According to the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment report, energy-efficient appliances can reduce global electricity consumption even though there is an expected increase in the number and ownership of appliances. The International Energy Agency (IEA) expects a high increase in energy efficiency in traditional appliances (refrigerators, washing machines, television, etc.), and in the number of new appliances installed (also called plug loads). The bibliometric study of publications related to energy-efficient appliances carried out in this paper shows that research on this topic is growing in developed regions (North America and Europe) and even more in some developing regions (Asia Pacific) with a high emphasis on China and India. The results indicate that, in general, policies are always implemented before the core of publications on the topic, with time spans ranging from 3 to 30 years. However, the trend seems to be changing with publications related t... [more]

This work presents an investigation of the fully strained GaAsN/GaAs heterostructures obtained by atmospheric pressure metalorganic vapor phase epitaxy, focusing on the analysis of the strain generated in the GaAsN epilayers and its correlation with the formation of split interstitial complexes (N-As)As. We analyzed strained GaAsN epilayers with nitrogen contents and thicknesses varying from 0.93 to 1.81% and 65 to 130 nm, respectively. The composition and thickness were determined by high resolution X-ray diffraction, and the strain was determined by Raman spectroscopy, while the N-bonding configurations were determined by X-ray photoelectron spectroscopy. We found that the strain generated in the GaAsN epilayers is mainly caused by a lattice mismatch with the GaAs substrate. This macroscopic strain is independent of the amount of (N-As)As interstitial defects, while the local strain, induced by an alloying effect, tends to decrease with an increasing ratio of (N-As)As interstitial de... [more]

The effect of stylolite caused by the pressure dissolution process on the reservoir petro-physical properties is still controversial. This study aims to reveal the effect of stylolite on the porosity and permeability of packstone and wackestone in the Mishrif Formation from the Ah oilfield in the Middle East. Based on the observation of thin sections and cores, X-ray diffraction analysis and porosity and permeability measurement, the lithofacies, diagenesis and patterns of stylolites have been investigated. There are six lithofacies in the Mi4 member, including bivalve green algae packstone, green algae packstone, pelletoid green algae packstone, echinoderm packstone, rudist packstone, planktonic foraminifera wackestone and bioclastic wackestone. The mechanical compaction and pressure dissolution could be observed in these lithofacies, with the development of dissolution seams and stylolites. The density of stylolite has a relationship with the lithofacies and early cementation. The bo... [more]

In this study, a torque enhancement principle for a stator permanent-magnet (PM) Vernier machine with a consequent pole structure is proposed. The novelty of the manuscript is the explanation of how stator PM Vernier machines benefit from consequent pole structure. Although a similar concept of stator PM Vernier machines with a consequent pole structure has been investigated in previous studies, a clear torque enhancement principle was absent. The keys to torque enhancement are the decrement of nonworking harmonics and increment of working harmonics. To demonstrate these phenomena, the torque contributions from the harmonics were calculated. Subsequently, the performances of the conventional machine and consequent pole machine were compared to verify the enhancement principle. The electromagnetic performances, including the back electromotive force and torque, were compared. The results show that the stator PM Vernier machine benefits significantly from torque enhancement using the con... [more]

The cement industry confronts significant challenges in raw materials, energy demands, and CO2 emissions reduction, which are global and local environmental concerns. Life cycle assessment (LCA) has been used in many studies to assess the environmental impact of cement production and investigate ways to improve environmental performance. This study aims to analyse the environmental impact of Portland cement (CEM I) on the South African cement industry using the life cycle impact assessment (LCIA), based on the Recipe 2016 v 1.04 midpoint method. The study was conducted using data modeled after the South African cement plant, considered a cradle-to-gate system boundary, starting from the extraction of the raw material to the cement production process that produces cement as the main product. The data were obtained from the Ecoinvent database v3.7.1, integrated with SimaPro 9.1.1. software, used to assess the impact categories. For simplicity, the study merged the entire production proce... [more]

The accuracy of the intelligent diagnosis of rolling bearings depends on the quality of its vibration data and the accuracy of the state identification model constructed accordingly. Aiming at the problem of “poor quality” of data and “difficult to select” structural parameters of the identification model, a method is proposed to integrate data cleaning in order to select effective learning samples and optimize the selection of the structural parameters of the deep belief network (DBN) model. First, by calculating the relative energy fluctuation value of the finite number of intrinsic function components using the variational modal decomposition of the rolling bearing vibration data, the proportion of each component containing the fault component is characterized. Then, high-quality learning samples are obtained through screening and reconstruction to achieve the effective cleaning of vibration data. Second, the improved particle swarm algorithm (IPSO) is used to optimize the number of... [more]

With the large-scale volatility and uncertainty of the centralized grid connection of wind power, the dimensionality disaster problem of wind farm cluster (WFC) scheduling optimization calculation becomes more and more significant. In view of these challenges, a distributed active power optimal dispatch model for WFC based on the alternating direction multiplier method (ADMM) is proposed, and the analytical description of the distribution characteristics of the active power output of wind farms is introduced into the proposed model. Firstly, based on the wake effect, the Weibull distribution of wind speed is transformed by the impulse function to establish an analytical model of the active output distribution of the wind farm. Secondly, the optimization goal is to minimize the expected sum of the deviations of the dispatch instructions and the output probability density function of each wind farm, constructing a WFC active power optimal dispatch model considering uncertainty. Finally,... [more]

Changing asset ownership models in the energy sector is spurring established companies and startups to implement customer-centric smart services. In this sense, startups are pioneers of innovative business models, and unbundle the energy value chain to provide various services to final customers. Although service business models have received large attention in the energy sector, the role of startups in service business model innovation (S-BMI) is not fully understood in the literature. To put this into perspective, the proposed work analyzes the six most practiced energy service categories, specifically, Comfort and Heating, Flexibility and Trading, Energy Efficiency and Management, Solar and Microgrid, Charging and Battery, and Energy Software Solutions are taken into account, accompanying service business model archetypes in the energy sector. Data from two different company databases are combined, and a list of 432 startups dealing with energy services are analyzed. The operating r... [more]

Fuel cell electric vehicles (FCEVs) can be used during idle times to convert hydrogen into electricity in a decentralised manner, thus ensuring a completely renewable energy supply. In addition to the electric power, waste heat is generated in the fuel cell stack that can also be used. This paper investigates how the energy demand of a compiled German neighbourhood can be met by FCEVs and identifies potential technical problems. For this purpose, energy scenarios are modelled in the Open Energy System Modelling Framework (oemof). An optimisation simulation finds the most energetically favourable solution for the 10-day period under consideration. Up to 49% of the heat demand for heating and hot water can be covered directly by the waste heat of the FCEVs. As the number of battery electric vehicles (BEVs) to be charged increases, so does this share. 5 of the 252 residents must permanently provide an FCEV to supply the neighbourhood. The amount of hydrogen required was identified as a pr... [more]

This work includes calculations of the cumulative CO2 emissions of two comparable cars—the VW Golf VII—one with a combustion engine and the other with an electric motor. Calculation of CO2 emissions was performed, taking into account the stages of production, utilization and use of the above-mentioned vehicles. For the use phase, it was assumed that the total mileage of the car will be 150,000 km over 10 years. For the electric vehicle, calculations were made assuming five different sources of electricity (from coal only, from natural gas only, from PV and wind turbines, an average mix of European power sources and an average mix of Polish power sources; W1−W5 designations, respectively). For individual sources of electricity, cumulative CO2 emissions were taken into account, that is, resulting both from the production of electricity and the use of the resources (for example, technical service per 1 kWh of electricity produced). The obtained results of the analysis show that for the ad... [more]

The presented article aims to design an educational test bench setup for smart grids and renewable energies with multiple features and techniques used in a microgrid. The test bench is designed for students, laboratory engineers, and researchers, which enables electrical microgrid system studies and testing of new, advanced control algorithms to optimize the energy efficiency. The idea behind this work is to design hybrid energy sources, such as wind power, solar photovoltaic power, hydroelectric power, hydrogen energy, and different types of energy storage systems such as batteries, pumped storage, and flywheel, integrating different electrical loads. The user can visualize the state of the components of each emulated scenario through an open-source software that interacts and communicates using OPC Unified Architecture protocol. The researchers can test and validate new solutions to manage the energy behavior in the grid using machine learning and optimization algorithms integrated i... [more]

The need for environmentally benign portable energy storage drives research on organic batteries and catalytic systems. These systems are a promising replacement for commonly used energy storage devices that rely on limited resources such as lithium and rare earth metals. The redox-active TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl-4-yl) fragment is a popular component of organic systems, as its benefits include remarkable electrochemical performance and decent physical properties. TEMPO is also known to be an efficient catalyst for alcohol oxidation, oxygen reduction, and various complex organic reactions. It can be attached to various aliphatic and conductive polymers to form high-loading catalysis systems. The performance and efficiency of TEMPO-containing materials strongly depend on the molecular structure, and thus rational design of such compounds is vital for successful implementation. We discuss synthetic approaches for producing electroactive polymers based on conductive and n... [more]

The objective of Poland’s energy policy is to guarantee energy security while enhancing economic competitiveness and energy efficiency, thus minimizing the power sector’s environmental impact and optimizing the use of energy resources in the country. Poland is not the only European country to rely on coal for power generation. Historical factors and large coal deposits act as natural barriers to increasing the share of renewable energy in the Polish power sector. Yet, today, environmental concerns and climate change are prompting many countries to move away from fossil fuels. Renewable energy sources, such as solar and wind energy, are an alternative to traditional energy generated from fossil fuels. However, investors developing solar and wind farms in Poland encounter numerous problems at each stage of the project. These difficulties are associated mainly with the location, technical requirements, infrastructure and formal and legal documents. This study aimed to identify the key fac... [more]

Thermal management is an important research area for the automotive sector in order to make high-efficiency and low-impact future vehicles. The transition from internal combustion engines to battery systems in the automotive field requires new skills to be achieved in the shortest possible time. The well-consolidated knowledge of thermal management of engine systems can be rearranged to face new challenges regarding the thermal control of batteries. The present work aims to show the analogies between the thermal behavior of an engine component, such as the piston, and of a battery. The thermodynamic processes involved during the operation are described, experimentally investigated, and modeled. The external temperature of the piston window is measured once per cycle with a K-type sheathed thermocouple, while the surface temperature of the battery is detected via infrared imaging. An almost-fixed stabilization time of 500 s is observed for the engine while it varies with the current loa... [more]

The intermittent and uncertain properties of wind power have presented enormous obstacles to the planning and steady operation of power systems. In this context, as an effective technique to study wind power uncertainty, the development of an accurate wind speed scenario generation method is of great significance for evaluating the impact of wind power in the power system. In the case of several wind farms, accurate scenario generation involves precise acquisition of the correlation between wind speeds and the greatest retention of statistical properties of wind speed data. Under this goal, this research provided a new method for scenario development based on principle component (PC) and R-vine copula theories that incorporates the spatiotemporal correlation of wind speeds. By integrating with PC theory, this strategy avoids the dimension disaster induced by employing R-vine copula alone while taking benefit of its flexibility. The simulation results utilizing the historical wind speed... [more]

In this paper the design of the two channel opto-isolation circuit for measurements of the differential voltage is presented. It is used to ensure high impedance of the measuring channel(s) in the differential system to ensure the rated operation of connected voltage divider(s). Its conversion accuracy tests are oriented to determine the ratio and phase errors introduced by a tested device under three test conditions. The opto-isolation circuit is tested for the internal noise at various levels of common voltage. In the next step the calibration of the zero output voltage at zero differential voltage is tested. In the last step of the testing procedure, the values of conversion ratio and phase errors are determined. In the first case the analysis is performed during an operation with an additional common voltage divider when both inputs ensure high impedance. In the second case the values of the conversion ratio and phase errors are tested in conditions when only one input ensures high... [more]

Sustainable biofuel production is the most effective way to mitigate greenhouse gas emissions associated with fossil fuels while preserving food security and land use. In addition to producing bioenergy, waste biorefineries can be incorporated into the waste management system to solve the future challenges of waste disposal. Biomass waste, on the other hand, is regarded as a low-quality biorefinery feedstock with a wide range of compositions and seasonal variability. In light of these factors, biomass waste presents limitations on the conversion technologies available for value addition, and therefore more research is needed to enhance the profitability of waste biorefineries. Perhaps, to keep waste biorefineries economically and environmentally sustainable, bioprocesses need to be integrated to process a wide range of biomass resources and yield a diverse range of bioenergy products. To achieve optimal integration, the classification of biomass wastes to match the available bioprocess... [more]

In recent years, collective action initiatives in the energy field, such as energy communities and cooperatives, have been gaining relevance both in the policy and in the social research domains as primary actors of energy transition. [...]

Renewable energy has become a crucial factor for circular economies, sustainable development, and the environment given the limited non-renewable energy reserves and global environmental degradation mainly resulting from non-renewable energy use. This study explores the effect of educational attainment and economic growth on renewable energy use in a sample of selected emerging markets over the 2000−2018 period through causality and cointegration analyses. Causality analysis points out a significant unidirectional causality from indicators of educational attainment and economic growth to renewable energy use. In other words, educational attainment indicators and economic growth are significant determinants of renewable energy in the short run. Furthermore, the cointegration analysis ascertains a positive influence of indicators of educational attainment and economic growth on renewable energy use in the long run. The findings of both analyses indicate that educational attainment and ec... [more]

The article presents the hydrographic and hydrochemical characteristics of post-exploitation reservoirs formed in peat excavations. Two natural bog lakes were selected as the control objects for the study. The research indicated that both the waters of post-exploitation peat reservoirs and natural bog lakes show low electrolytic conductivity (<100 µS/cm) and acidic water reaction (pH < 5.5). The concentration of major cations and anions is also very low. The concentration of calcium and magnesium does not exceed a few mg/L. Hydrochemically, all post-exploitation peat reservoirs are bi-ionic sulphate−calcium (SO42−-Ca2+). This distinguishes post-exploitation peat reservoirs from natural bog lakes in which multi-ion waters were found, for example, sulphate−chloride−calcium (SO42−-Cl−-Ca2+) and sulphate−calcium−sodium (SO42−-Ca2+-Na+). The calculated water humic state index (HSI) allowed the classifying of the examined reservoirs as polyhumous. The value of this index, in all reservoir... [more]

Currently, gear pumps are developed with a aim to increase their efficiency, reduce internal leaks, and increase their working pressures. This development direction requires new solutions which would compensate backlash while ensuring an optimal size of the gaps for the entire range of working pressures. One of the solutions intended to meet this demand is to design circumferential compensation with the so-called integrated lips. The presented backlash compensation method is the result of research performed as part of a project named Designing High-Pressure Gear Pumps. The project was granted funding under path A of the Applied Research Program, contract No. PBS3/A6/22/2015. The research works were performed in the Laboratory of Hydraulic Drives and Vibroacoustics of Machines at Wrocław University of Science and Technology, and in cooperation with Hydrotor SA.

The research described in this article was carried out on samples of sandstone obtained from the underground excavations of four hard coal mines that operate in the region of Poland with the highest energy resources, i.e., Upper Silesia. The majority of underground tunnel excavations are mainly drilled using roadheaders, the organs of which are equipped with conical picks. The selection of pick type is usually based on rock compressive strength. However, sandstones often cause more problems during cutting compared to other waste rocks because of their variety. This article’s primary purpose is to emphasize the importance of researching various properties of waste rock in addition to uniaxial compression strength, which is crucial in the selection of both the appropriate cutting method and appropriate cutting tools. Accordingly, relations between mineralogical, petrographic, physical and mechanical properties were examined in this study, with special attention paid to the abrasive prope... [more]

The water blocking damage to the reservoir caused by the invasion of external fluid is one of the main factors that affect the efficient development of tight sandstone gas reservoirs. In this paper, microfluidic chip technology is used to explore the causes of water blocking damage in porous media and find suitable recovery solutions. The research results show that reducing the gas-liquid capillary pressure can effectively reduce the rate and quantity of spontaneous speed of cores. After chemical treatment, the liquid phase fluidity of the non-fractured matrix core is increased by 1.72 times, and that of the fractured core is increased by 2.13 times. In water wetting porous media, there are mainly four types of liquid hold-up: (1) Liquid hold-up in the dead volume of a non-connected pore; (2) The water phase in the pore throat with a small inner diameter cannot be driven away due to its larger capillary pressure; (3) Adsorption viscous force, the wetting phase is adsorbed on the surfac... [more]

Due to a high conductivity of about 0.1 S·cm−1, Li-Na-K carbonate eutectic and Sm-doped ceria composite material is a good electrolyte candidate for hybrid fuel cells operating between 500 °C and 600 °C. The present paper aims at a deeper understanding of the species and mechanisms involved in the ionic transport through impedance spectroscopy and thermal analyses, in oxidizing and reducing atmospheres, wet and dry, and during two heating/cooling cycles. Complementary structural analyses of post-mortem phases allowed us to evidence the irreversible partial transformation of molten carbonates into hydrogenated species, when water and/or hydrogen are added in the surrounding atmospheres. Furthermore, this modification was avoided by adding CO2 in anodic and/or cathodic compartments. Finally, a mechanistic model of such composite electrical behavior is suggested, according to the surrounding atmospheres used. It leads to the conclusions that cells based on this kind of electrolyte would p... [more]

A company’s productivity and success measure its effectiveness. This article presents the problem of economic efficiency and aspects related to environmental protection. The basic parameters analysed were the engine type and how it affects the environment. Over three months, the analysis was carried out and used the data envelopment analysis. As a result of the research carried out, the comparison of the amount of fuel used with the amount of transported goods should answer the following questions: What type of engine should be ordered for new trucks to show the best efficiency during operation? What is the efficiency of the currently used engines? How do they affect the environment? The method proposed in the article makes it possible to define the initial requirements for the definition of truck units, which is included in the conclusions of this paper.