Latent heat thermal energy storage (LHTES) technology can alleviate the mismatch between the supply and demand of solar energy and industrial waste heat, but the low thermal conductivity of phase change materials (PCMs) is an issue that needs to be solved. In this work, the effects of the bifurcated fins on melting and solidification are studied, and local and global entropy generation are discussed. The radial lag time and the circumferential lag time were defined to evaluate thermal penetration and thermal uniformity. Subsequently, a novel arc-shaped fin configuration was proposed to further enhance the heat transfer. The results showed that attaching the bifurcated fins could effectively reduce the global entropy generation. Increasing the trunk fin length was beneficial to enhance the thermal uniformity and promote the melting process, while increasing the branch fin was more effective in the solidification process. Overall, thermal uniformity determined the phase change process. M... [more]

We present a concise mini overview on the approaches to the disposal of nuclear waste currently used or deployed. The disposal of nuclear waste is the end point of nuclear waste management (NWM) activities and is the emplacement of waste in an appropriate facility without the intention to retrieve it. The IAEA has developed an internationally accepted classification scheme based on the end points of NWM, which is used as guidance. Retention times needed for safe isolation of waste radionuclides are estimated based on the radiotoxicity of nuclear waste. Disposal facilities usually rely on a multi-barrier defence system to isolate the waste from the biosphere, which comprises the natural geological barrier and the engineered barrier system. Disposal facilities could be of a trench type, vaults, tunnels, shafts, boreholes, or mined repositories. A graded approach relates the depth of the disposal facilities’ location with the level of hazard. Disposal practices demonstrate the reliability... [more]

Amorphous metal (AM), specifically amorphous ferromagnetic metal, is considered as a satisfactory magnetic material for exploring electromagnetic devices with high-efficiency and high-power density, such as electrical machines and transformers, benefits from its various advantages, such as reasonably low power loss and very high permeability in medium to high frequency. However, the characteristics of these materials have not been investigated comprehensively, which limits its application prospects to good-performance electrical machines that have the magnetic flux density with generally rotational and non-sinusoidal features. The appropriate characterization of AMs under different magnetizations is among the fundamentals for utilizing these materials in electrical machines. This paper aims to extensively overview AM property measurement techniques in the presence of various magnetization patterns, particularly rotational magnetizations, and AM property modeling methods for advanced el... [more]

This review focuses on the consequences of the early and rapid deployment of carbon dioxide (CO2) capture and storage (CCS) technologies, which is currently recognized as a critical problem in fulfilling climate change mitigation objectives and as a viable alternative for countries throughout the world. Currently, the geological storage of CO2 is the most effective and, in many cases, the only viable short- to medium-term alternative for considerably moving towards CO2 sequestration in geological sinks and, thus, lowering net carbon emissions into the atmosphere. Furthermore, this review explores the global and environmental measurements of CO2 emissions, as well as the emphasis behind more efficient energy usage. The components of the CCS system are briefly examined, with an emphasis on the technologies that have been developed by previous scholars to support carbon capture, as well as the kinds of carbon geological formations that are suitable sinks for CO2. Additionally, the importa... [more]

Power electronic devices play an important role in energy conversion. Among the options, matrix converters, in combination with predictive control, represent a good alternative for the power conversion stage. Although several reviews have been undertaken on this topic, they have been conducted in a non-systematic manner, without indicating how the studies considered were chosen. This paper presents results from a systematic literature review on predictive control applied to matrix converters that included 142 primary papers, which were selected after applying a defined protocol with clear inclusion and exclusion criteria. The study provides a detailed classification of predictive control methods and strategies applied to different matrix converter topologies. Research findings require to be understood in combination to develop a common understanding of the topic and ensure that future research effort is based on solid premises. In light of this, this study identifies and characterizes... [more]

To investigate the influence of flowback time and flowback difference on flowback behavior of shale fracturing fluid, we carried out the permeability test experiment of Longmaxi Formation shale under different flowback pressure gradients and analyzed the retention characteristics of water phase in shale pores and fractures after flowback by nuclear magnetic resonance (NMR) instrument. The results indicate that after flowback under the pressure gradient ranges of 0.06~0.18 MPa/cm, the content of retained water phase in shale samples ranges from 9.68% to 16.97% and the retention of fracturing fluid in shale does not decrease with the increase of flowback pressure difference. Additionally, increasing the flowback pressure difference will reduce the shale permeability damage rate, but the permeability damage rate is still above 80%. After the flowback, the water phase mainly stays in the pore space with D < 100 nm, especially in the pore space with 2~10 nm and 10~50 nm. It is extremely... [more]

To maintain reservoir pressure, water is injected into oil reservoirs. In carbonate rock, water quickly breaks through fractures and highly permeable formations to production wells. This study analyzes the effect of the permeability, oil viscosity, pressure drop, and distance on the water velocity from an injection well to a production well. In the Tempest MORE hydrodynamic simulator (Roxar), a three-layer model of an oil reservoir was created, and water flow from an injection well to a production well was simulated with various values of the permeability, oil viscosity, and bottom hole pressure. The water velocity in the reservoir was estimated based on the mobility factor (k/µo). The results showed that at a mobility factor of less than 2 μm2/Pa s at a distance of 100 m in the reservoirs, the time of water migration from the injection well to the production well increased sharply, and at a mobility factor of more than 2 μm2/Pa s, it became shorter. An analysis of the time of water mi... [more]

In this study, a series of solid solutions of (1−x)BaTiO3-xCa(Sn1/2Zr1/2)O3 (abbreviated as (1−x)BT-xCSZ, x = 0.00−0.15) ceramics have been prepared by the conventional solid-state reaction method to search for high performance lead-free piezoelectric materials. The structural evolution, microstructure, and piezoelectric properties are investigated. X-ray diffraction (XRD) results indicate that the phase symmetry strongly depends on the CSZ content. A tetragonal phase is well-maintained in the compositions of 0 ≤ x ≤ 0.03, and coexistence of tetragonal and cubic phases is obtained in the range of x = 0.06−0.09, beyond which a pure cubic phase becomes stable. More importantly, a significantly enhanced piezoelectric coefficient of d33 = 388 ± 9 pC/N is attained in the composition of x = 0.06 in the MPB region, where a tetragonal ferroelectric phase and an ergodic relaxor phase with average cubic symmetry coexist. Based on the analysis of crystal structure and dielectric properties, a tem... [more]

The study examines the relationship between electricity prices and household welfare in South Africa. The study employs a demand system framework on annual time-series data from 2000 to 2018 and the analysis involves the calculation of price elasticities and measurement of welfare changes. The price elasticities in this study are drawn from the linear expenditure demand model. To analyse welfare change, we consider the impact of electricity pricing policies on cost of living (proxied by the consumer price index and households’ expenditure patterns). The study achieves this: (i) by comparing electricity price movements to changes in the rate of inflation between 2000 and 2018; (ii) by regressing total household energy expenditure against household expenditure on electricity, to examine how electricity costs affect a household’s overall energy bills; and (iii) thirdly, by regressing household food expenditure against households’ electricity expenditure to determine how the latter affects... [more]

Although there are many studies on the Jurassic source rocks in the northern margin of the Qaidam Basin, the characteristics of biomarkers and products with the same source rock in different evolutionary stages are still not well understood. Such an understanding is essential for accurately estimating oil and gas resources. In order to explore the hydrocarbon-generation potential of high-quality source rocks of the Middle Jurassic and the evolution of liquid hydrocarbons and biomarkers, we carried out simulation research (under hydrous conditions) at various temperatures (250, 300, 350, 400 and 450 °C) with the mudstone of the Yu 33 well in the Yuka Sag. The results revealed that the “oil window” of the Middle Jurassic source rocks in the Yuka area was 300 °C (simulation temperature, Ro = 0.84%), but this was not the peak of hydrocarbon expulsion, which was gradually reached and stabilized above 350 °C. Overall, the concentration of alkanes and aromatics increased with temperature; alt... [more]

This paper presents the results of theoretical and experimental studies to determine the optimal thickness of thermal insulation from basalt fiber and aerogel products for pipelines at temperatures of 300 and 600 °C. We carried out a comparison of the key thermophysical characteristics of the claimed heat-insulating materials. We performed a thermal imaging survey of the furnace chimney, insulated with basalt fiber and aerogel, while controlling the temperature of the flue gases by establishing the required ratio of the flow rate of natural gas and oxidizer. The temperature gradient along the thickness of the thermal insulation was obtained using a numerical tool developed in ANSYS. The results show that aerogel surpasses basalt fiber in all key thermophysical characteristics. At the same time, the only barrier to widespread industrial production and use of aerogel in the high-temperature thermal insulation segment is its market cost, which is still several times higher than that of ba... [more]

With the increase in renewable energy generation, microgrid has put forward higher requirements on the power density and performance of the photovoltaic inverter. In this paper, the dynamic process of inverter based on the cascode Gallium nitride (GaN) high electron mobility transistor (HEMT) for the photovoltaic (PV) application is analyzed in detail. The parasitic inductors and capacitors have been considered in our proposed equivalent model, which can explain the phenomenon that the crossover time of the voltage and current is prolonged by the parasitic parameters. The influence of the parasitic parameters is identified through theoretical analysis. By analyzing the influence of parasitic parameters, the design process of high-frequency inverter can be optimized. A 500 W inverter based on the cascode GaN HEMT is built, and the correctness of theoretical and simulation analysis is verified by the experimental results.

In this paper, a novel fault detection and diagnosis technique for a grid-tied photovoltaic (GTPV) with the ability of module-level fault location and differentiation is proposed. The proposed system measures the voltage, current, and temperature of the PV modules using low-cost sensors and critically compares them with the mathematical evaluated data to locate the type and location of the fault in the system. Additionally, a power line communication (PLC)-based low-cost PV monitoring system for tracking the operation of individual modules along with a fault detection algorithm is proposed to detect and locate the fault in the system. An intuitive online web application is also created to make it simple for users to view monitored data online. The suggested method is shown to have reduced computing needs; thus, the transmission of data and fault diagnosis is performed using the same microcontroller without the need for extra hardware or simulation software. The usefulness of the propos... [more]

Global warming, along with increasing global energy demands, has led to the need for a sustainable and low-carbon-based energy economy. In addition to renewable energy technologies, such as biomass, solar, hydro, and wind, another possible strategy to mitigate climate change is the capture/conversion and recycling of CO2. In recent years, many methods for both CO2 capture (mainly adsorption, absorption, and membrane) and conversion (many electrolysis, catalyst, and plasma) have been investigated. Conversion technology is less studied but seems to be very promising. Within that, non-thermal plasma technology has received much interest because it works at low temperatures and atmospheric pressure, and there is no need for high temperature and high electricity consumption, which are typical of the catalyst and electrolysis conversion processes, respectively. Therefore, in order to optimize this emerging technology, simulative kinetic models have been developed with the aim of maximizing b... [more]

Red sandstone samples treated at high temperatures feature complex creep properties. Uniaxial compression tests and the incremental creep tests at different stress gradients were conducted on 10 red sandstone samples of the same specifications divided into five groups on an RLW-2000 triaxial servo rheometer in the laboratory. Relationships of the instantaneous strain and creep strain of red sandstone samples treated at high temperatures with the stress level were explored, and the creep properties and strength of the samples at different temperature gradients were investigated. In addition, the creep failure patterns and failure mechanism of the red sandstone samples were determined, and a creep constitutive model was established for the samples considering the effects of temperature. The conformity between test data and theoretical curves was discussed. Results show that as the stress increases, the instantaneous strain tends to decrease rapidly, slowly, then increase slowly; the cree... [more]

After the excavation of an underground cavern, how the surrounding rock and the support work together to bear the excavation load is an important prerequisite to correctly analyze the joint force characteristics; effectively play the role of support; and ensure the safety, efficiency, and economy of underground cavern construction. Starting from the elastic-plastic load release characteristics of surrounding rock, this paper proposes a calculation method of the elastic load coefficient of surrounding rock and a graded release method of plastic load, which ensures the actual effect of the synergistic action of the first support and surrounding rock. Based on the elastic-plastic damage evolution characteristics of surrounding rock, a weighted iterative calculation method of elastic-plastic damage is proposed, and an evaluation method of load release ultimate bearing capacity of surrounding rock is determined. By monitoring the change law of rock acoustic wave velocity with surrounding ro... [more]

Reverse osmosis (RO) desalination is considered a viable alternative to reduce water scarcity; however, its energy consumption is high. Photovoltaic (PV) energy in desalination processes has gained popularity in recent years. The temperature is identified as a variable that directly affects the behavior of different parameters of the RO process and energy production in PV panels. The objective of this study was to evaluate the effect of temperature on energy consumption and polarization factor in desalination processes at 20, 23, 26 and 30 °C. Tests were conducted on a RO desalination plant driven by a fixed 24-module PV system that received spray cooling in the winter, spring and summer seasons. The specific energy consumption was lower with increasing process feed temperature, being 4.4, 4.3, 3.9 and 3.5 kWh m−3 for temperatures of 20, 23, 26 and 30 °C, respectively. The water temperature affected the polarization factor, being lower as the temperature increased. The values obtained... [more]

Distributed energy resources have been increasingly integrated into electrical grids. Consequently, electricity markets are expected to undergo changes and become more complex. However, while there are many scientific publications on the topic, a broader discussion is still necessary. Therefore, a systematic literature review on electricity markets in the context of distributed energy resources integration was conducted in this paper to present in-depth discussions on the topic, along with shedding light on current perspectives, the most relevant sources, authors, papers, countries, metrics, and indexes. The software R and its open-source tool Bibliometrix were used to perform the systematic literature review based on the widely recognized databases Web of Science and Scopus, which led to a total of 1685 articles after removing duplicates. The results demonstrate that demand response, renewable energy, uncertainty, optimization, and smart grid are the most-used keywords. By assessing h... [more]

This work proposes and develops an implementation of a fault location method to provide a fast and resilient protection scheme for power distribution systems. The method analyzes the transient dynamics of traveling waves (TWs) to generate features using the discrete wavelet transform (DWT), which are then used to train several graph convolutional network (GCN) models. Faults are simulated in the IEEE 34-node system, which is divided into three protection zones (PZs). The goal is to identify the PZ in which the fault occurs. The GCN models create a distributed protection scheme, as all nodes are able to retrieve a prediction. Given that message-passing between nodes occurs both during training and in the execution of the model, the resiliency of such schemes to communication losses was analyzed and demonstrated. One of the models, which only uses voltage measurements, was implemented on a Texas Instruments F28379D development board. The execution times were monitored to assess the speed... [more]

Energy plays a crucial role in the sustainable development of modern nations. Today, hydrogen is considered the most promising alternative fuel as it can be generated from clean and green sources. Moreover, it is an efficient energy carrier because hydrogen burning only generates water as a byproduct. Currently, it is generated from natural gas. However, it can be produced using other methods, i.e., physicochemical, thermal, and biological. The biological method is considered more environmentally friendly and pollution free. This paper aims to provide an updated review of biohydrogen production via photofermentation, dark fermentation, and microbial electrolysis cells using different waste materials as feedstocks. Besides, the role of nanotechnology in enhancing biohydrogen production is examined. Under anaerobic conditions, hydrogen is produced during the conversion of organic substrate into organic acids using fermentative bacteria and during the conversion of organic acids into hydr... [more]

The energy storage is an important character for sustainable energy structures and the prospective future economy. This paper aims to propose a multi-attribute decision analysis (MADA) approach to prioritize and choose the energy storage system (ESS) alternatives in terms of the different technical, economic, environmental and social aspects of them. In this line, an integrated approach is developed with the combination of intuitionistic fuzzy sets (IFSs), a method using the removal effects of criteria (MEREC), rank sum (RS) and the measurement of the alternatives and ranking based on compromise solution (MARCOS) methods for prioritizing the ESSs. The IF-MEREC-RS was used to find the integrated weight by combining the objective and subjective weights of the different indicators for prioritizing the ESSs. The MARCOS method was implemented to rank the various ESSs over several crucial indicators of sustainability. The practical outcome illustrates that the Li-ion battery (LIB) is the bes... [more]

The European Union’s relative disregard for the economic, geopolitical and climatic concerns of its peripheral Eastern countries has contributed to making the war in Ukraine possible. Its consequences are now returning in the form of energy dependence and economic instability on the Union as a whole and the risk of economic crisis and deindustrialisation. This should prompt a re-assessment of the EU’s strategy towards its eastern neighbours, particularly in the energy and climate policy field. This evaluation starts from the issue of control over cheap energy as a key material foundation of state and interstate power. On this basis, we analyse the struggle between Russia and the European core states over Ukraine in terms of the ability to extract an economic surplus through the unequal exchange of energy. The current escalation should be understood as an attempt by the Russian petrostate to preserve the economic basis of its regime, which is threatened by the prospect of a low-carbon t... [more]

The consequent-pole (CP) Vernier permanent-magnet (VPM) machine has been developed over the last decade. In VPM machine, the CP structure can produce considerable torque with a half volumn of the PMs compared with the regular structure, so the cost is reduced and the mechanical strength is increased. In this paper, an improvement of chamfering structure on a CPVPM machine is proposed to alleviate the flux leakage and increase the torque density. The chamfered structure is easily machined and will not influence the robustness of the rotor. The comparison results show that under the same volume and copper loss constraint, the proposed structure has smaller cogging torque, smaller torque ripple, larger torque density and larger power factor.

With the completion of the Lianghekou Reservoir, with a multiyear regulation capacity, the operation relationship of the cascade reservoirs in the Yalong River is becoming increasingly complex. In order to study an optimal operation mode of the cascade reservoirs in the Yalong River under different inflow frequencies, based on the shortcomings of the existing single reservoir operation mode and the local joint operation mode of the cascade reservoirs, this paper first proposed a global joint operation mode for the cascade reservoirs to develop the power generation potential of daily regulating reservoirs and then gave a solution method for the cascade reservoirs’ operational model based on an improved stochastic fractal search (ISFS) algorithm. Finally, taking the maximum power generation as the goal and the inflow data of five typical years as the model inputs, this paper analyzed the differences in the power generation and water abandonment results of the cascade reservoirs in the mi... [more]

Recently, significant breakthroughs have been made in exploring northeast China’s shale part of the Q formation. On-site observation reveals that the appearance of oil at the wellhead is only seen a long time after fracturing in many wells. Strong coupling between phase behavior and relative permeability curves in the reservoir with the near-critical point initial condition restricts the efficient development of this kind of shale oil. A series of compositional models are constructed to address the issues to reveal the cause of the late oil breakthrough. Nanopore confinement is checked by including this phenomenon in the numerical model. Before the simulations, the work gives detailed descriptions of the geology and petrophysics background of the target formation. Simulation results show that the delayed oil breakthrough is highly related to the coexistence of three phases at the beginning of production, which is not seen in common reservoirs. The extended period of purely water produc... [more]