A Review of Contact Electrification at Diversified Interfaces and Related Applications on Triboelectric Nanogenerator

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.

To Open Up a New Aspect of Rural Hydropower and Electrification——Excerpted from Speeches on Working Conferences of National Rural Hydropower and Electrification Counties Construction

The Role and status of rural hydropower and electrification are reviewed, and the situation and tasks are putforward simultaneously.

An investigation into intermittent electrification strategies and an analysis of resulting CO_(2) emissions using a high-fidelity train model

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.

Prospects of key technologies of integrated energy systems for rural electrification in China

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.

Flow Electrification of Insulated Liquid in Metal Pipes

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.

Analysis of rail potential and stray current in MVDC railway electrification system

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.

Design of a Photovoltaic Mini-Grid System for Rural Electrification in Sub-Saharan Africa

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 an 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 were 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/m2/day with the worst month being August with 5.22 kWh/m2/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.

Microgrids-as-a-Service for Rural Electrification in Sub-Saharan Africa

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.

PV-Hybrid Off-Grid and Mini-Grid Systems for Rural Electrification in Sub-Saharan Africa

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.

First-principles study of electronic properties of interfacial atoms in metal-metal contact electrification

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.

Evolution of surfaces and mechanisms of contact electrification between metals and polymers

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.

Electrification of mineral particles by electron beam irradiation

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.

Solar PV Electrification in Nigeria: Current Status and Affordability Analysis

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 policy targets and reality. The solar resource potential across the six geo-political zones in Nigeria is also presented, which ranges from 3.393 - 6.669 kWh/m2/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.

The Role of Mini-grids in Rural Electrification Programmes in Africa and beyond:“The State of Art Paper”

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.

Micro Hydro Power Plant for Sustainable Energy in Rural Electrification: A Case Study in Cameroon

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.

Addressing Barriers to Off-Grid Rural Electrification in Africa： The Botswana and Namibia Experience

Africa is the most affected continent with energy poverty. Wood fuel is the main source of energy for remote and rural populations. At the same time, most parts of Africa are endowed with abundant solar energy. Together with a highly developed global solar industry and ever declining cost of solar systems, solar has unprecedented potential to combat energy poverty in Africa. However, dissemination of solar systems is faced with a number of barriers and challenges amongst where sustainable financing and lack of technological support for installation, maintenance and repair of systems are the most significant. This paper discusses the cases of Botswana and Namibia where financing schemes based on different partnership models have been successfully implemented. These schemes have the potential for success and adaptation by countries with similar socio-economic conditions. We conclude with recommendations on training programs for different levels of intervention to overcome the lack of technological support.

Provincial-level analysis of electrification feasibility and climate policy interactions

Improving electrification feasibility is essential for reducing emissions from non-electric energy sources,thereby enhancing air quality and public health.Concurrently,climate mitigation actions,such as carbon pricing policies,have significant potential to alleviate increasing carbon dioxide(CO_(2))and other co-emitted air pollutants.However,the interactions between climate policy and the improvement of electrification feasibility at the provincial level remain unclear,collectively impacting the net-zero transition of energy-intensive sectors.Here we combine a technologically rich economic-energy-environment model with air quality modeling across China to examine the health,climate,and economic implications of large-scale upgrades in electrification feasibility and climate policies from 2017 to 2030.The results indicate that advancing electrification feasibility,coupled with adopting carbon pricing policies,is likely to facilitate a transition towards electricity-dominant energy systems.Improved electrification feasibility is projected to yield a 7-25%increase in nationwide climate benefits and a 5-14%increase in health benefits by 2030.These incremental benefits,coupled with reduced economic costs,result in a 22-68%increase in net benefits.However,regionally,improvements in electrification feasibility will lead to heightened power demand and unintended emissions from electric energy production in certain provinces(e.g.,Nei Mongol)due to the coal-dominated power system.Additionally,in major coal-producing provinces like Shanxi and Shaanxi,enhanced electrification feasibility exacerbates the negative economic impacts of climate policies.This study provides quantitative insights into how improving electrification feasibility reshapes energy evolution and the benefit-cost profile of climate policy at the provincial level.The findings underscore the necessity of a well-designed compensation scheme between affected and unaffected provinces and coordinated emission mitigation across the power and other end-use sectors.

Water–solid contact electrification and catalysis adjusted by surface functional groups

Chemical functional groups on solid surfaces greatly influence contact electrification(CE)at water–solid interfaces.Previous studies of their effects mainly swapped materials or bonded related molecules to a substrate,introducing other factors of influence.This work aims at unambiguously demonstrating the role of functional groups in water-polymer CE.We study the contribution of functional groups,by using ion coupled plasma etching to modify a high-density polyethylene(HDPE)film,a polymer with a naturally quasi-null charge transfer ability.Fluoride(HDPE–F)and hydroxyl(HDPE–OH)functional groups are generated and endowed HDPE with charge withdrawing ability.HDPE–F withdraws 2.5–2.7 times more charges than HDPE–OH.Concurrently,the surface charges accumulated generate electrostatic forces,altering the droplets motion.This phenomenon provides another approach to study CE,helping to evaluate the contribution of electrons to solid–liquid CE.Finally,employing HDPE–F to perform contact-electro-catalysis shows its activity is 2.4 times higher than that of commercial fluorinated films.

The Sequential Pricing of Ride-Hailing System with Rental Service in the Context of Fleet Electrification

Surging demand and reduced capacity in the ride-hailing industry have prompted numerous ride-hailing platforms to build their own car-rental services catering to drivers who do not possess private vehicles. However, the trade-off between the ride-hailing service and the car-rental service is an important issue that is still unclear in theory. Moreover, ride-hailing platforms are transitioning towards all-electric fleets in the context of Carbon Neutrality goals and government regulations. This paper considers a ride-hailing system comprising a monopolist ride-hailing platform, an electric vehicle (EV) rental firm, and a gasoline vehicle (GV) rental firm. Furthermore, we build a stylized model to study the sequential pricing of the system. The equilibrium outcomes show the significant impact of the ride-hailing platform’s decision to continue or withdraw offering EV rental services on EV and GV drivers’ net earnings, rental prices, and wages. The ride-hailing platform providing EV rental services increases EV drivers’ net earnings but decreases the GV driver wages and rental prices. However, the EV rental service offered by the ride-hailing platform does not necessarily lead to an increased total profit for the system. The improved profitability of the system by the ride-hailing platform providing EV rental services is contingent upon lower rider prices and higher fuel costs. The ride-hailing platform’s EV rental services provision also effectively fosters the ride-hailing fleet’s electrification. Furthermore, as the number of riders increases, the ride-hailing platform should reduce the commission rate for EV drivers to maintain competitiveness and profitability.

Effect of contact- and sliding-mode electrification on nanoscale charge transfer for energy harvesting

The process of charge transfer based on triboelectrification （TE） and contact electrification （CE） has been recently utilized as the basis for a new and promising energy harvesting technology, i.e., triboelectric nanogenerators, as well as self- powered sensors and systems. The electrostatic charge transfer between two surfaces can occur in both the TE and the CE modes depending on the involvement of relative sliding friction. Does the sliding behavior in TE induce any fundamental difference in the charge transfer from the CE？ Few studies are available on this comparison because of the challenges in ruling out the effect of the contact area using traditional macro-scale characterization methods. This paper provides the first study on the fundamental differences in CE and TE at the nanoscale based on scanning probe microscopic methods. A quantitative comparison of the two processes at equivalent contact time and force is provided, and the results suggest that the charge transfer from TE is much faster than that from CE, but the saturation value of the transferred charge density is the same. The measured frictional energy dissipation of -11 eV when the tip scans over distance of I A sheds light on a potential mechanism： The friction may facilitate the charge transfer process via electronic excitation. These results provide fundamental guidance for the selection of materials and device structures to enable the TE or the CE in different applications; the CE mode is favorable for frequent moderate contact such as vibration energy harvesting and the TE mode is favorable for instant movement such as harvesting of energy from human walking.