Brush seals can improve engine performance by reducing leakage. Wear models of brush seals provide methods to predict wear and leakage. However, rotor eccentricity, radial deformation, and hysteresis effect of bristles are not considered systematically in the existing models, which may lead to large errors in some cases. To investigate the influence of rotor-stator eccentricity and radial deformation on the wear process and leakage performance of brush seal, a brush seal test was planned and executed, in which the air leakage rates were measured at different testing times and operating conditions, the eccentricity and radial deformation was measured using eddy current sensors. The test results showed that the eccentricity and radial deformation significantly affected the wear behavior and leakage performance. In the theoretical research, the abrasive wear equation is adopted to describe the material loss of bristles, and a simplified description is used to express the rotor-stator ecce... [more]

The dewatering process reduces the water quantity in sludge, allowing the decrease in its volume, which facilitates its storage, transport, stabilization, and improves the post-treatment efficiency. Chemical polymers including aluminum sulphate and polyaluminum chloride were applied as flocculants in the conditioning process in order to prepare sludge for dewatering. However, these synthetic polymers may cause risks for human health, and should be substituted with ecofriendly and safe materials. These materials include plant-based flocculants, animal-based flocculants, and microbial-based flocculants. Sludge dewaterability was evaluated by considering many parameters, such as moisture content (MC), dry solids (DS), specific resistance to filtration (SRF), capillary suction time (CST), and sludge volume index (SVI). The use of microorganisms for sludge dewatering is an available option, since many strains (R. erythropolis, A. ferrooxidans, P. mirabilis, T. flavus, etc.) demonstrated the... [more]

Energy storage is an important technical means to increase the consumption of renewable energy and reduce greenhouse gas emissions. Electrochemical energy storage, represented by lithium-ion batteries, has a promising developmental prospect. The performance of lithium-ion batteries continues to decline in the process of application, and the differences between batteries are increasing. Therefore, accurate estimation of the state of health (SOH) of batteries is the key to the safe and efficient operation of energy storage systems. In this paper, the electrochemical impedance spectroscopy (EIS) characteristics of Li-ion batteries under different states of charge and health were studied. Three groups of Li-ion battery impedance module values under different frequencies were selected as characteristic parameters, and the SOH estimation model of Li-ion batteries was built by using the support vector regression (SVR) algorithm. The results show that: the model with the second group of freque... [more]

The oceans cover 71% of Earth’s surface and are an enormous source of renewable energy which comes from tides, waves, ocean currents, and salinity and temperature differences [...]

This research work aims to develop a fault detection and performance monitoring system for a photovoltaic (PV) system that can detect and communicate errors to the user. The proposed system uses real-time data from various sensors to identify performance problems and faults in the PV system, particularly for encapsulation failure and module corrosion. The system incorporates a user interface that operates on a micro-computer utilizing Python software to show the detected errors from the PV miniature scale system. Fault detection is achieved by comparing the One-diode model with a controlled state retrieved through field testing. A database is generated by the system based on acceptable training data and it serves as a reference point for detecting faults. The user is notified of any deviations based on the threshold value from the training data as an indication of an error by the system. The system offers real-time monitoring, easy-to-understand error messages, and remote access capabi... [more]

Wind mapping has played a significant role in the selection of wind harvesting areas and engineering objectives. This research aims to find the best clustering method to cluster the wind speed of Malaysia. The wind speed trend of Malaysia is affected by two major monsoons: the southwest and the northeast monsoon. The research found multiple, worldwide studies using various methods to accomplish the clustering of wind speed in multiple wind conditions. The methods used are the k-means method, Ward’s method, hierarchical clustering, trend-based time series data clustering, and Anderberg hierarchical clustering. The clustering methods commonly used by the researchers are the k-means method and Ward’s method. The k-means method has been a popular choice in the clustering of wind speed. Each research study has its objectives and variables to deal with. Consequently, the variables play a significant role in deciding which method is to be used in the studies. The k-means method shortened the... [more]

The pretreatment of biomass through torrefaction is an effective means of improving the fuel quality of woody biomass and its suitability for use in existing facilities burning thermal coal. Densification of torrefied biomass produces a fuel of similar energy density, moisture content, and fixed carbon content to low-grade coals. Additionally, if the torrefaction conditions are optimized, the produced torrefied pellet will be resistant to weathering and biological degradation, allowing for outdoor storage and transport in a manner similar to coal. In untreated biomass, lignin is the primary binding agent for biomass pellets and is activated by the heat and pressures of the pellet extrusion process. The thermal degradation of lignin during torrefaction reduces its binding ability, resulting in pellets of low durability not suitable for transportation. The use of a binding agent can increase the durability of torrefied pellets/briquettes through a number of different binding mechanisms d... [more]

The IEC 61850 standard aims at digitization substations and provides interoperability between various Intelligent Electronic Device vendors. The digitization process is accompanied by several challenges related to data transmission on the ethernet network and the protection behavior under these conditions. Among the challenges, we can mention packet loss, delay, and duplicate frame, which occurs when the merging units (publisher) transmit the sampled values and, for some reason, these packets do not reach the subscriber or are duplicated. Nowadays, most Intelligent Electronic Device manufacturers block the protection function when some sampled value packets are corrupted. The effects of blocking protection when packet loss occurs under normal operating conditions do not cause significant problems. However, when a fault occurs, the corrupted packets can cause a delay in fault clearance, causing even more damage to the grid. The purpose of this article is to present the effects of corrup... [more]

Chemical looping gasification (CLG) is an effective coal utilization technology. In this work, the CLG of bituminite was investigated through fixed-bed batch experiments using NiFe2O4 oxygen carrier (OC) to achieve high-quality syngas. The changes in the phase of the oxygen carrier during the chemical looping reaction and the reaction mechanism were explored. The results show that elevated temperature and adding a fraction of steam facilitate the gasification reaction. Adding an appropriate amount of ZrO2 into the NiFe2O4 and modification with alkali metal can enhance the performance of the oxygen carrier. A carbon conversion of 95% and a syngas (CO and H2) selectivity of 86% were obtained under the optimized reaction conditions of 950 °C, an oxygen-carrier-to-bituminite (O/B) ratio of 7:3, a NiFe2O4/ZrO2 ratio of 7:3, and a steam rate of 0.08 mL/min. Modification of the NiFe2O4 by doping alkali metal can significantly facilitate the CLG process. Alkali lignin ash has a more pronounced... [more]

The European steel industry is experiencing new challenges related to the market situation and climate policy. Experience from the period of pandemic restrictions and the effects of Russia’s armed invasion of Ukraine has given many countries a basis for including steel along with raw materials (coke, iron ore, electricity) in economic security products (CRMA). Steel is needed for economic infrastructure and construction development as well as a material for other industries (without steel, factories will not produce cars, machinery, ships, washing machines, etc.). In 2022, steelmakers faced a deepening energy crisis and economic slowdown. The market situation prompted steelmakers to impose restrictions on production volumes (worldwide production fell by 4% compared to the previous year). Despite the difficult economic situation of the steel industry (production in EU countries fell by 11% in 2022 compared to the previous year), the EU is strengthening its industrial decarbonisation pol... [more]

The organic Rankine cycle (ORC) is an efficient technology for electricity generation from low- and medium-temperature heat sources. In this type of power cycle, the radial inflow turbine is the option usually selected for electricity generation. As a critical ORC component, turbine performance markedly affects the efficiency of the system. Therefore, the challenge is to model the behavior of the radial inflow turbine operating with organic fluids for heat recovery applications. In this context, various groups of fluids are highlighted in the scientific literature, including R-123, R-245fa, and R-141b, which are the fluids used in this research. Since little research has focused on the turbine efficiency effect on the power cycle design and analysis, this study presents an analysis of a radial inflow turbine based on a mathematical model of a one-dimensional design of the turbine. From this analysis, geometric, thermal, and operating parameters were determined, as well as volute, stato... [more]

Lignin is a polymer found in the cell walls of plants and is an important component of wood. Lignin-derived fuels have attracted attention as a means of producing biofuels from biomass in recent years. There are two basic methods for converting lignin into fuel: thermochemical and catalytic. Lignin-derived fuels have the potential to reduce dependency on fossil fuels and reduce greenhouse gas emissions. However, more research is needed to optimize the production of lignin-derived fuels and to determine their environmental impact. This review aims to evaluate the development of lignin-derived fuels from an economic and environmental point of view while presenting a broad perspective.

The increased voltage loading of transformers has led to research on improving transformers’ lifespans to meet demand. Insulation oil acts as cooling medium that can significantly affect the performance of a transformer. This paper discusses an experimental study on the influences of the doping of carbon nanotube (CNT) particles and magnetic fields on the electrical properties of mineral oil (MO). An analysis of electrical properties was conducted using AC breakdown tests, Tan Delta tests, Raman measurements, and simultaneous thermal analysis. Proper preparation was considered before starting the analysis of the electrical properties. The AC breakdown voltages before and after modification were measured. The experiment results indicated that the AC breakdown of mineral oil with a suitable amount of carbon nanotube particles (0.005 g/L) and a suitable magnetic field (0.45 T) gives the highest breakdown voltage. It was found that the proper treatment of nanofluid also greatly influences... [more]

This study analyses the expected utilization of an urban distribution grid under high penetration of photovoltaic and e-mobility with charging infrastructure on a residential level. The grid utilization and the corresponding power flow are evaluated, while varying the control strategies and photovoltaic installed capacity in different scenarios. Four scenarios are used to analyze the impact of e-mobility. The individual mobility demand is modelled based on the largest German studies on mobility “Mobilität in Deutschland”, which is carried out every 5 years. To estimate the ramp-up of photovoltaic generation, a potential analysis of the roof surfaces in the supply area is carried out via an evaluation of an open solar potential study. The photovoltaic feed-in time series is derived individually for each installed system in a resolution of 15 min. The residential consumption is estimated using historical smart meter data, which are collected in London between 2012 and 2014. For a realist... [more]

Hydrogen is attracting attention as a good energy-storage medium for renewable energy. Among hydrogen production technologies using renewable energy, water electrolysis is drawing attention as a key technology for green hydrogen production using renewable energy. In particular, polymeric electrolyte membrane water electrolysis systems have several advantages compared to other types of water electrolysis technologies, such as small size and mass, high efficiency, low operating temperature, and low power consumption. However, until now, proton-exchange membrane (PEM) water electrolysis systems have not been reliable. In this study, system failure diagnosis techniques were presented among the various methods for improving reliability. We developed PEM water electrolysis stack models and system models to predict the performance of the system and analyze the dynamic properties using MATLAB/Simulink® 2018a, which have been validated under various conditions. The developed dynamic characteris... [more]

Recently, with the large-scale integration of renewable energy sources into microgrid (μGs) power electronics, distributed energy systems have gained popularity. However, low inertia reduces system frequency stability and anti-disturbance capabilities, exposing power quality to intermittency and uncertainty in photovoltaics or wind turbines. To ensure system stability, the virtual inertia control (VIC) is presented. This paper proposes two solutions to overcome the low inertia problem and the surplus in capacities resulting from renewable energy sources. The first solution employs superconducting magnetic energy storage (SMES), which can be deemed as an efficient solution for damping the frequency oscillations. Therefore, in this work, SMES that is managed by a simple proportional-integral-derivative controller (PID) controller is utilized to overcome the low inertia. In the second solution, the hydrogen storage system is employed to maintain the stability of the microgrid by storing s... [more]

The continual generation and discharge of waste are currently considered two of the main environmental problems worldwide. There are several waste management options that can be applied, though anaerobic digestion (AD) process technology seems to be one of the best, most reliable, and feasible technological options that have attracted remarkable attention due to its benefits, including the generation of renewable energy in the form of biogas and biomethane. There is a large amount of literature available on AD; however, with the continuous, progressive, and innovative technological development and implementation, as well as the inclusion of increasingly complex systems, it is necessary to update current knowledge on AD process technologies, process variables and their role on AD performance, and the kinetic models that are most commonly used to describe the process-reaction kinetics. This paper, therefore, reviewed the AD process technologies for treating or processing organic biomass... [more]

An oil recovery technique, different composition waterflooding (DCW), dependent on the varying injected water composition has been the subject of various research work in the past decades. Research work has been carried out at the lab, well and field scale whereby the introduction of different injection water composition vis-a-vis the connate water is seen to bring about improvements in the oil recovery (improvements in both macroscopic and microscopic recoveries) based on the chemical reactions, while being sustainable from ease of implementation and reduced carbon footprint points of view. Although extensive research has been conducted, the main chemical mechanisms behind the oil recovery are not yet concluded upon. This research work performs a data analysis of the various experiments, identifies gaps in existing experimentation and proposes a comprehensive experimentation measurement reporting at the system, rock, brine and oil levels that leads to enhanced understanding of the und... [more]

This paper presents the results of a simulation study on the selection of an energy-optimal refrigeration system based on natural refrigerants as a function of outdoor climate parameters as a decision variable in a supermarket application. Simulations were conducted for twelve locations. Three new original refrigeration systems were presented: Cascade R744/R717 which is an advanced booster extended with an ammonia condensing system (CASC_1); Cascade R744/R717 with CO2 pump-fed MT and pressure-fed LT evaporators (CASC_2); and the R717 booster with CO2 pump-fed MT and LT evaporators (CB_NH3). As a reference system, a CO2 booster system with multi-ejectors and flooded evaporators (CB_EJ) was adopted. The CB_EJ system has been confirmed to be energy optimal for cold and temperate climates (Cfb, Dfa and cooler). In warm temperate climates (Csa, BSk, Cfa and similar), the energy consumption of CB_NH3 was the lowest. CASC_2 and CB_NH3 are energy optimal for hot climates (BWh, Af, Aw). The CB_... [more]

The article describes the impact of hydrogen-containing vegetable fuels consumption with modern injection apparatus. The fuel in question is B100 rapeseed oil ethyl ester. The process of atomizing fuel in the engine at high temperature and in a high pressure chamber plays an important role in the combustion processes in the CI engine. The elements responsible for supplying fuel to the engine’s combustion chamber are the injectors and the injection pump. The paper presents the construction and operation of modern injection pumps and fuel injectors, the methods of their diagnosis are discussed, the important role of precision, and the course of their wear phenomenon are indicated. The paper discusses the impact of hydrogen-containing “green” vegetable fuels on the durability and reliability of injection pumps and fuel injectors used in Common Rail systems. In addition, the tests on the operating parameters of the fuel injector and pump operating on conventional fuel and hydrogen-containi... [more]

With the development of the new energy vehicle market, the pricing of battery swapping stations (BSS) is becoming a concern. The pricing models of BSS usually only consider the interaction between the distribution system operator (DSO) and the BSS or between the BSS and electric vehicles (EVs). The impact of DSO and EVs on the pricing strategy of BSS has received less attention, which does not reflect the actual complex situation. Therefore, we propose a three-level BSS pricing method that includes market clearing and EV behaviors. Firstly, the distribution locational marginal price (DLMP) is modeled to determine the impact of the DSO on BSS. Secondly, the EV demand response is used to estimate the impact of EVs on BSS. Thirdly, to increase the adaptability of this model, an iteration algorithm with approximations and relaxations is used with mixed integer linear programming, effectively solving the pricing optimization. According to this optimization, it is evident that the BSS make d... [more]

In the authors’ previous research, a new method for partial discharge detection in the switchgear based on near-field detection was proposed. The content of this paper is the continuation of the authors’ previous research. In order to realize the reasonable layout of the near-field magnetic field probe for partial discharge detection in the switchgear, this paper simulates and analyzes the influence of the internal structure of the switchgear on the near-field propagation characteristics of the electromagnetic wave signal generated by partial discharge, and determines the installation position of the near-field probe in the switchgear. Firstly, the propagation characteristics of electromagnetic wave signals in the different media of the switchgear are analyzed, and the switchgear model is established. Then, based on the finite difference time domain method, the influence of different devices in the switchgear on the near-field propagation of the partial discharge electromagnetic wave s... [more]

Lightweight design is a common approach to reduce energy demand in the use stage of vehicles. The production of lightweight materials is usually associated with an increase in energy demand, so the environmental impacts of lightweight structures need to be assessed holistically using a life cycle assessment. To estimate the life cycle environmental impacts of a product in its developmental stage, for example, by life cycle engineering, future changes in relevant influencing factors must be considered. Prospective life cycle assessment provides methods for integrating future scenarios into life cycle assessment studies. However, approaches for integrating prospective life cycle assessment into product development are limited. The objective of this work is to provide the methodological foundation for integrating future scenarios of relevant influencing factors in the development of lightweight structures. The applicability of the novel methodology is demonstrated by a case study of a str... [more]

There is always a need to analyze current signals generated by various DC−DC converters. For example, to determine the current stress experienced by semiconductor devices and to evaluate active and reactive power consumption in converters. The study demonstrates that the shape of a current signal dictates the analytical expressions required to determine the average and RMS values of a signal as well as the RMS value of the ripple of that signal. The study also shows that current signals can be treated as composite waveforms comprising various combinations of trapezoidal, rectangular, and triangular pulses. The current literature lacks a unified approach to analyze current stresses in DC−DC converters. This study will propose a unified and generalized analytical technique that is applicable to any type of DC waveform that can be treated as a composite waveform made up of a combination of triangular, rectangular, or trapezoidal sections or sub-intervals. Furthermore, the rectangular and... [more]

Electric vehicles (EVs) have been garnering wide attention over conventional fossil fuel-based vehicles due to the serious concerns of environmental pollution and crude oil depletion. In this article, we have conducted a systematic literature survey to explore the battery raw material supply chain, material processing, and the economy behind the commodity price appreciation. We present significant areas of concern, including resource reserves, supply, demand, geographical distribution, battery reuse, and recycling industries. Furthermore, details of the battery supply chain and its associated steps are illustrated. The authors believe the presented study will be an information cornerstone in boosting manufacturing and understanding the key components and materials required to facilitate EV battery production. Further, this study discusses the major industries, and their policies and global market share in each material category.