Increasing environmental pollution is driving an increase in the production and use of biofuels. The cost price of biodiesel could be reduced by using low-quality oilseeds unfit for human consumption and by applying the simultaneous oil extraction and transesterification process, avoiding the oil pressure stage. The purpose of this study was to investigate the enzymatic biofuel production process (in situ) by using rapeseed with high oil acidity for simultaneous oil extraction and transesterification with a mixture of butanol and mineral diesel fuel. The investigation of the in situ process was performed using a mixture of butanol and mineral diesel and the most effective biocatalyst Lipozyme TL IM was selected. The novelty of this paper consists of the fact that mineral diesel was used as the oil extractant, and the amount chosen was such that, at the end, a mixture of fuel with a ratio 9:1 of mineral diesel to biodiesel was be produced. The experiments were carried out using ground r... [more]

The use of biofuels to power compression−ignition engines makes it possible to reduce emissions of certain harmful components of exhaust gases. The purpose of this study was to determine the influence of second-generation biofuels on the course of indicator graphs and heat release characteristics of the Perkins 1104D-44TA compression−ignition engine. For comparative purposes, the same tests were carried out by feeding the engine with first-generation biofuel and diesel fuel. Babassu butyl esters (BBuE) were used as the second-generation biofuel. The second fuel was a first-generation biofuel—rapeseed oil methyl esters (RME). Analysis of the results made it possible to draw conclusions about the effect of using 2nd and 1st generation biofuels on the parameters of the combustion process. When the DF engine was powered, the lowest fuel dose per work cycle was obtained. In the case of RME and BBuE fuels, it depends on the engine load. For low loads, higher consumption is for RME, and for h... [more]

The theoretical feasibility of the power output strategy based on rotor cone angle control for ultra-scale downwind wind turbines is studied in this paper via the Open FAST simulation platform. The performance of five cases, namely UW, DW, DWC, DW6, and DW6IC, which have different rotor parameters or control strategies compared with the reference DTU 10 MW wind turbine, are calculated and analyzed. It is found that the downwind rotors have significant advantages in reducing the blade root load. The DW case reduces the peak load at the blade root by 22.54% at the cost of 1.57% annual energy production loss. By extending the length and redesigning the stiffness of the blade, the DW6 case achieves 14.82% reduction in the peak load at the blade root and 1.67% increase in the annual energy production under the same blade weight as that of the UW. The DWC case with rotor cone angle control has the same aerodynamic performance as the DW case with the same blade parameters. However, when the w... [more]

Agro-industrial residues such as bagasse, pomace, municipal residues, vinasse and cheese whey are an environmental problem around the world, mainly due to the huge volumes that are generated because of the food production to satisfy the nutritional needs of the growing world population. Among the above residues, cheese whey has gained special attention because of its high production with a worldwide production of 160 million tons per year. Most of it is discarded in water bodies and land causing damage to the environment due to the high biological oxygen demand caused by its organic matter load. The environmental regulations in developing countries have motivated the development of new processes to treat transform cheese whey into added-value products such as food supplements, cattle feed and food additives. In addition, during the last decade, several processes and technologies have been developed to produce bioenergy through the biotechnological process using cheese whey as a potenti... [more]

Natural polymers have been investigated as part of the endeavors of green chemistry practice in the oil field. However, natural polymer studies are still preliminary. The current study examines okra’s (natural polymer) efficiency for polymer flooding, particularly in Kazakhstan. The evaluation targets the heavy oil trapped in carbonate reservoirs. SEM and FTIR were used to characterize morphology and chemical composition. A rheology study was conducted under different shear rates for three plausible concentrations: 1 wt.%, 2 wt.% and 5 wt.%. The core flooding was challenged by the low porosity and permeability of the core. The results showed that okra’s size is between 150−900 μm. The morphology can be described by rod-like structures with pores and staking as sheet structures. The FTIR confirmed that the solution contains a substantial amount of polysaccharides. During the rheology test, okra showed a proportional relationship between the concentration and viscosity increase, and an i... [more]

South Korea has a plan to realize a hydrogen economy, and it is essential to establish a main hydrogen pipeline for hydrogen transport. This study develops a cost estimation model applicable to the construction of hydrogen pipelines and conducts an economic analysis to evaluate various scenarios for hydrogen pipeline construction. As a result, the cost of modifying an existing natural gas to a hydrogen pipeline is the lowest, however, there are issues with the safety of the modified hydrogen pipes from natural gas and the necessity of the existing natural gas pipelines. In the case of a short-distance hydrogen pipeline, the cost is about 1.8 times that of the existing natural gas pipeline modification, but it is considered a transitional scenario before the construction of the main hydrogen pipeline nationwide. Lastly, in the case of long-distance main hydrogen pipeline construction, it takes about 3.7 times as much cost as natural gas pipeline modification, however it has the advantag... [more]

A single independent voltage source (Vin or Vbat) is used to regulate the speed of an E-vehicle (EV) with the same interval of switching pulses to generate different voltage ratios by charging/discharging the flying capacitors using a novel single-input multi-output (SIMO) DC-DC switched capacitor converter. In this work, various speed transmissions are generated for controlling the speed of EVs. The selected and regulated battery voltage are generated using the SIMO DC-DC converter. The proposed converter is used to generate seven different transmission in total, of which four transmissions are used for motoring (forwarding operation) and the other three transmissions act as regenerative braking. For motoring operation, the battery, fuel cell, and photovoltaic cell are used as a sources of energy, and for the regenerative braking, the regenerated voltage is fed back to store the battery. The SIMO DC-DC converter is used to support electronic accessories, such as LED lights, the EV aud... [more]

With the development of society and the increase in energy demand, the electric power system and natural gas system become larger and larger, where the network is increasingly complex. The continuous and stable supply of energy is also important. The reliability evaluation of the power system and natural gas system is an essential part of maintaining efficient operation of the system. In this paper, the concept of the integrated electricity-gas system is introduced first, and then the importance of the reliability evaluation of the power system and natural gas system is emphasized. In addition, the main reliability indices and reliability evaluation method of the two systems are presented, and some practical examples are given. Finally, conclusions on the reliability evaluation of the integrated electricity-gas system are drawn.

A battery management system (BMS) plays a crucial role to ensure the safety, efficiency, and reliability of a rechargeable Li-ion battery pack. State of charge (SOC) estimation is an important operation within a BMS. Estimated SOC is required in several BMS operations, such as remaining power and mileage estimation, battery capacity estimation, charge termination, and cell balancing. The open-circuit voltage (OCV) look-up-based SOC estimation approach is widely used in battery management systems. For OCV lookup, the OCV−SOC characteristic is empirically measured and parameterized a priori. The literature shows numerous OCV−SOC models and approaches to characterize them and use them in SOC estimation. However, the selection of an OCV−SOC model must consider several factors: (i) Modeling errors due to approximations, age/temperature effects, and cell-to-cell variations; (ii) Likelihood and severity of errors when the OCV−SOC parameters are rounded; (iii) Computing system requirements to... [more]

This article presents a study on the performance characteristics of a Francis turbine operating with various guide vane openings to determine the best operating point based on unit quantities. The guide vane openings were specified based on the width between the vanes at their exit, i.e., 10 mm, 13 mm, 16 mm, and 19 mm. The performance characteristic curves of the Francis turbine—head versus speed, torque versus speed, discharge versus speed, and efficiency versus speed—were obtained at various input power and guide vane openings. From these data, unit curves were plotted and the corresponding best efficiency points were obtained. The highest efficiency of 50.25% was obtained at a guide vane opening of 19 mm. The values of head, discharge, speed, and output power at BEP were 7.84 m, 13.55 lps, 1250 rpm, and 524 W, respectively.

Deep decarbonization is the goal of modern power systems, so it is inevitable that large-scale wind farms will be integrated into systems. This also gives rise to many problems, which have been studied in detail in the literature. However, these studies basically have two deficiencies. One is to assume that traditional generator units are fully loaded, and the other is not to compare the differences in the impact of different types of wind farm. This paper discusses these two points in detail. Taking a series-compensated transmission system as the research object, and assuming that the wind farm only replaces part of the power of the traditional generator unit in the transition period of energy conversion, the difference between the torsional vibration behaviors of the traditional unit caused by adopting different types of wind farm is discussed. The results of the study show that the impact of integration of the type 3 wind farm is dominated by the induction generator effect of doubly... [more]

Global fossil fuel reserves are declining due to differential uses, especially for power generation. Everybody can help to do their bit for the environment by using solar energy. Geographically, Bangladesh is a potential zone for harnessing solar energy. In March 2021, the renewable generation capacity in Bangladesh amounted to 722.592 MW, including 67.6% from solar, 31.84% from hydro, and 0.55% from other energy sources, including wind, biogas, and biomass, where 488.662 MW of power originated from over 6 million installed solar power systems. Concurrently, over 42% of rural people still suffer from a lack of electricity, where solar energy can play a vital role. This paper highlights the present status of various forms of solar energy progress in Bangladesh, such as solar parks, solar rooftops, solar irrigation, solar charging stations, solar home systems, solar-powered telecoms, solar street lights, and solar drinking water, which can be viable alternative sources of energy. This re... [more]

The long and tiring discussion of who are the best drivers, men or women, is not answered in this article. This article, though, sheds some light on the actual differences that can be seen in how men and women drive. In this study, GPS-recorded driving dynamics data from 123 drivers, 48 women and 75 men, are analysed and drivers are categorised as aggressive, normal or gentle. A total of 10% of the drivers was categorised as aggressive, with an even distribution between the genders. For the gentle drivers, 11% of the drivers, the men dominated. The driving style investigation was extended to utilise machine learning, confirming the results from statistical tools. As driving style highly impacts a vehicle’s fuel consumption, while switching over to battery electric vehicles it is important to investigate how the different driving styles impact battery utilisation. Two Li-ion battery cell types were tested utilising the same load cycle with three levels of current amplitude, to represent... [more]

As the demand for ultra-low-power (ULP) devices has increased tremendously, system-on-chip (SoC) designs based on ultra-low-voltage (ULV) operation have been receiving great attention. Moreover, research has shown the remarkable potential that even more power savings can be achieved in ULV SoCs by exploiting the temperature effect inversion (TEI) phenomenon, i.e., the delay of the ULV SoCs decreases with increasing temperature. However, TEI-aware low-power (TEI-LP) techniques have a critical limitation in practical terms, in that dedicated power management-integrated circuits (PMICs) have not yet been developed. In other words, it is essential to develop PMICs that automatically bring out the full potential of the TEI-LP techniques as the chip temperature changes. With the aim of designing such PMICs, this paper first conducted a study to find the most suitable DC-DC converter for PMICs and then developed a control algorithm to maximize the effectiveness of the TEI-LP techniques. Furth... [more]

Despite the significant advancements in geomodelling techniques over the past few decades, it is still quite challenging to obtain accurate assessments of hydraulic fracture propagation. This work investigates the effect of fluid leak-off in a dual-porosity system on the hydraulic fracture propagation geometry, which, in turn, affects hydrocarbon recovery from tight and unconventional reservoirs. Fracture propagation within tight reservoirs was analyzed using the Pseudo Three-Dimensional-Carter II model for single- (P3D-C) and dual-porosity systems (P3D-C-DP). Previous studies have accounted for leak-off in single-porosity models; however, studies within dual-porosity systems are still quite limited. We present a novel approach to coupling fluid leak-off in a dual-porosity system along with a fracture-height growth mechanism. Our findings provide important insights into the complexities within hydraulic fracturing treatment design using our new and pragmatic modeling approach. The simu... [more]

The surface deposition of aviation fuel is a crucial and challenging issue in the application of air-to-fuel heat exchangers in aero-engines. The present study investigated the effect of pressure on the surface deposition of aviation fuel in a horizontal tube. Surface deposition distributions of aviation fuel RP-3 under different pressures (from 1.5 to 5.5 MPa) and different heat fluxes (from 0.08 to 0.4 MW/m2) were measured. Some experimental cases were numerically simulated to analyze the intrinsic mechanism of pressure affecting deposit formation. It was shown that pressure affects oxidative and pyrolytic deposition differently. Elevated pressure promotes the formation of pyrolytic deposits, whereas the oxidative deposition rate increases as pressure decreases. Pressure affects surface deposit formation via the physical properties of aviation fuel, especially density. The phase transition of fuel from liquid to vapor greatly accelerates the precipitation and deposition of insoluble... [more]

In this paper, the effects of simultaneous air and water cooling on the energy performances of a single-pass hybrid PV/T system are experimentally investigated. Both air and water are used as coolants and are tested at four different mass flow rates, ranging from 0.0014 to 0.0026 kg/s. It is found that the overall efficiency of the PV/T system is dependent on the solar intensity and mass flow rate of coolants. Maximum PV/T system efficiency is found to be 62.2% for a simultaneous flow of water and air at a 0.0026 kg/s flow rate, which is 35.5% higher than the efficiency found at 0.0014 kg/s coolant flow rate. Maximum thermal energy outputs are 85.8 and 211.84 W/m2 while using air- and water-based coolants, respectively. Exergy analysis of the developed system indicates that exergy efficiency increased by up to two times by introducing simultaneous air and water cooling in this PV/T system.

The dynamic characteristics of pipe piles are of considerable importance for the dynamic foundation design of offshore wind turbines. In this study, we develop an analytical model for the lateral vibration of offshore pipe piles with consideration of the inertia effect and axial loading from the superstructure. A coupled dynamic saturated soil−pile interaction model is established based on Biot’s poroelastic theory and Euler−Bernoulli theory. The potential function, operator decomposition method, variable separation method and matrix transfer method are introduced herein to obtain the lateral force of the inner and outer soil acting on the pile shaft. Then, the analytical solution of the pile dynamic impedance in the frequency domain is derived by employing the soil−pile continuous deformation conditions and the boundary conditions of the pile. The rationality and accuracy of the presented solution have were by comparing its results with those predicted by existing solutions. The influ... [more]

An external thermal high-temperature continuous feed moving bed tubular reactor was used for the gasification of high moisture content lignite (30.41 wt.%) under CO2 and an auto-generated steam atmosphere. The objectives of this study are to illustrate the synergistic gasification characteristics of high moisture content lignite and CO2 in the tubular reactor; CO2 and auto-generated steam (steam released from the lignite) were used as gasification agents for lignite gasification. The effects of temperature and CO2 flow rate were also investigated. Experimental results showed that when the gasification temperature increased from 800 °C to 1000 °C, the H2 yield also increased from 8.45 mol kg−1 to 17.86 mol kg−1. This may indicate that the H2O-CO2 gasification of semi-coke was enhanced with the rise in temperature. At 900 °C, the gas yield increased with the increase in CO2 flow rate, while the yield of char and liquid product showed an opposite trend. The lower heating value of the H2-r... [more]

With the gradual increase in load demand due to population and economic growth, integrating renewable energy sources (RES) into the grid represents a solution for meeting load demand. However, integrating RES might change the power system type from radial to non-radial, where the current can flow forward and backward. Consequently, power system analysis methods must be updated. The impact on power systems includes changes in the load flow affecting the voltage level, equipment sizing, operating modes, and power system protection. Conventional power system protection methods must be updated, as RES integration will change the power flow results and the short circuit levels in the power system. With an RES contribution to short circuit, existing settings might experience missed coordination which will result in unnecessary tripping. This paper considers the impact of integrating renewable energy sources into power system protection on overcurrent time delay settings. A new method to upgr... [more]

A battery management system (BMS) is an important link between on-board power battery and electric vehicles. The BMS is used to collect, process, and store important information during the operation of a battery pack in real time. Due to the wide application of lithium-ion batteries in electric vehicles, the correct estimation of the state of charge (SOC) of lithium-ion batteries (LIBS) is of great importance in the battery management system. The SOC is used to reflect the remaining capacity of the battery, which is directly related to the efficiency of the power output and management of energy. In this paper, a new long short-term memory network with attention mechanism combined with Kalman filter is proposed to estimate the SOC of the Li-ion battery in the BMS. Several different dynamic driving plans are used for training and testing under different temperatures and initial errors, and the results show that the method is highly reliable for estimating the SOC of the Li-ion battery. T... [more]

The solar module output power is the power generated by all individual cells in their specific electrical circuit configuration, multiplied by the cell-to-module power ratio. The cell-to-module power ratio thus reflects the sum of the losses and gains produced by the structure of the module. The biggest process change in module design during the last few years was the introduction of half cells. Another important trend is the use of bifacial cells to build bifacial modules. These two trends increase parts of the module that correspond to the intercell gaps, and the light does not meet the cell in its path. This part of the radiation is therefore not used efficiently. Scientific efforts focus on the texturing surface of covering glass and cells, and the introduction of narrower ribbons and encapsulation materials with improved UV performance, etc. The concept of a diffusor that actively redirects light from the intercell space into the cell was proposed in the past, in the form of a mic... [more]

The presented work contains the comparison of a different photovoltaic system approach, in terms of monthly energy production profiles, with detailed user needs profiles. Two types of investors were taken into account—a company where the yearly energy consumption exceeded 50 MWh and a standard household where the yearly energy consumption was around 6 MWh. Moreover, two different scenarios were considered; the first one was focused on the maximization of the energy production during a year by choosing optimal azimuth and tilt angles, whereas the second PV system was based on the East−West azimuth angles, which usually enables one to have better energy self-consumption, which leads to sustainable energy usage. Energy production profiles, along with users’ energy needs profiles, were analyzed in terms of sustainability, investment payback time, and energy loss in the face of the new Polish Renewable Energy Law. Recent changes in the Renewable Energy Law in Poland, which came into force o... [more]

Bike-sharing systems implemented in cities with good bike lane networks could potentiate a modal shift from short car trips, boosting sustainable mobility. Both passenger and last-mile goods transportation can benefit from such systems and, in fact, bike sharing (dockless or with docking stations) is increasing worldwide, especially in Europe. This research focused on a European city, Lisbon, and the e-bike sharing system GIRA, in its early deployment, in 2018, where it had about 409 bikes of which 30% were non-electric conventional bikes and 70% were e-bikes. The research aims at answering the main research questions: (1) What is the number of trips per day and travel time in conventional bikes and e-bikes?; (2) Do the daily usage peaks follow the trends of other modes of transport in terms of rush hours?; (3) Are there seasonality patterns in its use (weekdays and weekends, workdays and holiday periods)?; (4) How do climate conditions affect its use?; and finally, (5) What would be t... [more]

Ferry operators in Sweden provide transportation for tens of millions of people annually. As electric vehicles (EVs) are becoming more commonplace, ferries and ferry terminals seem like suitable places for providing charging services. However, high costs and low occupancy rates means that it is challenging to design profitable business models for charging services in general. This paper reports on a market review of the charging services that ferry operators in Sweden provide and a case study of suitable business model design elements for operators that intend to offer charging on board or in terminals. While only two of fifteen ferry operators offer EV charging on board, four more operators indicated that they were planning to provide such services in the near future. Nine operators offered charging in or close to ferry terminals. The results also indicate that business model design focuses primarily on safety, leading to higher costs for onboard charging due to hardware and staffing... [more]