Solar photovoltaic (PV) deployment is rapidly expanding around the world. However, the soiling factor has an impact on its performance. Saudi Arabia has high solar irradiation and plans to diversify its energy mix for electricity generation by deploying more solar PV across the country. However, it is located in an arid and desert environment, making it a challenging project due to dust accumulation on solar modules. The soiling and PV performance in Saudi Arabia are examined in this paper. Furthermore, it highlights several mitigation techniques that can be used to maintain PV performance through preventive and restorative measures. Furthermore, this study looks into the size and characterization of dust in Saudi Arabia, as well as the entire life cycle of dust accumulation on PV modules. In this review study, the performance of solar PV systems is evaluated under soiling in different regions of Saudi Arabia. Depending on the local environment and other factors, the PV performance has... [more]

At present, the trend of all sectors and industries, especially the oil and gas industry, is towards reducing carbon dioxide emissions. Along with the modernization of technological processes, special attention has been paid to the reduction in greenhouse gas emissions from vehicles that run on gasoline and diesel. An effective solution in this field is the transition from vehicles with combustion engines to electric vehicles, similar to the use of the electric bus in public transportation. How to charge these electric buses is a challenge for researchers. By proposing a flash charging method for electric buses, the feasibility of using these buses is obtained. Due to the pulsating nature of the power demand in this charging method, the prevention of negative effects on the network by this type of load should be considered. These negative effects can include power quality problems, voltage drop, frequency instability, and overload of transmission lines and transformers. This paper pres... [more]

High voltage direct current (HVDC) transmission systems play a critical role to optimize resource allocation and stabilize power grid operation in the current power grid thanks to their asynchronous networking and large transmission capacity. To ensure the operation reliability of the power grid and reduce the outage time, it is imperative to realize fault diagnosis of HVDC transmission systems in a short time. Based on the prior research on fault diagnosis methods of HVDC systems, this work comprehensively summarizes and analyzes the existing fault diagnosis methods from three different angles: fault type, fault influence, and fault diagnosis. Meanwhile, with the construction of the digital power grid system, the type, quantity, and complexity of power equipment have considerably increased, thus, traditional fault diagnosis methods can basically no longer meet the development needs of the new power system. Artificial intelligence (AI) techniques can effectively simplify solutions’ com... [more]

To solve the problems of the low energy efficiency and slow penetration rate of drilling, we took the geological data of adjacent wells, real-time logging data, and downhole engineering parameters as inputs; the mechanical specific energy and unit footage cost as multi-objective optimization functions; and the machine pump equipment limit as the constraint condition. A constrained Bayesian optimization algorithm model was established for the optimization solution, and drilling parameters such as weight-of-bit, revolutions per minute, and flowrate were optimized in real time. Through a comparison with NSGA-II, random search, and other optimization algorithms, and the application results of example wells, we show that the established Bayesian optimization algorithm has a good optimization effect while maintaining timeliness. It is suitable for real-time optimization of drilling parameters, can aid a driller in identifying the drilling rate and potential tapping area, and provides a decis... [more]

In this paper, the method and a control algorithm for detecting resonant destruction of a resonant auxiliary power supply for railway vehicle are proposed. It is essential to reduce the weight of the electric equipment attached to the lower part of the railway vehicle because it greatly affects the life of the railway vehicle, such as wheel and bearing. In order to reduce the weight and volume of the auxiliary power supply, in the case of windings, high-speed switching should be performed by lowering the input voltage. Therefore, in this paper, the auxiliary power supply control algorithm using an LLC resonant converter to reduce the weight of auxiliary power supply for railway vehicle is proposed, and the method of detecting resonant destruction due to device failure of a resonant converter is proposed. The proposed algorithm steps down the wire voltage using an input buck converter for high-speed switching, and the inverter input voltage is controlled through the LLC resonant convert... [more]

Supercritical multi-thermal fluid is an emerging and efficient heat carrier for thermal recovery of heavy oil, but the generation of supercritical multi-thermal fluid and its feasibility in thermal recovery are rarely discussed. In this paper, generation and flooding experiments of supercritical multi-thermal fluid were carried out, respectively, for the generation and feasibility of supercritical multi-thermal fluid. During the experiment, the temperature and pressure in the reactor and sand-pack were monitored and recorded, the fluid generated by the reaction was analyzed by chromatography, and enthalpy of the reaction product and displacement efficiency were calculated, respectively. The experimental results showed that the change in temperature and pressure in the reactor could be roughly divided into three stages in the generation process of supercritical multi-thermal fluid. The higher the proportion of oil in the reactant, the higher the maximum temperature in the reactor. When... [more]

The second-order sliding mode control has strong robustness. Its application has greatly improved the anti-jamming ability of permanent magnet synchronous motor(PMSM) speed control systems. However, the influence of noise is unavoidable due to the introduction of a differentiator in the second-order sliding mode control, and the steady-state performance of the system is poor due to the absence of a q-axis current loop. This paper proposes a second-order sliding mode control method based on singular perturbation, which decouples the PMSM speed control system into two subsystems, the slow subsystem, including the speed variable, adopts second-order sliding mode control, and the fast subsystem, including the current variable of q-axis, adopts linear control. The design of a sliding surface for the slow subsystem avoids the application of the differentiator, which reduces the chattering better. Besides this, the steady-state performance of the system is improved due to the introduction of... [more]

In present electrical power systems, wind energy conversion systems based on doubly fed induction generators represent one of the most commonly accepted systems in the global market due to their excellent performance under different power system operations. The high wind energy penetration rate makes it challenging for these wind turbines to follow grid code requirements. All operations of a wind energy system during a dip in voltage require special attention; these operations are critically known as fault ride-through and low voltage ride-through. In this paper, various fault ride-through techniques of doubly fed induction generator-based wind energy conversion systems, such as protective circuitry, reactive power injection, and control methods for transient and steady state operations, have been presented to improve the performance. During system disturbances, protective circuitry or control mechanisms are typically used to limit the over-current of the rotor and the generated inappr... [more]

The Xishan coalfield is an important coking coal-producing area in China. The No. 8 and No. 9 coals of the Taiyuan formation were sampled and tested from nine mines in the center and north of the Xishan coalfield, and the coal’s quality characteristics, element occurrence characteristics, enrichment characteristics, and sedimentary environment characteristics were analyzed to provide a foundation for clean and efficient coal utilization and identification of associated coal resources. The results obtained from the experiment show that Li in No. 8 coal is the enrichment element. The enrichment coefficient of the U element of ML8 is 13.78, which is close to the industrial index of recycling. The enrichment hazardous elements are Cu, Mo, Cd of ML8, Mo of DQ8, and Th of ZCD8. Along with K value and Sr/Ba ratio, seawater has a greater influence on the south of No. 8 coal than on the north and on the east of No. 9 coal than on the west. No. 8 coal (except ML8) was formed under an oxidation e... [more]

The utilization of condensate water as a compressor-discharge cooler results in subcooling on the condenser outlet. On the other hand, a split-type air conditioner (A/C) with R32 as working fluid can provide higher compressor-discharge temperatures than other refrigerants used in the same A/C. Therefore, A/C working with R32, equipped with a heat exchanger by utilizing waste-condensate water as the compressor-discharge cooler, has promising potential to produce the largest subcooling effect in air-conditioning systems. The aim of this study is to investigate the effect of condensate water as the compressor-discharge cooler on the performance of an A/C using R32 as the working fluid with different sizes of heat exchanger. The experimental study was carried out on the A/C with a compressor capacity of 1.1 kW, using three different heat-exchanger lengths, i.e., 18, 20 and 22 cm. The results indicated that longer heat exchangers produced higher degrees of subcooling; the heat exchangers wi... [more]

Imaging concentrators like the parabolic trough solar concentrators have been widely employed for energy production in solar power plants. The conventional imaging solar concentrators form a non-uniform Gaussian distribution on receiving absorbers yielding the highest temperatures. The traditional CSP system normally truncated a peripheral region of heat flux to better use the central part. CPV/T systems using the waste heat recovery method can largely improve the total efficiency. However, for the CPV module, the coolant temperature was usually below 80 °C, which limited the applications of the thermal cycle such as the ORC system. In this article, a novel trough-type free-form secondary solar concentrator (TFSC) for PV/Thermal hybrid application has been proposed. Different from other CPV/T concepts using a combined PV panel and cooling tunnel/tube, the current concept separates the receiver in two parts. The secondary free-form reflector is generated by the geometric construction me... [more]

By operating over a large bandwidth, the terahertz (THz) frequency band (0.3−3 THz) promises to deliver extremely high data rates. While the use of this band in cellular communications systems is not expected to happen within the next decade, various other use-cases such as wireless backhauling and point-to-point wireless access are on the immediate horizon. In this study, we develop an analytical propagation model for the case of ground-to-aircraft communications by explicitly accounting for THz-specific propagation phenomena including path loss, attenuation by different types of clouds, and atmospheric absorption at different altitudes. To this aim, we first exhaustively characterize the geometric, molecular, and structural properties of clouds for different weather conditions and Earth regions. Then, by applying the tools of stochastic geometry, we present the closed-form expression for received power at the aircraft. Our numerical results show that the type of weather forming diffe... [more]

Due to its sedimentary characteristics and natural fractures, oil shale shows anisotropy in heat transfer characteristics. Moreover, the anisotropic thermal conductivity will change with the temperature. This change in the anisotropic thermal conductivity coefficient affects the temperature field distribution and heating efficiency during the in situ electric heating pyrolysis of oil shale. Therefore, it is very important to study the evolution of the anisotropy thermal conductivity coefficient of oil shale with temperature. In this study, the variation of weight loss and the specific heat of an oil shale with temperature is investigated using a differential scanning calorimeter. The variation of the anisotropic pore and fracture structure of the oil shale with temperature is studied through CT scanning technology. The variation of the anisotropic thermal conductivity with temperature is studied through the hot disk method. Finally, the relationship between the change in the anisotropi... [more]

In recent years, micro turbine technology has become a continuously reliable and viable distributed generation system. The application of distributed energy power generation sources, such as micro gas turbines (MGT), to charge electric vehicles offers numerous technical, economical benefits, and opportunities. MGT are considered as they are smaller than conventional heavy-duty gas turbines. They also are capable of accepting and operating with different fossil fuels in the range of low−high pressure levels as well as co-generation opportunities. The MGT could provide the fast and reliable output power guaranteed and needed for grid stability. This paper provides a mathematical representation, modelling, and simulation of a low-cost fast charging station based on a micro gas turbine and a super capacitor forming altogether a power generation system suitable for use especially as energy source in fast charging stations and dynamic power systems. All the micro gas turbine’s parameters are... [more]

The production of low-carbon hydrogen based on renewable energy sources is considered a promising direction in the development of the modern world economy. The purpose of the presented research is to develop technologies and study the processes of converting biogases into hydrogen, as well as its use in low-temperature fuel cells. The methodology for organizing a multi-stage laboratory experiment for obtaining biogas, its purification from impurities and, in the future, the production of biohydrogen was developed based on field studies in Peter the Great St. Petersburg Polytechnic University. The results of modeling studies have shown that during biogas reforming, it is possible to obtain a hydrogen mixture with a hydrogen content of 98% vol and methane 2% vol. Based on the results of the research, the possibility of using the significant potential of “weak” biogas containing methane 30−45% vol to produce biohydrogen (more than 93% vol) was proved. A technique for using biohydrogen in... [more]

Fluid−structure interactions (FSI) can significantly affect flow and the acoustic field generated by it. In this article, simulations of the flow over a rectangular cavity are conducted with and without taking FSI into account. The aim of this research is to conduct a numerical study of the flow over a cavity and to verify whether interactions between the flow and the elastic structure can significantly affect the flow itself or the acoustic pressure field. Four cases involving flexible walls with different material parameters and one reference case with rigid walls were analysed. The two-directional fluid−structure coupling between the flow and cavity walls was simulated. The simulations were performed with the volume and finite element methods using OpenFOAM software to solve the fluid field, CalculiX software to solve the displacement of the structure, and the preCICE library to couple the codes and computed fields. The acoustic analogy of Ffowcs-Williams and Hawkings and the libAco... [more]

The stimulation method of the marine natural gas hydrate (NGH) reservoir through hydraulic fracturing has been proposed to resolve the problem of the low production capacity in the conventional development method of pressure drawdown. Nevertheless, due to the strong plasticity and high argillaceous siltstone content of the marine NGH reservoir, conventional small-particle-size proppant cannot form effective support for fractures after fracturing because of serious embedding in the reservoir. To solve this problem, the large-size phase change proppants were developed in this study. First, an epoxy resin curing system that can reduce curing time to 40 min in low temperature and humid environment was developed. Then, the epoxy resin and curing system was emulsified, and through the optimization of the emulsification process, the particle size of the proppant can be controlled in 0.5−4.5 mm and the cementation between the proppant particles during the curing process can be prevented. Final... [more]

A large number of spatially dispersed nodes on the wireless network create Wireless Sensor Networks (WSNs) to collect and analyze the physical data from the environment. The issues that affected the network and had an impact on network energy consumption were cluster head random selection, working node redundancy, and cluster head transmission path construction. Consequently, this energy constraint also has an impact on the network lifetime and energy-efficient routing. Therefore, the primary goals of this research are to decrease energy consumption and lengthen the network’s lifespan. So, using improved optimization algorithms, this paper presents a dynamic cluster head-based energy-efficient routing system. The Improved Coyote Optimization Algorithm (ICOA), in this case, consists of three phases setup, transmission, and measurement phase. The Improved Jaya Optimization Algorithm with Levy Flight (IJO-LF) then determines the route between the BS and the CH. It selects the most effecti... [more]

Power angle stability of power systems is one of the main factors which restricts the power transmission capacity. In order to prevent the power angle instability of power systems, phase sequence exchange (PSE) is a recently developed emergency control technique that reduces the power angle by 120°. This paper proposes a new phase sequence exchange technology based on a modular multi-level converter (MMC). In this paper, the concept of deceleration area ratio is proposed, that is used to characterize the power angle stability of the power system, and the phase sequence exchange theory based on an MMC is analyzed. A phase sequence exchange circuit based on a modular multilevel converter (MMC) is designed. In this paper, the system parameters of the MMC-based PSE are optimized. Finally, a model is developed on PSCAD. The simulation results show that the MMC-based phase sequence exchange technology can effectively improve the power angle stability of the power system.

This communication discusses the energy, exergy, and economic feasibility of novel heat storage based on a single-slope solar still coupled with a solar air heater (SAH). The analysis was conducted on three different solar stills, i.e., a single-slope solar still (SSSS), single-slope solar still with latent heat storage, and a single-slope solar still with latent heat storage coupled with a solar air heater. The performance evaluation of all types of solar still has been compared to evaluate the best-performing solar still. Paraffin wax as a phase change material (PCM) has been used at the bottom of the solar still to provide proper thermal storage. The experiments were conducted on different depths, i.e., 3 cm, 6 cm, 9 cm, 12 cm, and 15 cm. The efficiency of a single-slope solar still with PCM and SAH was 65.58% higher than a conventional solar still. The average exergy efficiency of a single-slope solar still with latent heat storage coupled with a solar air heater is 83.19% higher t... [more]

Energy consumption schedulers have been widely adopted for energy management in smart microgrids. Energy management aims to alleviate energy expenses and peak-to-average ratio (PAR) without compromising user comfort. This work proposes an energy consumption scheduler using heuristic optimization algorithms: Binary Particle Swarm Optimization (BPSO), Wind Driven Optimization (WDO), Genetic Algorithm (GA), Differential Evolution (DE), and Enhanced DE (EDE). The energy consumption scheduler based on these algorithms under a price-based demand response program creates a schedule of home appliances. Based on the energy consumption behavior, appliances within the home are classified as interruptible, noninterruptible, and hybrid loads, considered as scenario-I, scenario-II, and scenario-III, respectively. The developed model based on optimization algorithms is the more appropriate solution to achieve the desired objectives. Simulation results show that the expense and PAR of schedule power u... [more]

In normal operation, there is no significant thermal stratification phenomenon in the tube bundle area of the steam generator of the nuclear power plant. However, this phenomenon is detected in marine nuclear power plant isolation loops in the presence of feedwater leakage. Therefore, an experiment was designed to verify the presence of thermal stratification, and the influence factors were analyzed by the RELAP5/MOD3.2 program. The results show that thermal stratification is mainly influenced by the initial water level at isolation, the initial pressure at isolation, the total leakage mass, and the internal circulation of the steam generator. Leakage flow has little effect on it. This phenomenon causes the coolant temperature at the primary side of the steam generator in the isolated loop to be lower than the temperature measured in the reactor inlet pipe or outlet pipe. This study aids the operator in determining the real coolant temperature at the primary side of the steam generator... [more]

Concrete, an integral part of a nuclear power plant (NPP), experiences degradation during their operational lifetime of the plant. In this review, the major causes of concrete degradation are extensively discussed including mechanisms that are specific to NPPs. The damage mechanism could be chemical or physical. The major causes of chemical degradation include alkali−aggregate reactions, leaching, sulfate attack, bases and acids attack, and carbonation. Physical degradation is a consequence of both environmental and mechanical factors combined. These factors are mainly elevated temperature, radiation, abrasion and erosion, salt crystallization, freeze−thaw distortions, fatigue and vibration. Additionally, steel reinforcements, prestressing steels, liner plates, and structural steel also experience degradation. The prospective areas in the structural components of the NPP where the degradation could occur are mentioned and the effective solutions to the causes of degradation are highlig... [more]

We present a data prepossessing method for parameter identification based on clustering and hypothesis testing in a power distribution network to successfully achieve a more accurate result. This method considers the similarities of data in both spatial relationship and statistical theory, then builds a sophisticated data processing method to improve the performance of dynamic model-based parameter identification models, i.e., Markov chain Monte Carlo and sequential model-based global optimization. We applied this data processing method to the actual feeder data with no adjustment of the other condition. The experiment shows that our method achieves a 4.8% improvement in accuracy at most.

The geochemical characteristics of water produced from coalbed methane (CBM) wells contain rich information about the associated geology, environment, and production. This study was conducted in the Southern Qinshui Basin, where produced water samples were collected from 10 typical CBM wells and their ionic compositions and water quality parameters were tested. The differences in the chemical characteristics of the produced water between different producing coal seams and between single-seam production wells (SPWs) and multi-seam co-production wells (MCWs) were compared, and the geochemical formation process of the produced water was revealed. The following conclusions were obtained: (1) the water produced samples that were mainly Na-HCO3-type and were generally weakly alkaline and moderately mineralized. The water produced from No. 15 coal seam was more enriched in SO4, Ca, and Mg compared to that of No. 3 coal seam, and the variations were more intense, reflecting a more complex wate... [more]