Nowadays, due to the increasing use of electric vehicles, manufacturers are making more and more innovations in the batteries used in electromobility, in order to make these vehicles more efficient and provide them with greater autonomy. This has led to the need to evaluate and compare the efficiency of different batteries used in electric vehicles to determine which one is the best to be implemented. This paper characterises, models and compares three batteries used in electromobility: lithium-ion, lead-acid, and nickel metal hydride, and determines which of these three is the most efficient based on their state of charge. The main drawback to determine the state of charge is that there are a great variety of methods and models used for this purpose; in this article, the Thévenin model and the Coulomb Count method are used to determine the state of charge of the battery. When obtaining the electrical parameters, the simulation of the same is carried out, which indicates that the most... [more]

This study examines the effects on combustion, engine performance and exhaust pollutant emissions of a modern Euro 6, dual-loop EGR, compression ignition engine running on regular EN590-compliant diesel and hydrotreated vegetable oil (HVO). First, the potential of HVO as a “drop-in” fuel, i.e., without changes to the original, baseline diesel-oriented calibration, was highlighted and compared to regular diesel results. This showed how the use of HVO can reduce engine-out emissions of soot (by up to 67%), HC and CO (by up to 40%), while NOx levels remain relatively unchanged. Fuel consumption was also reduced, by about 3%, and slightly lower combustion noise levels were detected, too. HVO has a lower viscosity and a higher cetane number than diesel. Since these parameters have a significant impact on mixture formation and the subsequent combustion process, an engine pre-calibrated for regular diesel fuel could not fully exploit the potential of another sustainable fuel. Therefore, the e... [more]

As an unconventional clean resource with huge reserves and a wide distribution, natural gas hydrates (NGHs) have good application prospects. However, due to limited understanding and available production technology for NGHs, there is still a large gap between current production tests and commercial exploitation. A breakthrough in reservoir stimulation technologies is key to realizing the industrialization of NGHs in the future. Through a comprehensive summary of hydrate production test cases in Japan and China, this paper highlights the difficulties in the transformation of weakly-consolidated reservoirs. By systematically reviewing the theory and technology of hydrate reservoir transformation and engineering applications, this paper elucidates in detail the technical principles and mechanisms of several available stimulation technologies for weakly-consolidated reservoirs, and assesses the feasibility of their application to increase the production of NGHs. Existing problems and chall... [more]

Hydraulic fracturing or hydro-frac fluids can impede well production due to the damage caused to the reservoir formation and fracture face, generated from adverse interactions with reservoir rock. Understanding the mechanisms of hydraulic fracturing, optimum treatment designs, and pumping/pressure profiles is critical for hydro-frac success. However, to realize the full potential of fracturing and the mitigation strategies for reservoir and fracture conductivity damage during and after its occurrence, fracturing must be considered during the design phase itself. This article provides a brief overview of hydro-frac techniques, including design, optimization, modeling, commonly used proppants, and fracturing fluid benefits and consequences based on critically reviewed case studies. However, the primary focus of this article is on the potential of fracture conductivity damage and the intrinsic mechanisms in hydraulic fracturing. The article presents updated information on various damage m... [more]

In the context of the increasing penetration of intermittent renewable energy resources (RES), one of the significant challenges facing traditional bulk power systems and microgrids is the scheduling generation units problem. Many studies have focused on solving the energy management problem for microgrids integrating RES. To address the intermittency caused by RES, flexible components such as battery energy storage systems (BESS) or demand response (DR) are considered. To clarify the problem of integrating these flexible components, a mixed-integer programming (MIP) approach for the unit commitment (UC) problem for microgrids with BESS and DR is proposed in this paper. An incentive-based demand response model as a negative power source and a detailed model for the vanadium redox battery (VRB) are introduced to improve the efficiency and reliability of microgrids. The objective optimization function, including the costs of generation, emissions, and maintenance, is minimized considerin... [more]

Global warming and the depletion of fossil fuels have spurred many efforts in the quest for finding renewable, alternative sources of fuels, such as biodiesel. Due to its auxiliary functions in areas such as carbon dioxide sequestration and wastewater treatment, the potential of microalgae as a feedstock for biodiesel production has attracted a lot of attention from researchers all over the world. Major improvements have been made from the upstream to the downstream aspects related to microalgae processing. One of the main concerns is the high cost associated with the production of biodiesel from microalgae, which includes drying of the biomass and the subsequent lipid extraction. These two processes can be circumvented by applying direct or in situ transesterification of the wet microalgae biomass, hence substantially reducing the cost. In situ transesterification is considered as a significant improvement to commercially produce biodiesel from microalgae. This review covers the metho... [more]

The microchannel heat exchanger is one of the most compact and effective heat exchangers used for cooling devices in building air conditioning system, while application of nanofluids in microchannel further enhance its thermal performance due to its much higher thermal conductivity. Considering the continuous rapid increase in energy consumption in the building sector, especially in air conditioning systems, the heat transfer performance of a microchannel with nanofluids should be further enhanced to realize energy savings. This study analyzes the influence of combining nanofluid and flow disturbance structure on the heat transfer enhancement of a microchannel, which is also the noted novelty. A rectangular grooved microchannel (RGMC) is proposed, and its thermal performance using Al2O3/water nanofluids is investigated using the CFD method, with the mixture model to simulate the Al2O3/water nanofluids considering the slip velocity between the base fluid and nanoparticles. The results s... [more]

Proppant placement in hydraulic fractures is crucial for avoiding fracture closure and maintaining a high conductivity pathway for oil and gas flow from the reservoir. The curving fracture is the primary fracture form in formation and affects proppant−fluid flow. This work experimentally examines proppant transport and placement in narrow curving channels. Four dimensionless numbers, including the bending angle, distance ratio, Reynolds number, and Shields number, are used to analyze particle placement in curving fractures. The results indicate that non-uniform proppant placement occurs in curving fractures due to the flow direction change and induces an irregular proppant dune. The dune height and covered area are lower than that in the straight fracture. The curving pathway hinders proppant distribution and leads to a dune closer to the inlet. When the distance increases between the inlet and curving section, a large depleted zone in the curving section will be formed and hinder oil... [more]

The aim of this article is to identify the associations that young Polish recipients have with green energy, considering their self-assessment of the level of knowledge about green energy and the importance attributed to the energy sources they use on a daily basis. An analysis of the world literature on the subject indicates that there is a cognitive and research gap in the level of market awareness of individual recipients regarding green energy and its sources. This issue has been neglected even more among young people in the context of their associations with this type of energy. To eliminate these research gaps, five hypotheses were formulated. To this end, primary research was carried out using the survey method to collect data. The research covered 311 individual representatives of recipients in Poland aged between 18 and 24. The primary data collected was subjected to quantitative analysis, using specific tests and statistical analysis. Among other things, the following was dis... [more]

We conducted an experimental study on the breakdown process of oil shale by high-voltage power frequency electric heating in-situ pyrolyzing (HVF) technology to examine the impact mechanisms of the electric field intensity, initial temperature, and moisture content on a breakdown, using Huadian oil shale samples. A thermal breakdown occurred when the electric field intensity was between 100 and 180 V/cm. The greater the electric field intensity, the easier the thermal breakdown and the lower the energy consumption. The critical temperature of the oil shale thermal breakdown ranged from 93 to 102 °C. A higher initial temperature increases the difficulty of breakdown, which is inconsistent with the classical theory of a solid thermal breakdown. The main factor that affects the electrical conductivity of oil shale is the presence of water, which is also a necessary condition for the thermal breakdown of oil shale. There should be an optimal moisture content that minimizes both the breakdo... [more]

The composite electrode structure plays an important role in the optimization of performance of the intermediate-temperature solid oxide electrolysis cell (IT-SOEC). However, the structural influence of the composite electrode on the performance of IT-SOEC is not clear. In this study, we developed a three-dimensional macroscale model coupled with the mesoscale model based on percolation theory. We describe the electrode structure on a mesoscopic scale, looking at the electrochemical reactions, flow, and mass transport inside an IT-SOEC unit with a composite electrode. The accuracy of this multi-scale model was verified by two groups of experimental data. We investigated the effects of operating pressure, volume fraction of the electrode phase, and particle diameter in the composite electrode on electrolysis reaction rate, overpotential, convection/diffusion flux, and hydrogen mole fraction. The results showed that the variation in the volume fraction of the electrode phase had opposite... [more]

The limited availability of fossil fuel and the growing energy demand in the world creates global energy challenges. These challenges have driven the electric power system to adopt the renewable source-based power production system to get green and clean energy. However, the trend of the introduction of renewable power sources increases the uncertainty in the production, control, and operation of power systems due to the erratic nature of the environment. To overcome these meteorological conditions, some support systems, such as storage devices, are integrated with renewable energy sources (RES). A number of storage devices are hybridized to get the hybrid energy storage system (HESS) to get a potential solution for these microgrid problems. For maintaining the robustness and reliability of the power system, proper control, and management of power in the microgrid is very important. In this paper, an analytical study related to power management strategies is given along with different... [more]

Steam explosion pretreatment of sawdust and oat straw under mild, medium, and severe conditions was conducted to improve the quality of pellets generated from these feedstocks. This work examined the effects of temperature, time, and moisture content on the mechanical properties of biomass pellets. From the ANOVA conducted, the p-values of the regression models for all the response variables (dimensional stability, tensile strength, and pellet density) studied were significant (p < 0.05), except for the pellet density of steam-pretreated oat straw pellets. The interaction of these three factors did not significantly affect the response variables of oat straw pellets. In addition, the higher heating value (HHV) of treated biomass increased up to a maximum of about 9.5% and 7% as compared with the non-treated sawdust and oat straw, respectively. In addition, an increment of about 3.6-fold and 3.1-fold in pellet tensile strength of steam-pretreated sawdust and oat straw was observed, r... [more]

Driven by the goals of carbon neutral and carbon peak, coal power units need increased flexibility in peak shaving to accommodate intermittent renewables, especially for a region with a large proportion of combined heat and power (CHP) units in China. In this study, the data-mining-based method is proposed for revealing and utilizing the heat−power coupling mechanism of CHP units, which can be used to solve the mentioned issues. Specifically, extraction-condensing (EC) units, high-back-pressure (HBP) units and low-pressure turbine zero power output (LZPO) units are introduced into the proposed dispatch model for maximizing renewable energy accommodation. The operation schemes and the feasible minimum output power of the CHP system under one certain heat load are obtained via the genetic algorithm. Results show that the CHP system is capable of reducing its output power by 18.7% to 41.7% in the heating season, compared with the actual operation data. Furthermore, the influence of multi-... [more]

A flexible silver-zinc fabric-based primary battery that is biocompatible, conformable, and suitable for single-use wearable biomedical devices is reported. The planar battery was fabricated by screen printing silver/silver-chloride and zinc electrodes (14 mm × 8 mm) onto a silk substrate. A biologically relevant fluid, phosphate buffered saline was used as a liquid electrolyte for characterization. Cyclic voltammetry, electrochemical impedance spectroscopy, and current discharge properties at constant densities of 0.89 μA/cm2, 8.93 μA/cm2, and 89.29 μA/cm2 were used to quantify battery performance. Nine cells were placed in series to generate a greater open circuit voltage (>6 V) relevant to previously reported biomedical applications. The nine-cell battery was evaluated for operation under mechanical strain due to likely placement on curved surfaces of the body in wearable applications. The nine-cell battery was discharged over 4 h at 8.93 μA/cm2 in an unstrained condition. The mecha... [more]

This paper reviews the heat transfer model for geothermal reservoirs, the fracture network in reservoirs, and the numerical model of hydraulic fracturing. The first section reviews the heat transfer models, which contain the single-porosity model, the dual-porosity model, and the multi-porosity model; meanwhile the mathematical equations of the porosity model are summarized. Then, this paper introduces the fracture network model in reservoirs and the numerical method of computational heat transfer. In the second section, on the basis of the conventional fracture theory, the PKN (Perkins−Kern−Nordgren) model and KGD (Khristianovic−Geertsma−De Klerk) model are reviewed. Meanwhile, the DFN (discrete fracture network) model, P3D (pseudo-3D) model, and PL3D (planar 3D) model are reviewed. The results show that the stimulated reservoir volume method has advantages in describing the fracture network. However, stimulated reservoir volume methods need more computational resources than conventio... [more]

The paper presented the dynamics of a vehicle fueled by hybrid fuel, i.e., LPG−DME mixture. The basis for the assessment was the T-ω characteristics of the SI engine with a capacity of 1.6 dm3, determined by the authors for several selected loads and DME mass shares in the engine supply mixture. The analysis and comparison of the impact of the composition of the LPG−DME mixture on the dynamic properties were carried out for the passenger car OPEL Astra, powered by an engine for which T- ω characteristics were determined earlier on the test bench. It has been shown that the mass share of DME in the LPG−DME mixture does not significantly reduce the dynamic index of the car. In addition, the scope of changes in the mass fraction of DME in the mixture was also determined, which will ensure the vehicle performance similar to the power and torque parameters obtained for an engine powered solely by LPG. The received results have made it possible to determine changes in the value of the maximu... [more]

The implementation of Industry 4.0 technology and meeting the expectations of employers, the labour market, and, in fact, sustainable development are new challenges for industry employees, especially for their knowledge and skills. The changes introduced during industrial revolutions have always affected the job market and employees’ required competencies. The same can be said for the latest industrial revolution, Industry 4.0, in which the human factor plays an important role, mainly because new challenges are posed by human beings’ role in digitised reality. Our research aimed to identify the employee competencies that are required in the context of Industry 4.0. We investigated two groups of respondents (employees and students). These groups were subjected to a comparative analysis of their digital, technical, social and personal competencies. As a result of the analysis, we identified the highest-ranked competencies in defined groups. Our results show that technical and soft skills... [more]

The decarbonization of the transport sector, and thus of road-based transport logistics, through electrification, is essential to achieve European climate targets. Battery electric trucks offer the greatest well-to-wheel potential for CO2 saving. At the same time, however, they are subject to restrictions due to charging events because of their limited range compared to conventional trucks. These restrictions can be kept to a minimum through optimal charging stop strategies. In this paper, we quantify these restrictions and show the potential of optimal strategies. The modeling of an optimal charging stop strategy is described mathematically as an optimization problem and solved by a genetic algorithm. The results show that in the case of long-distance transport using trucks with battery capacities lower than 750 kWh, a time loss is to be expected. However, this can be kept below 20 min for most battery capacities by optimal charging stops and sufficient charging infrastructure.

Energy demands have been increasing worldwide, endangering the future supply−demand energy balance. To provide a sustainable solution for future generations and to comply with the international goal to achieve Carbon Neutrality by 2050, renewable energies have been at the top of the international discussions, actively contributing to the energy transition and climatic policies. To achieve the international goal, Angola proposed a long-term strategy that promotes a fair and sustainable development of the national territory by means of improving the electric sector. Among all the renewable resources, solar energy is found to be the most promising solution since it has the second major renewable energy potential in Angola. However, the main problem related to solar energy is the efficiency of the solar systems and the electrical and thermal energy storage. As part of the solution, Concentration Solar Power (CSP) can make a sounder contribution to the transformation of the Angolan energy s... [more]

A Wind Diesel Hybrid System (WDHS) is an isolated power system that combines Diesel Generators (DGs) and Wind Turbines (WTGs). The WDHS has three operation modes: Diesel Only (DO), Wind Diesel (WD) and Wind Only (WO). The latter mode is the only one resulting in substantial savings, as the DG consumes fuel even with no load. Moreover, adding an energy storage system (ESS) can significantly reduce the start/stop cycles in the DG. The FESS is robust, immune to deep discharges and its state of charge (SOC) is simple to monitor. The WDHS considered in this article uses a friction clutch to disengage the diesel engine (DE) from the synchronous generator (SG) in WO mode. The AVR regulates the voltage amplitude and the frequency regulation results from balancing the power produced by the DG and WT with the power consumed by the load and dump load along with the FESS utilisation. The control algorithms of the different elements present in the WHDS are explained, as well as the general control.... [more]

Biodiesel production through transesterification or catalytic hydrogenation using vegetable oil is a sustainable method, but it has the downsides of by-product generation and a higher cost. Therefore, in this study, waste cooking oil was selected as a raw material, and fluidized catalytic cracking was carried out on the catalyst (LDO-75) through a fixed-fluidized-bed (FFB) reactor. The effects of the reaction temperature, catalyst−oil ratio and weight hourly space velocity (WHSV) on the yield of pyrolysis gas, gasoline, diesel and heavy oil fractions were studied. The composition of the pyrolysis gas was determined by gas chromatography (GC), the composition of the gasoline fraction was analyzed by gas chromatography-mass spectrometry (GC-MS), and the characteristics of the diesel and heavy oil fractions were determined by nuclear magnetic resonance (NMR). The results show that light olefins are the main products of pyrolysis gases, and the liquid products are mainly composed of aromat... [more]

Shale reservoirs contain a certain amount of clay minerals, which can hydrate through imbibition when in contact with various water-based fluids during drilling and completion. Shale hydration can lead to structural changes in the shale such as the expansion of bedding planes and propagation of microfractures, consequently affecting the initiation and propagation of hydraulic fractures. However, the effect of shale hydration under confining pressure on hydraulic fracture propagation and stimulation effect is still unclear. To this end, a novel experimental method integrating shale hydration and hydraulic fracturing was proposed based on the laboratory triaxial hydraulic fracturing simulation system. This method enables a more realistic simulation of shale hydration and hydraulic fracturing process happening in downhole conditions. The experimental results show that under simulated reservoir conditions, water imbibition increases over time with the imbibition rate reaching its peak with... [more]

Solar energy is the most promising green energy resource, as there is an enormous supply of solar power. It is considered a good potential solution for energy crises in both domestic and industrial sectors. Nowadays, many types of solar systems are used for harvesting solar energy. Most of the research is focused on direct absorption solar collectors (DASCs) due to their ability to capture more solar energy. The effectiveness of DASCs is dependent on various factors, such as working fluid properties, geometry, and operating parameters. This review summarizes the impact of different design and operating parameters on the performance of DASCs. Many effective parameters are considered and their impact on optical and thermal properties is summarized. The influence of working fluid parameters, such as base fluid type, nanoparticle type, nanoparticle size, nanoparticle shape, and nanoparticle concentration on heat transfer performance, was discussed and their optimum range was suggested. The... [more]

With the goal of reducing greenhouse gas emissions, the logistics sector is increasingly coming into focus. While increasing electrification is taking place in the road transport sector, the numbers in heavy-goods transport have so far been vanishingly small. Payload limitations, high investment costs, and charging times make it difficult for logistics companies to think about a conversion. An e-highway on Austria’s highways could provide an approach to counter these problems. Based on route data of an entire truck fleet in the construction logistics sector and by creating a model with Openrouteservice and MATLAB, calculations are carried out to show the savings potential of required battery capacities and charging infrastructure. The results show a high potential for reducing battery capacities and the required charging infrastructure at the locations approached. The results show high reduction potential, keeping the average required capacities in all scenarios below 350 kWh. Having a... [more]