This study proposes a broken rotor bar (BRB) fault diagnosis method for an induction motor using the sum of the weighted Fourier series coefficients squares of a complex current as a diagnosis signal. First, the sum of the squares of the Fourier series coefficients confirms the very narrow band-pass filter characteristics to derive a specific frequency component. This assists us in obtaining a BRB fault diagnosis signal that exists in a limited frequency range. Second, the magnitude of the Fourier series coefficients of the BRB fault signal is proportional to the slip frequency and load condition. A weighting factor is proposed to render the BRB fault signal irrelevant to the slip frequency and load condition. Consequently, the proposed fault diagnosis can be conducted without the slip frequency information or searching for the maximum coefficient component. Finally, the proposed fault diagnosis method is validated through experiments using a 55 kW induction motor with and without a BR... [more]

Mini-channel heatsinks have proven useful in removing high heat fluxes from microelectronic devices. However, further miniaturization of electronic devices requires significant enhancement in the mini-channel heatsinks’ thermohydraulic characteristics, which depend greatly on the coolant and geometrical configuration of the channel. Therefore, the current study explores the potential of mini-channel heatsinks’ using different coolants (water, nanofluid and supercritical carbon dioxide) and various channel configurations. The effect of various channel configurations on the thermohydraulic characteristics of the mini-channel heat sinks is evaluated numerically for different coolants employing three flow rates (17 g/s, 34 g/s and 50 g/s). Hence, the effects of fin height, spacing and thickness, and mass flow rate on the overall heat transfer coefficient (CHT) and pressure drop (ΔP) are reported for the abovementioned coolants. It is found that increasing the mass flow rate increases both... [more]

Photovoltaic solar energy is booming due to the continuous improvement in photovoltaic panel efficiency along with a downward trend in production costs. In addition, the European Union is committed to easing the implementation of renewable energy in many companies in order to obtain funding to install their own panels. Nonetheless, the nature of solar energy is intermittent and uncontrollable. This leads us to an uncertain scenario which may cause instability in photovoltaic systems. This research addresses this problem by implementing intelligent models to predict the production of solar energy. Real data from a solar farm in Scotland was utilized in this study. Finally, the models were able to accurately predict the energy to be produced in the next hour using historical information as predictor variables.

Different types of deep-hole blasting techniques are needed to solve gas drainage problems in complex and variable cases. Blasting parameters suitable for mines are selected based on the relationship between blast stress field changes and gas flow combined with field application and numerical simulation. The Datong Mine was a background to study the blast crush zone and drainage influence range following deep-hole blasting with holes laid in coal seams, which resulted in a 24% increase in gas flow in the drainage hole 6 m from the blast hole. In response to the difficulty of forming blast holes in the soft coal seam of the Yuyang Mine, drilling and blasting in the floor rock stratum adjacent to the coal seam increased the gas flow in the drainage holes by 125%. When applying the deep-hole technique with holes crossing multi-seams for gas drainage in Shiping Mine, the volume of gas drainage increases significantly with increased effective stress in the drainage hole. For example, when t... [more]

Existing building carbon emissions contribute to global climate change significantly. Various Green Building Rating Systems (GBRS) have considered low-carbon requirements to regulate the emissions. Low-carbon retrofitting is an important way to reduce existing building CO2 emissions. However, low-carbon retrofitting of existing public buildings is not sufficient and systematic, and there is a lack of research on low-carbon retrofitting from the perspective of GBRS. The purpose of this study is to propose a carbon emission control framework for existing public buildings based on GBRS analysis and guide the low-carbon retrofitting. This study makes comparisons among the Leadership in Energy and Environmental Design (LEED), Building Research Establishment Environmental Assessment Method (BREEAM), Green Mark (GM), and Assessment Standard for Green Retrofitting of Existing Buildings (ASGREB). A low-carbon retrofit pathway for existing public buildings is proposed from the GBRS research for... [more]

In this study, the impact of hydrogen concentration on deflagration to detonation transition (DDT) and detonation diffraction mechanisms was investigated. The combustion chamber was an ENACCEF facility, with nine obstacles at a blockage ratio of 0.63 and three mixtures with hydrogen concentrations of 13%, 20%, and 30%. Detonation diffraction mechanisms were numerically investigated by a density-based solver of OpenFOAM CFD toolbox named ddtFoam. In this simulation, for the low Mach numbers, the pddtFoam solver was applied, and for high speeds, the pddtFoam solver switched to the ddtFoam solver to simulate flame propagation without resolving all microscopic details in the flow in the CFD grid, and to provide a basis for simulating flame acceleration (FA) and the onset of detonation in large three-dimensional geometries. The results showed that, for the lean H2−air mixture with 13% hydrogen concentration, intense interaction between propagating flame and turbulent flow led to a rapid tra... [more]

The trend regarding providing more distributed solutions compared to a fully centralized operation has increased the research activities conducted on the improvement of active regional communities in the power system operation in the last decades. In this study, an energy management-oriented decision-making mechanism for residential end-users based local community is proposed in a mixed-integer linear programming context. The proposed concept normally includes inflexible resiliency-sensitive load−demand activated as flexible during abnormal operating conditions, fuel cell electric vehicles (FCEVs) fed via the hydrogen provided by an electrolyzer unit connected to the residential community and capable of acting in vehicle-to-grid (V2G) mode, common energy storage and photovoltaic (PV) based distributed generation units and dispersed PV based generating options at the end-user premises. The combination of the hydrogen−electricity chain with the V2G capability of FCEVs and the resiliency-... [more]

An experimental study was carried out on the ignition characteristics of the HAN/(Emim)(EtSO4) (hydroxylammonium nitrate and 1-ethyl-3-methyl-imidazolium ethyl sulfate) dual-mode ionic liquid monopropellant in chemical propulsion mode in model thrusters. Firstly, a model thruster with a detachable convergent nozzle was designed and fabricated. Secondly, catalytic ignition experiments at different flow rates were carried out in atmosphere and in high chamber pressure environment, respectively, using a model thruster, with and without the convergent nozzle. During the catalytic ignition process, measurement methods such as thermocouple, pressure sensor, and flue gas analyzer were employed to obtain the temperature at different depths of the catalytic bed, the pressure of the combustion chamber, and the concentration variations of gaseous products CO, CO2, CH4, SO2, NO, and NO2. Then the three characteristic stages of water evaporation, HAN decomposition, and (Emim)(EtSO4) combustion were... [more]

The growing economic efforts and investment for the production of green hydrogen make the definition of new competitive and environmentally friendly storage methods. This article deals with the proposal of gas hydrate production with binary or ternary H2-based gaseous mixtures for hydrogen storage. In the text, the physical and chemical elements necessary to confirm the technical feasibility of the process are given. The proposed solution is also compared with the traditional ones in terms of energy costs, energy density, environmental sustainability, safety, ease of transport, future perspectives, and innovation level.

Regional integrated energy systems (IESs) have emerged to satisfy the increasing diversified energy demand in Tibet. However, limited resource allocation of a given IES can occur because of the uncertainty in the output and prediction error of distributed renewable energy (DRE). A distributionally robust optimization (DRO) model was proposed for the joint operation of multiple regional IESs, and multi-energy sharing and multi-energy flow coupling of electricity, heat, and oxygen were considered. The probability distribution of the DRE output was described using 1− norm and ∞− norm constraints, and the minimum operating cost under adverse scenarios was determined through DRO. Furthermore, on the premise of ensuring cluster profit, a pricing mechanism of the energy supply within the cluster was proposed. Finally, a typical model involving eight cases was established and analyzed. The results revealed that multi-energy sharing and multi-energy flow coupling improved the economy of IES clu... [more]

The work delineated in this paper deals with the reduced sensor-based operation of PV-DSTATCOM (Photovoltaic distribution static compensator) focusing on the voltage source inverter (VSI) switch current limiting control. In this study, the soft computing technique of PV-DSTATCOM control based on the variable leaky least mean square (VLLMS) algorithm is modified to incorporate both reduced sensor and switch current limiting schemes. DSTATCOM is predominantly introduced to improve current related power quality issues by providing non-real power (i.e., the reactive and harmonic component) of the load demand. However, during uncertain increase in the non-real power requirement at the load end due to sudden change in the load demand or any other transient conditions, the non-real current injected by the DSTATCOM may increase to a level which is beyond the current handling capacity of the DSTATCOM switches. As a consequence, the switches may become permanently damaged and, subsequently, the... [more]

is a commercially exploitable source of bioactive compounds and biofuels with potential applications in microalgae-based industries. Despite this, little taxonomical information is available. Therefore, proper identification and characterization are needed for the sustainable utilization of isolated microalgae. In this study, an axenically isolated unicellular green alga from the Geumgang Estuary, Korea was investigated for its morphological, molecular, and biochemical characteristics. The morphological characteristics were typical of G. emersonii. Molecular phylogenetic analysis of the 18S rDNA sequence verified that the isolate belonged to G. emersonii and was subsequently named G. emersonii GEGS21. It was isolated from brackish water, and its optimal growth temperature, salinity, and light intensity were at 28−32 °C, 0 M NaCl, and 130−160 µmol m−2 s−1, respectively. The strain thrived over a range of temperatures (5−40 °C) and withstood up to 0.5 M NaCl. The isolate was rich in omeg... [more]

This paper benchmarks the performance of three practical electric vehicle (EV) charging scheduling methods relative to uncontrolled charging (UNC) in low-voltage (LV) distribution grids. The charging methods compared are the voltage droop method (VDM), price-signal-based method (PSM) and average rate method (ARM). Trade-offs associated with the grid performance, charging demand fulfilment and economic benefits are explored for three different grid types and four increasing levels of EV penetration for summer and winter. This study was carried out using grid simulations of six existing Dutch distribution grids, and the EV charging demand was generated based on 1.5 M EV charging sessions; therefore, the findings of this research are relevant for actual case studies. The results suggest that the PSM can be a preferred strategy for achieving a charging cost reduction of 6−11% when the grid performance is not a bottleneck for the given EV penetration. However, it can lead to an increased pe... [more]

The elevated energy demand and high dependency on fossil fuels have directed researchers’ attention to promoting and advancing hydraulic fracturing (HF) operations for a sustainable energy future. Even though previous studies have demonstrated that the proppant suspension and positioning in slickwater play a vital role during the shut-in stage of the HF operations, minimal experimental work has been conducted on the fundamental proppant−proppant interaction mechanisms, especially a complete mapping of the interactions. This study utilizes high-speed imaging to provide a 2D space- and time-resolved investigation of two-particle (proppant models: 2 mm Ø, 2.6 g·cm−3) interactions during gravitational settling in different initial spatial configurations and rheological properties. The mapping facilitates the identification of various interaction regimes and newly observed particle trajectories. Pure water results at a settling particle Reynolds number (Rep) ~ 470 show an unstable particle−... [more]

In this article, an unsupervised learning method is presented with the objective of modeling, in real-time, the main operating modes (OM) of distribution transformers. This model is then used to assess the operational condition through use of two tools: the operation map and the health index. This approach allows, mainly, for a reduction in the need for the interpretation of results by specialists. The method used the concepts of k-nearest neighbors (k-NN) and Gaussian mixture model (GMM) clustering to identify and update the main OMs and characterize these through operating mode clusters (OMC). The evaluation of the method was performed using data from a case study of almost one year in duration, along with five in-service distribution transformers. The model was able to synthesize 11 magnitudes measured directly in the transformer into two latent variables using the principal component analysis technique, while preserving on average more than 86% of the information present. The opera... [more]

Multilevel inverters (MLI) consist of a wide range of power converters. They have many designs and have been introduced with different circuit topologies such as neutral point clamped, diode clamped, cascaded H-bridges, and flying capacitors. Some of these MLIs have disadvantages, including design complexity, size, and losses due to the large number of switching devices required when they produce many output voltage levels. They are also bulky in size and may require several DC power sources. This paper presents a review of the various topologies of single-phase T-Type MLIs (T-MLIs). These MLIs are used to convert DC power from renewable energy sources (RES)” into AC with a near-sine waveform and low total harmonic distortion (THD). Simple and complex MLI designs are discussed. The major types of modulation techniques are discussed, including sinusoidal pulse width modulation (SPWM), selective harmonic elimination (SHE), and preprogrammed PWM. Various methods of output voltage control... [more]

A comprehensive review of modelling techniques for the flow-induced vibration (FIV) of bluff bodies is presented. This phenomenology involves bidirectional fluid−structure interaction (FSI) coupled with non-linear dynamics. In addition to experimental investigations of this phenomenon in wind tunnels and water channels, a number of modelling methodologies have become important in the study of various aspects of the FIV response of bluff bodies. This paper reviews three different approaches for the modelling of FIV phenomenology. Firstly, we consider the mathematical (semi-analytical) modelling of various types of FIV responses: namely, vortex-induced vibration (VIV), galloping, and combined VIV-galloping. Secondly, the conventional numerical modelling of FIV phenomenology involving various computational fluid dynamics (CFD) methodologies is described, namely: direct numerical simulation (DNS), large-eddy simulation (LES), detached-eddy simulation (DES), and Reynolds-averaged Navier−Sto... [more]

Iron−chromium redox flow batteries (ICRFB) possess the advantage of low raw material cost, intrinsic safety, long charge−discharge cycle life, good life-cycle economy, and environmental friendliness, which has attracted attention from academia and industry over time. The proton exchange membrane (PEM) is an important part of the ICRFB system, impacting the efficiency and lifetime of the battery. Currently, the most widely used PEMs in the market are per-fluorinated sulfonic acid (PFSA) membranes, which possess high electrolyte stability and achieve the separation of positive and negative electrolytes. In addition, the complex preparation process and extremely high market price limited the usage of PEM in ICRFB. In this paper, we developed a remanufactured membrane (RM) strategy from waste PFSA resins. The RM has higher electrical conductivity and better proton transport ability than the commodity membrane N212. In the cell performance test, the RM exhibits similar coulombic efficiency... [more]

Environmental taxes, including energy taxes, are applied in all EU Member States. They are considered important instruments in the implementation of the EU energy and climate policies. The main purpose of the research presented in this article is to identify trends in the EU Member States in shaping environmental tax revenues, with particular emphasis on their most important group, i.e., energy taxes. The researchers sought answers to the research question regarding the existence of converging trends in this respect. The “letter values” method was used in the research procedure, which is an extension of the box-plots method. The analysis covered 27 EU Member States. The data used in the research came from the Eurostat database (2009−2020). As a result of the research, it was found that in the EU as a whole, there is a slight downward trend in the share of environmental tax revenues in GDP and the share of environmental tax revenues in total tax revenues, while the share of energy tax r... [more]

With the development of electric vehicles, more attention has been paid to the role of the driving cycle in vehicle performance testing. At present, the K-means algorithm is often used in the development of driving cycles. However, it is sensitive to the outlier points and also difficult to determine the K value. To solve this problem, the hierarchical cluster method is applied in this study. First, the real-world driving data are collected and denoised through wavelet domain denoising. Then, the data are divided into micro-trips and the characteristic parameters are extracted. The hierarchical cluster method is adopted to classify the micro-trips into different categories. An appropriate number of micro-trips are selected from each group in proportion to each category to assemble the driving cycle. Finally, both the economic simulation and the statistical analysis prove the accuracy of the generated driving cycle and the feasibility of the development method proposed in this paper.

Nitrogen foam is expected to be an effective method to extinguish large-scale fires and suppress explosions. The key to its foaming process is that gas nitrogen (N2) and a foam solution are mixed uniformly in a foam generator. Moreover, liquid nitrogen (LN2) has been proposed as a source of gas nitrogen to generate nitrogen foam in previous experimental works. In this paper, the flow and heat transfer characteristics between liquid nitrogen and the foam solution are explored by numerical methods, which are then utilized to optimize the parameters of the foam generator. It is found that the flow pattern of the foam generator with a cone spoiler is a stratified flow by establishing the mixture and Lee’s evaporation-condensation model in ANSYS Fluent. Moreover, the spoiler in the foam generator plays a crucial role in breaking LN2 into droplets and increasing the contact area between phases, and a distance of 10 mm from the inlets to the spoiler is recommended. From previous results, an u... [more]

Changes observed in the Polish energy sector, including the demand for and use of heat, require the introduction of appropriate measures aimed at diversifying the available heat sources, increasing the share of renewable and low-emission sources in heat production, and increasing waste heat recovery and its usage. There is an increasing emphasis on issues such as reducing the carbon footprint, reducing pollution, reducing the use of raw materials, reducing waste heat, and improving the energy efficiency of businesses. Increasingly, the question arises—what technologies can be used as an answer to the identified problems and needs. The solution proposed in this publication to support these needs is the use of mobilized thermal energy storage (M-TES) technology. The use of this technology has great potential, but also involves a number of conditions that need to be taken into account when undertaking the design, construction, and use of this type of technology. The primary purpose of thi... [more]

The change in the European Union’s policy related to the energy transformation of Europe and the departure from fossil energy resources may contribute to the accelerated closure of many coal mines. Therefore, it is necessary to solve the problem of surface subsidence after the end of underground mining and the related suitability of post-mining areas for the re-use of the so-called problem of the reclamation of post-mining areas. In the case of areas suitable for re-use, it is necessary to determine the value of the final subsidence. It is also important to specify the time after which mining influences will no longer have a significant impact on the surface infrastructure and the environment. Analyses of the observed subsidence after the end of the mining operation indicate that this process may last from several months to several dozens or even several hundreds of years. It depends on the individual characteristics of the mining area, including the depth of exploitation, mining syste... [more]

Performed gels are widely used in fields to support profile modification and Enhance Oil Recovery. Previous studies of profile modification of performed gels mainly used the index of pressure, resistance factor, or residual resistance factor to represent their ability. However, there is a lack of methods available to directly study their modification ability. In this article, the preformed gels with fluorescence properties, CQDs@PPG, would provide a new way to explore the profile modification of preformed gels. This paper uses poly (acrylamide, sodium p-styrene sulfonate), carbon quantum dots, and N,N-methylenebisacrylamide to prepare the CQDs@PPG via inverse emulsion polymerization. The morphology, size distribution, structure, fluorescence characteristics, surface potential thermal stability, viscosity changes, and viscoelastic properties of CQDs@PPG were analyzed. Moreover, the fluorescence properties of CQDs@PPG under different temperature, salinity, and pH were examined. Results i... [more]

Due to a large amount of particulate matter in industrial flue gas, the formation of particulate deposits on the flue wall will increase the instability of equipment operation, which needs to be solved urgently. In this paper, a numerical investigation on the characteristics of particulate deposition and removal in the furnace flue was carried out for waste heat and energy recovery. This research adopted a comprehensive fouling model combined with the discrete phase model (DPM) which was performed by the CFD framework and extended by user-defined functions (UDFs). Firstly, the particulate deposition and removal algorithms were proposed to develop the judgment criterion of particle fouling based on the Grant and Tabakoff particle−wall rebound model and the Johnson−Kendall−Roberts (JKR) theory. This model not only considered the particles transport, sticking, rebound, and removal behaviors, but also analyzed the deposition occurring through the multiple impactions of particles with the f... [more]