Ebook: New Energy and Future Energy Systems

The 7th International Conference on New Energy and Future Energy Systems (NEFES 2022) was held from 25 to 28 October as an online conference (virtual conference without any physical participation). NEFES 2022 was originally planned to be held in Nanjing. Considering the health and safety of all the participants, pervasive travel restrictions as well as most authors’ appeals under COVID-19, it was finally changed into a full online conference. The technical program included Keynote Speeches, Invited Speeches, Oral Presentations and Poster Presentations.

Previous editions of the NEFES were held in Beijing (2016), Yunnan (2017), Shanghai (2018), Macao (2019), and online in 2020, 2021 due to the restrictions caused by the COVID-19 pandemic.

NEFES 2022 was co-organized by the School of Mechanical Engineering, Southeast University, China and it provided a platform for researchers, scientists, engineers and professionals from all over the world to present their latest research results and new ideas in terms of new energy and future energy systems. This volume records the proceedings of NEFES 2022 and it contains 34 peer-reviewed papers, selected from more than 170 submissions.

The topics of NEFES 2022 covered all aspects of energy, including solar thermal energy, smart grids, power transmission and distribution, electric vehicles, solar and wind energy, biomass, biofuel, and bioenergy, new energy materials, energy-saving materials, energy storage materials, energy and nanotechnology, energy storage technology, hybrid energy systems, advanced energy technologies, energy generation and conversion, clean coal technology, renewable technology, fuel cells, hydro-energy, geothermal energy.

The Organizing Committee would like to thank all the keynote and invited speakers, the authors who contributed to NEFES 2022, the anonymous reviewers who provided their valuable comments and suggestions, as well as the technical program committee members who devoted their time to the assessment of the papers submitted for publication in the NEFES 2022 proceedings.

Editor

Dr. Grigorios L. Kyriakopoulos

School of Electrical and Computer Engineering, National Technical University of Athens, Greece

The transportation industry is the second largest energy consumption sector in China and has become the main contributor to greenhouse gas emissions and air pollutants. To support the low-carbon development of the automobile industry, China has taken measures to replace traditional fuel vehicles with new energy vehicles. The reduction of carbon dioxide emission of new energy vehicles model is estimated in this paper, in which the driving situation, per 100km energy consumption, proportion of clean energy, gasoline emission factor and national average grid emission factor, etc. are all considered. The annual carbon dioxide (CO₂) emission of a new energy vehicle is 2.24 tons and the annual emission reduction is 1.09 tons in 2020. Through correlation analysis, it is concluded that there is a high negative correlation between the average emission factor of the power grid and the proportion of green energy, and the correlation coefficient is −0.9662. The ownership of civil vehicles will be 457.16 million vehicles in 2030, and it will get to its peak in 2050. Besides, the peak of CO₂ emission of civil vehicles will be got in 2030. Moreover, new energy vehicles charring new energy electricity is an effective way for the automotive industry to achieve carbon peak and carbon neutralization.

Aiming at the problems that the modelling parameters of hydropower units are difficult to obtain and the simplified models of hydropower units are not accurate enough, this paper proposes a mid- and long-term unit system model and sequence update power generation strategy for hydropower stations suitable for engineering applications. A set of methods for simulating annual hourly inflow flow based on scenario division are proposed, and the obtained simulation data is used as the input for the modelling of hydropower stations. Then, according to the measured data of the power station, a medium and long-term hydropower station system model considering the change of the reservoir water level and without the variable of the water volume of the reservoir is given. Finally, combined with the timing power generation strategy of the hydropower station, the medium and long-term unit scheduling method of the hydropower station is obtained.

The development of the photovoltaic industry is an important support for the promotion of a low-carbon economy. The rapid expansion of photovoltaic power station has also gradually exposed many operating failures. These operating failures will directly affect the operating life, power generation and revenue of the power station. This paper firstly introduces the common quality problems at each stage of the photovoltaic power station operation failure based on the field investigation of the power station, and analyzes the main reasons for the quality problems. The whole process quality control strategy of the photovoltaic power station is proposed, which provides a reference for the development and quality control of the photovoltaic industry.

In this paper, an anode and cathode material scheme with a continuous gradient variation of components is presented. The residual stress distribution of each part of the electrode model under the new material structure is derived by calculating the residual stress during the sintering process, and the optimal material component distribution curve is derived from the analysis of the results. A multi-physics 3D model covering heat transfer, mass transfer, flow, electrochemistry and solid mechanics is developed with the help of the finite element analysis software COMSOL Multiphysics 5.5. Simulation experiments are conducted to verify the effectiveness of the method for mitigating thermal stress mismatch, reducing residual stresses and increasing the working life of the fuel cell. The results show that the use of functional gradient materials for one side electrode significantly reduces the residual stresses generated in the other side electrode during sintering, and the effect of the sinusoidal distribution curve is the most significant. The stress concentration at the electrode-electrolyte interface can be improved when both side electrodes are used with functional gradient materials at the same time, and the sinusoidal and primary linear distributions are more effective.

Solid oxide fuel cells convert chemical energy into electrical energy directly through electrochemical methods, and the residual stress in the preparation process endangers its reliability. In this study, the cosine function is used to approximate the non-flat cathode-electrolyte interface, and the effects of different wavelengths on residual stress and failure probability are clarified. The results show that the electrolyte is under compressive stress and the cathode is subjected to tensile stress at the non-flat interface. The compressive stress of electrolyte is the largest at the trough, while the tensile stress of cathode is the largest at the peak. The smaller the wavelength, the stronger the stress fluctuation. In the process of anode reduction, the failure probability of cathode is the largest. The longer the wavelength, the smaller the residual stress and the smaller the failure probability.

A single wind turbine can no longer meet the increasing installed capacity and reliability requirements. Therefore, the power level and stability requirements of the wind power generation system can be improved through the parallel connection of three-level back-to-back converters. However, the zero-sequence circulating current (ZSCC) will distort the three-phase current, increase the power loss and reduce the system efficiency. Therefore, this paper establishes the ZSCC equivalent model of the back-to-back parallel converter, and analyzes the generation principle of the zero-sequence circulating current. In order to reduce the switching loss of the system and increase the system efficiency, a novel DPWM modulation strategy is proposed. At the same time, in order to control the zero-sequence circulating current of the parallel system, a hybrid switching modulation strategy using DPWM1 and DPWM3 based on hysteresis control is proposed. The simulation and experimental results verify the effectiveness of the zero-sequence circulation suppression strategy for the parallel system.

With the increase of the thickness of the main beam of the wind turbine blade, the lack of glue between the thickest area of the main beam and the web after the blade is clamped has become an important issue that affects the quality of the blade, product production cycle, and repair cost. The traditional glue deficiency repair method has high technical requirements, and the quality after repair cannot meet the design requirements, so this study designed a new glue deficiency repair method. According to the requirements of the wind turbine blade web bonding process, through defect analysis, simulation calculation and test, etc., this paper analyzes the repair method of punching holes in the main beam when the web is glued and lacking, which affects the strength of the wind turbine blade main beam and the bonding performance of the web.

As an important part of transmission lines, composite insulators are susceptible to aging and failure due to contamination, UV and other factors during operation, leading to flashover accidents. This paper studies the aging characteristics of composite insulators and anti-pollution flashover coatings operating in coastal areas of Fujian province with different ages. The physical and chemical properties were characterized by fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), water contact angle (WCA) and volume resistivity. The results show that the content of Si-O bond and Si-CH₃ bond, hydrophobicity and surface roughness can be used to evaluate the aging degree of insulators.

With the depletion of energy, the increasingly prominent problem of environmental pollution and the proposal of carbon peaking and carbon neutrality goals, photovoltaic (hereinafter referred to as “PV”) power generation technology has become a hot spot for many countries to develop, and PV power plants can make a significant contribution to the development of a sustainable energy system. However, PV modules pollution have become a serious problem for PV power plants, which have a great influence on power generation and operating costs. Air pollution, rainfall, module dust accumulation, and ground conditions are key factors that affect the performance and output power of PV modules. This article provides an overview of recent research on the impact of module contamination on PV systems. The study found that the PV power loss caused by component pollution in some power plants reached 5%–20%. This paper aims to analyze the source of module pollution and evaluate the research status of its influence on power generation, so as to provide guidance for the design, operation, and maintenance of PV power plants.

The electromagnetic coupling braking energy recovery system (EC-BERS) was proposed with the advantages of zero friction, none impact of electromagnetic coupler and higher power and efficiency of flywheel. It is potentially cost-effective between a wheel and a small flywheel. The proposed EC-BERS, which requires only a motor and a converter, can capture more of the mechanical energy, and the rest needs to be processed by the converter. In this paper, the electromagnetic coupler model was established based on Simulink software. Then a coupler test platform was built to verify the effectiveness of the model. Finally, energy conversion process of EC-BERS under deceleration and cruise state was simulated. The results show that most of the energy between wheels and flywheels is transferred as mechanical energy, and the battery had a low participation in this state.

In order to guide the practical application of lead-bismuth alloy (LBE) bubble lift pump, the dynamic characteristics of nitrogen bubbles with different diameters in liquid Lead-bismuth alloy (LBE) were studied based on the Volume of Fluid (VOF) model, and the changes of bubbles’ morphology and velocity during the movement were analyzed. The results show that the smaller the radius of the bubble is, the more drastic the change of its initial velocity and the smaller its maximum velocity are. For the small bubble, there is no bubble shedding in the process of its movement, only when the radius of the bubble reaches a certain value, the phenomenon of small bubble shedding will occur.

The article presents approaches to the development of a feasibility study, taking into account economic and political risks. It is important to note that it is political risks that will promote the use of renewable energy sources when choosing technical and technological solutions that do not require the purchase of expensive and not always affordable traditional energy sources. The article can be useful for energy auditors, managers of industrial enterprises, heads of state regulatory bodies, as well as graduate students and undergraduates of universities.

The gasification of COVID-19 plastic waste to methanol was simulated by using Aspen plus software. The effects of main operating parameters on the syngas yield and methanol yield were explored. An industrial Cu/ZnO/Al₂O₃ catalyst was applied for synthetic methanol production, and the relevant kinetic model was built for the methanol synthesis process. The effects of gasification temperature and pressure on the syngas yields and calorific values of syngas and methanol yields from the gasification of medical plastic waste were discussed. The pressure of the synthetic methanol reactor promoted methanol yields, and the external addition of H₂ was optimized for methanol production. It is concluded that the optimal working condition to obtain the highest methanol yield from a suitable HHV of the syngas is when the gasification of plastic waste was carried out at 900 unmapped: inline-formula unmapped: math unmapped: msup unmapped: mrow unmapped: mrow unmapped: mo ∘C under atmospheric pressure with an external H₂ mass flow of 96 kg/hr and the pressure of methanol synthesis at 47 bar.

Taking lauric acid-paraffin wax (LA-PW) volcanic rock (VR) shape-stabilized phase change materials with particle sizes of 1–3mm and 4–6mm as the research objects, analysis was made on the enthalpy, infrared spectrum, leakage characteristics, heat storage, heat release of shape-stabilized phase change materials. The results show that shape-stabilized phase change material has lower enthalpy with the increase in mass fraction of volcanic rock, but the material melting point and freezing point remain basically unchanged, and the shape-stabilized phase change material does not produce new substances, displaying stable composition. It can be seen from the leakage characteristics that, under the same ratio, shape-stabilized phase change material with a volcanic rock particle size of 1–3 mm has greater thermal stability than that with a volcanic rock particle size of 4–6 mm.

The belt type assembly of proton exchange membrane fuel cell is more compact and have higher power density than the screw assembly method. The uniform distribution of fuel cell stack clamping load directly affects the efficiency, reliability and durability of the stack. The design of high-strength and light-weight packaging structure is conducive to improving the lightweight level of the whole stack system. In this paper, the finite element model of the belt type clamping stack was established by numerical simulation, and the effects of the number of belts and endplate radius on the stress of the stack and the clamping structure were analyzed. The results reveal that increasing the number of belts can improve the uniformity of contact pressure distribution inside the stack, increasing the width of the belt can improve the bearing capacity of the belt and the uniformity of the contact pressure of the stack better than increasing its thickness. When different numbers of belts are clamping, the stress of each belt is not consistent, and the middle belt first yields. Increasing the endplate radius has little effect on the uniformity of the contact pressure distribution of the stack, but can improve the bearing capacity of the belt.

Helium discharge experiments were carried out in the linear plasma device which is based on hollow cathode discharge. The variation of helium plasma parameters with experimental conditions and the spectral characteristics of helium discharge were studied. The plasma density and temperature in the experiment were measured by the plasma probe, and the spectral results were measured by the spectrometer. The results show that the plasma density increases with the helium injection flux and the magnetic induction intensity, but the plasma temperature does not. The spectral results show that the relative intensity of helium spectrum also increases with the helium injection flux and magnetic induction intensity, which is consistent with the density results. The relative spectral intensity of HeI is much greater than that of HeII, beneficial to the detection of neutral helium on the linear plasma device. These results accumulated experimental basis for the study of neutral helium density through the linear plasma device, then simulation study on helium ash in divertor area of the future fusion reactor.

Using ANSYS software, the heat transfer process of hot water storage tank in spherical, cylindrical and square shapes was numerically simulated, and the distribution of the external wind velocity field and the temperature field under the same working conditions was studied. According to the change of average hot water temperature with time, it is concluded that spherical hot water storage tank can help reduce heat loss. Based on velocity field and temperature field distribution, it is found that the heat loss of the spherical hot water storage tank mainly occurs on the annular surface perpendicular to the windward side. By thickening the thermal insulation layer, it is possible to reduce the heat loss on the surface of the spherical water storage tank and improve the thermal insulation effect.

On account of Main transformer CT (current transformer)’s wrong connection leading to additional circuit, differential loop’s circuit is calculated according to transformer’s load status. Detail analysis is made. In conclusion, potential fault trip exists in RCS-978E stable ratio differential protection. Measures are brought forward to avoid fault trip, so that reliability of transformer protection is improved.

The paper presents an application instance of CZX-22A controlbox mal-operation from secondary circuit’s mistaken wiring, and analyzes academic reason of controlbox mal-operation in detail. Mistaken wiring leads to DC source parataxis existing in the breaker control circuit, when one route control source is broken down for some reason, it could result in controlbox mal-operation and the accidental trip. By experiment and calculation, this paper brings forward a view of preventing controlbox mal-operation, which alters components’ parameters on circuit board of controlbox, thus ensuring the reliability of relaying protection and the security of the grid.

firstly, this paper analyzes the necessity of market transaction of distributed generation, and summarizes the current situation of distributed generation transaction in the world. Then it discusses and analyzes the relevant policies of the Chinese government for distributed generation transaction, including photovoltaic subsidy policies, support policies for virtual power plants to participate in power trading, and support policies for distributed generation transaction pilot projects. According to China’s current electricity market rules and distributed generation transaction support policies, a distributed generation transaction platform system suitable for Chinese electricity market is designed based on blockchain technology. This paper compares and analyzes the two modes of virtual power plant and peer-to-peer transaction from the aspects of DG investor’s revenue and trading model. Finally, for the development of distributed generation trading in China, we draw conclusions and suggestions, and put forward the problems to be solved in the next step.

Circuit breaker trip circuit (also known as control circuit) is the most important secondary circuit for relay protection. Among them, the “communication triple trip” (CTT) hard contact connected to the operation exit circuit of the protection device increases the complexity of the trip circuit and the difficulty of analyzing the trip circuit failure. When the system runs normally, the signal of “control circuit disconnection” cannot be accurately and timely uploaded to the operation monitoring background. When the system short-circuit fault occurs, the circuit breaker cannot operate correctly due to the trip circuit break, so the adjacent interval is connected by the near backup protection, thus causing the expansion of the accident scope. In this paper, it is proposed for the first time that the CTT hard contact protected by circuit breaker should be replaced by the soft CTT (i.e. the control word) of the protection device, so as to make the trip circuit reliable, clear and simple, and at the same time ensure the accuracy of the “control circuit break” signal.

The use of phase change material (PCM) in thermal energy storage systems can overcome the instability and intermittent problems of solar energy. Heat storage unit (HSU) with capsule structure is introduced in this study to improve the flow characteristics and thermal performance of macroscopically encapsulated PCM HSU. The external flow characteristics and thermal performance of HSU with capsule-shaped and sphere are numerically analyzed. Compared with the traditional sphere HSU, the natural convection in the capsule-shaped HSU is more intense, and the melting time is reduced by 10.1% compared with the sphere HSU. In addition, the flow characteristics of the capsule HSU are more excellent than the sphere HSU, which has lower resistance and resistance coefficient. The optimization results show that with the increase of dimension parameter α, the capsule-shaped HSU has faster melting times and lower resistance coefficient. The capsule-shaped HSU can provide a better external flow characteristic and thermal performance when the dimension parameter α is 2.6.

In this study, a numerical model is built to analyze the leakage current of a proton conductor solid oxide fuel cell. The transports of electron-hole and proton transfer in a mixed conductor electrolyte is described by the Nernst-Planck equation. The model is validated using experimental data. The leakage current, potential distribution, Faraday efficiency and energy efficiency are analyzed. When the output voltage of the fuel cell is greater than 0.5 V, the leakage current will cause the energy efficiency in a significant reduction. The lower the temperature, the lower the leakage current density. Lowering the temperature will improve the Faraday efficiency and energy efficiency of the fuel cell. Lower output voltage helps improve the Faraday efficiency.

In the present work, hydrodynamics of a fluidized bed with binary solid mixture have been studied using CFD simulations. Two different cases one with binary mixtures of 20% large and 80% small particles and other with 40% large particles 60% small particles respectively (both of Geldart B type) are chosen. Transient and steady state flow patterns have been reported for understanding the stability and increase in bed height for the chosen mixtures. Further, the velocity, turbulence parameters and solid volume fraction profiles have been analyzed to understand the characteristics like mixing and segregation in the beds