An advanced break or a vast region of pressurisation may occur when the working face passes through an abandoned roadway, resulting in a roof falling or water inrush. The stress evolution of the working face passing through an abandoned roadway in a coal mine was comprehensively discussed using theoretical analysis, numerical simulation, and field monitoring. In this study, the calculated critical width of the abandoned roadway where the main roof was bound to an advanced break was 5.4 m. Reducing the suspended length of the main roof is beneficial to the stability of the working face’s passage across the abandoned roadway. The maximum abutment stress on the roof occurred at the working face through a semi-abandoned roadway, reaching 44.3 MPa. Subsequently, it decreased sharply until the working face completely passed and returned to the normal level. The damage depths of the floor strata from the field monitoring were 15 and 20 m, which showed that the use of hydraulic fracturing tech... [more]

This article describes an approach for comparing material intensity values for residential buildings with different construction types. Based on the working drawings of the different construction types (wood and mineral), material intensities are calculated at the building level. Material intensities describe the materials used in a building in mass (tonnes (t)) in relation to the square meters (m2) of gross floor area (GFA) or the cubic meters (m3) of gross volume (GV). The method for determining material intensities at the building level is demonstrated. The results show that material intensities range from 0.61 t/m2 GFA to 1.95 t/m2 GFA for single-family residential buildings and from 1.36 t/m2 GFA to 1.54 t/m2 GFA for multi-storey residential buildings. The average material intensity for mineral buildings is twice as high as that for wood buildings, which means that there is a beneficial resource efficiency in building with wood instead of mineral materials. Therefore, benchmarks f... [more]

Greenhouse gases (GHG) concentration (CO2, CH4, and NOx mainly) in the Earth’s atmosphere has dramatically increased since 1960; in particular, the atmospheric CO2 levels have increased from 320 ppm to 412 ppm from 1960 to 2019 [...]

Transportation and portable applications already use hydrogen as fuel, but it is essential to use highly-efficient hydrogen storage methods to increase its usage in the future. The compressed form is the most utilized for transportation applications, but mechanical compressors have low efficiency when compressing low quantities of gas to high pressure. The most suitable device for hydrogen compression is the Electrochemical Hydrogen Compressor (EHC). It has the same structure as a Proton Exchange Membrane Fuel Cell (PEM-FC), but it works at very high-pressure ( 700 bar). The present work analyses the monopolar plate of an Electrochemical Hydrogen Compressor prone to hydrogen embrittlement. Irregular shape variations generate peaks of stress magnitude and triaxiality, further contributing to decreasing metal ductility at the local scale. The calculation of the stress field in such components is essential due to the possibility of failure due to the material embrittlement caused by hydro... [more]

Jevons Paradox has fundamental implications on sustainable development and the UN Sustainable Development Goals (SDGs). The paradox states that technological improvements aiming to increase the energy efficiency risk causing a rebound effect, and an increase in demand, production, and resource exploitation. Third world countries undergoing early-stage technological development may be particularly vulnerable, but it is also relevant in complex economic systems, where policymaking on climate and energy building on insufficient knowledge and attention to rebound effects can impair the desired outcome in terms of climate change mitigation, resource use and sustainable development.

Electricity has a crucial function in contemporary civilization. The power grid must be stable to ensure the efficiency and dependability of electrical equipment. This implies that the high-voltage equipment at the substation must be reliably operated. As a result, the appropriate and dependable use of systems to monitor the operating status of high-voltage electrical equipment has recently gained attention. Partial discharge (PD) analysis is one of the most promising solutions for monitoring and diagnosing potential problems in insulation systems. Noise is a major challenge in diagnosing and detecting defects when using this measurement. This study aims to denoise PD signals using a data decomposition method, improved complete ensemble empirical mode decomposition with adaptive noise algorithm, combined with statistical significance test to increase noise reduction efficiency and to derive and visualize the Hilbert spectrum of the input signal in time-frequency domain after filtering... [more]

Terrestrial tight oil has extremely strong diagenesis heterogeneity, so a large number of rock thin slices are needed to reveal the real microscopic pore-throat structure characteristics. In addition, difficult identification, high cost, long time, strong subjectivity and other problems exist in the identification of tight oil rock thin slices, and it is difficult to meet the needs of fine description and quantitative characterization of the reservoir. In this paper, a method for identifying the characteristics of rock thin slices in tight oil reservoirs based on the deep learning technique was proposed. The present work has the following steps: first, the image preprocessing technique was studied. The original image noise was removed by filtering, and the image pixel size was unified by a normalization technique to ensure the quality of samples; second, the self-labeling image data augmentation technique was constructed to solve the problem of sparse samples; third, the Mask R-CNN alg... [more]

Carbonate reservoirs commonly have significant heterogeneity and complex pore systems due to the multi-scale characteristic. Therefore, it is quite challenging to predict the petrophysical properties of such reservoirs based on restricted experimental data. In order to study the heterogeneity and size of the representative elementary volume (REV) of vuggy dolostones, a total of 26 samples with pore sizes ranging from micrometers to centimeters were collected from the Cambrian Xiaoerbulake Formation at the Kalping uplift in the Tarim Basin of northwestern China. In terms of the distribution of pore size and contribution of pores to porosity obtained by medical computed tomography testing, four types of pore systems (Types I−IV) were identified. The heterogeneity of carbonate reservoirs was further quantitatively evaluated by calculating the parameters of pore structure, heterogeneity, and porosity cyclicity. The results indicate that different pore systems yield variable porosities, por... [more]

EAF steelmaking based on renewable electricity allows for low-CO2 steel production. However, the increased integration of volatile renewable energies into the energy system requires the provision of flexibility options. In view of the substantial oxygen consumption in the steel mill, flexible on-site generation and storage holds a significant potential for demand-side management. The utilization of by-product oxygen from an electrolysis plant not only contributes to load flexibility but also generates a climate-neutral fuel. In the present study, different process layouts are developed based on state-of-the-art technologies. The proposed supply systems for oxygen, hydrogen, and synthetic natural gas are subjected to design and operational optimization and assessed with respect to the overall demand-side flexibility, carbon dioxide emission reduction, and economic viability.

Marine energy resources could be crucial in meeting the increased demand for clean electricity. To enable the use of marine energy resources, developing efficient and durable offshore electrical systems is vital. Currently, there are no large-scale commercial projects with marine energy resources, and the question of how to design such electrical systems is still not settled. A natural starting point in investigating this is to draw on experiences and research from offshore wind power. This article reviews different collection grid topologies and key components for AC and DC grid structures. The review covers aspects such as the type of components, operation and estimated costs of commercially available components. A DC collection grid can be especially suitable for offshore marine energy resources, since the transmission losses are expected to be lower, and the electrical components could possibly be made smaller. Therefore, five DC collection grid topologies are proposed and qualitat... [more]

Renewable energy is predicted to play a crucial role in the energy sector as transitioning from fossil fuels to biofuels is key to achieving carbon neutrality. The comprehensive utilization of livestock manure and crop residues as a viable source of biofuels can play a significant role in Ghana’s future energy system. This current study aims to examine and predict the biofuel potential in Ghana from animal manure and crop residues. The biogas-biomethane potential of animal manure is determined using anaerobic digestion technology, whereas crop residues’ bioethanol potential is assessed using computational and analytical approaches. The findings demonstrate that animal manure biogas potential is 237.72 normal million cubic meters (NMm3). The highest manure-biogas potential per animal is from cattle (27.15 Nm3) and pigs (18.15 Nm3), while the least contribution is from chickens (1.80 Nm3). In addition, the annual bioethanol production is 3.74 gigaliters (GL), and residues from maize (0.8... [more]

The reuse of waste materials such as carbon fiber (CF) as filling additive for closed-loop vertical geothermal probes in shallow geothermal systems has been evaluated as a new grout mixture for the improvement of geothermal energy systems efficiency and a sustainable supply of raw materials from special waste. The study evaluates the improvement in both thermal exchange characteristics and mechanical properties of the filling grout for geothermal purposes through the addition of 5% of CF to standard (ST) materials currently on the market. Uniaxial and flexural tests investigating the material response after 14 and 28 days from sample preparation on samples of both standard and mixed grout material as well as non-stationary hot wire method were used to define the thermal conductivity for both the standard and innovative mixtures. The experimental analysis provides evidence for increasing the thermal conductivity by about 3.5% with respect to standard materials. Even the mechanical prope... [more]

The complex temperature and pressure conditions of deepwater wells have a serious impact on cementing quality. Therefore, the integrity of the cement seal becomes a critical factor that can restrict the safety of the wellbore, especially for wells ranging from the conventional deep water to deep water with more prominent deep stratum problems. The operating conditions of deep wells in deep water (referred as the dual-deep well) are complex and harsh. For the conventional evaluation device, it is difficult to accurately simulate the alternating HTHP conditions and to clarify the location and situation of the cement sheath leakage, which directly leads to the deviation of the evaluation results from the engineering reality. To solve this defect, based on the condition and structure characteristics of dual-deep wells, a device and method for casing/cement sheath/formation seal integrity evaluation for dual-deep wells at HTHP has been developed and established. Combined with the analysis o... [more]

The integration of distributed generation systems, including intermittent solar photovoltaic (PV) and wind, has a significant impact on the power system [...]

At the Changning block and at the Luzhou block, the genetic mechanism of low-resistivity shale and its impact on reservoir quality are currently a hot topic on a world-wide scale. Shale with resistivity lower than 20 Ω·m is widely developed at the Wufeng-Longmaxi Formation in the Southern Sichuan Basin, bringing a considerable challenge for reservoir prediction using the electromagnetic method. This paper discusses the genetic mechanisms and reservoir qualities of three low-resistivity shale reservoir types in the Southern Sichuan Basin (the Changning block and Luzhou block). Three primary elements controlling low-resistivity shale distribution in the Southern Sichuan Basin have been deduced: widely distributed gravity flow deposits, poor structural preservation conditions and shale graphitization caused by Emeishan basalt. Specifically, (1) the shale reservoir with a resistivity <12 Ω·m was uniformly distributed with gravity flow deposits in the Southern Sichuan Basin. High clay mi... [more]

Microalgae have been intensively studied for CO2 capture, nutrient removal from wastewater, and biofuel production applications [...]

Corporate responsibility is an effective management strategy which, through conducting social dialogue at the local level, contributes to increasing the competitiveness of enterprises at a global level and simultaneously shaping favourable conditions for social and economic development. A review of the literature on the subject provided the theoretical motivation to undertake an emirical study of the implemented social innovations by the property manager and their reception by resource residents. The main aim of this study was to diagnose the attitudes of residents towards the implementation of social innovations by the municipal property manager. The research presented in the above article has been conducted in the first and second quarter of 2021 among residents of the Department of Housing “TBS” (ZGM TBS) in Częstochowa, Silesian voivoideship, Poland. The research was conducted using the survey method. The measurement instrument was a prepared questionnaire. The survey was completed... [more]

After hydraulic fracturing, some treatments intended for production enhancement fail to yield predetermined effects. The main reason is the insufficient research about the fracture propagation mechanism. There is compelling evidence that I-shaped fracture, two horizontal fractures at the junction of coalbed and cover/bottom layer, and one vertical fracture in the coalbed have formed in part of the coalbed after hydraulic fracturing. Therefore, this paper aims at I-shaped fracture propagation simulation. A novel propagation model is derived on the basis of a three-dimensional (3D) model, and the coupling conditions of vertical fracture and horizontal fractures are established based on the flow rate distribution and the bottom-hole pressure equality, respectively. Moreover, an associated PDA (pressure decline analysis of post-fracturing) model is established. Both models complement with each other and work together to guide fracturing treatment. Finally, a field case is studied to show t... [more]

Aiming at the electromagnetic vibration and noise problem of an 8-pole 48-slot permanent magnet synchronous motor for a vehicle, the multi-physics coupling simulation model of the motor is introduced to optimize the rotor structure of the motor to reduce the vibration and noise of the permanent magnet synchronous motor. The effectiveness of the research method is verified by the bench test in the anechoic chamber. Finite element software was used to establish the stator core and system model considering the anisotropy of materials, and the simulation model was verified by modal experiment. For the 2in1 electric drive system, the electromagnetic-structure-acoustic multi-physics coupling noise prediction model is established. Based on the three-dimensional distributed electromagnetic force excitation, the electromagnetic radiation noise of the motor under full load acceleration is calculated, and the characteristics of electromagnetic noise are analyzed. The accuracy of the electromagnet... [more]

Progress in science and technology drives the continuous innovation of energy collection and utilization. In the field of sports, the information collection and analysis based on Internet of things have attracted particular attention. Moreover, triboelectric nanogenerator (TENG) has promising applications in the field of sports. Here, we introduce the working principle of the TENG then the progress of the TENG as a wearable energy sensor is examined in the two fields of basic human activities and sports, especially competitive sports. On this basis, it is considered that the stability of devices, the universality of materials, and the scientificity of application of the TENG in the future need to be improved. We provide a direction for further upgrading energy collection technology to promote the high-quality development of human mechanical energy sensing in the field of sports.

This paper is a review of research undertaken, and subsequent policy change enacted, in the years 2018 to 2022 regarding the integration of cooking loads and needs into modern energy planning. Building on an earlier paper which described how the dominant global approaches to tackling the enduring problem of biomass-fuelled cooking was failing, and how a new UK Aid programme (Oct 2018) would be seeking to intentionally change international energy policy towards cooking and enable a significant transition in energy use, in this paper we review whether this strategy is being adopted by researchers, governments, and the private sector across the world and whether it is likely to make a significant contribution to the fulfilment of Sustainable Development Goal 7. In particular, the call is for integrated planning of modern energy inclusive of cooking loads—the potential ‘Mutual Support’ that both can lend to each other. The review considers the international commitments made by donors and g... [more]

Nowadays, power converters with reduced cost, compact size and high efficiency are evolving to overcome the emergent challenges of renewable energy integrations. In this context, there is an increased demand for well-designed power converters in renewable energy applications to reduce energy utilization and handle a variety of loads. This paper proposes a center-tapped bridge cascaded series-resonant LC dual active bridge (DAB) converter for DC-DC conversion. The low part count of the proposed converter enables a high-power density design with reduced cost. The proposed converter offers reduced conduction losses as the reverse current is eliminated by adopting current blocking characteristics. Reverse current blocking also enables zero voltage switching (ZVS) and zero current switching (ZCS) over a wide operating range. Therefore, using a simple fixed frequency modulation (FFM) scheme offers a wide operating range compared to a conventional DAB converter. A thorough comparison of the p... [more]

Low-temperature solar thermal energy is a viable and mature alternative to reduce the use of fossil fuels for domestic hot water heating. The impact of the inclusion of this technology in the energy matrix in the Andean city of Cuenca, Ecuador, is analyzed. In Ecuador, liquefied petroleum gas (LPG) is currently used to heat water due to the high state subsidy, with a cost of 0, 11 USD for an LPG kg compared to the international price of 1.18 USD a Kg of LPG in 2021. Sustainability indicators show that the urban energy matrix would be minimally affected by a high penetration of solar thermal systems. The indicators that are positively affected are related to energy self-sufficiency, emissions, and employment at the expense of an increase in the cost of energy. Moreover, the analysis of the impact on consumption exclusively in the residential sector shows that liquefied petroleum gas consumption would drop from 73 to 64%, mainly because the liquefied gas is used in cooking. However, the... [more]

A solution to the inverse heat transfer problem (IHP) occurring in steam pipelines is presented in the paper. The transient steam temperature at the pipeline inlet was determined from the steam temperature measured at the pipeline outlet. Temporary changes of steam temperature at the turbine inlet are set by the turbine manufacturer and result from the conditions of safe starting of the turbine and maintaining high durability of its components. The boiler start-up should be carried out so that the time-temperature changes at the boiler outlet equal the time-temperature changes determined using the inverse problem. In this paper, the inverse problem of heat transfer in the pipeline was solved by the finite volume method using data smoothing, future times steps, and Tikhonov regularization that stabilized the solution of the inverse problem. The determined transient steam temperature at the pipeline inlet was compared with the measured temperatures. The steam temperature at the inlet to... [more]

To address time delay and noise problems in control systems, in this study, we integrated an extended state filter for signal filtering into an active disturbance rejection control (ADRC) system and derived an improved ADRC approach. In addition to the active anti-disturbance and active tracking estimation functions of the existing ADRC, the proposed approach also includes active filtering and active advance prediction functions, which can filter out the effect of measurement noise on system state observation while reducing the delay between the system control output and the detection of the sensor input. We verified through an evaluation in a simulation environment that the proposed approach may be expected to achieve improved control accuracy and increase the stability of closed-loop control systems.