for aggressive PV penetration in Nigeria’s energy mix, especially in rural communities. At present, distributed PV penetration in Nigeria is comparatively low based on the International Energy Association’s recommended PV market potential. This shows that there is a gap between the government’s <span>policy targets and reality. The solar resource potential across the six</span><span> geo-political zones in Nigeria is also presented, which ranges from 3.393 - 6.669 kWh/</span><span>m<sup></sup></span><span><sup>2</sup></span><span>/day, with the Northern zones exhibiting better potentials over the Southern zones. It is shown that the levelised cost of electricity from PV system ranges from 0.387 - 0.475 $/kWh, whereas it is 0.947 US$/kWh and 0.559 US$/kWh for the diesel generator and glass-covered kerosene lamp, respectively. While this study shows that PV for rural household lighting is more affordable as compared to glass-covered kerosene lamps and fossil-fuelled generators for lighting, fiscal and energy policies for market creation are critical if PV systems are to deliver on their promise for rural electrification and climate change mitigation.</span> </div>展开更多
Rural electrification remains a great challenge for Sub-Saharan Africa (SSA) as access to electricity is a prerequisite to accelerate its development. The present paper reviews the measures adopted to promote access t...Rural electrification remains a great challenge for Sub-Saharan Africa (SSA) as access to electricity is a prerequisite to accelerate its development. The present paper reviews the measures adopted to promote access to electricity in rural and remote areas of SSA. The main barriers to rural electrification in these developing countries are presented before showing technologies used for the aforementioned purpose. Then, adopted methods for enhancing the use of renewable energy in SSA are shown. Moreover, the policy adopted by decision makers and project planners are also highlighted. In addition, the optimal solutions proposed by researchers are given such as the cost-effective off-grid system type that might be a viable alternative to diesel power generation.展开更多
The effect of contact electrification on adhesion has been debated in recent years for gecko and bio-inspired dry adhesion material.To understand the fundamentals of this issue for Carbon Nanotube(CNT)dry adhesives,co...The effect of contact electrification on adhesion has been debated in recent years for gecko and bio-inspired dry adhesion material.To understand the fundamentals of this issue for Carbon Nanotube(CNT)dry adhesives,contact electrification and its relationship with adhesion are systematically studied using the first-principles calculation.Charge transfers from CNT or its special form,graphene,to the metal surface during the contact,and the transferred charge linearly correlates with the work function difference.Meanwhile,the adhesion energy is linearly related to the transferred charge for both CNT and graphene.More charge transfers from the flat graphene to metal surfaces than the curved CNT,leading to higher adhesion between graphene and metal surfaces.The curved structure of the CNT causes an irregular change of charge at the interface and hinders the charge transfer.Moreover,the curved structure induces electronic localization,which also decreases the interfacial charge transfer.The structure affects contact electrification,and hence adhesion is further demonstrated by the CNT with different deformation when contacting different surfaces.This study advances our understanding of contact electrification and its relationship with adhesion at the interface for bio-inspired carbon adhesive materials and sheds light on the control of them for engineering applications.展开更多
The mechanism of contact electrification between metals was studied using the first-principles method, taking the Ag-Fe contact as an example. Charge population, charge density difference, the orbitals and densities o...The mechanism of contact electrification between metals was studied using the first-principles method, taking the Ag-Fe contact as an example. Charge population, charge density difference, the orbitals and densities of states （DOS） were calculated to study the electronic properties of the contacting interfacial atoms. Based on the calculation, the amount of contact charge was obtained. The investigation revealed that the electrons near Fermi levels with higher energies transfer between the outermost orbitals （s orbitals for Ag and d orbitals for Fe）. Meanwhile, polarized covalent bonds form between the d electrons in the deep energy states. These two effects together lead to an increase of charge magnitude at the interface. Also, the electrons responsible for electrification can be determined by their energies and orbitals.展开更多
Contact electrification(CE)is a pretty common phenomenon,but still is poorly understood.The long-standing controversy over the mechanisms of CE related to polymers is particularly intense due to their complexity.In th...Contact electrification(CE)is a pretty common phenomenon,but still is poorly understood.The long-standing controversy over the mechanisms of CE related to polymers is particularly intense due to their complexity.In this paper,the CE between metals and polymers is systematically studied,which shows the evolution of surfaces is accompanied by variations of CE outputs.The variations of CE charge quantity are closely related to the creep and deformation of the polymer and metal surfaces.Then the relationship between CE and polymer structures is put forward,which is essentially determined by the electronegativity of elements and the functional groups in the polymers.The effects of load and contact frequency on the CE process and outputs are also investigated,indicating the increase of CE charge quantity with load and frequency.Material transfer from polymer to metal is observed during CE while electrons transfer from metal to polymer,both of which are believed to have an influence on each other.The findings advance our understanding of the mechanism of CE between metal and polymers,and provides insights into the performance of CE-based application in various conditions,which sheds light on the design and optimization of CE-based energy harvest and self-powered sensing devices.展开更多
A novel way for electrification of mineral particles by electronbeam irradiation was proposed. The effect of irradiation dose oncharge/mass ratio was investigated experimentally. The charge/massratio of electrified mi...A novel way for electrification of mineral particles by electronbeam irradiation was proposed. The effect of irradiation dose oncharge/mass ratio was investigated experimentally. The charge/massratio of electrified mineral powders after irradiation was meas- uredby an instrument based on the principle of electrostatic induction.The experimental results showed that the charge/mass ratio is lar-gely dependent on radiation dose and electric physical properties ofminerals. The mechanism of electrification by electron beam irradi-ation is discussed. it is suggested that the essential ofelectrification by electron beam irradiation is a process ofretardation and charge deposition of incident electrons in materials.展开更多
During the last two decades,there has been an outcry on how the shortage of power in rural areas can be sorted.Most Developed Countries(MDCs)like the USA,China,German,UK,Taiwan,and Singapore started using renewable en...During the last two decades,there has been an outcry on how the shortage of power in rural areas can be sorted.Most Developed Countries(MDCs)like the USA,China,German,UK,Taiwan,and Singapore started using renewable energy sources to minimize power shortages in rural areas.Less Developed Countries(LDCs)mostly African countries also followed suit.This was not only to solve the power problem but also to be on the safe side after researches anticipated that in the near future,fossil fuels would be depleted.Over 50 years ago,several countries have attempted to harness power using hydro-power,biomass,solar,tidal,wave thermal,and wind energies.Different researches show that hydro-power has been most developed worldwide due to high levels of investment.Of recent,solar and biomass energies have come on board steadily,gaining trust from people.This still has benefited towns’more than rural areas due to transmission barriers,expected financial returns,and high cost of maintenance.Recently,there has been encouragement and development of solar PV systems and the utilization of mini-grids for rural electrification to minimize the challenge,especially in African countries.International Energy Agency(IEA)has high expectations in mini-grids in playing a significant role in rural electrification.Mini-grid energy solutions are emerging as the next best alternative to rural electricity access coming between the option of large-scale grid extension and solar home systems.This paper,therefore,has discussed the status,Strengths,Weaknesses,Opportunities and Threats(SWOT)strategies,financing options,risk management systems and current trends in renewable energy mini-grid development in Africa and beyond in an attempt to enhance rural electrification.This research used secondary data,internet resources,published data,and World Bank reports to synthesize the evolution and the update status of mini-grids.展开更多
The state of Cameroon, faced with the situation the electricity deficits, is promoting the development of renewable energies in general and to meet rural electrification needs in particular. The purpose of this work i...The state of Cameroon, faced with the situation the electricity deficits, is promoting the development of renewable energies in general and to meet rural electrification needs in particular. The purpose of this work is to study the feasibility of the MHP of Batcheu, to show its contribution to sustainable development in this locality and to prove that it is a profitable project. After study, it appears that the waterfall of Batcheu is favourable to the establishment of a MHP with an installed power of 260 kW with an operating diagram corresponding to a Francis turbine. Given that it is a renewable energy that can supply more than 800 households in rural areas, its contribution to sustainable development is obvious. Its investment cost is estimated at 171,465,396 FCFA. It is a profitable project with a payback time of 7 years and 2 months.展开更多
文摘Energy access remains a critical challenge in rural South Sudan,with communities heavily relying on expensive and unfriendly environmental energy sources such as diesel generators and biomass.This study addresses the predicament by evaluating the feasibility of renewable energy-based decentralized electrification in the selected village ofDoleibHill,UpperNile,South Sudan.Using a demand assessment and theMulti-Tier Framework(MTF)approach,it categorizes households,public facilities,private sector,Non-GovernmentalOrganizations(NGOs)and business energy needs and designs an optimized hybrid energy system incorporating solar Photovoltaic(PV),wind turbines,batteries,and a generator.The proposed system,simulated in Hybrid Optimization Model Electric Renewable(HOMER)Pro,demonstrates strong economic viability,with a present worth of$292,145,an annual worth of$22,854,a return on investment(ROI)of 36.5%,and an internal rate of return(IRR)of 42.1%.The simple payback period is 2.31 years,and the discounted payback period is 2.62 years.The system achieves a levelized cost of energy(LCOE)of$0.276/kWh and significantly reduces dependence on diesel,producing 798,800 kWh annually fromwind energy.This research provides a replicable model for cost-effective,sustainable rural electrification,offering valuable insights for policymakers and energy planners seeking to expand electricity access in off-grid communities.
文摘The Hong Kong Observatory(HKO)installed an X-band dual-polarization Phased Array Weather Radar(PAWR)at its wind profiler station at Sha Lo Wan(SLW)in 2021 to monitor high-impact weather in Hong Kong.The PAWR could complete a volume scan in one minute with a spatial resolution of 30 meters.Dual polarimetric variables from the SLW PAWR,including differential reflectivity(ZDR),specific differential phase(KDP),and hydro-classification(HCL)products,were used to diagnose the vertical motion and lightning characteristics of mesoscale convective storms(MCS).Through variational data assimilation,three-dimensional(3-D)wind fields were constructed to validate the SLW PAWR observations.Two MCS events that occurred on 18 September 2022 and 17 June 2023 are central to this study.The findings include(1)negative ZDR serves as a good indicator of the occurrence of intense downdrafts associated with an MCS,a premise further supported by the 3-D wind field analysis results,(2)negative KDP suggested the formation of vertically aligned ice crystals which facilitated cloud electrification,and(3)HCL products indicated the presence of mixed ice crystals and graupel above the 0℃melting layer which promoted active cloud-to-cloud and cloud-to-ground lightning strokes.These results show that the SLW PAWR provides essential observations,which,when coupled with 3-D wind field analysis,can aid in enhancing the understanding of the dynamics and electrification processes within an MCS.
基金the National Natural Science Foundation of China for Excellent Young Scholar(Grant No.52322313)National Key R&D Project from Minister of Science and Technology(2021YFA1201601)+6 种基金National Science Fund of China(62174014)Beijing Nova program(Z201100006820063)Youth Innovation Promotion Association CAS(2021165)Innovation Project of Ocean Science and Technology(22-3-3-hygg-18-hy)State Key Laboratory of New Ceramic and Fine Processing Tsinghua University(KFZD202202)Fundamental Research Funds for the Central Universities(292022000337)Young Top-Notch Talents Program of Beijing Excellent Talents Funding(2017000021223ZK03).
文摘The triboelectric nanogenerator(TENG)can effectively collect energy based on contact electrification(CE)at diverse interfaces,including solid–solid,liquid–solid,liquid–liquid,gas–solid,and gas–liquid.This enables energy harvesting from sources such as water,wind,and sound.In this review,we provide an overview of the coexistence of electron and ion transfer in the CE process.We elucidate the diverse dominant mechanisms observed at different interfaces and emphasize the interconnectedness and complementary nature of interface studies.The review also offers a comprehensive summary of the factors influencing charge transfer and the advancements in interfacial modification techniques.Additionally,we highlight the wide range of applications stemming from the distinctive characteristics of charge transfer at various interfaces.Finally,this review elucidates the future opportunities and challenges that interface CE may encounter.We anticipate that this review can offer valuable insights for future research on interface CE and facilitate the continued development and industrialization of TENG.
文摘In the field of rail transit,the UK Department of Transport stated that it will realize a comprehensive transformation of UK railways by 2050,abandoning traditional diesel trains and upgrading them to new environmentally friendly trains.The current mainstream upgrade methods are electrification and hydrogen fuel cells.Comprehensive upgrades are costly,and choosing the optimal upgrade method for trams and mainline railways is critical.Without a sensitivity analysis,it is difficult for us to determine the influence relationship between each parameter and cost,resulting in a waste of cost when choosing a line reconstruction method.In addition,by analyzing the sensitivity of different parameters to the cost,the primary optimization direction can be determined to reduce the cost.Global higher-order sensitivity analysis enables quantification of parameter interactions,showing non-additive effects between parameters.This paper selects the main parameters that affect the retrofit cost and analyzes the retrofit cost of the two upgrade methods in the case of trams and mainline railways through local and global sensitivity analysis methods.The results of the analysis show that,given the current UK rail system,it is more economical to choose electric trams and hydrogen mainline trains.For trams,the speed at which the train travels has the greatest impact on the final cost.Through the sensitivity analysis,this paper provides an effective data reference for the current railway upgrading and reconstruction plan and provides a theoretical basis for the next step of train parameter optimization.
基金gratefully acknowledge the finan-cial support of the EPSRC’s DTE Network+(EP/S032053/1)and the RSSB(COF-IPS-02).
文摘A near-term strategy to reduce emissions from rail vehicles,as a path to full electrification for maximal decarbonisation,is to partially electrify a route,with the remainder of the route requiring an additional self-powered traction option.These rail vehicles are usually powered by a diesel engine when not operating on electrified track and are referred to as bi-mode vehicles.This paper analyses the benefits of discontinuous electrification compared to continuous electrification using the CO_(2)estimates from a validated high-fidelity bi-mode(diesel-electric)rail vehicle model.This analysis shows that 50%discontinuous electrification provides a maximum of 54%reduction in operational CO_(2)emissions when compared to the same length of continuously electrified track.The highest emissions savings occurred when leaving train stations where vehicles must accelerate quickly to line speed.These results were used to develop a linear regression model for fast estimation of CO_(2)emissions from diesel running and electrification benefits.This model was able to estimate the CO_(2)emissions from a route to within 10%of that given by the high-fidelity model.Finally,additional considerations such as cost and the embodied CO_(2)in electrification infrastructure were analysed to provide a comparison between continuous and discontinuous electrification.Discontinuous electrification can cost up to 56%less per reduction in lifetime emissions than continuous electrification and can save up to 2.3 times more lifetime CO_(2)per distance electrified.
基金supported by the National Natural Science Foundation of China(No.51977141)headquarters technology project of State Grid Corporation of China(No.5400-202025208A-0-0-00)
文摘Owing to increasing environmental concerns and resource scarcity, integrated energy system shave become widely used in communities. Rural energy systems, as one of the important links of the energy network in China, suffer from low energy efficiency and weak infrastructure. Therefore, it is particularly important to increase the proportion of electricity consumption and build an integrated energy system for rural electrification in China(IESREIC) with a rural distribution network as the core, in line with national conditions. In this study, by analyzing the Chinese regional differences and natural resource endowments, the development characteristics of the IESREIC are summarized. Then, according to the existing rural energy problems, key technologies are proposed for the IESREIC, such as those for planning and operation, value sharing, infrastructure, and a management and control platform. Finally, IESREIC demonstration projects and business models are introduced for agricultural production, rural industrial systems, and rural life. The purpose is to propose research concepts for the IESREIC, provide suggestions for the development of rural energy, and provide a reference for the construction of rural energy systems in countries with characteristics similar to those of China.
基金supported by Qianjiang Talent Project Foundation of China(Grant No. 2010R10013)
文摘When relative motion occurs between a liquid and a solid, the two phases carry electric charge with opposite signs. The created charge easily accumulates in the liquid, and the amount of the charge carried in an insulated liquid refers to many factors, such as contact area with the solid surface, the contact time, and so forth. However, current theories agree that the amount of charge created during flow electrification is proportional to the contact surface. In this paper, the classical wall current theory is applied to establish an interfacial electrical double-layer model of flow electrification phenomena when an insulated liquid passes over metal pipe surface. Meanwhile, in conjunction with charge relaxation function, the relation between the charge density and flow velocity, the contact time and the contact area is obtained during the liquid flowing process. The experimental result demonstrates that the flowing charge carried in the insulated liquid is not simply proportional to the contact area, but has a non-linear dependence on the contact area and the contact time. Moreover, down flow experimental equipment pipes of different length and diameter, and dielectric hydraulic oil VG46 are used in an experimental study of laminar flow, in order to understand electrification phenomena in dielectric liquid flowing over metal pipes of different length and aperture. If they both increase linearly, charge relaxation will increase exponentially. As a result, the test result verifies related theoretical analysis, and the method given provides a theoretical basis to analyze interracial electrical phenomena.
文摘In contrast to the conventional direct current railway electrification system(DC-RES),the medium voltage direct current(MVDC)-RES is considered promising for long-distance high-speed corridors.In the MVDC-RES,traction substations(TSSs)are placed much farther and train loads are much heavier than in the conventional DC-RES.Hence,the MVDC-RES brings a drastic change in catenary voltage,TSS spacing,and train loading,which affects rail potential and stray current.In this connection,this work performs some significant quantitative analysis of rail potential and stray current in the MVDC-RES environment.An MVDC simulation model is proposed and different grounding schemes are analyzed for a single-train and two TSSs scenario as well as for a multi-train multi-TSS scenario.According to the simulation and analysis,the maximum values of rail potential and stray current at MVDC-RES distances and the maximum safe distance between adjacent TSSs are determined.
文摘This paper presents a detailed design of a photovoltaic (PV) system for use in the rural electrification of remote settlements that are far off from the electricity grid. Since investment in building transmission lines from the grid to these localities is not viable, a good solution is <span>an</span><span> installation in these areas of standalone photovoltaic systems. The design process comprises the choice and dimensioning of the solar panels, the battery storage, DC-AC inverter, and mini transmission grid to the different homes. The design is for a 15 kW PV system including an economic evaluation and analysis using Hybrid Optimization of Multiple Energy Resources (HOMER) software. Data on the average monthly solar radiation and temperature w</span><span>ere</span><span> obtained from various sources, including, Photovoltaic Geographical Information System (PVGIS) for Africa. From this data the study area receives a monthly average solar insolation of 6.16 kWh/</span><span>m</span><sup><span style="vertical-align:super;">2</span></sup><span>/day with the worst month </span><span>being </span><span>August with 5.22 kWh/</span><span>m</span><sup><span style="vertical-align:super;">2</span></sup><span>/day. The total daily electrical energy consumption is estimated to be about 72.525 kWh. Simulation results using HOMER software shows that the overall capital cost of the PV system components is $122,337, a replacement cost of $12,889 and an operation and maintenance cost of $29,946 over 10years. A financial analysis of the system showed that the design was both viable and sustainable with low maintenance cost</span><span>.</span>
基金supported by the National Natural Science Foundation of China(No.52103278).
文摘Triboelectric nanogenerators(TENGs)based on conjunctive effects of contact electrification(CE)and electrostatic induction are emerging as a new mechanical energy harvesting and sensing technique for promising applications in smart wearables,Internet of Things(IoTs),etc.The surface microstructure of a flexible triboelectric material for the increase of surface area is a common strategy for performance enhancement of TENGs,but the real roles of surface microstructures on their output performance are still not explicit due to the lack of suitable analysis tool and rational experimental design.Taking advantages of the surface-sensitive characteristic of CE effect,this work exploited and developed the electric signal patterns generated by single impact of TENGs as a kind of CE spectrum to analyze and speculate the real roles of surface microstructures of flexible triboelectric materials on the output performance of TENGs.Firstly,four different kinds of surface microstructures,namely planar surface(PS)and three combinations of two basic surface microstructures,i.e.,micro lens arrays(MLAs),fabric textures(FTs),and hierarchical structures of MLAs on FTs(MLA/FTs),were elaborately designed and introduced for an identical triboelectric material(i.e.,silicone elastomer)by a(micro)molding synthesis route.Then they were used for assembly of TENGs based on vertical contact mode to conduct performance evaluation under the same triggering conditions.Through systematic analysis and comparison of their highly repeatable CE spectra by programmed machine,it was found that the surface microstructure for a flexible triboelectric material to maximally enhance the output performance of a TENG shall achieve a positive synergistic effect of increasing triboelectric charge density,effective contact area and contacting/separating velocity,rather than simple increase of its surface area.
基金This work has received funding from the European Union Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement no.701697Major Program of the National Social Science Fund of China(Grant No.17ZDA092)+1 种基金Basic Research Programs(Natural Science Foundation)of Jiangsu Province(BK20180794)333 High-Level Talent Cultivation Project of Jiangsu Province(BRA2018332)and the PAPD fund.
文摘The majority of the population on the African continent is unable to access basic electricity services,this despite the abundance of renewable energy sources(RESs).The inability to adequately tap into these RESs has led to the continued dependence on non-renewable energy sources such as coal for electricity generation,and kerosene for cooking and lighting,the resulting use of which is poor health conditions.The use of Microgrids(MGs)is being extensively researched as a feasible means of tackling the challenge of electrification,especially in rural and remote areas.Recent times have seen an increasing number of research works focusing on Sub-Saharan Africa(SSA),which is one of the regions with the lowest electrification rates in the world.MGs provide the most suitable means to integrate RESs into the electricity generation process,paving the way towards clean energy for the African continent.This paper presents a review of recent literature on the usage of MG technology for rural electrification,with a specific focus on the applicability of MGs in the SSA context.The paper additionally presents the challenges and opportunities to date.Research findings indicate that SSA has already begun the transition towards clean energy via implementation of RES-based MGs.However,two resonating challenges in the literature are adequate support via policy,and proper planning of project implementation.These two major barriers are needed to be overcome in order to fully utilize MGs for rural electrification in SSA.The key methodology derived from this study is that any effort towards rural electrification requires a sufficient amount of investigation,incorporating both the technological and socio-economic aspects into a suitable design for the target location.
文摘<div style="text-align:left;"> Rural households represent, by far, the greater percentage of dwellings globally without access to the electricity supply. For reasons of low loads, distance from the grid and speed of deployment, distributed energy systems are now considered viable options for rural electrification. This paper presents the status of solar Photovoltaic (PV) in Nigeria and discusses the way forward for aggressive PV penetration in Nigeria’s energy mix, especially in rural communities. At present, distributed PV penetration in Nigeria is comparatively low based on the International Energy Association’s recommended PV market potential. This shows that there is a gap between the government’s <span>policy targets and reality. The solar resource potential across the six</span><span> geo-political zones in Nigeria is also presented, which ranges from 3.393 - 6.669 kWh/</span><span>m<sup></sup></span><span><sup>2</sup></span><span>/day, with the Northern zones exhibiting better potentials over the Southern zones. It is shown that the levelised cost of electricity from PV system ranges from 0.387 - 0.475 $/kWh, whereas it is 0.947 US$/kWh and 0.559 US$/kWh for the diesel generator and glass-covered kerosene lamp, respectively. While this study shows that PV for rural household lighting is more affordable as compared to glass-covered kerosene lamps and fossil-fuelled generators for lighting, fiscal and energy policies for market creation are critical if PV systems are to deliver on their promise for rural electrification and climate change mitigation.</span> </div>
文摘Rural electrification remains a great challenge for Sub-Saharan Africa (SSA) as access to electricity is a prerequisite to accelerate its development. The present paper reviews the measures adopted to promote access to electricity in rural and remote areas of SSA. The main barriers to rural electrification in these developing countries are presented before showing technologies used for the aforementioned purpose. Then, adopted methods for enhancing the use of renewable energy in SSA are shown. Moreover, the policy adopted by decision makers and project planners are also highlighted. In addition, the optimal solutions proposed by researchers are given such as the cost-effective off-grid system type that might be a viable alternative to diesel power generation.
基金supported by the National Natural Science Foundation of China(Grant Nos.51505217,51435008,and 51705247)the Fundamental Research Funds for the Central Universities(Grant No.1011/56XAA19014).
文摘The effect of contact electrification on adhesion has been debated in recent years for gecko and bio-inspired dry adhesion material.To understand the fundamentals of this issue for Carbon Nanotube(CNT)dry adhesives,contact electrification and its relationship with adhesion are systematically studied using the first-principles calculation.Charge transfers from CNT or its special form,graphene,to the metal surface during the contact,and the transferred charge linearly correlates with the work function difference.Meanwhile,the adhesion energy is linearly related to the transferred charge for both CNT and graphene.More charge transfers from the flat graphene to metal surfaces than the curved CNT,leading to higher adhesion between graphene and metal surfaces.The curved structure of the CNT causes an irregular change of charge at the interface and hinders the charge transfer.Moreover,the curved structure induces electronic localization,which also decreases the interfacial charge transfer.The structure affects contact electrification,and hence adhesion is further demonstrated by the CNT with different deformation when contacting different surfaces.This study advances our understanding of contact electrification and its relationship with adhesion at the interface for bio-inspired carbon adhesive materials and sheds light on the control of them for engineering applications.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 50823003 and 90923018)
文摘The mechanism of contact electrification between metals was studied using the first-principles method, taking the Ag-Fe contact as an example. Charge population, charge density difference, the orbitals and densities of states （DOS） were calculated to study the electronic properties of the contacting interfacial atoms. Based on the calculation, the amount of contact charge was obtained. The investigation revealed that the electrons near Fermi levels with higher energies transfer between the outermost orbitals （s orbitals for Ag and d orbitals for Fe）. Meanwhile, polarized covalent bonds form between the d electrons in the deep energy states. These two effects together lead to an increase of charge magnitude at the interface. Also, the electrons responsible for electrification can be determined by their energies and orbitals.
基金supported by the National Natural Science Foundation of China(Grant Nos.52075249,51505217,51435008,and 51705247)。
文摘Contact electrification(CE)is a pretty common phenomenon,but still is poorly understood.The long-standing controversy over the mechanisms of CE related to polymers is particularly intense due to their complexity.In this paper,the CE between metals and polymers is systematically studied,which shows the evolution of surfaces is accompanied by variations of CE outputs.The variations of CE charge quantity are closely related to the creep and deformation of the polymer and metal surfaces.Then the relationship between CE and polymer structures is put forward,which is essentially determined by the electronegativity of elements and the functional groups in the polymers.The effects of load and contact frequency on the CE process and outputs are also investigated,indicating the increase of CE charge quantity with load and frequency.Material transfer from polymer to metal is observed during CE while electrons transfer from metal to polymer,both of which are believed to have an influence on each other.The findings advance our understanding of the mechanism of CE between metal and polymers,and provides insights into the performance of CE-based application in various conditions,which sheds light on the design and optimization of CE-based energy harvest and self-powered sensing devices.
基金[This work was financial supported by the National Natural Science Foundation of China (No.59874002).]
文摘A novel way for electrification of mineral particles by electronbeam irradiation was proposed. The effect of irradiation dose oncharge/mass ratio was investigated experimentally. The charge/massratio of electrified mineral powders after irradiation was meas- uredby an instrument based on the principle of electrostatic induction.The experimental results showed that the charge/mass ratio is lar-gely dependent on radiation dose and electric physical properties ofminerals. The mechanism of electrification by electron beam irradi-ation is discussed. it is suggested that the essential ofelectrification by electron beam irradiation is a process ofretardation and charge deposition of incident electrons in materials.
文摘During the last two decades,there has been an outcry on how the shortage of power in rural areas can be sorted.Most Developed Countries(MDCs)like the USA,China,German,UK,Taiwan,and Singapore started using renewable energy sources to minimize power shortages in rural areas.Less Developed Countries(LDCs)mostly African countries also followed suit.This was not only to solve the power problem but also to be on the safe side after researches anticipated that in the near future,fossil fuels would be depleted.Over 50 years ago,several countries have attempted to harness power using hydro-power,biomass,solar,tidal,wave thermal,and wind energies.Different researches show that hydro-power has been most developed worldwide due to high levels of investment.Of recent,solar and biomass energies have come on board steadily,gaining trust from people.This still has benefited towns’more than rural areas due to transmission barriers,expected financial returns,and high cost of maintenance.Recently,there has been encouragement and development of solar PV systems and the utilization of mini-grids for rural electrification to minimize the challenge,especially in African countries.International Energy Agency(IEA)has high expectations in mini-grids in playing a significant role in rural electrification.Mini-grid energy solutions are emerging as the next best alternative to rural electricity access coming between the option of large-scale grid extension and solar home systems.This paper,therefore,has discussed the status,Strengths,Weaknesses,Opportunities and Threats(SWOT)strategies,financing options,risk management systems and current trends in renewable energy mini-grid development in Africa and beyond in an attempt to enhance rural electrification.This research used secondary data,internet resources,published data,and World Bank reports to synthesize the evolution and the update status of mini-grids.
文摘The state of Cameroon, faced with the situation the electricity deficits, is promoting the development of renewable energies in general and to meet rural electrification needs in particular. The purpose of this work is to study the feasibility of the MHP of Batcheu, to show its contribution to sustainable development in this locality and to prove that it is a profitable project. After study, it appears that the waterfall of Batcheu is favourable to the establishment of a MHP with an installed power of 260 kW with an operating diagram corresponding to a Francis turbine. Given that it is a renewable energy that can supply more than 800 households in rural areas, its contribution to sustainable development is obvious. Its investment cost is estimated at 171,465,396 FCFA. It is a profitable project with a payback time of 7 years and 2 months.
