Historically, the power system has relied on synchronous generators (SGs) to provide inertia and maintain grid stability. However, because of the increased integration of power-electronics-interfaced renewable energy sources, the grid’s stability has been challenged in the last decade due to a lack of inertia. Currently, the system predominantly uses grid-following (GFL) converters, built on the assumption that inertial sources regulate the system stability. Such an assumption does not hold for the low-inertia grids of the future. Grid-forming (GFM) converters, which mimic the traditional synchronous machinery’s functionalities, have been identified as a potential solution to support the low-inertia grids. The performance analysis of GFM converters for small-signal instability can be found in the literature, but large-signal instability is still an open research question. Moreover, various topologies and configurations of GFM converters have been proposed. Still, no comparative study c... [more]

The social acceptability of wind farms has been researched for several decades now, with the first research tracing back to the 1980s. This paper aims to deliver a literature review within the structural framework proposed by the paper of variables influencing the acceptability of wind farms. The large amount of research published on the social acceptability of wind farms requires an effort to identify and categorise variables to deliver a holistic understanding of opposition and support to wind energy. We classify the variables into three main categories: first, ‘psychological variables’, including perceived benefits and costs, emotions, and attitudes; second, ‘contextual variables’, including community energy schemes and media influence; and finally, third, ‘personal resources’, including income or wealth, place of residence, and relevant knowledge in relation to the wind farm. In agreement with other scholars, we argue that NIMBYism (not in my backyard) is an outdated and simplistic... [more]

The residual biogas potential (RBP) test is a procedure to ensure the anaerobic digestion process performance and digestate stability. Standard protocols for RBP require a significant time for sample preparation, characterisation and testing of the rig setup followed by batch experiments of a minimum of 28 days. To reduce the experimental time to obtain the RBP result, four biogas kinetic models were evaluated for their strength of fit for biogas production data from RBP tests. It was found that the pseudo-parallel first-order model and the first-order autoregressive (AR (1)) model provide a high strength of fit and can predict the RBP result with good accuracy (absolute percentage errors < 10%) using experimental biogas production data of 15 days. Multivariate regression with decision trees (DTs) was adopted in this study to predict model parameters for the AR (1) model from substrate physicochemical parameters. The mean absolute percentage error (MAPE) of the predicted AR (1) mode... [more]

Energy systems have played an essential role in the history of human civilization [...]

Anthracite in a specific area of Shanxi Province is the subject of this essay’s research. In the creep studies, different porosity intervals and pore water pressures were employed to evaluate the mechanical properties of creep under various test paths. The conventional Burges model was coupled in series with the nonlinear viscous elements and plastic elements. The key parameters in the equation are fitted, and a creep model is created to describe the nonlinear viscosity-elastic-plastic characteristics of coal under the influence of pore water pressure with varying porosities. The creep tests used varied porosity intervals, pore water pressures, and test paths to study the mechanical properties of creep. The conventional Burges model was coupled in series with the nonlinear viscous element and plastic element. To represent the nonlinear viscosity-elastic-plastic properties of coal under the effect of pore water pressure with variable porosities, the main parameters in the equation are f... [more]

Greenhouse gases, the main cause of global warming, are generated largely in the energy sector. As the need for technology that has reduced greenhouse gas emissions while producing energy is on an increase, CCU technology, which uses CO2 to produce CH4 (SNG energy, synthetic natural gas), is drawing attention. Thus, the reaction for converting CO2 to CH4 at a specific temperature using a catalyst is CO2 methanation. The field of CO2 methanation has been actively studied, and many studies have been conducted to enhance the activity of the catalysts. However, there is a lack of research on the variables that may appear when CO2 methanation is attempted using emissions containing CO2 generated from industrial fields and bio-plants. According to previous studies, it is reported that realistic feed gases from gasification or biomass plants contain a significant amount of CO. this study is a follow-up study focused on the application of CO2 methanation in various real processes. In the CO2 m... [more]

Traditional microchannel needs to face the flow-reversal difficulty in high heat fluxes due to limited space. It results in large pressure and temperature fluctuation. Porous microchannels arouse more interest to provide a new solution to this problem. Flow boiling experiments in porous microchannels with PFA were investigated. Porous microchannels were sintered by 10 μm (or 30 μm) spherical copper particles with pore-forming agent (Na2CO3, 60−90 μm). Porous microchannels were composed of 23 parallel porous microchannels with 600 μm in width and 1200 μm in depth.The addition of PFA (pore-forming agent) could increase the sample porosity. For Q10 series, sample porosities increase from 20.4% to 52.9% with the PFA percentage change from 0% to 40%, while for the Q30 series they increase from 26.6% to 47.5%. Experimental results showed the boiling heat transfer coefficient (HTC) reached the maximum at the moderate porosity for both Q10 and Q30 series. Too large or too small porosity would... [more]

Mechanical loads considerably impact wind turbine lifetime, and a reduction in this load is crucial while designing a controller for maximum power extraction at below-rated speed (region II). A trade-off between maximum energy extraction and minimum load on the drive train shaft is a big challenge. Some conventional controllers extract the maximum power with a cost of high fluctuations in the generator torque and transient load. Therefore, to overcome the above issues, this work proposes four different integral synergetic control schemes for a wind turbine at region II using a two-mass model with a wind speed estimator. In addition, the proposed controllers have been developed to enhance the maximum power extraction from the wind whilst reducing the control input and drive train oscillations. Moreover, a terminal manifold has been considered to improve the finite time convergence rate. The effectiveness of the proposed controllers is validated through a 600 kW Fatigue, Aerodynamics, St... [more]

The creep damage behavior of rocks is very important for evaluating the stability and safety of key rock engineering. Based on the Lianhua Tunnel Project in China, this paper aims to study the creep damage mechanics, the influencing factors and the creep constitutive models of sandy shale. In order to achieve these goals, a uniaxial compressive strength test and a creep test under different moisture contents and load levels were carried out. According to the test results, the creep parameters (elastic coefficients E1 and E2 and viscosity coefficients η1 and η2) of the Burgers Model were achieved, and the relationship between the creep parameters and moisture content, ω, was established accordingly (E1 = f(ω), E2 = f(ω), η1 = f(ω), η2 = f(ω)). A fully weathered sandy-shale creep constitutive model considering moisture content was finally obtained. Test results showed that creep deformation increases with any increase in load level or moisture content, and the influence of moisture conte... [more]

Carbon capture, utilization, and storage (CCUS) refers to technologies that capture carbon dioxide (CO2) emissions from sources such as power plants, industrial facilities, and transportation, and either store it underground or use it for beneficial purposes. CCUS can play a role in reducing greenhouse gas emissions and mitigating climate change, as CO2 is a major contributor to global warming. In the Baltic Sea region countries (BSR), patent searches from 2000 to 2020 reveal that CCUS technologies are focused on CO2 storage, monitoring, utilization, and transport. However, the adoption and deployment of these technologies has been slow due to a variety of factors, including a lack of government action on climate change, public skepticism, increasing costs, and advances in other options such as renewables and shale gas. Overall, CCUS has the potential to significantly reduce CO2 emissions and contribute to climate change mitigation efforts, but more work is needed to overcome the barri... [more]

The NiO-MgO solid solution has been proven to be an efficient catalyst for the carbon dioxide reforming of methane (CRM). However, the challenge is still there for the facilely controlled synthesis of the single-phase solid solution with the uniform composition, and the interactions between NiO and MgO are not consistently correlated with the CRM performance. To address these issues, in this work, the complex-decomposition method was applied to regulate the chemical and structural properties of NiO-MgO catalysts via simply changing the complexing agent, calcination temperature, and Ni/Mg molar ratio. The catalysts were comparatively evaluated for CRM under severe reaction conditions of 750 °C, 0.1 MPa, CH4/CO2 = 1, and a gas hourly space velocity of 60000 mL·g−1·h−1. Irrespective of the complexing agents investigated, NiO-MgO solid solution was exclusively formed. However, the structural and reductive properties of the NiO-MgO catalysts were strongly dependent on the complexing agent,... [more]

The solution-processed and conductive MoO3−PEDOT:PSS (Mo−PPSS) composite layer in a MoO3/Au/MoO3−PEDOT:PSS (MoAu/Mo−PPSS) multilayer electrode in ITO-free organic solar cells (OSCs) was optimized in terms of electrical conductivity, interfacial contact quality, work function, and process wettability of the conductive composite thin film. The surface composition of the PEDOT:PSS film onto different electrodes was observed by using X-Ray Photoelectron Spectroscopy. The PEDOT:PSS-MoO3 composite protects the dissolution of individual MoO3 with PEDOT:PSS, which was confirmed by Auger Electron Spectroscopy. The UV-Visible spectroscopy showed that the photoactive layer of P3HT:PCBM absorbs in the wavelength range of 300−650 nm with the maximum absorption at 515 nm (2.40 eV). The device performance of 3.97% based on an MoAu/Mo−PPSS conductive composite electrode exhibited comparable enhancement and only 6% enhancement compared to an ITO-based electrode (3.91%). The enhancement of device effici... [more]

A large number of aromatic substances can be found in so-called coal tar (containing >10,000 individual compounds), which is a mixture of heavy liquid fractions (dense viscous black liquor, tended to solidification) obtained after the pyrolysis of coal (solid product—coke, gas products, and light liquid products are also produced during the process). Volatile monocyclic aromatic hydrocarbons, which are naturally occurring in coal tar, can be exploited as premium raw materials for the production of graphene by chemical vapor deposition (CVD). Moreover, aromatic chemicals (compounds with benzene rings) can produce graphene at lower temperatures than other small-molecule gas feedstocks (for graphene growth via methane gas, the temperature must be at least 900 °C). The intermediate reaction mechanism involved in the creation of graphene from various temperature ranges of monocyclic aromatic hydrocarbons in benzene ring structures has long been a fascinating enigma. Accordingly, in this pap... [more]

The growing demand for energy and the concern about environmental impacts reinforce the necessity for renewable energy sources such as biofuels. In this study, cake generated in the babassu oil extraction was evaluated as a potential feedstock for solid biofuel production, and it contains a blend of cashew nutshell, sugarcane bagasse, carnauba straw, and carnauba stalk. All samples were characterized by proximate analysis and Higher Heating Value. Carbonization was used to improve energy performance and compaction to understand the mechanism and the characteristics of the biomasses compacted. In the extraction of babassu oil, fresh and aged (90 days) kernel samples were used. The fresh samples reached a yield of 59.8%, and the aged samples reached a yield of 70.66%. The carbonization of babassu cake was carried out in a Muffle furnace at temperatures of 250, 300, 350, and 400 °C. The fresh babassu cake showed an HHV of 23.06 MJ kg−1 and after carbonization of 28.07 (250 °C), 30.69 (300... [more]

Heavy-fuel aviation piston engines (HF-APEs) are widely used in general aviation and unmanned aerial vehicle (UAV) due to their safety and fuel economy. This paper describes a numerical and experimental study of scavenging and combustion processes on a 2-Stroke Direct Injected HF-APEs for light aircraft, with its cylinder specifically designed as cross scavenging. A 3-Dimentional transient model of in-cylinder flow and combustion process is established by the Forte platform, and the engine test system is set up. By comparing the simulation results to the experimental results, it showed that multi-ports cross scavenging can generate unbalanced aerodynamic torque in the cylinder. In the compression process, the swirl ratio (SR) gradually increases, and the peak SR reaches 15. Moreover, approximately 25% of exhaust residual gas in the cylinder is conducive to the fuel atomization and evaporation process in a high-altitude environment. When the injection timing is between −8 °CA and −16 °C... [more]

The aim of is paper is to address the problem of identifying critical factors in the analysis of non-coal mine explosion accidents as well as to improve the rationality and accuracy of the risk analysis results. Hence, we developed a risk identification method for non-coal mine explosion accidents, combining the Systems-Theoretic Accident Model and Process (STAMP) and the Rank-order Centroid (ROC) method based on the Poset decision-making theory. The proposed method was applied to identify risk in engineering cases. Findings showed that four main dangerous events (out of twelve identified ones) were the primary culprits of related accidents, which were the events “Blasters without licenses and illegal operation” at the basic level, the event of “the confusion about the safety management system of non-coal mine companies” at the control level, and the event of “the failure about the emergency management departments” and “public security departments” at the supervision level. The approxi... [more]

The worldwide use of renewable energy sources has been growing significantly year by year, accompanied by continuous technological development [...]

In the original article [...]

An integrated energy system (IES) is vulnerable to network attacks due to the coupling features of multi-energy systems, as well as the deep integration between a physical system and an information system. The anomaly detection of the time-series data in an IES is a key problem to defend against network attacks and ensure the cyber-physical security of IES. Aiming at false data injection attacks (FDIAs) on IES, this paper proposes an anomaly detection method for time-series data in a cyber-physical integrated energy system based on time-frequency feature prediction. The time-frequency features of the time-series data are extracted based on three time-frequency transform methods (DWT, EMD, and EWT). Then the extracted time-frequency features are input to the autoencoder (AE) to capture the hidden features and nonlinear structure of the original data in the frequency domain. The time-domain data within the detected time period are predicted by applying regression prediction on the top-la... [more]

With the expansion of E-mobility technology, the demand for Medium-Voltage (MV) Electric Buses (E-buses) charging infrastructure has significantly increased. In this regard, the effective connection of E-bus chargers to a medium voltage power grid is essential to provide fast charging and carry out multiple charging processes simultaneously. One of the main building blocks for E-bus charging is the DC-DC converter stage responsible for regulating the power flow and matching the different voltage and power levels. Accordingly, this paper presents a comprehensive review of DC-DC converter topologies applicable to MV E-bus fast charging. This review discusses and compares the basic isolated DC-DC converter topologies. In addition, the DC-DC converters are classified based on their conversion stages. Moreover, isolated DC-DC converter topologies applicable for MV E-bus fast charging applications, including Dual Active Bridge (DAB) modular-based structure converter and Modular Multilevel Co... [more]

According to data from the International Energy Agency (IEA), in order to achieve net-zero CO2 emissions by 2050, approximately 306 million tonnes of green hydrogen (H2) must be produced annually [...]

For a wind energy system, main speed-increasing gearboxes, pitch drives and yaw drives are composed of a multistage planetary gear system. However, inevitable errors in the manufacturing and assembling of the gears lead to uneven load of distribution in the planetary gear system; thus, its service life and reliability decrease greatly, which would eventually affect the normal operation of the whole wind power system. In this study, a dynamic load sharing model of pitch drive is established with a lumped-parameter method. Given the manufacturing and assembly errors and central floating gear, the dynamic equations for each component, the stiffness matrix and damping matrix, the dynamic load sharing coefficient and the floating displacement of the sun gear are obtained according to the dynamic meshing force and damping load. Furthermore, the load sharing coefficient for external and internal meshing of the pitch drive for a 2 MW wind turbine with a three-stage planetary gear are achieved.... [more]

For a PEMFC to work better, adding baffles to a flow channel can improve reactant transfer. As a result, the work starts by developing a 3-D numerical model for the vanadium redox flow battery (VRFB) using COMSOL Multiphysic Simulation Software. By incorporating baffles into the serpentine flow channel, it is possible to simulate changes in ion concentration and terminal voltage. The findings indicate that the battery efficiency will be impacted by adding baffles. The authors also studied the effect of baffle height and baffle count. The baffle height of 0.9 times the channel height and baffle number of 9 has a better performance on the battery. There are four cases for installing nine baffles and four arranging types in the entire serpentine flow using such baffle height and number. In Case 4, baffles are placed uniformly at the location of channel numbers 1, 9, and 17 in the serpentine flow path. It has a better voltage and ion concentration reaction than the other cases. The unit te... [more]

Liquified natural gas (LNG) is a clean primary energy source that is growing in popularity due to the distance between natural gas (NG)-producing countries and importing countries. The large amount of cold energy stored in LNG presents an opportunity for sustainable technologies to recover and utilize this energy. This can enhance the energy efficiency of LNG regasification terminals and the economic viability of the LNG supply chain. The energy stored in LNG in the form of low temperatures is referred to as cold energy. When LNG is regasified, or converted back into its gaseous form, this cold energy is released. This process involves heating the LNG, which causes it to vaporize and release its stored energy. The current state-of-the-art techniques for LNG cold energy utilization, including power generation, air separation, traditional desalination, and cryogenics carbon dioxide (CO2) capture are discussed in this review. While most of the current LNG cold energy utilization systems a... [more]

The effects of contact conditions at the wire−die interface on the temperature distribution of the specimen and die are investigated to understand the wire drawing process. Finite element analysis and experiments are performed to analyze the temperature distribution of a drawn wire and die based on different contact conditions using a low-carbon steel wire. The maximum temperature (Tmax) of the die decreases as the contact heat transfer coefficient at the wire−die interface increases, whereas that of the wire increases with the contact heat transfer coefficient. The Tmax of the die and wire decreases with the thermal conductivity of the die. As the thermal conductivity of the die increases, the heat generated by friction is rapidly absorbed into the die, and the Tmax of the die decreases, thus resulting in a decrease in the surface temperature of the wire. The Tmax of both the die and wire linearly increases with the friction factor. In particular, the Tmax of the die more sensitively... [more]