The development of biogas upgrading technologies is now an essential issue in recovering fuel-grade methane. Nowadays, trends in biogas upgrading include investigations of low-cost and renewable materials as sorbents for biogas enrichment to produce biomethane. Therefore, in this work, wastewater anaerobic sludge stabilized with calcium oxide was used as the bio-waste sorbent to capture carbon dioxide from biogas, employing a fixed bed column. The biogas flow rate was the parameter considered for examining the breakthrough responses. It was observed that breakthrough time decreases with increasing biogas inflow rate from 570 ± 10 min at 5 mL/min to 120 ± 12 min at 35 mL/min. The maximum sorption capacity of 127.22 ± 1.5 mg CO2/g TS of sorbent was estimated at 15 mL/min. Biomethane concentration in biogas increased from 56.5 ± 1.7 v% in the raw biogas to 98.9 ± 0.2 v% with simultaneous low carbon dioxide content of 0.44 ± 0.2 v%. A strong positive correlation (R2 = 0.9919) between the s... [more]

The transportation sector produces a large portion of greenhouse gas emissions in the United States. Meeting ambitious reductions in greenhouse gasses requires large-scale adoption of battery electric vehicles and has led to several policies and laws aimed at incentivizing their sales. While electric vehicles comprise a small percentage of the overall fleets of vehicles, the expected production of electric vehicles is soon expected to be in the millions. This will create challenges in providing an adequate charging infrastructure, as well as the ensuing management of the overall electricity demand at the grid level. In this work, a novel smart-charging protocol for battery electric vehicle charging at workplace parking structures is proposed. The Octopus Charger-based Mixed Integer Linear Programming protocol allows octopus chargers (i.e., charging stations with multiple cables) to independently schedule charging periods for their assigned vehicles. The proposed protocols can manage a... [more]

The main aim of this study was to develop a method for assessing the level of robustness of timetabled transport performance in rail transport. When the railway lines are supplied by DC networks, lower voltages are observed, and consequently, current values are often ten times higher than in AC networks. This is an operational problem, as high currents make it easier to overload the supply network. Based on a literature review, the authors show that the problem of running railway traffic when the capacity of the power supply network is limited (by the size of the permitted currents) is not well studied. The authors propose a method based on the Markov approach supplemented by classical theoretical vehicle traffic dynamics to improve the operational robustness of the rail transport system using DC power supply system. Each train run was parameterised in such a way that it is possible to determine the state that the train is in during the run, the transitions between states, and the dete... [more]

In marine storage and transportation, the sloshing of liquid oxygen disturbs the thermodynamic equilibrium and induces stress on tank walls. Numerous problems are associated with the sloshing mechanism and demand a detailed investigation. In this study, a numerical model is developed by coupling the Eulerian framework and the algebraic interface area density (AIAD) method while considering the interphase drag force to investigate the thermal behavior of sloshing liquid oxygen. The effect of the sloshing frequency on the evaporation performance of liquid oxygen is studied. Moreover, anti-sloshing is conducted by employing a T-shaped baffle. The results show that the sloshing induced a vapor explosion phenomenon due to the invalidation of the surface impedance and thermal destratification to enhance free convection, resulting in rapid depressurization and increased evaporation loss. In addition, maximum evaporation loss occurred under the vapor−liquid coupling excitation condition. The T... [more]

Most countries, notably those that signed the Paris Climate Agreement, prioritize achieving the zero carbon or carbon neutrality aim. Unlike earlier studies, this one assesses the contribution of environmental policy, clean energy, green innovation, and renewable energy to the E7 economies’ achievement of carbon neutrality goals from 1990 to 2019. Findings emanating from the study show that the EKC hypothesis is valid in E7 countries. Implying that emissions in the E7 countries increased with the kick-off of development but declined later due to possible potent environmental regulatory policies put in place. Similarly, across all models, renewable energy (REN), green innovations (GINNO), environmental tax (ETAX), and technological innovations (TECH) were found to exert a negative and significant impact on carbon emissions in the E7 countries both in the short and long run. On the other hand, economic expansion (GDP) positively impacts environmental deterioration. Furthermore, the count... [more]

With China’s carbon peak and target proposed and the power system as an important source of carbon emissions, its carbon reduction issues are of great concern. However, the mismatch between power demand, resources, and generation facilities in different regions of China creates enormous carbon reduction pressures, especially in the region covered by China’s Northeast Power Grid (NE Grid). Therefore, in this study, a two-stage power optimization model considering Carbon Capture, Utilization, and Storage (CCUS) was established to optimize the national power generation and transmission in China from 2020 to 2060 first and then to optimize the regional road map of energy structure adjustment for China’s NE grid and its CO2 storage strategy. The first stage optimization results show that the national power interaction in China can make full use of the energy resource advantages of the NE grid, especially Jilin and Mengdong, delivering clean electricity to the North China grid as it reaches... [more]

The photovoltaic (PV) module is a key technological advancement in renewable energy. When the PV modules fail, the overall generating efficiency will decrease, and the power system’s operation will be influenced. Hence, detecting the fault type when the PV modules are failing becomes important. This study proposed a hybrid algorithm by combining the symmetrized dot pattern (SDP) with a convolutional neural network (CNN) for PV module fault recognition. Three common faults are discussed, including poor welding, breakage, and bypass diode failure. Moreover, a fault-free module was added to the experiment for comparison. First, a high-frequency square signal was imported into the PV module, and the original signal was captured by the NI PXI-5105 high-speed data acquisition (DAQ) card for the hardware architecture. Afterward, the signal was imported into the SDP for calculation to create a snowflake image as the image feature for fault diagnosis. Finally, the PV module fault recognition wa... [more]

This paper analyses the profile of individuals who decide to purchase a Sport Utility Vehicle (SUV) in a medium-sized isolated island system such as Tenerife Island. To achieve this objective, we used a survey conducted in 2017 to identify the characteristics of the individuals most likely to choose an SUV or another type of vehicle or be undecided. Subsequently, a discrete choice model was estimated to assess the probability that an individual chooses one of the three options as a function of their socio-economic characteristics, mobility routines, vehicle attributes and psychosocial traits. The results show the need to adopt energy policy measures related to vehicle choice, as they put the fulfilment of the decarbonization objectives for the energy transition in the Canary Islands at risk. Firstly, the authorities should carry out campaigns to achieve a more environmentally conscious behaviour by highlighting the higher consumption and emission levels of this type of vehicle. Secondl... [more]

Since accurate load forecasting plays an important role in the improvisation of buildings and as described in EU’s “Green Deal”, financial resources saved through improvisation of the efficiency of buildings with social importance such as hospitals, will be the funds to support their mission, the social impact of load forecasting is significant. In the present paper, eight different machine learning predictors will be examined for the short-term load forecasting of a hospital’s facility building. The challenge is to qualify the most suitable predictors for the abovementioned task, which is beneficial for an in-depth study on accurate predictors’ applications in Intelligent Energy Management Systems (IEMS). Three Artificial Neural Networks using a backpropagation algorithm, three Artificial Neural Networks using metaheuristic optimization algorithms for training, an Adaptive Neuro-Fuzzy Inference System (ANFIS), and a Long-Short Term Memory (LSTM) network were tested using timeseries ge... [more]

Today, science faces the problem of rethinking the incentives for the transition to sustainable development, including the expansion of the “green” economy, renewable energy and recycling of materials, in keeping with the fact that not all the goals set by global organizations in this area [...]

The present study is focused on the synthesis of zirconium dioxide (ZrO2) nanomaterials using the hydrothermal method assisted by microwave irradiation and solution combustion synthesis. Both synthesis techniques resulted in ZrO2 powders with a mixture of tetragonal and monoclinic phases. For microwave synthesis, a further calcination treatment at 800 °C for 15 min was carried out to produce nanopowders with a dominant monoclinic ZrO2 phase, as attested by X-ray diffraction (XRD) and Raman spectroscopy. The thermal behavior of the ZrO2 nanopowder was investigated by in situ XRD measurements. From the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images, the presence of near spherical nanoparticles was clear, and TEM confirmed the ZrO2 phases that comprised the calcinated nanopowders, which include a residual tetragonal phase. The optical properties of these ZrO2 nanopowders were assessed through photoluminescence (PL) and PL excitation (PLE) at room temp... [more]

Magnetic couplers (MC) are the key element that enable the power transfer over large air gaps in inductive power transfer (IPT) systems. Numerous designs with different coil and core arrangements have been proposed in the literature. However, the MC sizing process still involves several trial and error iterations to meet the desired specifications. This paper presents a profile methodology that uses fitting equations to extrapolate the coupling profiles and minimize the required number of finite element analysis (FEA) simulation results. A non-polarized circular coupler (FLCP) can be characterized as function of the air gap and lateral displacements using only six charging positions, whereas polarized couplers, such as the bipolar (BPP) or double-D pad (DDP), can be characterized using 18 charging positions. The methodology is validated experimentally using the FLCP, and an average error of 3% was found under different charging positions.

This paper deals with a method of quantifying the harmonic contribution of each harmonic source to system voltage distortion. Assessing the harmonic contribution of individual harmonic sources is essential for mitigating and managing system harmonic levels. Harmonic contributions can be evaluated using the principle of voltage superposition with equivalent voltage models for harmonic sources. In general, the parameters of equivalent voltage models are estimated numerically because it is difficult to measure them directly. In this paper, we present an effective method for estimating equivalent model parameters based on the random sample consensus (RANSAC) and recursive least square (RLS) with a variable forgetting factor. The procedure for quantifying harmonic contributions using equivalent models is also introduced. Additionally, we propose a network diagram of harmonic contributions that makes it easy to understand the harmonic distortion contributions of all harmonic sources.

Back-to-back current source converters play an important role in high power applications. However, this back-to-back converter system uses a larger number of power switches, which is associated with more cost and the power density of the converter system can be affected. To address this issue, in this paper, a novel nine-switch back-to-back current source converter is proposed. To realize proper modulation of this nine-switch converter system, the concept of ampere balance is revisited at first. Then, its relationship with the traditional modulation scheme is revealed. Moreover, based on the ampere balance, the real-time dwell time calculation method is developed, where the tracking of rectifier current and inverter current is taken into consideration simultaneously. Finally, simulation results verify the effectiveness of the proposed modulation scheme.

Electrified ports using medium-voltage DC (MVDC) renewable energy microgrids require current-fed dc/dc converters in application scenarios such as battery or ultracapacitor charging units and hydrogen production systems. This paper designs a three-level phase-shift full-bridge (TL-PSFB) converter that interfaces with the MVDC microgrid. Its operation in the current source mode requires a wide output voltage range and small output current ripple. Firstly, the dual-output TL-PSFB topology is introduced, and the principle of phase-shift pulse width modulation (PS-PWM) is presented. Secondly, the principle of the traditional constant-conduction-duty-cycle (CCDC) strategy is analyzed. Then, a minimum-output-current-ripple (MOCR) strategy is proposed by analyzing the relationship between output current ripple, conducting-duty cycle, and phase-shift duty cycle, and a constant current control combined with the MOCR strategy is designed. The output current ripple of the MOCR strategy is smaller... [more]

The development of environmentally friendly technologies, including additive technologies, contributes to the formation of sustainable production in city multifloor manufacturing clusters (CMFMCs). This paper discusses an approach to the implementation of energy-intensive technological processes in such clusters using examples of the manufacturing of ceramic and metal−ceramic products. The manufacturing of ceramic and metal−ceramic products in high-temperature furnaces is associated with an increased electricity consumption. The use of modern ceramic micro- and nanopowders makes it possible to switch to more energy-saving technologies by reducing the sintering temperature and shortening the technological cycle. This requires the use of additional activating and inhibiting additives in the initial powder mixtures to obtain products with the necessary physical and mechanical properties. The purpose of this paper is to present a model and indicators to assess the energy efficiency of the... [more]

This paper presents a single-phase and three-phase compatible isolated on-board charger for electric vehicles. The charger is compatible with the single-phase and three-phase AC voltage input and is composed of two-stage circuits. Based on the three-phase six-switch power factor correction (PFC) circuit, by switching on and off, the front stage is transformed into a cascade topology of a totem-pole PFC circuit and boost circuit. The rear stage is a full-bridge LLC resonant converter. In the single-phase or three-phase working mode, the front-stage control strategy is a double closed-loop control. The current inner loop controller is improved for the three-phase six-switch PFC circuit. The PI controller and repetitive controller are connected in parallel to form the current inner loop compound controller, which can effectively reduce the total harmonic distortion of the input current. By using simulation software MATLAB/Simulink, the circuit model was built. The simulation results verif... [more]

The G-7 economies comprise a few of the global, mainly economically developed countries. On the other hand, in conjunction with these high economic development performances, the ecological behaviors in G-7 anions have concurrently provoked to elevate deep apprehensions among the stakeholders. Therefore, the present research aims to empirically investigate the environmental influences of nuclear energy, industrialization, fossil fuel energy, and foreign direct investment (FDI) in the G-7 nations between 1991 and 2018. After checking the cross-sectional dependency, this study employed the first-generation ((full modified ordinary least square (FMOLS), dynamic ordinary least square (DOLS)) and second-generation (Driscoll and Kraay (D-K), feasible generalized least square (FGLS)) approaches for robust and reliable findings. The findings explore that nuclear energy production is ineffective in curbing the figure of ecological footprints in the long-run. Moreover, the industrialization proce... [more]

In the present scenario, the integration of distributed generation (DG) sources into the grid is inevitably required for meeting demand and ameliorating the power quality. High integration levels can form unintentional islands which need to be recognized to provide safety. In this context, 64 passive parameters have been tested in the MATLAB/SIMULINK environment for extensive islanding and non-islanding switching events on standard IEEE 13, 34, and 37 bus distribution test feeders (DTFs) integrated with photovoltaic (PV) inverter-based and rotating-based (induction generator) DG sources at multiple locations. In order to obtain effective passive parameters, a modified averaging approach-based computation (MAAC) methodology has been proposed. The proposed methodology computes the averaged islanding and non-islanding values of all ‘64’ parameters and prioritizes them accordingly by threshold value comparison. Additionally, it lessens the computational burden. The parameter threshold sett... [more]

This paper describes the effect of the incidence angle of the bucket on the performance of the axial turbine stage. The off-design operating conditions of the turbine stage result in a change in the velocity diagrams. This results in a positive or negative incidence. One of the basic objectives in turbine stage design is to estimate the flow behaviour of the turbine stage during off-design operation as accurately as possible and to quantify the corresponding decrease in efficiency. The available loss prediction models allow the estimation of the loss distribution when the incidence angle changes in the preliminary design phase. However, the incidence angle is actually affected by the velocity of circulation, which changes the input velocity vector (induced incidence). Thus, the blade row angle of attack is different from the angle based on the velocity diagram calculations. The result of our paper is a relation for estimating the angular difference of the input flow angle to the bucket... [more]

Modeling IT equipment is of critical importance for the simulations of flow and thermal structures in air cooled data centers. Turbulent flow undergoes a significant pressure drop through the server due to the energy losses originating from the internal components. Therefore, there is an urgent need to develop a fast and an accurate method for the calculation of pressure losses inside server components for data center applications. In this study, high resolution numerical simulations were performed on an OCP (Open Compute Project) server under various inlet flow rates for inactive and active conditions. Meanwhile, one key challenge of modeling complete geometry of the server results from using an intense mesh even for a single server. To address this challenge, the server was modeled as a porous zone to mimic inertia and viscous resistance in a realistic way. Comparison of the results of porous and complete models showed that the proposed model could calculate pressure drop accurately... [more]

As a kind of clean energy, shale gas has attracted much attention, and the exploration and development potential of shale gas resources in the middle and deep layers is huge. However, due to the changeable geological and burial conditions, complex geophysical responses are formed. Therefore, studying the characteristics of reservoir rock minerals and their complex resistivity response characteristics is helpful to deepen the understanding of the electrical characteristics of shale gas reservoirs and provide theoretical basis and physical basis for exploration and development. The study is based on shale samples from the Longmaxi Formation to the Wufeng Formation of a shale gas well in southern Sichuan, China, and the mineral composition and complex resistivity of shale are measured. Through inversion of complex resistivity model, four IP parameters, namely zero-frequency resistivity, polarizability, time constant and frequency correlation coefficient, are extracted, and the relationshi... [more]

An energy storage system based on a Proton Exchange Membrane (PEM) electrolyzer system, which could be managed by a nanoGrid for Home Applications (nGfHA), is able to convert the surplus of electric energy produced by renewable sources into hydrogen, which can be stored in pressurized tanks. The PEM electrolyzer system must be able to operate at variable feeding power for converting all the surplus of renewable electric energy into hydrogen in reasonable time. In this article, the dynamic electric simulation model of a PEM electrolyzer system with its pressurized hydrogen tanks is developed in a proper calculation environment. Through the calculation code, the stack voltage and current peaks to a supply power variation from the minimum value (about 56 W) to the maximum value (about 440 W) are controlled and zeroed to preserve the stack, the best range of the operating stack current is evaluated, and hydrogen production is monitored.

Bidirectional DC/DC converters are widely adopted in new energy power generation systems. Because of the low conversion efficiency and non-isolation for conventional, bidirectional DC/DC converters in the photovoltaic energy storage complementary system, this paper proposes a bidirectional isolation LLC converter topology, with compensating inductance for the energy storage system; it has excellent characteristics, such as wide input voltage range and soft switching in full-load range. First, an AC equivalent model based on the fundamental wave equivalent method is established to derive the voltage gain. Meanwhile, a small signal model is also built to design a reasonably closed-looped controller. Finally, the improved bidirectional LLC resonant converter is applied to the photovoltaic energy storage complementary system. The correctness and feasibility for the bidirectional LLC converter topology under the proposed charging and discharging control strategy of the DC bus are verified b... [more]

Transformer failures have a significant cost impact on the operation of an electrical network. In many utilities, transformers have been operating for many years past their expected usable life. As power demand has surged, transformers in some areas are being loaded beyond their rated capacity to meet the demand. One of the vital components in a transformer is the on-load tap changer (OLTC), which regulates the voltage in the distribution network. This study aims to review several condition-monitoring techniques (online and offline) that can monitor the health of the OLTC and assure the safety of the transformer’s OLTC from irreparable damage by detecting the defect at an earlier stage, which is preceded by the specification of typical faults. This paper also discussed the common faults of the OLTC and the root causes of these faults. The OLTC is prone to mechanical faults due to its frequently changing mechanism in the tap operation. The OLTC are also prone to oil as well as thermal f... [more]