During the service of a landfill, uneven soil settlement and earthquakes can cause changes to the pore structure and cracks in the covering layer. The use of a biochar−methanotroph−clay mixture as a new landfill covering layer, can improve its engineering properties. The biochar−methanotroph−clay mixture’s shear-wave velocity and compression-wave velocity were measured by the bender−extender element test, and the elastic parameters under small-strain conditions, such as maximum shear modulus, Gmax, maximum constrained modulus, Mmax, and Poisson’s ratio, ν, were obtained. The parameters showed that the elastic characteristics and lateral deformation capacity were of great significance for settlement, seismic field, and stress−strain analysis. Based on the bender−extender element test, the effects of different compaction degrees, and biochar content on Gmax, Mmax, and ν of the biochar−clay mixture, and different methane cultivation days on the biochar−methanotroph−clay mixture, were inve... [more]

The formation of a rich underground-seam network is the key problem in the development of low-permeability hot dry rock (HDR) resources. Considering the lack of macroscopic continuum theory to study hydraulic fracturing having preset fracture-interface element, the particle-flow method of micro-mechanical discrete-element theory is introduced to simulate the mechanical behavior of hydraulic fracturing for HDR low permeability reservoirs. The reservoir is simulated as a round particle; the fracturing fluid movement is described by the seepage field equation, and rock movement is described by the displacement field equation. Finally, the particle-flow numerical model of hydraulic fracturing for HDR low permeability reservoirs is established under the condition of fluid-solid coupling: the model contains two parts (rock and fracture). Based on the parallel-bond model, a definition of micro-fractures of hydraulic fracturing is given. The relation between the fracturing effect and influence... [more]

The paper presents the possibilities of low-emission-powered vehicles based mainly on compressed hydrogen. It shows currently used forms of powering vehicles based on their genesis, process of obtention, and popularity. They are also compared to each other, presenting the advantages and disadvantages of a given solution. The share of electricity in transport, its forecasts for the future, and the possibilities of combination with conventional energy sources are also described. Based on current technological capabilities, hydrogen plays a crucial role, as presented in the above work, constituting a fundamental basis for future transport solutions.

Wettability in CO2-brine-mineral/rock systems is an important parameter influencing CO2 storage capacities and leakage risks in saline reservoirs. However, CO2 tends to react with various minerals and rocks at subsurface conditions, thus causing temporal and spatial wettability changes. Although many relevant research works have been published during past years, a thorough overview of this area is still lacking. Therefore herein, reaction-induced wettability changes are reviewed, and the underlying mechanisms are discussed. Current research gaps are identified, future outlooks are suggested, and some conclusions are drawn. The fundamental understanding of reaction-induced mineral and rock wettability changes during CO2 storage in saline reservoirs is analyzed and the guidance for long-term CO2 containment security evaluations is provided.

The possibilities for reducing the fuel consumption of internal combustion engines focus mainly on developing combustion systems, as one such solution is a two-stage combustion system using jet ignition. The combustion of gaseous mixtures with a high excess air ratio leads to an increase in overall efficiency and a reduction in the emissions of selected exhaust components. In such a convention, gas combustion studies were conducted in the methane/propane configuration. Using an active prechamber where spark plugs were placed and direct injection through a check valve, the fuel dose was minimized into the prechamber. The tests were conducted for a constant center of combustion (CoC). The combustion process in both the prechamber and main chamber was analyzed using a test stand equipped with a 0.5 dm3 single-cylinder engine. The engine was controlled by varying the fuel supply to the prechamber and main chamber in excess air ratio λ = 1.3−1.8. The study analyzed thermodynamic indices suc... [more]

Delamination damage to spar caps seriously endangers the operation safety of offshore wind turbines. The effect of initial delamination of various depths and areas on the ultimate tensile load of laminates is studied based on experiments and numerical simulation, and an effective method for predicting the residual tensile strength of laminates with high thickness is proposed. Three groups of initial delamination specimens with different characteristics were fabricated, and static displacement tensile tests were carried out. An accurate three-dimensional numerical analysis model was established, and the results were in good agreement with the experimental values, with the overall error of the failure load being less than 6%. Furthermore, a numerical model for a 20-ply high-thickness spar cap laminate was established to predict the effect of delamination on tensile strength. The results showed that, for the same depth of initial delamination, the difference in delamination area had littl... [more]

Recently, the demand for small, low-cost electronics has increased the use of cost-effective tiny inductors in power-management ICs (PMICs). However, the conduction loss caused by the parasitic DC resistance (RDCR) of a small inductor leads to low efficiency, which reduces the battery usage time and may also cause thermal problems in mobile devices. In particular, these issues become critical when a conventional boost converter (CBC) is used to achieve high-output voltage due to the large inductor current. In addition, as the output voltage increases, a number of issues become more serious, such as large output voltage ripple, conversion-ratio limit, and overlap loss. To solve these issues, this paper proposed a high-voltage boost converter with dual-current flows (HVDF). The proposed HVDF can achieve a higher efficiency than a CBC by reducing the total conduction loss in heavy load current conditions with a small inductor. Moreover, because in the HVDF, the current delivered to the ou... [more]

Appropriate frequency response is an issue of great importance in power system management, especially in an islanded one. An energy-based method for assessing a system’s response, which is needed to prevent under frequency load shedding (UFLS), is introduced. Renewable generation, such as wind turbine (WT) and photovoltaic (PV) facilities, reduces the ability of the power system to resist power imbalances and increases the risks of consumer disconnections by UFLS system, and even of total collapse. To estimate the amount of additional fast power reserve, an equation was developed, relating the moment of inertia, the system demand dynamics, and the available response of synchronous generating units. Clustering units based on their ability to respond to frequency changes in low inertia conditions allows the potential synchronous response to be assessed, providing information of its deficiency in a defined system state. The proposed method was applied to the Israeli power system and up to... [more]

To date, the majority of energy supply is still generated by non-renewable sources, which places a dramatic burden on our environment [...]

As one of the crucial factors contributing to coal spontaneous combustion, the oxidation of pyrite is a complex process involving multiple reactions, particularly in the presence of oxidants (Fe3+ and O2) and bacteria. However, experimental results based on mineral-pyrite are not entirely applicable to coal-pyrite due to their differences in formation environments and compositions. This study selected two types of coal-pyrite and one type of mineral-pyrite as research to conduct oxidation experiments with the participation of oxidant (Fe3+) and bacteria (Acidithiobacillus ferrooxidans), respectively, to obtain the following conclusions. Under natural conditions, the chemical oxidation rate of pyrite is slow, but the addition of oxidant Fe3+ and bacteria can significantly accelerate the oxidation rate. The promotion effect of oxidant Fe3+ on the oxidation reaction is stronger than that of bacteria. Under the same conditions, the oxidation rate of coal-pyrite samples is slightly higher t... [more]

Electric vehicles (EVs) have the advantage of being resilient to natural disasters. However, users hesitate to donate electricity when they lose the chance to recharge at the utility. Solar electric vehicles (SEVs) save energy through vehicle-integrated photovoltaics (VIPV) and make it possible to voluntarily donate excess energy, thus maintaining facility resilience. Given that the supply of solar energy to VIPV systems is not continuous and is difficult to forecast, the contribution of VIPV to the resilience of the larger energy system has been called into question. This is the first study in which the potential of VIPV to maintain utility resilience is investigated in the context of physical factors, such as irradiance, and social factors. The actual energy yield of a VIPV car was determined using an advanced 3D solar irradiation model under a nonuniform shading distribution, with validation from actual measures of solar irradiance on five orthogonal sides of the car body. The Monte... [more]

To enhance the operational dependability of renewable energy power systems with high proportions, this study proposes a multi-timescale optimization strategy based on the inertia evaluation model. Firstly, the inertia evaluation model is established based on the factors influencing the inertia demand of the power system, and the concept of the inertia margin coefficient is introduced. Secondly, to address the uncertainties associated with sustainable energy output and the cost of carbon emissions, a multi-timescale optimization operation model is formulated for day-ahead, intraday, and real-time operations, aimed at economic optimization. The output status of each unit is obtained and adjusted in a timely manner in the next stage, while meeting the system’s inertia demand, to derive the final scheduling strategy. Lastly, a sensitivity analysis of the inertia margin coefficient is conducted through simulations to validate the effectiveness and cost-efficiency of the proposed scheduling... [more]

The timely discovery of low-frequency oscillations in power systems and accurate identification of their modal parameters is critical in numerous applications. Therefore, we investigated the feasibility of using multi-channel signals and established a relative theory. An algorithm based on the underdetermined blind source separation (UBSS) algorithm was proposed using this theory. First, the energy ratio function was used to determine the fault occurrence time. Then, the Bayesian information criterion was used to estimate the number of fault sources, and the boundary conditions were set to determine the number of fault sources. Next, the UBSS algorithm was used to analyze raw data, extract individual components that characterize faults, and subsequently measure low-frequency oscillation modal parameters through the Hilbert transform. Finally, the fast independent component analysis (FastICA) algorithm was used to separate noise signal from raw data. This separation considerably reduced... [more]

Expansion energy is the main factor of coal and gas outbursts, and the gas desorption around the outburst hole is developed in variable pressure conditions. While studying the impact of moisture on gas desorption characteristics, atmospheric pressure desorption is usually used, but its characteristics under variable pressure conditions have not been thoroughly investigated. In this study, typical outburst coal samples with different water contents from the Jincheng mining area of China were selected as research objects, and the effects of water on gas displacement, desorption, desorption rate, and gas desorption index (K1) of drilling cuttings under step-by-step depressurization were analyzed by means of stepwise depressurization and atmospheric desorption experiments. The research conclusions suggest that (1) the amount of gas replacement, which augments rapidly during the inception, increases with the growth of water content under the experimental conditions, and then the rate decrea... [more]

The energy conversion of nickel-impregnated coconut shells using supercritical water has not yet been explored. The impregnation process was conducted at room temperature and a pH of 5.80 for 72 h. Characterization of the prepared sample confirmed the presence of nickel nanoparticles with an average size of 7.15 nm. The gasification of control and impregnated samples was performed at 400−500 °C, biomass loading from 20 to 30 wt% and residence time from 20 to 60 min. The response surface methodology (RSM) approach, with a Box−Behnken method, was used to design the experiments. The optimization model showed that the non-catalytic process at 500 °C, 60 min and 20 wt% of biomass loading could promote an H2 yield of 8.8 mol% and gasification efficiency of 47.6%. The gasification of nickel-impregnated coconut shells showed significantly higher gasification efficiency (58.6%) and hydrogen yield (17.2 mol%) with greater carbon and hydrogen efficiencies (109.4 and 116.9%) when compared to the n... [more]

Electric vehicles (EVs) are becoming increasingly popular, and it is important for utilities to understand their charging characteristics to accurately estimate the demand on the electrical grid. In this work, we developed simulation models for different EV charging scenarios in the home sector. We used them to predict maximum demand based on the increasing penetration of EV consumers. We comprehensively reviewed the literature on EV charging technologies, battery capacity, charging situations, and the impact of EV loads. Our results suggest a method for visualizing the impact of EV charging loads by considering factors such as state of charge, arrival time, charging duration, rate of charge, maximum charging power, and involvement rate. This method can be used to model load profiles and determine the number of chargers needed to meet EV user demand. We also explored the use of a time-of-use (TOU) tariff as a demand response strategy, which encourages EV owners to charge their vehicles... [more]

Kitchen waste (KW) has high water content and organic matter, which has great potential for energy application, but how to treat it effectively has always been a difficult problem. In this study, the feasibility of transforming kitchen waste into hydrochar as a solid fuel to replace the primary energy by hydrothermal carbonization (HTC) is put forward. An experimental study of proportioned KW under HTC conditions (reaction temperature, residence time, liquid−solid ratio) is carried out by elemental analysis, industrial analysis, energy density calculation, and calorific value measurement. The results show that a proper extension of the residence time to 3.5 h at a liquid−solid ratio of 10 and a reaction temperature of 265 °C for the kitchen waste after HTC would result in a maximum calorific value of 30.933 MJ/Kg for the prepared hydrochar. The maximum ash content of hydrochar at a 265 °C reaction temperature is 3.94% < 10%, which is much lower than the standard of extra-low-ash coa... [more]

The residential sector is currently responsible for approximately 30% of the final energy consumption and 12% of direct CO2 emissions in Italy, mainly due to the heating and cooling of buildings and the use of domestic hot water. Such figures show a significant potential for reducing non-renewable primary energy utilization to comply with the decarbonization constraints of the European Union. In this context, the purpose of this work is to provide a quantitative assessment of the effect of a different number of actions (eight for energy savings, four for energy efficiency and two for the installation of renewable energy plants) that could be implemented at the national level to reduce the consumption of natural gas in the residential sector. Two typical residential buildings are dynamically simulated using Trnsys®, and the savings from energy, economic and CO2 emissions points of view are evaluated in the different climatic zones of Italy. The most effective action foresees the replace... [more]

Due to the fact that the European Union is striving to achieve its sustainable development goals, in particular goal No. 7, which is to provide users with low-emission, and cheap access to, energy, this article’s aim is to verify whether there is a relationship between R&D expenditure and key energy variables in the EU countries in 2010−2020. Data on R&D expenditures incurred by the EU Member States in the period 2010−2020 were used for the research and were tested using the Autoregressive Distributed Lags Model (ARDL). The study identified a strong positive relationship between total R&D expenditure and the increase in energy consumption from renewable energy sources, and a smaller impact of total R&D expenditure as well as enterprise R&D expenditure on the increase in fossil energy consumption. Also noted was a weak relationship between R&D expenditure and electricity and gas prices for both household and non-household customers. The obtained results prove that in the context of the... [more]

This paper introduces a simple diesel train energy consumption model that calculates the instantaneous energy consumption using vehicle operational input variables, including the instantaneous speed, acceleration, and roadway grade, which can be easily obtained from global positioning system (GPS) loggers. The model was tested against real-world data and produced an error of −1.33% for all data and errors ranging from −12.4% to +8.0% for energy consumption of four train datasets amounting to a total of 5854 km trips. The study also validated the proposed model with separate data that were collected between Valencia and Cuenca, Spain, which had a total length of 198 km and found that the model was accurate, yielding a relative error of −1.55% for the total energy consumption. These results show that the proposed model can be used by train operators, transportation planners, policy makers, and environmental engineers to evaluate the energy consumption effects of train operational project... [more]

This paper presents the status regarding electric vehicles (EVs) and public charging stations managed by Cluj-Napoca City Hall. The types of charging stations and the quantity of the used energy were stated. The behavior of EV owners in charging their vehicles was also studied. The presented work proposes an extension of the EV charging infrastructure to support current and future EV owners. Simulations were carried out in Simulink to create an overview of the existing infrastructure. The simulation results showed the amount of greenhouse gas (CO2 emissions) reduced by using EVs. An estimated number of kilometers traveled with EVs was calculated by tracking the loads in all public charging stations.

With the aim of CO2 emissions reduction in the maritime sector, dual fuel engines operating on natural gas are the most prominent technical and commercially available solution. A promising variant is the two-stroke high-pressure natural gas injection engine, utilizing diesel pilot fuel injection for ignition of the gaseous fuel while being able to operate in diesel-only mode. In this study, a comparative analysis of the performance and the combustion mechanism of dual fuel and diesel mode for this engine type is conducted using experimental data. Studies based on measurements conducted on actual scale are limited in the literature due to the engines’ sheer size not allowing lab testing. The analysis was conducted using measurements acquired during the factory acceptance tests involving conventional operating data and cylinder pressure data acquired using a piezoelectric sensor. In terms of the mean pressure and temperature, only minor differences were found. The specific fuel consumpti... [more]

Nowadays, energy generation systems that include renewable energies, substations, distribution, transmission, control, measurement, and storage applications, among others, and are interrelated are known as Smart Grids. All these techniques and technologies involve extensive research and development, which allows for the solving of key aspects, such as control, diagnosis, and fault recovery, as well as communication systems focused directly on the operation of the electrical networks. Due to the relevance of knowledge concerning developments in these areas of Smart Grids, this paper presents a review of the research related to the control systems applied to Smart Grids and Micro Grids, both in supply and demand. Likewise, some control models relate to different processes, with a special focus on techniques related to Petri nets. The paper shows, among other outcomes, the advances in the control of smart grids, the types of generation and their influence on the design of transmission lin... [more]

Power flow calculation is the foundation of security analyses in a power system, and the phenomenon of convergence failure is becoming more prominent with the expansion of the power grid. The existing convergence failure diagnosis methods based on optimization modeling and local feature recognition are no longer viable for bulk power systems. This paper proposes a diagnosis method based on intermediate iteration data and the identification of the transmission power congested channel. Firstly, the transmission power congestion index is constructed, and then a method for identifying transmission congestion channels is proposed. The reasons for convergence failure of the power flow are diagnosed from two aspects: excessive power to be transmitted and insufficient transmission capacity. Finally, with the aim of alleviating transmission channel congestion, a correction strategy for power flow injection space data was constructed, which generates relaxation schemes for operational variables.... [more]

Low load is one of the most challenging combustion stages for a fixed-speed diesel electric generator. Due to incomplete combustion during this phase, a significant proportion of contaminants form inside the cylinder. This can lead to numerous chemical and mechanical harms to the diesel engine, resulting in friction, efficiency reduction, increased fuel consumption, and prematurely ending the generator’s life. These phenomena are qualified as underperformance, possibly due to a misfire and/or a low-efficiency value (air fuel−fuel ratio). Therefore, detecting and preventing underperformance and reducing its extended operation is crucial. This paper deals with the performance and emission analysis of a multicylinder fixed-speed diesel engine driving an electric generator (300 kW) fueled with ultra-low sulfur diesel (≤15 mg/kg) to provide energy in an isolated Canadian community. The tests were carried out according to ISO 3046-1:2002 standard in a remote site to identify clues that can p... [more]