Tidal power generation technology has advanced quickly in recent years. In this study, the Hilbert-Huang transform (HHT) was used to examine the electrical energy distribution law of tidal power generation according to the time periods of days, months, and years based on observed data for tidal power generation. Our analysis summarized the tidal power generation law as follows: in the span of one day, the motor ran for 14 h before shutting off for 10 h. The frequency was 28 Hz, and the maximum voltage was 259 V. The tidal power generation swung twice a month, reaching its peak in the middle of the month and its trough at the beginning. The tidal power output fluctuated twice a year, reaching its peak in August, September, and October and its trough in February, March, and April. In the investigation of tidal power generation patterns, the HHT transformation’s precision and potency were confirmed.

Against the backdrop of China’s carbon emission reduction targets and the promotion of the construction of a unified domestic market, what kind of carbon emission effect has market integration had in weakening regional barriers and optimizing resource allocation? This paper adopts a two-way fixed effects analysis based on China’s provincial panel data from 2003 to 2019. It uses a mediation model to explore the relationship between market integration and carbon emissions. Furthermore, industrial rationalization and upgrade are the basis for examining whether a competitive or cooperative relationship exists between the carbon emission effects generated and promoting market integration between regions. The study finds a negative relationship between market integration and carbon emissions. In addition, there is significant heterogeneity in the effect of market integration on carbon emissions, and the influence effect is mainly in central China; industrial rationalization can play an enhan... [more]

Access to energy resources and broadly understood energy security are some of the critical factors influencing the economic development of countries. This article deals with the problem of assessing the energy security of countries, considering this problem in various periods of time, examining the past, present and forecasted future conditions at the same time. For this purpose, the Dynamic Multi-Criteria Decision Making (DMCDM) methodology was developed and applied, based on the classic and fuzzy Multi-Criteria Decision Making (MCDM) methods and the International Energy Security Risk Index (IESRI). In particular, the Simple Additive Weighting (SAW)/Fuzzy SAW and New Easy Approach to Fuzzy PROMETHEE II (NEAT F-PROMETHEE) methods were used. These methods are significantly different from each other in the calculation procedures used. The study showed that methodological differences between these methods cause large differences in the results of the assessment of energy security of count... [more]

Currently, we are living through the implementation of the electrical smart grid, a network that can intelligently integrate the actions of all users connected to it in order to efficiently deliver the sustainable, economical and secure supply of electricity [...]

A centered water nozzle steam−water injector is driven by cold water to pump steam at a low pressure and to produce a high outlet water pressure. It can be used as a safety pump in a light water reactor to inject cooling water into the reactor core with no power supply in case of an accident. In this study, a modified calculation method for a centered water nozzle steam−water injector is proposed and verified by experimental data in the literature. The calculation method consists of a water nozzle model, a steam nozzle model, a mixing section model, and a shock wave model. Comparisons between the calculated results and the experimental results under different inlet steam pressures, inlet water pressures, and back pressures are conducted, and the calculated results show good agreement with the experimental results. The calculated results with different back pressures show that no shock wave occurs in the mixing section when the back pressure is small, but with the back pressure increasi... [more]

The detonation initiation characteristics of a single tube liquid-fueled pulse detonation combustor (PDC) is investigated at different inlet air temperatures in this paper. The inner diameter of the PDC is 62 mm. Gasoline and air are used as fuel and oxidant, respectively. The inlet air temperature is 288−523 K and the operating frequency of the PDC is 10~30 Hz. The experimental results show that the deflagration to detonation transition (DDT) distance, detonation initiation time, DDT time and jet ignition time decrease with the increasing operating frequency at the same inlet temperature. When the inlet temperature is 288 K, the DDT distance is shortened from 860.5 mm to 787.7 mm as the operating frequency increases from 10 Hz to 30 Hz. The detonation initiation time, the jet ignition time and the DDT time are reduced from 10.01 ms, 7.66 ms and 2.35 ms to 6.55 ms, 4.99 ms and 1.56 ms, respectively. When the inlet air temperature increases, the atomization and evaporation of the gasoli... [more]

The aim of the article is to analyse the impact of selected conditions on the use of municipal solid waste in energy production processes. The authors in this publication indicated that the factors determining the effective use of solid municipal waste may be, in particular, formal and legal conditions, methods used in the processes of thermal waste transformation, recovery logistics or emergency situations such as pandemics or armed conflicts. Their knowledge can be very useful in the processes of the effective use of municipal waste for the production of thermal energy, especially in the current period of the energy crisis faced by most EU countries. This paper also emphasizes the importance of RDF (refuse-derived fuel) for the thermal energy sector, which can be used both in large combustion plants and in less powerful facilities, including local heating and combined heat and power plants as an alternative to traditional fossil fuels. The article was prepared by means of the systema... [more]

The energy sector has been a pioneer in the use of information and communication technologies for many years, and has undergone enormous changes in recent years as a result of the transition resulting from the fourth industrial revolution. In the paper, we examine and analyse relevant studies and their findings in order to show the current status of research on three selected aspects of digitalisation in energy sector enterprises. The paper sheds light on the diverse drivers influencing the digitalisation processes of energy sector companies. It also provides an overview of business models that are or will soon be implemented in the energy sector thanks to opportunities offered by digitalisation in response to observed trends in the energy market. Finally, it illustrates open research challenges and future dilemmas related to various aspects of energy sector digitalisation. The paper was prepared using the critical literature review method. It covers a large volume of the most recent a... [more]

Offshore wind is poised for huge growth in the coming years, the UK government has set targets of 40 GW of offshore wind, including 1 GW of floating wind, to be installed in the UK by 2030. Many proposed wind development sites are in deeper waters, farther from shore and will therefore need to be developed as floating wind sites. Developing sites in deeper waters provides access to higher, more consistent wind speeds, however this also means increased wave heights and tougher operating conditions. This makes the challenge of site accessibility critical to the goal of lowering the costs of offshore wind. Accessibility is the amount of time that vessels can safely access a given site. The objective of this study was to make a comparison of the accessibility of potential future floating wind sites to existing fixed bottom wind farm sites. Accessibility was calculated by developing Matlab code using established techniques and definitions found in the literature. A case study was then compl... [more]

Low field pulse nuclear magnetic resonance (LF-NMR) was used to analyze the effects of a polymeric ion retarder and the amount of acryloxyethyl trimethylammonium chloride (DMC) in the retarder on the distribution of T2, thickening property, and strength of cement paste. The effect of pressure and temperature on the thickening curve was investigated, and the hydration products were analyzed using XRD. The result shows that the wrapped water of the precipitation is the main reaction aqueous phase of cement slurry in the hydration, with short T2 time and a large relaxation peak area. The retarder weakens the van der Waals force and electrostatic adsorption force between the water and cement particles, reducing the hydration rate of cement particles. An appropriate increase in the cationic content of polymeric ion retarder can improve the early strength of cement slurry.

By studying M&A deals completed by European energy and power companies between 2002 and 2021, the paper inquires into the impact of corporate consolidation on the competitive positioning of individual energy firms and the concentration of market power on the national energy markets in the EU countries. Our evidence suggests that the European energy market may be moving towards a greater concentration of market power as market leaders are shown to primarily acquire their peers from national markets, while outsiders are more likely to diversify into non-energy sectors, which may further endanger their competitive positioning in the future. We also find that M&As allow energy and power companies to substantially increase their market share within national markets. The said impact is stronger in case of cross-border deals, including those within and outside of the EU. At the same time, only cross-border deals are associated with sufficiently strong revenue growth to advance firms’ relative... [more]

For attack detection in the smart grid, transfer learning is a promising solution to tackle data distribution divergence and maintain performance when facing system and attack variations. However, there are still two challenges when introducing transfer learning into intrusion detection: when to apply transfer learning and how to extract effective features during transfer learning. To address these two challenges, this paper proposes a transferability analysis and domain-adversarial training (TADA) framework. The framework first leverages various data distribution divergence metrics to predict the accuracy drop of a trained model and decides whether one should trigger transfer learning to retain performance. Then, a domain-adversarial training model with CNN and LSTM is developed to extract the spatiotemporal domain-invariant features to reduce distribution divergence and improve detection performance. The TADA framework is evaluated in extensive experiments where false data injection... [more]

The compact, simple, and fast-reaction pneumatic microactuator is significant for the integration and high efficiency of pneumatic systems. In this work, the structure, working principle, and multiphysical model of an on-chip pneumatic microactuator are presented. The on-chip pneumatic microactuator is mainly composed of two parts: a polydimethylsiloxane (PDMS) thin membrane and an actuated chamber. The air pressure in the actuated chamber drives the thin elastic membrane to deformation. Dynamic response mathematical models of the actuated chamber for charging and exhaust with variable volume are established, and the deformation characteristics of the polydimethylsiloxane (PDMS) actuated membrane, the capacity of the actuated chamber, and the valve opening of the on-off membrane microvalve are simulated and analyzed to explore the response characteristics of the proposed pneumatic microactuator. Samples valving analysis of the on-chip membrane microvalve and mixing performance of the m... [more]

The influence of impellers system, baffles system and type of liquid on gas hold-up in a vessel has been presented in this paper. The analysis of gas hold-up was conducted on the basis of the data obtained in the vessel. The vessel used in the study was of inner diameter D = 0.288 m, and it was filled with liquid up to a height of H = 0.576 m. The vessel used in the study was equipped in four planar standard baffles or 24 vertical tubular baffles located on the circuit. A high-speed impellers system, consisting of two impellers located on the shaft, was used to agitate the liquid. The six gas−liquid systems were tested. The gas used in the study was air. The liquids were distilled water, aqueous solutions of NaCl (concentration c = 0.4 kmol/m3 or 0.8 kmol/m3), aqueous solution of sucrose (concentration c = 2.5% mass., 5% mass.), 5% mass. aqueous solution of sucrose and yeast suspension concentration ys = 1% mass. The obtained set of over 1600 experimental points allowed to derive the e... [more]

Nanoscale tungsten bronze can convert near-infrared light into thermal energy. For a chemical synthesis, intermediate products and processes are potentially positive or negative to an end product. In this study, (NH4)2SO4 was added into the hydrothermal system of WO3, CsCl, CH3CH2CHO, and NH3·H2O to increase the Cs/W ratio in solution. An intermediate, Cs1.1W1.65O5.5, was isolated. Subsequently, it was confirmed via a kinetics experiment conducted for different times. The results of the NH3·H2O and NH4COOCH3 system indicate there are two influence factors that influence the formation of Cs1.1W1.65O5.5: the leaching out of W and imine reactions. A low leaching out rate induces a high Cs/W ratio and low-concentration W in solution, leading to the formation of Cs1.1W1.65O5.5. The imine reaction decreasing CH3CH2CHO restrains the reduction in Cs1.1W1.65O5.5. The increase in CH3CH2COO− with the reduction reaction results in both the micron-size sticks and nano-size equiaxial particles in po... [more]

The hydrate dissociation is viewed as a phase change process in which hydrates transform from a solid phase into gas and liquid phase at a moving dissociation boundary. The boundary separates the dissociation zone containing gas and water from the undissociated zone containing the hydrates, leading to a density difference. Based on the assumption of a density difference between the dissociation zone and the hydrate zone, the authors propose a mathematical model to study hydrate dissociation under thermal stimulation in an infinite radially symmetrical reservoir. Analytical solutions to the temperature distribution are derived by using the self-similarity transformation. Considering the effect factors of the initial heated-water temperature and hydrate density, the authors conducted a thorough investigation of the temperature distribution and the location of the dissociation front for a sample hydrate reservoir. The results from our model show that the heated-water temperature and hydra... [more]

The transmission of electricity from the source to the load is mainly carried out using a three-phase line [...]

There has been growing interest in using underground locations for applications in various fields, including research. In Poland, for several years, attempts have been made to build an underground laboratory. For this purpose, selecting an appropriate location requires a detailed analysis of the level of natural radioactivity. The present study presents detailed characteristics of the natural background radiation in close vicinity to shaft L-VI of the Lubin mine, at the depth of 910 m (2275 m w.e.). The in situ measurement of the photon flux in the 7−3150 keV energy range was equal to 8.08 ± 0.90 cm−2s−1, and the gamma-ray dose rate of 0.070 ± 0.010 µSv/h with the highest contribution from 40K and 214B isotopes. The thermal neutron flux measured using helium counters was equal to 4.2 ± 0.9 × 10−6 cm−2s−1. The radon concentration in the air measured with the RAD7 monitor showed low values ranging from 0 to 15.3 Bq/m3. Laboratory measurements of rocks using alpha and gamma spectrometry t... [more]

In 2017, the 19th CPC National Congress proposed to “establish a sound economic system of green, low-carbon and circular development”, which indicates the direction of high-quality economic development in the new era of China. Clean power investment is a powerful way to promote high-quality economic development by adopting non-fossil-energy utilization and low-emission technologies, as well as creating new jobs. Meanwhile, large-scale investment and a long investment return period result in negative effects on local economies. To better understand the effect of clean power investment, this paper selects panel data of thirty provinces in China from 2010 to 2019 to establish a spatial Durbin model to explore the impact of clean power investment on regional high-quality economic development. The results show that inter-regional high-quality economic development shows significant spatial auto-correlation characteristics. Clean power investment has not only a positive direct effect on high-... [more]

The present investigation concerns the potentiality of Rhodopseudomonas sp. cells to produce clean energy such as molecular hydrogen (H2). The abovementioned goal could be reached by improving the capability of purple non-sulfur bacteria to produce H2 via a photofermentative process through the enzyme nitrogenase. Rhodopseudomonas sp. cells were immobilized in calcium alginate gel beads and cultured in a cylindrical photobioreactor at a working volume of 0.22 L. The semi-continuous process, which lasted for 11 days, was interspersed with the washing of the beads with the aim of increasing the H2 production rate. The maximum H2 production rate reached 5.25 ± 0.93 mL/h with a total output of 505 mL. The productivity was 40.9 μL (of H2)/mg (of cells)/h or 10.2 mL (of H2)/L (of culture)/h with a light conversion efficiency of 1.20%.

This work aims at investigating the kinetic mechanisms of the reduction/oxidation (redox) reactions of iron oxide/iron pellets under different operating conditions. The reaction principle is the basis of a thermochemical hydrogen storage system. To simulate the charging phase, a single pellet consisting of iron oxide (90% Fe2O3, 10% stabilising cement) is reduced with different hydrogen (H2) concentrations at temperatures between 600 and 800 °C. The discharge phase is initiated by the oxidation of the previously reduced pellet by water vapour (H2O) at different concentrations in the same temperature range. In both reactions, nitrogen (N2) is used as a carrier gas. The redox reactions have been experimentally measured in a thermogravimetric analyser (TGA) at a flow rate of 250 mL/min. An extensive literature review has been conducted on the existing reactions’ kinetic mechanisms along with their applicability to describe the obtained results. It turned out that the measured ki... [more]

Mining of minerals is an important part of the technical sciences, for which the certainty and unambiguity of terms and the correct application of definitions is an absolute requirement. At the same time, the expansion of Industry 4.0 technologies, both in practice and in scientific discussions, brings new terms to mining that are far from the original meaning. These terms include Data Mining and Mining 4.0, which, having a common digital core, refer to fundamentally different areas of human activity, and have the opposite meaning in relation to the use of resources (digital ones—endless, and the natural ones—finite). The indiscriminate use of the term “mining” is especially dangerous in the context of Mining 4.0, in which digital technologies allow the intensification of the exploitation of natural resources. This brief Perspective paper will show the role of terminology in Mining 4.0 and offer an interpretation of its relationship with Data Mining.

Large quantities of gas resources have been found in the Paleo-Mesozoic carbonate rocks in the Sichuan Basin. However, many wells cannot obtain high production in deep low porosity-permeability reservoirs. For this contribution, we provide a steerable pyramid method for identifying the fault damage zone in the Kaijiang−Liangping platform margin, which is infeasible by conventional seismic methods. The results show that steerable pyramid processing could enhance the seismic fault imaging and a series of NW-trending strike-slip faults are found along the trend of the carbonate platform margin. The steerable pyramid attribute presents distinct vertical and horizontal boundaries of the fault damage zone, and heterogeneous intensity of an un-through-going damage zone. The width of the fault damage zone is generally varied in the range of 100−500 m, and could be increased to more than 1000 m in the fault overlap zone, intersection area, and fault tips. Further, the fault damage zone plays a... [more]

Liquid dielectrics are different from each other, but are used to perform the same tasks in high-voltage electrical equipment, especially transformers. In similar conditions, the insulation performance of transformer oils under different types of voltage will provide dielectric resistance. In this study, three different dielectric liquids applied in transformers, namely mineral oil, natural ester and synthetic ester, were tested. Tests under AC and negative DC voltage were performed at electrode gaps of 2.5 mm, 2 mm and 1 mm using disk and VDE type electrodes as per ASTM D1816-84A and ASTM D877-87 standards, respectively. In turn, the impulse voltage tests were performed under an electrode configuration suggested by the IEC 60897 standard. The current data of 500 ms prior to breakdown under AC electrical field stress was decomposed using the empirical mode decomposition (EMD) and variational mode decomposition (VMD) methods. These analyses were conducted before the full electrical brea... [more]

The organic flash cycle (OFC) is a novel power cycle with small exergy loss in the endothermic process. However, the low-pressure throttle valve in the cycle has a large throttling loss. Aiming to reduce the cycle exergy loss and improve the system performance, this study constructs a new configuration named the organic flash Rankine cycle (OFRC). Using the R600/R245fa mixture as the circulating working fluid and 200 °C geothermal water as the heat source, the effects of the change in working fluid composition on the thermal properties of the OFRC were studied based on the first and second laws of thermodynamics. Then, the economic performance of the proposed OFRC was investigated and then compared with that of the conventional OFC. The results show that the OFRC system has a significant improvement in thermal performance and economy compared with the OFC system. When the mole composition of the R600/R245fa mixture is 0.5/0.5, the net output work, thermal efficiency, and exergy efficie... [more]