He−Xe, with a 40 g/mol molar mass, is considered one of the most promising working media in a space-confined Brayton cycle. The thermodynamic performance of He−Xe in different configuration channels is investigated in this paper to provide a basis for the optimal design of printed circuit board plate heat exchanger (PCHE). In this paper, the factors affecting the temperature distribution of the He−Xe flow field are analyzed based on the flow heat transfer mechanism. It is found that the flow patterns in the logarithmic and outer zones determine the temperature distribution pattern of the flow field. A series of numerical simulations verify the above conclusions, and it is found that reasonable channel structure and operating conditions can significantly improve the thermodynamic performance of the He−Xe flow. Based on the above findings, the Zig channel is optimized, obtaining Sine and Serpentine channels with different structural characteristics. Comprehensive thermodynamic comparison... [more]

Hydrogen is widely considered as the fuel of the future. Due to the challenges present during hydrogen production using conventional processes and technologies, additional methods must be considered, like the use of microorganisms. One of the most promising technologies is dark fermentation, a process where microorganisms are utilized to produce hydrogen from biomass. The paper provides a comprehensive overview of the biological processes of hydrogen production, specifically emphasizing the dark fermentation process. This kind of fermentation involves bacteria, such as Clostridium and Enterobacterium, to produce hydrogen from organic waste. Synthetic microbial consortia are also discussed for hydrogen production from different types of biomasses, including lignocellulosic biomass, which includes all biomass composed of lignin and (hemi)cellulose, sugar-rich waste waters, and others. The use of genetic engineering to improve the fermentation properties of selected microorganisms is also... [more]

Reducing energy consumption and increasing operational efficiency are currently among the leading research topics in the design of hydraulic systems. In recent years, hydraulic system modeling and design techniques have rapidly expanded, especially using artificial intelligence methods. Due to the variety of algorithms, methods, and tools of artificial intelligence, it is possible to consider the prospects and directions of their further development. The analysis of the most recent publications allowed three leading technologies to be indicated, including artificial neural networks, evolutionary algorithms, and fuzzy logic. This article summarizes their current applications in the research, main advantages, and limitations, as well as expected directions for further development.

Different standard methods for the assessment of the thermal performance of the building envelope are used: analogy with coeval building, theoretical method, heat flow meter measurement, simple hot box, infrared thermography, and thermometric method. Review papers on these methods, applied in situ and in laboratory, have been published, focusing on theory, equipment, metrological performance, test conditions and data acquisition, data analysis, benefits, and limitations. However, steps forward have been done and not been deepened in previous works: in fact, the representative points method and the weighted area method have been proposed, too, whilst artificial intelligence and data-driven methods have begun to prove the reliability also in the U-value prevision using available datasets. Considering this context, this work aims at updating the literature background considering exclusively in situ methods. The work starts from bibliometric and scientometric analysis not previously conduc... [more]

Gas hydrates, being promising energy sources, also have good prospects for application in gas separation and capture technologies (e.g., CO2 sequestration), as well as for seawater desalination. However, the widespread use of these technologies is hindered due to their high cost associated with high power consumption and the low growth rates of gas hydrates. Previous studies do not comprehensively disclose the combined effect of several surfactants. In addition, issues related to the kinetics of CO2 hydrate dissociation in the annealing temperature range remain poorly investigated. The presented review suggests promising ways to improve efficiency of gas capture and liquid separation technologies. Various methods of heat and mass transfer enhancement and the use of surfactants allow the growth rate to be significantly increased and the degree of water transformation into gas hydrate, which gives impetus to further advancement of these technologies. Taking the kinetics of this into acco... [more]

This paper presents a comprehensive study of model-based fault diagnosis (FD) and a fault-tolerant control (FTC) scheme for sensor and actuator faults of turbojet engines. For actuator FD, an unbiased estimation scheme with a modified Kalman filter (KF) was developed. For sensor FD, two approaches, the generalized likelihood ratio with robust KF and the pseudo actuator model with modified KF, were investigated in a comparative study. For fault detection and isolation, test statistics are commonly employed to detect fault behavior. For FTC, integral-type sliding mode control using control reconfiguration and the reconstruction of the sensor signal was adopted with the FD schemes. The effectiveness of the employed methods was demonstrated in this study and discussed with numerical simulations.

Investments in the development of the district heating system require a thorough analysis of the technical, economic, and legal aspects. Regarding the technical and economic context, a mathematical model of the district heating system has been proposed. It optimizes both the technical and economic aspects of the function and development of a district heating system. To deal with non-linearities, the developed linear programming model is divided into three phases: flow, thermal, and pressure. Therein, non-linear dependencies are calculated between the linear optimization phases. This paper presents the main assumptions and equations that were used to calculate the parameters of the heating system, along with the optimal level of heat production, the flow rate of the heating medium in the heat nodes and edges of the network graph, the heat, power, and temperature losses at each edge, and the purchase costs of heat and its transmission. The operation of the model was tested on a real-worl... [more]

This paper describes examples of energy crops that are profitable to burn, and whose cultivation is not complicated or expensive. Rapid growth of biomass, especially the green mass of energy crops, is indicated, which means that, in relation to fossil fuels, energy crops are considered renewable raw materials. An assessment of Polish non-food energy agriculture was conducted in the context of the prospects of a renewable energy source, namely, biomass. Recommendations for crop cultivation, the size of possible yields and the most important parameters of the obtained biomass, which have the greatest impact on the suitability of energy use, are presented. Materials of biological origin for combustion are divided into three groups: wood waste, by-products and plant products for the energy industry. It is indicated that 2 tons (Mg) of dry wood or straw is energetically equivalent to 1 Mg of coal, and 1 m3 of biogas is energetically equivalent to 1 kg of Polish coal. A novelty of this artic... [more]

To address the problems of “difficult to consume” renewable energy and the randomness of power output, we propose the CHP unit joint-operation model with power to gas (P2G) and carbon capture system (CCS) technologies and analyze the operation cost, carbon emission, and “electric-heat coupling” characteristics of this model. A dispatch optimization model is constructed based on the information-gap decision theory under the strategy to further consider the interval uncertainty of renewable energy unit output and load forecast. The optimized-dispatching model effectively solves the fate of renewable unit output and electric-thermal load and provides dispatching strategies for decision-makers to balance risk and capital management.

New strategies and market segments considering integrated approaches have emerged as critical components in the energy transition. Agrivoltaics is one approach that has shown a lot of promise for offering advantages in the food-energy-water nexus. The agrivoltaic system involves the installation of photovoltaic panels above agricultural lands to generate electricity while also allowing for crop production. The paper “SWOT and TOWS Matrix Analysis of Agrivoltaic System” comprehensively analyses the potential strengths, weaknesses, opportunities, and threats (SWOT) associated with implementing an agrivoltaic system. This study utilizes a SWOT analysis framework to identify and evaluate the internal and external factors that could impact the implementation and success of the agrivoltaic system. A TOWS matrix analysis is also conducted to formulate strategic recommendations based on the identified SWOT factors. The analysis results reveal that the agrivoltaic system has numerous strengths,... [more]

Biomass fuels play an important role in the field of fluidized bed combustion, but due to the diversity and uncertainty of fuels, there are usually some problems of high CO emission that cannot be directly solved by combustion adjustment. In this paper, a 75 t/h biomass fluidized bed was taken as the research object. It was observed from the field test that the gas incomplete combustion loss reached 12.13% when mono-combustion of wheat straw was conducted, and the CO concentration in the exhaust gas exceeded 30k ppm. Combined with the CPFD numerical simulation, the combustion characteristics and influence of secondary air layout on CO reduction performance were discussed in detail. The results revealed that the gas temperature gradually increased along furnace height under the initial condition, and the maximum temperature was more than 1000 °C at furnace outlet. The air curtain of the secondary air jets was insufficient, and the wheat straw rose rapidly as it entered into the furnace.... [more]

Affected by an insufficient understanding of oxidation characteristics and the CO production mechanism in low-rank coal goaf, the safety management of coal spontaneous combustion (CSC) faces severe challenges. In this study, in-depth research was conducted using ambient temperature oxidation (ATO), temperature-programmed, in situ FTIR experiments and DFT simulation after analyzing the oxidation scenario characteristics of low-metamorphic coal goaf. The results show the oxidation of low-rank coal goaf includes two processes of ATO in the dissipation zone and CSC in the oxidation zone. The CO production of ATO increases with a decrease in coal metamorphic degree, and the risk of CSC is influenced by ATO, with an inhibitory effect before the critical temperature, and an encouraging effect after that. The CO production mechanism of low metamorphic coal goaf from ATO to CSC is established. Before the critical temperature, CO mainly comes from the primary aldehyde functional groups, then per... [more]

A study of heat recovery in a façade ventilation unit was carried out under laboratory conditions using a climate chamber that allowed stable outdoor and indoor conditions to be simulated. The unit, equipped with a reversible fan and a chamber for the heat exchanger, controlled by an automation control system, was designed to exchange air in the room by alternating supply and exhaust cycles of specific durations. Three types of heat exchangers were tested, which were filled with different phase change materials, in order to estimate the efficiency of the façade ventilation unit in terms of its heat recovery capability. The efficiency of the unit was determined based on the temperature efficiency of heat recovery for 144 setting combinations. The best efficiency results between 73.56% and 76.29% were obtained with a solution using a heat exchanger consisting of cylinders with an external diameter of 10 mm and a wall thickness of 1 mm filled with jojoba oil in a one minute cycle. The tes... [more]

This study presents an innovative framework for leveraging the potential of AI in energy systems through a multidimensional approach. Despite the increasing importance of sustainable energy systems in addressing global climate change, comprehensive frameworks for effectively integrating artificial intelligence (AI) and machine learning (ML) techniques into these systems are lacking. The challenge is to develop an innovative, multidimensional approach that evaluates the feasibility of integrating AI and ML into the energy landscape, to identify the most promising AI and ML techniques for energy systems, and to provide actionable insights for performance enhancements while remaining accessible to a varied audience across disciplines. This study also covers the domains where AI can augment contemporary and future energy systems. It also offers a novel framework without echoing established literature by employing a flexible and multicriteria methodology to rank energy systems based on thei... [more]

Using photovoltaic (PV) energy to produce hydrogen through water electrolysis is an environmentally friendly approach that results in no contamination, making hydrogen a completely clean energy source. Alkaline water electrolysis (AWE) is an excellent method of hydrogen production due to its long service life, low cost, and high reliability. However, the fast fluctuations of photovoltaic power cannot integrate well with alkaline water electrolyzers. As a solution to the issues caused by the fluctuating power, a hydrogen production system comprising a photovoltaic array, a battery, and an alkaline electrolyzer, along with an electrical control strategy and energy management strategy is proposed. The energy management strategy takes into account the predicted PV power for the upcoming hour and determines the power flow accordingly. By analyzing the characteristics of PV panels and alkaline water electrolyzers and imposing the proposed strategy, this system offers an effective means of pr... [more]

This paper presents a low peak-to-average power ratio (PAPR) modulation scheme and demodulation method for low-cost terminals in sixth-generation (6G), which is called one plus delay (1 + D) pi/2(N + 1) BPSK. Explicitly, the modulation scheme is first generated based on pi/2 BPSK, then proceeded by interpolation and (1 + D) transformation. Simulation results show that the proposed (1 + D) pi/2(N + 1) BPSK scheme has lower PAPR and smaller out-of-band leakage in discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-s-OFDM). Moreover, better performance can be attained by increasing the value of N. Finally, similar block error ratio (BLER) performance can be obtained at the same spectral efficiency of the conventional pi/2 BPSK scheme.

Building cooling and heating, solar-powered energy production, energy recovery, and other energy-consuming industries have all seen an increase in the use of cold/hot latent thermal energy storage (LH-TES). Through energy recovery, LH-TES that uses phase-change materials (PCMs) as a storage medium helps to close the energy supply and demand gap and raises the possibility of energy savings. However, the stability, thermal, physical, and chemical properties of the PCM play a major role in how effectively it can be used. In recent years, adding gelling and thickening agents (GTAs) has gained popularity apart from the nanoparticles (NPs) and nucleating triggers (NTs), particularly for the creation of stable PCMs. Therefore, the current work’s goal is to provide an overview of how GTAs are used in the process of developing reliable PCMs for TES applications. It has been found that using GTAs not only increased stability but also decreased sedimentation, leakage, and the supercooling degree... [more]

A typical feature of shale gas reservoirs is that they contain a significant amount of adsorbed gas. The evaluation and prediction of adsorbed gas play important roles in shale gas exploration and development. However, the presence of water in shale reservoirs makes this work more difficult. In recent years, research related to the occurrence and distribution of water in shales and its effect on methane adsorption have become a prominent issue. In this paper, the factors controlling water in shale nanopores and its influence on methane adsorption were systematically reviewed. It is revealed that the connate water content in shales and their water absorption capacity vary widely, and both are mainly related to the organic matter contents and properties and mineral compositions. The water absorption capacity of organic matter in shales is mainly affected by its nanopore content, structure and surface chemical properties (such as the type and amount of oxygen-containing functional groups)... [more]

An experimental study of the ignition and combustion processes of coal-water slurry (CWS) droplets based on coal enrichment waste in a high-temperature oxidizer at 650−850 °C with a syngas addition was carried out. The fuel slurry was a mixture of finely dispersed solid combustible particles (coal sludge, 10−100 µm in size) and water. The syngas was a product of biomass pyrolysis and two waste-derived fuels in a laboratory gasifier. Composition of the syngas was controlled by a precision analytical gas analyzer. The feasibility of co-firing CWS with syngas was experimentally established. Under such conditions, the CWS droplets ignition process was intensified by 15−40%, compared to fuel combustion without the addition of syngas to the combustion chamber. The greatest positive effect was achieved by adding the gas obtained during the biomass pyrolysis. The ignition delay times of CWS droplets are 5.2−12.5 s versus 6.1−20.4 s (lower by 15−39%) when ignited in a high-temperature medium wi... [more]

Among the most widespread systems in industrial plants are automated drive systems, the key and most common element of which is the induction motor. In view of challenging operating conditions of equipment, the task of fault detection based on the analysis of electrical parameters is relevant. The authors propose the identification of patterns characterizing the occurrence and development of the bearing defect by the singular analysis method as applied to the stator current signature. As a result of the decomposition, the time series of the three-phase current are represented by singular triples ordered by decreasing contribution, which are reconstructed into the form of time series for subsequent analysis using a Hankelization of matrices. Experimental studies with bearing damage imitation made it possible to establish the relationship between the changes in the contribution of the reconstructed time series and the presence of different levels of bearing defects. By using the contribu... [more]

This paper presents a life cycle assessment (LCA) analysis of a new, high-concentration photovoltaic (HCPV) technology developed as part of the HIPERION project of hybrid photovoltaics for efficiency record using an integrated optical technology. In the LCA calculations, the production stage of a full module was adopted as a functional unit. SimaPro version 9.00.49, the recent Ecoinvent database (3.8), and the IPCC 2021 GWP 100a environmental model were applied to perform the calculations. The environmental impact of the HCPV panel was determined for constructional data and for recycling of the main elements of the module. The results of the calculations show that recycling of PMMA, rubber, and electronic elements reduced the total carbon footprint by 17%, from 240 to 201 kg CO2-eq. The biggest environmental load was generated by the PV cells: 99.9 kg CO2eq., which corresponds to 49.8% (41.7% without recycling) of the total environmental load due to the large number of solar cells used... [more]

The following paper presents an analytical study of the air-gap magnetic field distribution produced by the armature reaction of a linear machine. Based on the method of images, the magnetic field generated by a current carrying conductor inside the air-gap between two smooth infinitely permeable iron surfaces is modeled as a complex 2D function. The conductor model then becomes a current sheet model and horizontally oriented current sheets are used to model the magnetic field produced by the armature reaction for smooth ferromagnetic surfaces. Focus will be given to the study of the slot opening function in front of energized slots in comparison to the not energized ones of the classical theory pointing out some remarkable differences. Later, the model is extended to slotted geometries using a complex slotting function adapted for energized slots. At last, the Maxwell tensor expressed in complex formulation will be integrated to obtain the force components acting on the machine tooth... [more]

Anaerobic digestion is considered a beneficial treatment for biogas production (BP). To improve the performance of this bioprocess, the addition of well-selected inocula could be an interesting approach that affects the overall efficiency of the BP. In this study, the reactor performance and energy analysis of liquid-state anaerobic digestion of cattle manure (CM) at high solids concentration (TS%) (94.87%) with six different inocula—two cellulosic (C.I1, C.I2), one lipidic (Li.I), two lactic (La.I1, La.I2), and one saccharidic (Sacc.I)—were investigated. The results showed that inocula improved the biogas production and yield during anaerobic digestion of CM by 109%, 86%, and 52.4%, respectively, when the cellulosic (C.I1), lipidic (Li.I), and lactic (La.I1) inocula were added, compared with the substrate production alone at a substrate/inoculum (S/I) ratio of 5:3 (v/v). The addition of inocula in an appropriate range is useful for the performance of the anaerobic digestion process. I... [more]

This article presents the application of a self-excited acoustic SAS system for non-destructive testing (NDT) for roof-bolt housings in laboratory and real mine conditions. The proposed system with a filtering mechanism was applied to the J64-27 composite anchors. The conducted tests allowed successful confirmation of the usefulness of the system in the detection of rod defects, damage of the mechanism coupling the anchor to the rock mass and testing of the stress state of the anchor itself. The proposed filtering system allowed eliminating the effect of jump change of frequency in the limit cycle of self-excited system. The proposed method is a novel solution for safety diagnostics of bolt housings in mining applications.

In this research, two empirical correlations have been introduced to calculate the dynamic Biot coefficients of low-porosity and high-porosity sandstone samples from two open pit mines located in South-West Poland. The experiments were conducted using an acoustic velocity measurement apparatus. Under the undrained condition, firstly, the confining pressure was increased in increments of 200 psi, and the values of pore pressure and dynamic elastic modulus were recorded. This experiment was continued until the Skempton coefficient remained in the range of 0.98−1. Secondly, an experiment on the same sample was conducted under drained conditions, and the corresponding dynamic elastic moduli were calculated. Then, using the calculated dynamic elastic moduli, the dynamic Biot coefficient was determined for each sample under different confining pressure. Finally, two empirical correlations were formulated for each sandstone category. The results demonstrate that, as the confining pressure inc... [more]