Two di-ureasils incorporating oxyethylene segments with average molecular weights Y = 600 and 900 g mol−1, prepared by the sol-gel method, and doped with the ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) and lithium tetrafluoroborate (LiBF4) salt were prepared. The as-obtained films are translucent, flexible, and hydrophobic, and have a low level of nanoscale surface roughness. The ionic conductivity values exhibited by an optimized sample are 8.10 × 10−5 and 2.8 × 10−4 S cm−1 at room temperature and 55 °C, respectively. The main goal of the work was to employ the electrolytes in prototype electrochromic devices (ECDs) with the [glass/a-IZO/a-WO3/d-U(Y)LiBF4-[Bmim]Cl/c-NiO/a-IZO/glass], noted as ECD1 for Y = 600 and ECD2 for Y = 900, where a-WO3 and c-NiO stand for amorphous tungsten oxide and crystalline nickel oxide, respectively. At 555 nm the ECD1 device exhibited the highest coloration efficiency for coloring (CEin = −420.621 cm2·C−1), the highest optical density va... [more]

Acetic acid is the primary by-product generated from ethanol production by Fusarium oxysporum using glucose or xylose as a substrate. Aldehyde dehydrogenase (ALDH) is the critical enzyme in acetic acid metabolism. To decrease acetic acid yield in ethanol production, the 1509 bp DNA of aldh, encoding a 502 amino acid protein with a calculated molecular mass of 54.33 kDa and an isoelectric point of 6.21, was cloned from F. oxysporum. Sequence analysis confirmed that the screened proteins belonged to the ALDH family. A knockout vector, ∆aldh, containing positive (hygromycin resistance gene) and negative (thymidine kinase gene from the herpes simplex virus) selectable markers, was constructed. Ethanol production by the mutant (cs28pCAM-Pstal-∆aldh) in glucose- and xylose-containing media was 0.46 and 0.39 g/g, respectively, and these yields were 16.93% and 34.63% higher than those by the wild-type strain (0.393 and 0.289 g/g). Furthermore, the acetic acid yield of the mutant was 3.50 and 3... [more]

Photovoltaic (PV) technology is the symbol of a sustainable future in many countries around the globe [...]

In addition to active power generation, photovoltaic inverters can be used to provide ancillary services to grids, including reactive power compensation. This paper proposes a metaheuristic approach based on particle swarm optimization for the allocation and sizing of photovoltaic inverters that perform the complementary functions of static synchronous compensator (PV-STATCOM) units. The objective of the aforementioned approach is to reduce the initial investment cost in the acquisition of PV-STATCOM units. The proposed methodology considers both the daily load curve and generation and is applied to a 33-bus test system. The methodology is validated based on an exhaustive search algorithm and tested over 1000 consecutive simulations for the same problem; consequently, the methodology produces low standard deviations and errors, indicating its robustness. The methodology demonstrates an improved grid voltage profile throughout the day when applied to the 33-bus test system. Furthermore,... [more]

Pakistan has been facing energy crises for more than a decade as a result of its reliance on imported fossil fuels, circular debt, political instability, and absurd energy policies. However, the country has abundant renewable energy resources which, if harnessed, may help to effectively cope with ever-increasing energy demand. This review study investigates the country’s economic and energy situations, energy crises, and energy sector performance. A critical analysis of studies conducted on Pakistan’s energy planning since its independence in 1947 is, and policies announced to date are assessed. This review reveals that the economic situation of the country has remained severely stressed, and energy sector performance has been compromised over the years for various underlying reasons. The energy policy narrative in the early decades of the post-independence period focused on water resource management, whereas energy concerns were only realized in the late 1960s as demand grew. The firs... [more]

Permanent magnet (PM) machines inevitably suffer from cogging force, which does not contribute to the average output torque (force) but contributes as a type of torque (force) ripple. This paper provides an overview of the cogging force reduction methods for different types of PM machines. First, a systematic and comprehensive categorization of different kinds of cogging force reduction methods is given according to the reduction principle. Then, the cogging force reduction methods for different types of PM machines are analyzed and discussed based on the categorization. Finally, according to the versatility and feasibility of the cogging force reduction methods, practical methods are recommended for different types of PM machines. The categorization, analyses, and recommendations presented in the paper are useful for the design of different types of PM machines with the requirement of cogging force reduction or output torque (force) ripple suppression.

Hybrid DC microgrid clusters contain various types of converters such as BOOST, BUCK, and bidirectional DC/DC converters, making the control strategy complex and difficult to achieve plug-and-play. The common master−slave hierarchical control strategy makes it difficult to achieve accurate and stable system control. This paper proposes an accurate peer-to-peer hierarchical control method for the hybrid DC microgrid cluster, and the working principle of this hierarchical control method is analyzed in detail. The microgrid cluster consists of three sub-microgrids, where sub-microgrid A consists of three BUCK converters, sub-microgrid B consists of three BOOST converters, and sub-microgrid C consists of two bidirectional DC/DC converters. According to all possible operations of various sub-microgrids in the microgrid cluster, the top-, mid-, and bottom-level controls are designed to solve the coordination control problem among different types of sub-microgrids. In this paper, a hybrid mic... [more]

The article discusses the results of experimental studies on the course of pyrolysis oil injection through the high-pressure injector of a direct-injection engine. The pyrolysis oil used for the tests was derived from waste plastics (mainly high-density polyethylene—HDPE). This oil was then distilled. The article also describes the production technology of this pyrolysis oil on a laboratory scale. It presents the results of the chemical composition of the raw pyrolysis oil and the oil after the distillation process using GC-MS analysis. Fuel injection tests were carried out for the distilled pyrolysis oil and a 91 RON gasoline in order to perform a comparative analysis with the tested pyrolysis oil. In this case, the research was focused on the injected spray cloud analysis. The essential tested parameter was the Sauter Mean Diameter (SMD) of fuel droplets measured at the injection pressure of 400 bar. The analysis showed that the oil after distillation contained a significant proporti... [more]

This study aims to create a comprehensive, holistic approach to evaluate the environmental, energy, and economic impacts of air source heat pump deployment scenarios through: (i) a life cycle assessment of air source heat pumps in Orkney houses, (ii) energy systems optimisation modelling to optimise the performance of an air source heat pump coupled with thermal energy storage tank to reduce use phase related impacts in Orkney, (iii) modelling of Orkney’s domestic building stock to understand the housing condition, and (iv) economic modelling to analyse the life cycle cost of an air source heat pump and potential savings when replacing conventional heating systems. The results show that an 82% reduction in energy supply could be achieved when ambitious energy efficiency improvement measures are adopted in the circular economy scenario. The use phase related emissions could be reduced by 98% when the air source heat pump becomes the only heating technology in Orkney. However, the life c... [more]

To characterize the hydraulic fracture network of a conglomerate reservoir, a slant core well was drilled aimed to obtain direct information regarding hydraulic fractures through slant core at the conglomerate hydraulic fracturing test site (CHFTS). Core fracture classification was the fundamental issue of the project. In this study, three grade classifications for core fractures were proposed. Comprehensive classification of core fractures was carried out using the analytic hierarchy process (AHP)−fuzzy comprehensive evaluation (FCE) method. Finally, the fracture classification results were validated against numerical simulation. The grade-1 fracture classification included hydraulic fractures, drilling-induced fractures and core cutting-induced fractures. A total of 214 hydraulic fractures were observed. For the grade-2 classification, the hydraulic fractures were divided into 47 tensile fractures and 167 shear fractures. For the grade-3 classification, the shear fractures were subdi... [more]

The magnetic properties of magnetic cores are essential for the design of electrical machines, and consequently appropriate mathematical modeling is needed. Usually, the design and analysis of electrical machines consider only the one-dimensional (1D) magnetic properties of core materials, i.e., the relationship of magnetic flux density (B) versus magnetic field strength (H), and their associated power loss under 1D magnetization, in which the B and H are constrained in the same orientation. Some studies have also been performed with the two-dimensional (2D) magnetizations in which the B and H are vectorial, rotating on a plane, and they may not be in the same direction. It has been discovered that the 2D rotational property is very different from its 1D alternating counterpart. However, the magnetic fields in an electrical machine, in particular claw pole and transverse flux machines, are naturally three-dimensional (3D), and the B and H vectors are rotational and may not lie on the s... [more]

It is vital to further improve the design of TPV thermal emitters since the energy efficiency of thermophotovoltaic (TPV) systems is still not adequately high. In this paper, we propose a novel evaluator for the optimization of TPV thermal emitters, namely the percentage of effective figure (PEF) to replace the figure of merit (FOM). The associated algorithm, Bayesian optimization nesting simulated annealing (BOnSA), is developed to achieve better performance. By searching throughout the whole parameter space and then optimizing in a reduced space, BOnSA can lead to a satisfactory solution numerically for GaSb photovoltaic (PV) cells. When designing the emitter, the aperiodic material structure with an anti-reflection substructure and Fabry−Perot etalon is constructed from the material candidates. In particular, one of the optimal structures determined by BOnSA is {SiO2, ZnS, Ge, MgF2, W, Si, SiO2, W} with the value of PEF=0.822, which is better than the previous work by comparison. Mo... [more]

Driving cycles are commonly used to evaluate the fuel efficiency and mileage of internal combustion engine vehicles and electric vehicles (EVs). To improve the mileage of EVs, efficient propulsion motors and inverters must be employed, particularly at frequently used speed and torque points of driving cycles. In this study, the number of the stator winding turns of a tap-change permanent magnet synchronous motor (PMSM) used for EV propulsion was investigated to increase the motor and inverter energy efficiencies under an urban dynamometer driving schedule (UDDS), a highway fuel economy test (HWFET), and combined UDDS/HWFET driving cycles. The motor core loss due to the carrier harmonics, copper loss, and inverter loss were analyzed for various winding turn number combinations, and the most efficient combination was selected. Based on the analysis results, the tap-change motor winding turns that exhibited the least loss were rewound on a PMSM of a mass-produced EV. The demand energy of... [more]

The emissions from direct injection (DI) diesel engines remain a serious setback from the viewpoint of environmental pollution, especially for those who have been persuaded to use biofuel as an alternative fuel. The main drawbacks of using biofuels and their mixtures in DI diesel engines are increased emissions and decreased brake thermal efficiency (BTE) compared to using neat diesel fuel. The current study analyses the biodiesel made from cashew nut shell liquid (CNSL) using a single-cylinder, direct-injection diesel engine to validate the engine’s performance and discharge characteristics. In addition to the improved CNSL and a twin-fuel engine that runs on hydrogen, ethanol was added to the fuel at rates of 5%, 10%, and 15%. The investigation was conducted using a single-cylinder direct injection diesel engine at steady-state settings, above the sustained engine speed (1500 RPM). Several performance parameters and pollutant emissions, such as hydrocarbons (HC), carbon monoxide (CO)... [more]

Power system stability is greatly affected by two types of stochastic or random disturbances: (1) topological and (2) parametric. The topological stochastic disturbances due to line faults caused by a series of lightning strikes (associated with circuit breaker, C.B., opening, and auto-reclosing) are modeled in this paper as continuous-time Markov jumps. Additionally, the stochastic parameter changes e.g., the line reactance, are influenced by the phase separation, which in turn depends on the stochastic wind speed. This is modeled as a stochastic disturbance. In this manuscript, the impact of the above stochastic disturbance on power system small-disturbance stability is studied based on stochastic differential equations (SDEs). The mean-square stabilization of such a system is conducted through a novel excitation control. The invariant ellipsoid and linear matrix inequality (LMI) optimization are used to construct the control system. The numerical simulations are presented on a multi... [more]

The complex structure of gas-insulated switchgear (GIS) cable terminals leads to serious electric field concentration, which is a frequent fault position of a high-voltage cable system. At present, due to the differences in the frequency bands of sensors, various partial discharge detection technologies have certain differences in their scope of application and anti-interference performance, resulting in a low defect detection rate in GIS cable terminals. In this paper, a comprehensive diagnosis scheme is proposed, which integrates transient earth voltage (TEV), ultra-high frequency (UHF), high frequency (HF), and ultrasonic methods. Two abnormal discharge defects of GIS terminals in two 220 kV substations in Tianjin were tracked and monitored, and the joint diagnosis was carried out using the proposed scheme; the type of discharge defect and the phase sequence of the defect were determined, and the UHV was employed to precisely locate and analyze the defect source. Finally, through th... [more]

In this paper, the potential to reduce the energy consumption of end devices operating in a LoRaWAN (long-range wide-area network) is studied. An increasing number of IoT components communicating over wireless networks are powered by external sources. Designers of communication systems are concerned with extending the operating time of IoT, hence the need to look for effective methods to reduce power consumption. This article proposes two algorithms to reduce the energy consumption of end devices. The first algorithm is based on the use of a measured value prediction, and the second algorithm optimizes the antenna gain of the end device. Both algorithms have been implemented and tested. The test experiments for reducing energy consumption were conducted independently for the cases with the first algorithm and then for the second algorithm. The possibilities of reducing energy consumption were also investigated for the case when both algorithms work together. The proposed predictive alg... [more]

In the oil and gas industry, wax formation and deposition are common problems, particularly during production and transportation. To better understand the expected behaviour of a given waxy crude oil and consequently select the best solution to prevent wax deposition, it is vital to conduct laboratory tests or numerical simulations to model its performance. For a Brazilian oil field, the phase behaviour of 17 crude oils was modelled using Multiflash software. To tune the model, laboratory tests were used, including true boiling point curves and viscosity tests. This study followed two stages: the first allowed characterization of the wax appearance temperature (WAT) and determination of the expected precipitation curves for these crude samples, and the second stage was evaluation of the impact on wax precipitation after the addition of methane (CH4), carbon dioxide (CO2) or fatty acid (CH3(CH2)nCOOH). Results showed that WAT varied between 47.5 °C and 51.6 °C for these crude oil sample... [more]

Based upon the thermodynamic simulation of a biogas-SOFC integrated process and the costing of its elements, the present work examines the economic feasibility of biogas-SOFCs for combined heat and power (CHP) generation, by the comparison of their economic performance against the conventional biogas-CHP with internal combustion engines (ICEs), under the same assumptions. As well as the issues of process scale and an SOFC’s cost, examined in the literature, the study brings up the determinative effects of: (i) the employed SOFC size, with respect to its operational point, as well as (ii) the feasibility criterion, on the feasibility assessment. Two plant capacities were examined (250 m3·h−1 and 750 m3·h−1 biogas production), and their feasibilities were assessed by the Internal Rate of Return (IRR), the Net Present Value (NPV) and the Pay Back Time (PBT) criteria. For SOFC costs at 1100 and 2000 EUR·kWel−1, foreseen in 2035 and 2030, respectively, SOFCs were found to increase investmen... [more]

Biochar, known as “Black Gold”, has become a novel approach with potential benefits for soil amendment, such as improving soil physicochemical properties, reducing greenhouse gas emissions, and enhancing soil fertility. The previous research studies mainly focus on exploring different methods for the improvement of biochar enriched nutrients as fertilizers; however, the migration and transformation mechanisms of these nutrients induced by biochar are yet to be extensively investigated. This paper provides an overview of recent advances in the application and mechanisms of biochar for soil amendment focusing on soil properties and nutrients improvement. Biochar positively alters microbial-mediated reactions in the soil C and N cycles, i.e., mineralization of C and N, and N2 fixation, thus enhancing maximizing C and N use efficiency and reducing the potential losses. Moreover, biochar provides reactive surfaces where P and K ions are retained in soil microbial biomass and in exchange sit... [more]

Due to the rising trends in the adoption of smart systems such as smart grids, smart homes, and vehicle-to-grid, there has been a lot of research interest in these areas. To manage these complex systems effectively and intelligently, a reliable, high-speed, and secure data communication network is very essential. The key distinguishing feature between smart systems and traditional ones is that smart systems use a two-way communication system while traditional systems usually use one-way communication. The requirements and techniques needed to ensure safe, secure, and reliable communication in smart systems have been the focus of many researchers in recent times. This work is aimed at providing a comprehensive, all-encompassing, up-to-date review of smart systems communication to ascertain the research directions as well as challenges. This review will guide other researchers in delving into smart systems communication to identify potential research problems and future research directio... [more]

An increasing demand to repurpose used lithium-ion batteries in secondary applications is driving the need to develop methods of evaluating the state-of-health of used batteries. In this paper, we discover a self-terminated end-of-charge temperature rise (ECTR) phenomenon in 18650 lithium-ion cells, both recycled from the field and aged under controlled conditions in the lab. ECTR is characterized by an additional temperature rise near the end of the charging process and is accompanied by low coulombic efficiency. A higher charge rate and longer inactive time at low state-of-charge appear to increase the occurrence of ECTR. The intensity of ECTR is found to closely correlate with the excess charge capacity but is less affected by the charge current or cell impedance. ECTR is weakly dependent on the remaining cell capacity in recycled cells, and the controlled aging study shows that aging condition, not remaining capacity or internal resistance, determines the presence and intensity of... [more]

In this study, graphene is used as a photothermal material, which is added to the SiO2 superhydrophobic solution treated with fluorine silane, and then sprayed on the copper plate surface to prepare a new type of photothermal superhydrophobic surface with contact angles up to 160.5° and 159.8°. Under the conditions of natural convection, the effects of photothermal superhydrophobic surfaces on droplet condensation, freezing, and frost growth are investigated in different environments. The results show that the photothermal superhydrophobic surface can not only delay the freezing of surface droplets, prolong the freezing time of droplets, and reduce the thickness of the frost layer, but also allow for the rapid removal of droplets under near-infrared (NIR) irradiation. If the droplet is irradiated by an infrared laser emitter while the cooling system is still turned on, the internal temperature of the droplet will always be higher than the crystallization temperature under the illuminat... [more]

Production forecasting plays an important role in development plans during the entire period of petroleum exploration and development. Artificial intelligence has been extensively investigated in recent years because of its capacity to extensively analyze and interpret complex data. With the emergence of spatiotemporal models that can integrate graph convolutional networks (GCN) and recurrent neural networks (RNN), it is now possible to achieve multi-well production prediction by considering the impact of interactions between producers and historical production data simultaneously. Moreover, an accurate prediction not only depends on historical production data but also on the influence of neighboring injectors’ historical gas injection rate (GIR). Therefore, based on the assumption that introducing GIR can enhance prediction accuracy, this paper proposes a deep learning-based hybrid production forecasting model that is aimed at considering both the spatiotemporal characteristics of pro... [more]

Spray cooling has demonstrated advantages in the thermal control of avionic devices. In this study, a spray cooling system is established using liquid nitrogen (LN2) as a working fluid to investigate the effect of heat transfer characteristics on a large heating surface. The temperature response measurement and experimental analysis of the heating surface of a large-area shell structure under the boundary conditions of different heat flux and temperature regions were carried out. The temperature response curves for the outer surface of the shell structure from the initial temperature to the set temperature were obtained under different heat flows and temperature zones. The results show that the thermal response time of the surface spray phase cooling is less than 2 s, the stability time for the cooling temperature of the covering layer is longer than 60 s, and the cooling state can be maintained for 30 min under different working conditions. This study can provide a technical reference... [more]