Work safety can be a component of the broadly understood sustainable enterprise approach that goes beyond the idea of sustainable development. Sustainability in an unpredictable and turbulent environment has many constellations, many aspects and many fields of the enterprise’s activity and it complements the rationality of the business. The aim is to understand the sustainability of safety, because this is the term we have adopted for rationality in occupational safety management, in the context of the analysis of work accidents in the Polish steel industry, with particular emphasis on the methodology of forecast assessment in the studied area, proposed by us. The realized forecasts were used for the creation of a combined model which formed the basis for formulating conclusions from the analysis. The publication presents the modeling of the victims of work accidents in the steel sector in Poland. Based on the research of the forecasts obtained, a downward trend is recorded in the numb... [more]

Several natural threats characterize hard coal mining in Poland. The coexistence of methane and rock-burst hazards lowers the safety level during exploration. The most dangerous are high-energy bumps, which might cause rock-burst. Additionally, created during exploitation, safety pillars, which protect openings, might be the reason for the formation of so-called gas traps. In this part, rock mass is usually not disturbed and methane in seams that form the safety pillars is not dangerous as long as they remain intact. Nevertheless, during a rock-burst, a sudden methane outflow can occur. Preventing the existing hazards increases mining costs, and employing inadequate measures threatens the employees’ lives and limbs. Using two longwalls as examples, the authors discuss the consequences of the two natural hazards’ coexistence. In the area of longwall H-4 in seam 409/4, a rock-burst caused a release of approximately 545,000 cubic meters of methane into the excavations, which tripled metha... [more]

An increase in energy demand that is caused by fast economic development, a limited and constantly decreasing supply of traditional energy sources, as well as excessive environmental pollution that is caused by an increasing concentration of dust and gases in the atmosphere constitute the main factors that contribute to the ever-increasing interest in renewable sources of energy. The most important and promising renewable source of energy is thought to be solar energy. The aim of the paper is to assess the macroeconomic investment efficiency of photovoltaic installations in order to meet the demand for electric energy in single-family homes in Polish conditions. The conducted analysis comprises market characteristics and legal regulations concerning the sale of electric energy in Poland. Calculations were made for 320 variants that differed with regard to investment location, building orientation, and roof inclination. The results indicate that the most beneficial region for photovolta... [more]

Airtightness is nowadays one of the physical parameters which determine overall building energy performance. In a wide range of states, the upper limit for air change rate at a Pa (na), air permeability rate at a Pa (qa), or specific leakage rate at a Pa (wa) is determined by the formal regulations. It should be highlighted that airtightness requirements are mainly the same around the world, disregarding any site and climatic conditions. The main goal of the presented work was to reveal the effect of individual location and surrounding infiltration rate and heat demand. The analyses were done using numerical techniques and computational models of the three buildings developed and calibrated based on the blower door test results. The compared buildings characterize by a similar geometry but differ in the air change rate at 50 Pa (n50). Analyses done for different locations and levels of sheltering by surrounding elements allow the determination of the real effect of local conditions. Th... [more]

The number of wind farms is increasing every year because many countries are turning their attention to renewable energy sources. Wind turbines are considered one of the best alternatives to produce clean energy. Most of the wind farms installed supervisory control and data acquisition (SCADA) system in their turbines to monitor wind turbines and logged the information as time-series data. It demands a powerful information extraction process for analysis and prediction. In this research, we present a data analysis framework to visualize the collected data from the SCADA system and recurrent neural network-based variant long short-term memory (LSTM) based prediction. The data analysis is presented in cartesian, polar, and cylindrical coordinates to understand the wind and energy generation relationship. The four features: wind speed, direction, generated active power, and theoretical power are predicted and compared with state-of-the-art methods. The obtained results confirm the applica... [more]

The Internet has been going through significant transformations and changing the world around us. We can also see the Internet to be used in many areas, for innumerable purposes, and, currently, it is even used by objects. This evolution leads to the Internet of Things (IoT) paradigm. This new concept can be defined as a system composed of storage resources, sensor devices, controllers, applications, and network infrastructure, in order to provide specific services to its users. Since IoT comprises heterogeneous components, the creation of these systems, the communication, and maintenance of their components became a complex task. In this paper, we present a dependability model to evaluate an IoT system. Amid different systems, we chose to assess availability in a smart building. The proposed models allow us to calculate estimations of other measures besides steady-state availability, such as reliability. Thus, it was possible to notice that there was no considerable gain of availabili... [more]

The use of renewable energy sources increases the energy self-sustainability of cities, enabling citizens to reduce energy costs, which results in an increase in their standard of living. However, solar energy penetration in Bosnia and Herzegovina, and its capital Sarajevo, is not in line with the possibilities. Furthermore, the Sarajevo Canton is extremely polluted during the winter months because of the use of unacceptable heating fuel. The aim of this paper is to introduce photovoltaic power systems use in heating electrification system. In this paper AQI is calculated based on historical data and the hybrid model EMD-SARIMA for air pollution and a solar production forecast is presented. The methodology was tested in the Sarajevo Canton, taking into account 35,000 households. In order to ensure clean air, renewable electric energy use for household heating should be implemented. The widespread use of inefficient individual heating systems characterized by inefficient and expensive u... [more]

Neural network models are data-driven and are effective for predicting and interpreting nonlinear or unexplainable physical phenomena. This study collected building information and heating energy consumption data from 16,158 old houses, selected key input variables that affect the heating energy consumption based on the collected datasets, and developed a deep neural network (DNN) model that showed the highest accuracy for the prediction of heating energy consumption in an old house. As a result, 11 key input variables were selected, and an optimal DNN model was developed. This optimal DNN model showed the highest prediction accuracy (R2 = 0.961) when the number of hidden layers was five and the number of neurons was 22. When the optimal DNN model was applied for the standard model of low-income detached houses, the prediction accuracy (Cv(RMSE)) of the optimal DNN model, compared to the EnergyPlus calculation result, was 8.74%, which satisfied the ASHRAE standard sufficiently.

Environmental considerations are motivating the adoption of low global warming potential refrigerants. Most of these are mildly flammable, i.e., A2L. Their susceptibility to ignition from various ignition sources is poorly understood, particularly for the stoichiometric and quiescent mixtures that are emphasized here. The viability of fifteen residential ignition sources to ignite four A2L refrigerants is considered. Tests are performed in a windowed chamber with a volume of 26 L. The refrigerants are R-32 (difluoromethane); R-452B (67% R-32, 26% R-1234yf, and 7% pentafluoroethane); R-1234yf (2,3,3,3-tetrafluoropropene); and R-1234ze (1,3,3,3-tetrafluoropropene). Two types of ignition sources are confirmed here to be viable: a resistively heated wire at 740 °C and open flames. When the refrigerant concentration was increased slowly, candle flames and butane flames extinguished before initiating any large deflagrations. Eleven other sources were not viable: a smoldering cigarette, a but... [more]

Out of 2 TWe of coal power plant capacity in operation globally today, more than half is less than 14 years old. Climate policy related to limiting CO2-emissions makes the longer-term operation of these plants untenable. In this study, we assess the spectrum of available options for the future of both equipment and jobs in the coal power sector by assessing the full scope of “retrofit decarbonization” options. Retrofit decarbonization is an umbrella term that includes adding carbon capture, fuel conversion, and the replacement of coal boilers with new low-carbon energy sources, in each case re-using as much of the existing equipment as economically practicable while reducing or eliminating emissions. This article explores this idea using the Polish coal power fleet as a case study. Retrofit decarbonization in Poland was shown to be most attractive using high-temperature small modular nuclear reactors (SMRs) to replace coal boilers, which can lower upfront capital costs by ~28−35% and l... [more]

Genetic algorithms are used to parameter identification of the model of oscillatory processes in complicated motion transmission of electric drives containing long elastic shafts as systems of distributed mechanical parameters. Shaft equations are generated on the basis of a modified Hamilton−Ostrogradski principle, which serves as the foundation to analyse the lumped parameter system and distributed parameter system. They serve to compute basic functions of analytical mechanics of velocity continuum and rotational angles of shaft elements. It is demonstrated that the application of the distributed parameter method to multi-mass rotational systems, that contain long elastic elements and complicated control systems, is not always possible. The genetic algorithm is applied to determine the coefficients of approximation the system of Rotational Transmission with Elastic Shaft by equivalent differential equations. The fitness function is determined as least-square error. The obtained resul... [more]

Some types of biomass require great inputs to guarantee high conversion rates to methane. The complex structure of lignocellulose impedes its penetration by cellulolytic enzymes, as a result of which a longer retention time is necessary to increase the availability of nutrients. To use the full biogas potential of lignocellulosic substrates, a substrate pretreatment is necessary before the proper methane fermentation. This article discusses the impact of the pretreatment of maize silage with a pulsed electric field on biogas productivity. The experiment showed a slight decrease in cellulose, hemicellulose and lignin content in the substrate following pretreatment with a pulsed electric field, which resulted in a higher carbohydrate content in the liquid substrate fraction. The highest biogas production output was obtained for the pretreated sample at the retention time of 180 s for 751.97 mL/g volatile solids (VS), which was approximately 14% higher than for the control sample. The met... [more]

In this work, a computational study was carried out to simulate crushing tests on lithium-ion vehicle battery modules. The tests were performed on commercial battery modules subject to wedge cutting at low speeds. Based on loading and boundary conditions in the tests, finite element (FE) models were developed using explicit FEA code LS-DYNA. The model predictions demonstrated a good agreement in terms of structural failure modes and force−displacement responses at both cell and module levels. The model was extended to study additional loading conditions such as indentation by a cylinder and a rectangular block. The effect of other module components such as the cover and cooling plates was analyzed, and the results have the potential for improving battery module safety design. Based on the detailed FE model, to reduce its computational cost, a simplified model was developed by representing the battery module with a homogeneous material law. Then, all three scenarios were simulated, and... [more]

With the development of technology and the decrease in prices, power systems are facing a strong growth in the number of end-users with photovoltaics (PVs), battery storages and electric vehicles (EVs). A penetration of low carbon (LC) technologies has an impact not only on the financial aspect, but also on parameters of the power quality (PQ) in the power system. Since most of end-users with renewable energy sources (RES) are connected to a low-voltage (LV) distribution network, there is a high number of single-phase loads and distributed generators (DG) that can cause unwanted effects in LV networks. According to standards, electric energy must be of a certain quality in order to avoid harmful effects on the power system, being both the network or the end-users equipment. One of the PQ parameters is the voltage unbalance. Voltage unbalance occurs in networks with the high share of single-phase loads and generators. Since most loads in households are connected to the only one phase, t... [more]

Large-format lithium-ion batteries (LIBs) suffer from problems in terms of their product life and capacity due to large temperature differences in LIB cells. This study analyzes the effect of design factors on temperature distribution using a 3D electrochemical−thermal model. The design of experiments methodology is used to obtain the sampling points and analyze the effect of the cell aspect ratio, negative tab attachment position, and positive tab attachment position. These were considered as design factors for the maximum and minimum temperatures, as well as their difference, in large-format LIB cells. The results reveal that the cell aspect ratio, negative tab attachment position, and positive tab attachment position considerably influence temperature distribution. The cell aspect ratio has the most significant effect on the temperature distribution by changing the longest current pathway and the distance between tabs and the lowest temperature point in the LIB cell. A positive tab... [more]

With the rapid development of ecofriendly cars, various inverters are also being developed depending on the performance of motors. The DC-link capacitor is used as an inverter component; however, there are several limitations on its size, such as the requirement for wide films. Film width is a major factor that affects the capacitor’s equivalent series resistance (ESR) and is closely related to heat generation. When the temperature of the capacitor increases, the dielectric breakdown due to high voltage causes a reduction in capacitance, which leads to a decrease in inverter power and causes vehicle defects; this needs to be addressed to minimize the heat of the capacitor. Recently, genetic films that can be used at high temperatures have been developed. However, producing such films is difficult because of their 5 µm thickness; thus, the size increases when they are designed and they consequently cannot be used in practical applications. Based on a film width of 50 mm, this study anal... [more]

Permanent magnet synchronous machines provide many dramatic electromagnetic performances such as high efficiency and high power density, which make them more competitive in aircraft electrification, whereas, designing a permanent magnet starter−generator (PMSG), with given consideration to fault tolerance (FT), is a significant challenge and requires great effort. In this paper, a comprehensive FT PMSG design process is proposed which is applied to power systems of turboprops. Firstly, potential slot/pole combinations were selected based on winding factor, harmonic losses and manufacture issues. Then, pursuing high power density, a multiple objective optimization process was carried out to comprehensively rank performances. To meet a fault tolerance target, electrical, magnetic and thermal isolation topologies were investigated and compared, among which 18 slot/12 pole with dual three-phase was selected as the optimal one, with a power density of 7.9 kW/kg. Finally, a finite element an... [more]

In this paper, an LLC light-emitting diode (LLC LED) driver based on the current-sharing capacitor is presented. In the proposed LED driver, the LLC resonant converter is used to step down the high input voltage, to provide galvanic isolation, to offer a constant current for LEDs. Moreover, the current-sharing capacitor connected to the central-tapped point of the secondary-side winding is used to balance the currents in two LED strings. By doing so, the voltage stress on this capacitor is quite low. Above all, the equivalent forward voltages of the two LED strings are generally influenced by the temperature and the LED current, and this does not affect the current-sharing performance, as will be demonstrated by experiment on the difference in number of LEDs between the two LED strings. In addition, only the current in one LED string is sensed and controlled by negative feedback control, while the current in the other LED string is determined by the current-sharing capacitor. Moreover,... [more]

The paper presents results of numerical simulations and experimental investigations of a cyclone with a square inlet and different dimensions of a vortex finder. Investigations were conducted for five, different cyclone models. The main goal of the research was to determine the influence of cyclone vortex finder geometry (diameter, length) on key parameters for a cyclone operation, such as: gas flow pattern, gas velocity and pressure distribution, pressure drop and collection efficiency. The analysis of flow pattern inside the cyclone was carried out with the use of CFD (Computational Fluid Dynamics) simulations, verified using CTA (Constant Temperature Anemometry). Similarly, pressure distributions, pressure drop and collection efficiency for cyclones were determined numerically and with measurements. The study demonstrated that dimensions of the vortex finder have a significant effect on a cyclone performance. The numerical visualisations of flow showed some unfavorable and beneficia... [more]

Thermal conductivity, hydraulics properties and potential use in low-enthalpy geothermal applications of single and double U geothermal probes enhanced with carbon fibre are discussed in this work. Although the efficiency of a shallow geothermal installation is chiefly based on chemical and physical characteristics of rocks and hydrogeological aspects of the subsurface, the total heat extracted from the subsoil also depends on the intrinsic thermal characteristics of probes. New configurations and solutions aimed at enhancing the performance of components are therefore of considerable interest in this field of research. As a consequence of the economic and versatility advantages of the components, geothermal probes have been generally developed with materials like polyethylene, which presents, however, isolating behaviour that does not allow ideal heat exchange in ground source heat pump systems (GSHP). Innovative combinations of different materials are therefore necessary in order to... [more]

This study presents an analytical framework supporting coal regions in a strategy toward the clean energy transition. The proposed approach uses a combination of value chain analysis and energy sector analysis that enables a comprehensive assessment considering local specificities. Its application to a case study of the Slovakian region Upper Nitra demonstrates practical examples of opportunities and challenges. The value chain analysis evaluates the coal mining industry, from coal extraction to electricity generation, in terms of jobs and business that are at risk by the closure of the coal mines. The complementary energy system analysis focuses on diversification of the energy mix, environmental impacts, and feasibility assessment of alternative energy technologies to the coal combusting sources. The results show a net positive cost benefit for all developed scenarios of replacing the local existing coal power plant. Although the installation of a new geothermal plant is estimated to... [more]

New particulate matter (PM) filtering technologies are needed to meet the emission regulations for small combustion appliances. In this work, we investigate the performance of a novel electrical particle filtration system, the single needle shielded corona charger (SCC), which offers an advantageous solution for PM control in boilers by enhancing particulate deposition within existing boiler sections. Experiments under different operating conditions of a wood-fired boiler were performed, wherein the SCC was installed upstream of either a condensing heat exchanger (CHX) or a cyclone. PM reduction was found to be strongly affected by the SCC temperature and the following collection surface area, and reached its highest reduction efficiency of >90% at the temperature range of 400−500 °C when operating in combination with a CHX. The SCC−cyclone combination was less efficient, providing a 27% PM reduction, as a result of the low surface area and residence time in the cyclone. These results... [more]

We summarize our metadata analysis of the last 38 well-attended annual conferences, organized by the Society of Exploration Geophysicists. In 2018, Schlumberger and Saudi Aramco had the highest number of publications among service and production companies. In 2019, BGP and PetroChina took the lead. Throughout history, US academics have had the highest number of publications, but in 2019 Chinese academia came close to taking the lead. Analysis of the publication activity of oil-producing and oilfield service companies provides insights into the state of geophysical research. The number of publications from industrial companies in the energy sector reflects their financial standing and aspirations for the near future. Publications from academia in different countries tell us about state and private funding of research in each country, and indirectly reflect the geopolitical situation in the world. The changing number of publications over time reflects the dynamics of the transformation o... [more]

Supercritical carbon dioxide (SC-CO2) jet is capable of decreasing the threshold pressure of rock breakage and mitigating formation damage, owing to its low viscosity, high diffusivity, and extremely-low surface tension. The swirling-round jet holds the advantages of both a swirling jet and a round jet. Therefore, the comprehensive technique, swirling-round SC-CO2 (SR-SC-CO2) jet, is expected to substantially enhance rock-breaking efficiency. However, theoretical analysis of the flow field characteristics of SR-SC-CO2 has not been reported yet. This work aims to lay a theoretical foundation for employing SR-SC-CO2 in drilling and fracturing. The flow field is simulated using Naiver-Stokes equations and the RNG k-ε turbulence model. Sensitivity analysis, regarding pressure drop of the nozzle, confining pressure, fluid temperature, jetting distance, the diameter of the nozzle’s central hole, and grooving area, are performed. We show that the combined swirling-round SC-CO2 jet flow could... [more]

One of the methods of heat transfer enhancement is utilization of the turbulent impinging jets, which were recently applied, for example, in the heat exchangers. Their positive impact on the heat transfer performance was proven, but many questions related to the origin of this impact are still unanswered. In general, the wall-jet interaction and the near-wall turbulence are supposed to be its main reason, but their accurate numerical analysis is still very challenging. The authors’ aim was to construct the numerical model which can represent the real phenomena with good or very good accuracy. Starting with an analysis of single jet and obtaining the agreement with experimental data, it will be possible to extend the model towards the whole minijets heat exchanger. The OpenFOAM software, Bracknell, UK was used for that purpose, with our own implementation of the ζ-f turbulence model. The most difficult area to model is the stagnation region, where the thermal effects are the most intens... [more]