The study investigates how variable rate charging can affect PEV charging and identifies how this capability can be integrated into residential neighborhoods. The results show that creating PEV chargers that can deliver variable rates will enhance uncontrolled and controlled PEV charging. The integration is summarized into 4 phases. In phase 1, uncontrolled PEV chargers should be enabled to provide any rate to vehicles within 0 to 11.5 kW, which can reduce overloading by up to 28.34%. Phase 2 introduces smart chargers that use forecasted data to determine the optimal time intervals for PEVs to charge using a fixed rate of 4.8 kW, capable of reducing overloading by 42.69%. In Phase 3, a controlled smart charging strategy that can deliver any rate to a vehicle using SRVF’s approach is proposed, which will reduce overloading by up to 42.87%. Lastly, phase 4 recommends a smart charging control that can deliver any rate to a vehicle using RIVF’s approach, reducing overloading by up to 43.37... [more]

Hyper compressors are key facilities for producing the low-density polyethylene with discharge pressure up to 350 MPa. Such high pressure brings great challenges to the design of the hyper compressor in many aspects. In this paper, a 3D transient computational fluid dynamics (CFD) model with inlet and outlet pipelines is built to investigate the thermodynamic performance of a hyper compressor. To realize the interaction between the thermodynamic processes and the pressure pulsation through valve dynamics, the pressures across the valve surfaces were monitored to the dynamic equation of the poppet valve. Then, structured grids were generated for the flow domain inside the valve, and the entire numerical model was solved by a commercial code: ANSYS Fluent. Consequently, the p-V diagram, the valve motion and pressure pulsation could be acquired simultaneously. The results of the numerical model showed that the exponents of the expansion and compression processes were 5.12 and 13.22, which... [more]

With the increasing severity of climate change, the power industry, as one of the main sources of carbon emissions, is playing an extremely important role in the process of low-carbon energy transformation. The purpose of this paper is to try to find a general method to solve the optimal path for the low-carbon evolution of the power supply structure so as to meet the challenges faced by the low-carbon transformation of the power industry in the future. This paper first uses the capacity coefficient index (CCI) to represent the power generation ability of different technologies and proposes a forecasting method for the CCI of renewable energy generation. In this paper, a two-layer optimization model considering multiple constraints is established and solved using the MPC method. The results show that China’s installed capacity of renewable power could account for more than 50% in 2030, while the carbon emissions will decrease after reaching a peak in 2023. On the premise of ensuring su... [more]

The rotation precision of rotors determines the efficiency and quality of the overall aero-engine, as well as its long-term and reliable operation ability. As the terminal link of aero-engine manufacturing, the assembly is the last guarantee of precision control. Rotor assembly relates to the accurate expression of the connection form and design optimization of the assembly scheme. The existing variation model cannot adequately handle the partial parallel chain problem, ignoring the bayonet circular connector between the rotor parts, and it is still deficient in multistage gyration error control. In this paper, the partial parallel connection and multistage revolving characteristics of rotors were discussed, and a novel modeling and optimizing method for a partial parallel dimension chain was proposed. On the one hand, the variation expression of the connection features for the revolving components considering the partial parallel structure was researched. Contact point-based torsors w... [more]

In this paper, a method of power system equipment recognition based on image processing is proposed. Firstly, we carry out wavelet transform on the sound signal of power system equipment collected from the site, and obtain the wavelet coefficient−time diagram. Then, the similarity of wavelet coefficients−time images of different equipment and the same equipment in different periods is calculated, which is used as the basis of the feasibility of image recognition. Finally, we select the HOG features of the image, and classify the selected features using SVM classifier. The method proposed in this paper can accurately identify and classify power system equipment through sound signals, and is different from the traditional method of classifying sound signals directly. The advantages of image processing can be effectively utilized through image processing to avoid the limitations of sound signal processing.

Rapid industrial development and innovations in technology bring about the menace of congestion in deregulated power systems (DPS). The transmission lines are continuously working under a stressed condition with reduced power transfer capacity. In this situation, the power losses and voltage deviations at the load buses are increased and hence reduce the system stability. To mitigate congestion, improving available transfer capability (ATC) of the transmission system is one of the most feasible and practical solution. This paper focuses on the implementation of Thyristor Controlled Series capacitor (TCSC) to mitigate congestion by enhancing ATC and via reducing power losses. AC Power Transfer Distribution Factor (ACPTDF) is applied to calculate ATC and to find the location of TCSC. To optimize the TCSC parameter (reactance), a Teaching Learning Based Optimization (TLBO) is proposed in the present work. The proposed optimization is validated on the IEEE 30 Bus system. The results are va... [more]

This paper proposes centralized and distributed optimization models for V2G applications to provide frequency regulation in power systems and the electricity market. Battery degradation and dynamic EV usages such as EV driving period, driving distance, and multiple charging/discharging locations are modeled. The centralized V2G problem is formulated into the linear programming (LP) model by introducing two sets of slack variables. However, the centralized model encounters limitations such as privacy concerns, high complexity, and central failure issues. To overcome these limitations, the distributed optimal V2G model is developed by decomposing the centralized model into subproblems using the augmented Lagrangian relaxation (ALR) method. The alternating direction method of multipliers (ADMM) is used to solve the distributed V2G model iteratively. The proposed models are evaluated using real data from the Independent Electricity System Operator (IESO) Ontario, Canada. Simulation results... [more]

Since the DC-link of the dual-inverter two-stage matrix converter (TSMC) has no energy storage element, its grid-side current waveform is closely related to the load-side condition. The conventional modulation strategy of the dual-inverter TSMC is only the stack of the double inverters, without considering the cooperation between both modulation strategies. Thus, the fluctuations in the grid-side currents synthesized by both load-side currents will be obvious. To solve this problem, this paper analyzes the effect of the current pulse position on the grid-side current waveform quality, and relevant relationship between the pulse position and current harmonics is obtained according to Fourier transform. On this basis, the harmonic attenuation strategy for the dual-inverter TSMC is proposed. In the proposed strategy, the grid-side current harmonic is reduced based on the optimal duty-cycle combination, obtained from the harmonic optimization problem. The simulation and experimental result... [more]

The variety of possible solutions for the integration of heat pumps (HP) into the circuits of generation facilities dictates the need for preliminary selection of the most promising options. Determining the maximally economically efficient HP capacity may be the key limiting factor for the potential range of solutions. The purpose of the study is to analyze the influence of the type of power equipment of a thermal power plant (TPP) on the choice of HP capacity. In the course of the study, we identified factors that can influence the choice of HP capacity. The correlation between the limitation of the maximum capacity of HP (from the point of view of break-even operation in the electricity market) from the electric capacity and the efficiency of the TPP equipment was established. The ranges of HP capacity for the most common types of TPP power equipment in the Russian Federation were determined. The maximum HP capacity for TPPs based on a steam turbine unit (STU) of type K-300-170- 1P w... [more]

Currently, hydrogen energy is the most promising energy vector, while gasification is one of the major routes for its production. However, gasification suffers from various issues, including slower carbon conversion, poor syngas quality, lower heating value and higher emissions. Multiple factors affect gasification performance, such as the selection of gasifiers, feedstock’s physicochemical properties and operating conditions. In this review, the status of gasification, key gasifier technologies and the effect of solid-fuel (i.e., coal, biomass and MSW) properties on gasification performance are reviewed critically. Based on the current review, the co-gasification of coal, biomass and solid waste, along with a partial utilisation of CO2 as a reactant, are suggested. Furthermore, a technological breakthrough in carbon capture and sequestration is needed to make it industrially viable.

Graphene oxide, as a new two-dimensional material, has a large specific surface area, high thermal stability, excellent mechanical stability and exhibits hydrophilic properties. By combining the carboxyl groups on the surface of graphene oxide with hydrophilic groups, surfactant-like polymers can be obtained. In this paper, based on the molecular dynamics method combined with the first nature principle, we first determine the magnitude of the binding energy of three different coupling agents—alkylamines, silane coupling agents, and haloalkanes—and analytically obtain the characteristics of the soft reaction. The high stability of alkylamines and graphene oxide modified by cetylamine, oil, and water models was also established. Then, three different chain lengths of simulated oil, modified graphene oxide−water solution, and oil-modified graphene oxide−water systems were established, and finally, the self-aggregation phenomenon and molecular morphology changes in modified graphene oxide... [more]

A series of experimental tests were carried out in order to study the propagation characteristics of a liquid kerosene rotating detonation engine (RDE) with different diameters. Distinguished characteristics of spatial and temporal instability were found in the large-scale RDE due to the uneven circumferential distribution of kerosene supply pressure. As for the two counter-waves detonation system, the 500 mm-diameter RDE maintains a higher detonation wave velocity due to its longer injection recovery time. However, the 220 mm-diameter RDE can obtain a larger equivalence ratio operation range, higher specific thrust, and higher specific impulse. In addition, compared with the deflagration combustion, the detonation combustion has higher chamber pressure and thrust under the same operational conditions.

By reducing electricity consumption during peak times, peak shaving could reduce the need for carbon intensive resources and defer capacity related investments. Households, where they use electricity for space or water heating, are major contributors to the winter peak demand and promising candidates for related demand response (DR) initiatives. The impact of such initiatives is determined by comparing the actual consumption during a DR event to a baseline, i.e., the estimated consumption that would have occurred in the absence of an event. This paper explores the challenges associated with modeling a baseline in the context of residential winter DR programs with individual performance-based incentives. A sample of more than a thousand residential load profiles was used in this study to provide a statistical comparison of performance metrics for different baseline load models. Arithmetic, regression based, and matching-day models were considered. Results show that adjusted arithmetic m... [more]

The present article marks the 95th anniversary of the birth of Vladimir P. Skripov, author of the classic study of superheated and supercooled liquids. It presents a discussion based on the early work carried out by Skripov and his research team in Ekaterinburg during the 1950s and 1960s. Due to their pioneering nature, these works laid the foundation for the study of metastable liquid states. For various reasons, although they remain relevant to this day, these groundbreaking works remain unknown to most non-Russian-speaking readers. As well as elucidating the behavior of the heat capacity of a solution in the liquid−liquid critical region, the presented research also concerns the characteristic features of light scattering and free-convective heat transfer in the liquid−vapor critical region of a one-component system, discussing two options for the position of the superheated liquid spinodal on the phase diagram of water, including the area of supercooled states and negative pressure... [more]

The work presents the power-sharing in a standalone low voltage AC microgrid consisting of three parallel grid supporting inverters using a virtual impedance-based droop system. Typically, isolated microgrids suffer unique challenges regarding voltage, current, frequency regulation, power flow control, and power-sharing due to the absence of a stiff AC grid source. This work investigated the power flow and sharing technical challenges using three inverter-based distributed energy sources, three static loads, and one dynamic load. These distributed energy sources are interconnected with the loads using low voltage line impedance within the microgrid to implement the uneven power distribution. Furthermore, a distributed grid supporting control utilizing virtual impedance is proposed in this work to improve power-sharing. The microgrid model is developed with the MATLAB Simulink environment and validated using the Opal RT OP4510 simulator. The proposed technique ensured improved power-sha... [more]

Voltage control in modern electric power distribution systems has become challenging due to the increasing penetration of distributed energy resources (DER). The current state-of-the-art voltage control is based on static/pre-determined DER volt-var curves. Static volt-var curves do not provide sufficient flexibility to address the temporal and spatial aspects of the voltage control problem in a power system with a large number of DER. This paper presents a simple, scalable, and robust distributed optimization framework (DOF) for optimizing voltage control. The proposed framework allows for data-driven distributed voltage optimization in a power distribution system. This method enhances voltage control by optimizing volt-var curve parameters of inverters in a distributed manner based on a cellular computational network (CCN) representation of the power distribution system. The cellular optimization approach enables the system-wide optimization. The cells to be optimized may be prioriti... [more]

Proton exchange membrane fuel cells (PEMFCs) cathode catalysts’ robustness is one of the primary factors determining its long-term performance and durability. This work presented a new class of corrosion-resistant catalyst, Magnél TiO2 supported Pt (Pt/Ti9O17) composite, synthesized. The durability of a Pt/Ti9O17 cathode under the PEMFC operating protocol was evaluated and compared with the state-of-the-art Pt/C catalyst. Like Pt/C, Pt/Ti9O17 exhibited exclusively 4e− oxygen reduction reaction (ORR) in the acidic solution. The accelerated stress tests (AST) were performed using Pt/Ti9O17 and Pt/C catalysts in an O2-saturated 0.5 M H2SO4 solution using the potential-steps cycling experiments from 0.95 V to 0.6 V for 12,000 cycles. The results indicated that the electrochemical surface area (ECSA) of the Pt/Ti9O17 is significantly more stable than that of the state-of-the-art Pt/C, and the ECSA loss after 12,000 potential cycles is only 10 ± 2% for Pt/Ti9O17 composite versus 50 ± 5% for... [more]

In recent years, green finance has become a popular method for dealing with environmental issues. However, it remains to be seen whether green financing is effective in addressing current global environmental issues. In this article, we, therefore, analyze the diffusion patterns of green finance publications in the Global South and Global North to identify which section of the globe is under-researched from this perspective. The study tried to highlight the overall trends of research publications on green finance, continent, most contributing authors, countries, and journals. The study used a bibliometric approach with the help of R studio software. The Scopus database was used for extracting the resources and 522 documents utilized in this bibliometric analysis. The result demonstrates that the diffusion of green finance is more common in the Global North than in the Global South. However, the number of scientific studies produced over time, the number of active authors, and affiliati... [more]

This paper proposes a modelling technique for Synchronous Reluctance Motors (SynRMs) based on a generalized Magnetic Equivalent Circuit (MEC). The proposed model can be used in the design of any number of stator teeth, rotor poles, and rotor barrier combinations. This technique allows elimination of infeasible machine solutions during the initial machine sizing stage, resulting in a lower cohort of feasible machine solutions that can be further optimized using finite element methods. Therefore, saturation effects, however, are not considered in the modelling. This paper focuses on modelling a generic structure of the SynRM in modular form and is then extended to a full SynRM model. The proposed model can be iteratively used for any symmetrical rotor pole and stator teeth combination. The developed technique is applied to model a 4-pole, 36 slot SynRM as an example, and the implemented model is executed following a time stepping strategy. The motor characteristics such as flux distribut... [more]

During the use and management of lead−acid batteries, it is very important to carry out prediction and study of the state of the health (SOH) of the battery. To this end, this paper proposes a SOH prediction method for lead−acid batteries based on the CNN-BiLSTM-Attention model. The model utilizes the convolutional neural network (CNN) to carry out feature extraction and data dimension reduction in the input factors of model, and then these factors are used as the input of the bidirectional long short-term memory network (BiLSTM). The BiLSTM is used to learn the temporal correlation information in the local features of input time series bidirectionally. The attention mechanism is introduced to assign more attention to key features in the input sequence with more significant influence on the output result by assigning weights to important features, and finally, multi-step prediction of the battery SOH is realized. Compared with the prediction results of battery SOH using other neural ne... [more]

Thermoelectric harvesting technology is a clean and friendly energy-conversion technology. In the π-type traditional thermoelectric module (TEM), n- and p-type thermoelectric legs are electrically connected in a series to generate large temperature differences in the heat flow direction and to achieve a better module performance. However, damages to one thermoelectric leg could lead to the failure of the thermoelectric system. This work proposes a novel forked-finger electrode-structured thermoelectric module (FFTEM), which enables a simultaneous parallel electrical connection and thermal transfer in a homogeneous material’s thermoelectric leg set. The four thermoelectric legs share a common pair of electrodes, and this parallel structure makes the FFTEM benefit from low internal resistance, a high operating current, and high output power. The internal resistance and output power of the TEM are 4.25 mΩ and 1.766 mW, respectively, at a temperature difference of 40 °C. The internal resis... [more]

The lack of fresh water in the world has become a growing concern. As an open-source incremental technology for water resources, desalination has become an important method to solve the global water crisis. Based on the inherent safety, versatility, modularity, and advantages of high-temperature gas-cooled reactors, the Saudi Arabia desalination project is the relying background. This paper proposes a complete solution for the high-temperature gas-cooled reactor power and water coproduction project by selecting a combination of process-proven multi-effect distillation (MED) and reverse osmosis (RO). In the scheme, a tertiary circuit is designed for the isolation of radioactive entities. An innovative comparative analysis of the engineering investment and production costs of different desalination technologies, such as MED and RO, and a comparison of the investment estimates of the “thermal” and “membrane” methods for the production of 10,000 tonnes of fresh water per day are performed.... [more]

The purpose of this research is to design an energy-efficient off-grid vending machine that has a refrigeration system powered by an environmentally friendly refrigerant. The paper presents details from the equipment’s design phase in terms of the resistance structure, photovoltaic panels area dimensioning, but also in terms of the necessary cooling load to be provided by the refrigeration system. The refrigerant chosen was R290 following a comparative analysis, which showed that it has an efficiency 6.6% higher than R134a. During the monitoring periods, the outdoors temperature varied between −4−28 °C, the relative humidity between 22−100% and yet only a slight indoor temperature variation of ±1.5 °C compared to the set value was recorded. The battery module managed to store enough energy from the photovoltaic panels to keep the vending machine functional through three consecutive days with adverse environmental conditions, as evidenced by the low variation of indoor temperature

With little time left for humanity to reduce climate change to a tolerable level, a highly scalable and rapidly deployable solution is needed that can be implemented by any country. Offshore wind energy in international waters is an underused resource and could even be harnessed by landlocked countries. In this paper, the use of sailing wind turbines operating autonomously in high seas to harvest energy is proposed. The electrical energy that is generated by the wind turbine is converted to a renewable fuel and stored onboard. Later, the fuel will be transferred to shore or to other destinations of use. The presented idea is explored at the system level, where the basic subsystems necessary are identified and defined, such as energy conversion and storage as well as propulsion subsystems. Moreover, various operating possibilities are investigated, including a comparison of different sailing strategies and fuels for storage. Existing ideas are also briefly addressed and an example conce... [more]

Due to the complex operation characteristics of AC/DC hybrid power grids, it is a great challenge to comprehensively evaluate their stability and formulate appropriate strengthening schemes for them. To address this challenge, the following studies are carried out in this paper. First, an evaluation system including six indicators is established for AC/DC hybrid power grids. Next, aiming at the problems that may be revealed by the comprehensive evaluation, strengthening measures that can be utilized are introduced. Then, a comprehensive evaluation method for AC/DC hybrid power grids and their potential strengthening schemes is proposed. This method can deal with three issues, including normalization of the indicators, weighting of the indicators, and the trade-off of technology and cost. Finally, in the case study of the Qujing Power Grid, the main problems faced by regional power grids are pointed out, and four feasible strengthening schemes are formulated and evaluated.