A gas-lifted system in a mature oil well can experience casing-heading instability, which reduces the mean oil production and it is not healthy for the downstream equipment. This instability was removed by implementing a terminal equality-constrained nonlinear model predictive control (NMPC) having input targets with control zones in the system. The input-dependent stability behaviour of the gas-lifted system was visualised through the bifurcation diagram and the step responses of the linearised model at various operating points. The controller was then presented. Then, the close-loop feasibility, as well as the convergence, were discussed. The controller stabilised the undisturbed gas-lifted system, improving production by 5.63% compared to the open-loop operation when the system was in casing-heading instability. For the two input case, the steady-state production, aided by the high-input target, reached 12.25 kg/s, which was far more than 9.57 kg/s for the one input case. This contr... [more]

Thermal storage is very relevant for technologies that make thermal use of solar energy, as well as energy savings in buildings. Phase change materials (PCMs) are positioned as an attractive alternative to storing thermal energy. This review provides an extensive and comprehensive overview of recent investigations on integrating PCMs in the following low-temperature applications: building envelopes, passive systems in buildings, solar collectors, solar photovoltaic systems, and solar desalination systems. Moreover, techniques for improving heat transfer in PCM systems are described. All applications studies indicate that all applications improve their performance when applying a PCM. One of the most beneficiated technologies is the combined PV-Thermal systems (PVT), where some authors reported an increase in overall efficiency greater than 40%.

In order to realize an online power supply, this article develops an explicit design of induction power extraction technology combined with wireless power transmission (WPT) technology. Unlike the power supply mode of traditional batteries of online monitoring devices of high-voltage transmission lines, this technology solves the short battery life cycle problems. First, the principle of induction power extraction is analyzed. Based on the equivalent circuit of the mutual inductance model, expressions of induction power extraction without and with core saturation are derived, respectively. According to the current transformer (CT) magnetic coupling diagram, the open-circuit voltage of the secondary side of the CT is deduced. Therefore, the CT material and size could be selected. The CT coupling model is used to equivalent the current transformer to the ideal voltage source. Then, the four basic topological spaces of the magnetic coupling resonant WPT system are analyzed and calculated,... [more]

Accurate medium- and long-term power load forecasting is of great significance for the scientific planning and safe operation of power systems. Monthly power load has multiscale time series correlation and seasonality. The existing models face the problems of insufficient feature extraction and a large volume of prediction models constructed according to seasons. Therefore, a hybrid feature pyramid CNN-LSTM model with seasonal inflection month correction for medium- and long-term power load forecasting is proposed. The model is constructed based on linear and nonlinear combination forecasting. With the aim to address the insufficient extraction of multiscale temporal correlation in load, a time series feature pyramid structure based on causal dilated convolution is proposed, and the accuracy of the model is improved by feature extraction and fusion of different scales. For the problem that the model volume of seasonal prediction is too large, a seasonal inflection monthly load correcti... [more]

Compressed natural gas (CNG) main stations are critical components of the urban energy infrastructure for CNG distribution. Due to its high electrification and significant power consumption, researching the economic operation of the CNG main station in demand response (DR)-based electricity pricing environments is crucial. In this paper, the dehydration process is considered in the CNG main station energy consumption model to enhance its participation in DR. A bilevel economic dispatch model for the CNG main station is proposed, considering critical peak pricing. The upper-level and lower-level models represent the energy cost minimization problems of the pre-system and rear-system, respectively, with safety operation constraints. The bilevel programming model is solved using a genetic algorithm combined with a bilevel programming method, which has better efficiency and convergence. The proposed optimization scheme has better control performance and stability, reduces the daily electri... [more]

A vibrating blade was arranged in a channel to enhance heat transfer. The effects of the frequency and amplitude of the blade on the heat transfer characteristics were numerically researched. The phase space reconstruction and maximum Lyapunov index were used to analyze the transition path and degree of chaos. The results show that the vibrating blade can generate chaos; thus, the heat transfer is enhanced. The convective heat transfer performance is positively correlated with the degree of chaos. In addition, when the frequency is 10 Hz, and the inlet velocity is 0.5 m s−1, the heat transfer can be improved by 16%. When the maximum amplitude of the blade is 8 mm and the inlet velocity is 0.8 m s−1, the heat transfer can be improved by 15%.

Facing the goal of carbon neutrality, energy supply chains should be more low-carbon and flexible. A solar chemical heat pump (SCHP) is a potential system for achieving this goal. Our previous studies developed a silicone-oil-based phase-change material (PCM) mixture as a PCM fluid for enhancing heat recovery above 373 K in the solar collector (SC) of the SCHP. The PCM fluid was previously tested to confirm its dispersity and flow properties. The present study proposed a 3D computational fluid dynamics model to simulate the closed circulation loop between the SC and reactor using the PCM fluid. The recovered heat in the SC was studied using several flow rates, as well as the PCM weight fraction of the PCM fluid. Furthermore, the net transportable energy is considered to evaluate the ratio of recovered heat and relative circulation power. As a result, it was verified that the recovered heat of the SC in the experiment and simulation is consistent. The total recovered heat is improved us... [more]

The railway system is one of the safest, most efficient, and environmentally friendly means of land transport for people and goods. However, as the demand for mobility has increased, the current railway system has shown some weaknesses, requiring an increase in catenary power in order to be able to supply power to longer trains and faster locomotives, as well as to increase rail traffic. This paper proposes a control algorithm to be implemented in a sectioning post-Rail Power Conditioner (sp-RPC). The sp-RPC is connected to the neutral section between two traction power substations (TPS). With the control algorithm, it is possible to minimize the existing unbalance of the active powers of each TPS. In a regenerative braking condition, this surplus energy can be used to assist the traction of another locomotive on the existing overhead line. In this way, it is possible to increase the capacity of the overhead line. The analysis was performed with computer models using a modular multilev... [more]

This document deals with the design of a Permanent Magnet Synchronous Motor (PMSM) to peripherally drive a counter-rotating pump inducer. The motor/pump is associated using a rim-driven principle where the motor’s active parts are located at the periphery of the inducer blades. It proposes using a Halbach array of permanent magnets for the active rotor of the motor. This solution allows the generation of a Sinusoidal Electromotive Force (EMF). Therefore, a more stable electromagnetic torque is reached. An optimum geometry suitable for the inducer specifications while respecting operational constraints is determined. The obtained geometry is then simulated using the Finite Element Method. The results are satisfactory in terms of average torque and EMF waveform. Use of the Halbach array allows a significant improvement of the flux density in the air gap compared to a designed surface-mounted machine. The experimental validation will be performed once the prototype is realized in the Labo... [more]

The performance of a laboratory-scale 40 L anaerobic membrane bioreactor (AnMBR) treating municipal wastewater with and without iron supplementation was evaluated at ambient temperatures at a hydraulic retention time (HRT) of 6 h and sludge retention time (SRT) of 50 days. The system exhibited satisfactory performance during the summer and winter periods with average COD removal efficiencies of 73 ± 4% and 60 ± 4%, respectively. Moreover, two different FeCl3 dosages were studied for optimizing operation in terms of organic load removal, phosphorus removal, biogas production, membrane fouling, and emerging contaminant removal. The addition of 25 mg FeCl3 L−1 improved the performance of the AnMBR. More specifically, average effluent COD concentrations without FeCl3 addition were 177 ± 21 mg/L, while after the addition of 25 mg FeCl3 L−1 and 30 mg FeCl3 L−1, COD decreased to 147 ± 8 mg/L and 149 ± 11 mg/L, respectively. Moreover, effluent TP decreased by 75% with the dosage of 25 mg FeCl3... [more]

The first aim of this paper is to study the influence of four parameters of the transesterification reaction—reaction temperature (40−80 °C), time (1−3 h), the molar ratio of 1-octanol to sunflower oil (4:1−10:1) and mass fraction of the catalyst (1−3 wt%)—on the conversion of oil to biodiesel (octyl esters of fatty acids), with potassium hydroxide as a catalyst. The highest conversion, of 99.2%, was obtained at 60 °C, a molar ratio of 1-octanol to sunflower oil of 10:1, and with 2 wt% of the catalyst after an hour. The optimal conditions determined with response surface methodology (RSM) when aiming for the lowest possible parameter values and a conversion of 95% or higher were a temperature of 40 °C, time of 1 h, 1-octanol to oil molar ratio at 8.11:1 and mass fraction of catalyst of 2.01%. Furthermore, post-synthesis and purification (>99%), the application properties of pure fatty acid octyl esters (FAOCE) and their blends with mineral diesel and 1-octanol were evaluated. Standardi... [more]

The leading edges of aero-engine fan and compressor blades suffer from severe erosion due to the inhalation of suspended particulates in the low-altitude atmosphere during long-term transport. A small deformation of the leading edge can significantly change the aerodynamic performance under a strong non-linear effect, leading to increased operation and maintenance costs for engines. This review first focuses on leading-edge erosion morphology during service, and models of these damages. Secondly, the performance degradation caused by eroded leading edges on different classes of engine components, including airfoils, blades, compression systems, and the whole engine, are reviewed. Finally, optimization methods for eroded blade leading edges and their effects on performance recovery are summarized. This paper contributes to an in-depth understanding of the erosion mechanism of blade leading edges in terms of status and its effect, and is a good reference for establishing erosion leading... [more]

In this work, gallium arsenide (GaAs), which has an adjustable band gap and low cost, was adopted as an absorption layer in which KNbO3, having good dielectric, photoelectric, and piezoelectric properties, served as a scattering element for the improvement in absorption efficiency of solar cells. Benefited by the high absorption efficiency of KNbO3, the utilization of the ultraviolet and infrared bands for solar cells can be strengthened. In addition, the ferroelectric and photovoltaic characteristics of KNbO3 enable the realization of decreased thickness of solar cells. Based on the simulation of the shape, width, and period of the scattering element, the effect of the thickness of the scattering element on the absorption efficiency, quantum efficiency, and total efficiency of absorption efficiency was comprehensively simulated. The results show that the absorption layer delivers the optimal performance when using a hexagonal KNbO3 scattering element. The absorption efficiency of the... [more]

This study introduces the most important energy trends and global food systems, as well as the relationship between the human development index (HDI) and energy supply and the relationship between energy prices and food prices. Based on seven important indicators as variables in 18 relevant countries worldwide, before and after the pandemic, with the help of cluster analysis and comparative analysis, five different primary energy clusters were created and analyzed. Our results prove the high volatility of the composition of these clusters within a short period. Another important finding is that renewable energy sources (RES) are probably not viable options for the largest (developed and developing) countries in the short term. The human development index and food production per capita are the lowest in the renewable energy cluster and the highest in countries dominated by nuclear energy and oil with typically the highest GDP, since they are able to finance the price hike in both food a... [more]

In this paper, the possibility to obtain an alternative source of energy from methane fermentation, catalysed by biomass, has been discussed in detail. As a main substrate, the distillation residue from the distillery industry was taken in the case of mono-fermentation and its co-fermentation with sewage sludge. The results showed that higher biogas and methane production can be obtained in a mono-fermentation process. Fermentation lasted for 23 days, and during this time, 333.14 and 249.64 L/kg VS of the total biogas for mono- and co-fermentation was subsequently obtained, which gives around 63% and 50% of methane in both types of the process, respectively. Additionally, to interpret the experimental data obtained and to predict the trend of the accumulation curves, a simple Gompertz model has been applied. The application of the Gompertz model has enabled us to estimate some important parameters with a strict physical meaning, namely, the maximum production value of the biogas and it... [more]

Affected by the complex mechanism of organic−inorganic interactions, the generation−retention−expulsion model of mixed siliciclastic−carbonate sediments is more complicated than that of common siliciclastic and carbonate shale deposited in lacustrine and marine environments. In this study, mixed siliciclastic−carbonate shale from Lucaogou Formation in Junggar Basin was selected for semi−closed hydrous pyrolysis experiments, and seven experiments were conducted from room temperature to 300, 325, 350, 375, 400, 450, and 500 °C, respectively. The quantities and chemical composition of oil, gases, and bitumen were comprehensively analyzed. The results show that the hydrocarbon generation stage of shale in Lucaogou Formation can be divided into kerogen cracking stage (300−350 °C), peak oil generation stage (350−400 °C), wet gas generation stage (400−450 °C), and gas secondary cracking stage (450−500 °C). The liquid hydrocarbon yield (oil + bitumen) reached the peak of 720.42 mg/g TOC at 400... [more]

Due to the energy crisis that some countries are facing nowadays, the gasification process appears to be a good alternative to produce some energy from solid materials. Increasingly, gasification involves using wastes as a solid fuel, making the process green and reusing some materials that otherwise could end up in a landfill. However, the process of finding the best gasification parameters of a sample can be very expensive and time-consuming. In this sense, a refuse-derived fuel (RDF) char produced from an original RDF under 30 min at 400 °C was tested on a small-scale reactor using macro thermogravimetric analysis (TGA), as presented in this paper. The goal was to study and evaluate the devolatilization and residual carbon rate of the sample under several conditions and, at the same time, quantify and analyze the released gas. In the first round of tests, 5, 10, and 20 g of samples were tested at 750 °C with an excess of air coefficient (λ) = 0 and 0.2. It was possible to conclude t... [more]

In this paper, we address the problem of high greenhouse gas emissions from oil and gas platforms in Norway. We look at the potential of integrating an energy system composed of wind turbines and battery systems to unload the electrical power generated by gas turbines being the main source of emissions today. We propose a simulation model of the energy system, the power demand, the available wind speed, and different control strategies. By putting the models together, we evaluate the performance of various compositions of the system and determine their impact on emissions and battery lifetime. The numerical results show that changing today’s practices has great potential to reduce greenhouse gases, with amounts varying between 30% and 80% compared with today’s level.

Soft-wing kites for airborne wind-energy harvesting function as flying tensile membrane structures, each of whose shape depends on the aerodynamic load distribution and vice versa. The strong two-way coupling between shape and loading poses a complex fluid-structure interaction problem. Since computational models for such problems do not yet meet the requirements of being accurate and at the same time fast, kite designers usually work on the basis of intuition and experience, combined with extensive iterative flight testing. This paper presents a fast aero-structural model of leading-edge inflatable kites for the design phase of airborne wind-energy systems. The fluid-structure interaction solver couples two fast and modular models: a particle system model to capture the deformation of the wing and bridle-line system and a 3D nonlinear vortex step method coupled with viscous 2D airfoil polars to describe the aerodynamics. The flow solver was validated with several wing geometries and p... [more]

High-power electronic devices with multiple heat sources often require temperature uniformity and to operate within their functional temperature range for optimal performance. Micro-channel cooling could satisfy the heat dissipation requirements, but it may cause temperature non-uniformity. In this paper, simulations are performed for different geometric parameters of the channel and the position of the heat source. The results show that a flattened channel can effectively reduce the heat source temperature, broadening the straight channel can reduce the flow resistance and enhance heat transfer, while widening the channel at the bend may lead to local dryness. Meanwhile, a thermal model is established to analyze the influence of the position of the heat source. The results also show that with the increase in the curved channel radius, the phenomenon of vapor−liquid separation becomes more obvious, the pressure drop decreases, but the heat transfer effect worsens.

Self-consumption of the energy generated by photovoltaics (PV) is playing an increasingly important role in the power grid. “Prosumer” systems consume part of the produced energy directly to meet the local demand, which reduces the feed-in into as well as the demand from the grid. In order to analyse the effects of PV self-consumption in the power grid, we introduce a stochastic bottom-up model of PV power generation and local consumption in the control area of the German transmission system operator TransnetBW. We set up a realistic portfolio of more than 100,000 PV/prosumer systems to generate representative time series of PV generation and consumption as a basis to derive self-consumption and feed-in. This model allows for the investigation of the time-dependent behaviour in detail for the full portfolio whereas measurements are presently only available as aggregated feed-in time series over a nonrepresentative subset of systems. We analyse the variation of self-consumption with PV... [more]

The article presents an on-board power system designed for ships, aviation, and space vehicles using energy from photovoltaic panels. The power structure includes both DC and high-frequency AC power buses. As a result of pulse loads, this system is exposed to disturbances that cause electronic systems to reboot. To reduce the effect of the appearance of secondary disturbances in the AC bus to which the photovoltaic converter is connected, a new control strategy has been proposed. This strategy improves the operation of the proportional resonant regulator that controls the AC bus current by making the reference values linearly dependent on the DC bus voltage. A prototype of such a system was designed in the laboratory. The FPGA control board was pulse-disturbed, leading to start the auto-power procedure, and additional disturbances were observed in the AC bus for the standard system. Reduction in the impact of these disturbances was achieved using the proposed control method by reaching... [more]

In this paper, the simulation and design of a power converter suitable for a low-voltage photovoltaic (PV) battery energy storage converter was investigated. The converter was suitable for sources and loads with near voltage levels and were aimed at efficiency improvement. The converter was called a series partial power converter (SPPC). A continuous current and a boost SPPC topology based on an isolated Cûk converter was constructed. The operation modes of the converter were analyzed. The efficiency verification test of the SPPC in a laboratory environment was completed using an outdoor start-up test, a photovoltaic full cover test and a steady-state operation test under different power levels. The results show that the SPPC can achieve 95−98% converter efficiency within the 87 W−242 W power range. The incremental conductance method based on the SPPC can realize the dynamic MPPT under constant illumination and changing meteorological conditions.

Renewable power generation has increased in recent years, which has led to a decrease in the use of synchronous generators (SGs). These power plants are mainly connected to the power system through electronic converters. One of the main differences between electronic converters connected to power systems and SGs connected to the grid is the current contribution during faults, which can have an impact on protection systems. New grid codes set requirements for fast current injection, but the converters’ maximum current limitation during faults make it challenging to develop control strategies for such current contribution. This paper presents a positive and negative sequence current injection strategy according to the new Spanish grid code requirements for the novel grid-forming converter control algorithm based on virtual-flux orientation. The behavior of the proposed strategy is tested in a hardware in the loop (HiL) experimental set-up under balanced faults, meaning that the fault is... [more]

In the effort to decarbonise shipping, a number of measures can be taken, one of which is to switch from conventional to alternative fuels. However, without an active role for seaports in providing adequate bunkering infrastructure for alternative fuels, these targets may not be achieved. Hence, the aim of this article is threefold: (1) to provide an overview of some of the emerging alternative fuel technologies that are being used or tested for further use in maritime transport, (2) to analyse the bunkering infrastructure in seaports, and (3) to assess the level of advancement of Polish ports in relation to the bunkering of alternative fuels by ships and to explore the ports’ plans in this regard. To achieve these goals, several research methods were applied: a critical literature review, desk-study research, critical and comparative analyses, and semi-structured interviews with representatives of three major Polish seaports. The research showed that the level of advancement of Polish... [more]