The article presents the current situation with the implementation of electric cars in Poland against the background of pan-European trends and the current energy sector condition in Poland. The aim of the study was to show the ecological, economic, social, and technical difficulties and controversies related to the use of electric cars in Poland. The authors used statistical analysis and identified the main factors of electromobility development in Poland. Despite the declared electromobility in the Strategy of Responsible Development program, the degree of its implementation is far from the previously established goals. The article analyzes the feasibility of the above plan and indicates the factors inhibiting the development of electromobility in Poland. The strategy and decisions to further implement electric cars cannot be purely political. In justifying the need to promote the use of electric cars in Poland, one should take into account the specificity of the Polish economy, its... [more]

The robustness of the timetable is a sensitive issue in the daily realization of railway operations. As shown in the paper, robustness is a function of time reserves that helps to prevent unscheduled stops resulting from traffic disruptions and causing a higher energy consumption. The correct handling of time reserves while scheduling is a multidimensional issue, and it has a significant influence on the energy consumption of railway traffic. Therefore, the paper aims to show a simulation-based method, taking into account failure occurring probabilities and their consequences to get an acceptable level of robustness, that can be quantified by the probability of no delay propagation. This paper presents a method for the addition of time margins to the railway timetable. The iterative time buffer adding method is based on operational data as a knowledge source, to achieve the punctuality target. It was verified on a real railway line. An analysis of energy consumption for unscheduled tra... [more]

In cold and humid regions, ice accretion sometimes develops on the blades of wind turbines. Blade icing reduces the power generation of the wind turbine and affects the safe operation of the wind farm. For this paper, ultrasonic micro-vibration was researched as an effective de-icing method to remove ice from the wind turbine blade surface and improve the efficiency of wind turbine power generation. A blade segment with NACA0018 airfoil and the hollow structure at the leading edge was designed. The modal analysis of the blade was simulated by ANSYS, and the de-icing vibration mode was selected. Based on the simulation results, the blade segment sample with PZT patches was machined, and its natural frequencies were measured with an impedance analyzer. A return-flow icing wind tunnel system, and a device used to measure the adhesive strength of ice covering the airfoil blade, were designed and manufactured. The experiments on the adhesive strength of the ice were carried out under the ex... [more]

This paper aims to search for a high-performance low-cost standalone photovoltaic water pumping system (PVWPS) based on a three-phase induction motor (IM). In order to control the IM, a fuzzy direct torque control (FDTC) is proposed in this paper for overcoming the limitations of the conventional direct torque control (CDTC). In fact, the CDTC suffers from several problems such as torque ripples, current distortion, and switching frequency variations. These problems can be solved with the proposed FDTC. To ensure high performance of the PVWPS, the reference torque is generated using a fuzzy speed controller (FSC) instead of a conventional proportional integral speed controller. In order to extract the maximum amount of power, the proposed maximum power point tracking controller is based on variable step size perturb and observe to surmount the weakness of the conventional perturb and observe technique. The performance of the proposed FDTC based on the FSC under variable climatic condit... [more]

When the electromagnetic transients occur in a power transformer, an inrush current is generated in its winding. The inrush current not only affects the performance of the transformer windings, but also affects the lifetime of the transformer. Many factors affect the inrush current, the most influential ones among which are the closing phase angle and the residual flux. In this paper, a dry-type transformer simulation model is built to analyze the influence of the inrush current on the performance of transformer windings during no-load reclosing conditions. Firstly, the inrush current was generated in the transformer windings during the no-load reclosing operation under different residual fluxes. Secondly, the field-circuit coupling 3d finite element method is used to analyze the electromagnetic force at different locations of the transformer windings under the influence of different inrush currents. The results of winding structural parameter variations are obtained through electromag... [more]

A high content of asphaltene and wax in crude oil leads to difficulties in the recovery and transportation of crude oil due to the precipitation of asphaltenes and the deposition of waxes. Comb-like polymers were found to be capable of inhibiting the aggregation of asphaltenes and crystallization of waxes. In this work, comb-like bipolymers of α-olefins/ultra-long chain (C18, C22 and C28) alkyl acrylate were synthesized and characterized by FT-IR and 1H NMR spectra. The results show that, for a model oil containing asphaltene, the initial precipitation point (IPP) of asphaltene was prolonged by UV, and the asphaltene particle size was reduced after adding the biopolymers, as revealed by dynamitic light scattering (DLS). The bipolymer containing the longer alkyl chain had a better asphaltene inhibition effect. However, DSC and rheological results show that the wax appearance temperature (WAT) of the typical high asphaltene and high wax content of crude oil was obviously reduced by addin... [more]

Taking into account the evolution of the Common Agricultural Policy (CAP), it is wondered to what extent the “green” transformation of this policy and the accompanying change in the distribution of direct payments between farms contributed to the elimination of disproportions in agricultural income. The aim of the study was to investigate the changes in the proclaimed concepts related to the development of the EU agricultural sector in terms of their “green” transformation, and to assess the impact of “green” CAP payments on income inequalities between farms. The research was conducted based on the data representative for Polish commercial farms for the years 2004−2019, covering three financial perspectives of the agricultural policy. The methods of counterfactual modelling and assessment of income inequality were used in the study. The analyses showed that the evolution of the CAP priorities, and hence instruments, towards the pro-environmental (or, more broadly, towards sustainabilit... [more]

The electrical power sector plays an important role in the economic growth and development of every country around the world. Total global demand for electric energy is growing both in developed and developing economies. The commitment to the decarbonization of economies, which would mean replacing fossil fuels with renewable energy sources (RES) as well as the electrification of transport and heating as a means to tackle global warming and dangerous climate change, would lead to a surge in electricity consumption worldwide. Hence, it appears reasonable that the electric power sector should embed the principles of sustainable development into its functioning and operation. In addition, events such as the recent European gas crisis that have emerged as a result of the massive deployment of renewables need to be studied and prevented. This review aims at assessing the role of the renewable energy in the sustainable development of the electrical power sector, focusing on the energy provid... [more]

Magnetic-Liquid Double Suspension Bearing (MLDSB) is composed of an electromagnetic supporting and a hydrostatic supporting system. Due to greater supporting capacity and static stiffness, it is appropriate for occasions of middle speed, overloading, and frequent starting. Because of the complicated structure of the supporting system, the probability and degree of static bifurcation of MLDSB can be increased by the coupling of hydrostatic force and electromagnetism force, and then the supporting capacity and operation stability are reduced. As the key part of MLDSB, the controller makes an important impact on its supporting capacity, operation stability, and reliability. Firstly, the mathematical model of MLDSB is established in the paper. Secondly, the static bifurcation point of MLDSB is determined, and the influence of parameters of the controller on singular point characteristics is analyzed. Finally, the influence of parameters of the controller on phase trajectories and basin of... [more]

Nowadays photovoltaic trade in Poland is growing rapidly due to contemporary challenges in sustainable energy. The first Polish photovoltaic firms were established in the second decade of XXI century. It was the answer of looking for new innovative energy sources including solar energy. It was necessary to change the structure of energy sources in Poland mainly based on carbon and oil & gas. The aim of this article was the identification and assessment the key opportunities and barriers to photovoltaic industry enterprises in Poland in the context of technology entrepreneurship under conditions of information asymmetry. The paper was prepared based on the results of qualitative research using the case study method. A comparative analysis was performed based on results of a study of four purposefully selected enterprises. All of them are SMEs. The research was done in 2021. The case study method allowed for comparing the analysed enterprises in pairs, which is discussed more extensively... [more]

This paper presents a reversible heat pump based on CO2 as the refrigerant, able to provide heating, cooling, and domestic hot water to high energy demand buildings. The unit was developed and tested under the EU H2020 project MultiPACK, which has the main goal of assuring the market about the feasibility, reliability, and energy efficiency of CO2 integrated systems for heating and cooling and promoting a fast transition to low environmental impact solutions. Within the project, the confidence raising was performed by installation and monitoring of fully integrated state-of-the art CO2 systems in the Southern European Climate. With the aim of predicting the unit behaviour under variable load and boundary conditions, a dynamic model of the entire unit was developed with commercial software, considering actual components and the implemented control system and it was validated with experimental data, collected at the factory’s lab before commissioning. The validation against experimental... [more]

This paper contributes by investigating surface roughness effects on temporal history of aerodynamic loads and vortex shedding frequency of two circular cylinders in tandem arrangement. The pair of cylinders is immovable; of equal outer diameter, D; and its geometry is defined by the dimensionless center-to-center pitch ratio, L/D. Thus, a distance of L/D = 4.5 is chosen to characterize the co-shedding regime, where the two shear layers of opposite signals, originated from each cylinder surface, interact generating counter-rotating vortical structures. A subcritical Reynolds number of Re = 6.5 × 104 is chosen for the test cases, which allows some comparisons with experimental results without roughness effects available in the literature. Two relative roughness heights are adopted, nominally ε/D = 0.001 and 0.007, aiming to capture the sensitivity of the applied numerical approach. Recent numerical results published in the literature have reported that the present two-dimensional model... [more]

The dynamic development of aviation is associated with many benefits, but also, unfortunately, with negative effects. One of the adverse consequences is the exhaust emissions that have a negative impact on human health. It particularly affects the residents of areas neighboring airports, as airport activity deteriorates local air quality. Using the Emissions and Dispersion Modeling System, the activity of the Nicolaus Copernicus Airport was assessed in terms of the flight operations’ contribution to air contamination in the area adjacent to the airport. Emissions from three sources were compared: aircraft, ground support equipment and auxiliary power units. The concentrations of pollutants in inhabited areas located in three different directions in relation to the airport were also estimated. In addition, the effect of distance from the airport on contaminant concentrations was assessed as a function of wind direction. It was noticed that small values of pollutant concentrations, origi... [more]

The paper examines the impact of the COVID-19 pandemic on human resource management processes in project-oriented companies. It is proposed to use formal transformations on groups of performers. The use of formal transformations will reduce the influence of the subjective factor and improve the quality of sustainability management decisions made when forming a project team. The formalization of the selection process of applicants and the distribution of work among the performers have been considered. The existing methods of forming a project team with functional redundancy are approximate. Methodological support for the process of forming a project team with functional redundancy, based on a logical-combinatorial approach, and allowing to form project teams under given constraints, is proposed. A method of forming a functionally redundant project team based on formal transformations of groups of performers has been developed. The use of the apparatus of symbolic sequences for the forma... [more]

Quantifying frequency converters’ residual phase noise is essential in various applications, including radar systems, high-speed digital communication, or particle accelerators. Multi-input signal source analyzers can perform such measurements out of the box, but the high cost limits their accessibility. Based on an analysis of phase noise transmission theory and the capabilities of popular instrumentation, we propose a technique extending the functionality of single-input devices. The method supplements absolute noise measurements with estimates of the phase noise transfer function (also called the jitter transfer function), allowing the calculation of residual noise. The details of the hardware setup used for the method verification are presented. The injection of single-tone and pseudo-random modulations to the test signal is examined. Optional employment of a spectrum analyzer can reduce the time and number of data needed for characterization. A wideband synthesizer with an integra... [more]

Thermal energy storage based on phase change materials (PCMs) can improve the efficiency of energy utilization by eliminating the mismatch between energy supply and demand. It has become a hot research topic in recent years, especially for cold thermal energy storage (CTES), such as free cooling of buildings, food transportation, electronic cooling, telecommunications cooling, etc. This paper summarizes the latest research progress of the PCMs-based CTES. Firstly, the classification of PCMs for low temperature storage is introduced; the thermal physical properties (e.g., phase change temperature (PCT) and latent heat) of suitable PCM candidates (−97 to 30 °C) for CTES are summarized as well. Secondly, the techniques proposed to enhance the thermal properties of PCMs are presented, including the addition of nanomaterials, the microencapsulation and the shape stabilization. Finally, several representative applications (−97 to 65 °C) of PCMs in different CTES systems are discussed. The pr... [more]

This paper presents the results of the technological and economic analysis of mine water treatment systems before their discharge into the environment. The following analysis enabled us to determine the profitability of the investment, taking into account the TSS (total suspended solids) concentration in mine water. The simulation results showed that it is economically profitable to apply a water treatment system if natural sedimentation carried out in underground mine water passages, or in sedimentation tanks located on the ground, is ineffective for TSS removal. Economic and financial parameters allow us to conclude that all analyzed variants of the application of a pre-treatment system are characterized by high economic effectiveness. This mainly results from the high profitability of an analyzed investment, comparatively low capital expenditure, and present low market percentage rates. The most profitable variant (TSS concentration is 1000 mg/dm3) brings significant economic indica... [more]

This paper presents a method to design active suspension controllers for a 7-Degree-of-Freedom (DOF) full-car (FC) model from controllers designed with a 2-DOF quarter-car (QC) one. A linear quadratic regulator (LQR) with 7-DOF FC model has been widely used for active suspension control. However, it is too hard to implement the LQR in real vehicles because it requires so many state variables to be precisely measured and has so many elements to be implemented in the gain matrix of the LQR. To cope with the problem, a 2-DOF QC model describing vertical motions of sprung and unsprung masses is adopted for controller design. LQR designed with the QC model has a simpler structure and much smaller number of gain elements than that designed with the FC one. In this paper, several controllers for the FC model are derived from LQR designed with the QC model. These controllers can give equivalent or better performance than that designed with the FC model in terms of ride comfort. In order to use... [more]

Heating, ventilating, and air conditioning (HVAC) units account for a significant consumption share in buildings, namely office buildings. Therefore, this paper addresses the possibility of having an intelligent and more cost-effective solution for the management of HVAC units in office buildings. The method applied in this paper divides the addressed problem into three steps: (i) the continuous acquisition of data provided by an open-source building energy management systems, (ii) the proposed learning and predictive model able to predict if users will be working in a given location, and (iii) the proposed decision model to manage the HVAC units according to the prediction of users, current environmental context, and current energy prices. The results show that the proposed predictive model was able to achieve a 93.8% accuracy and that the proposed decision tree enabled the maintenance of users’ comfort. The results demonstrate that the proposed solution is able to run in real-time in... [more]

The development of technologies to improve the performance of photovoltaic (PV) module integrated converters (MICs) is fundamental to increase the use of distributed generation systems with photovoltaic power source in large urban centers, mainly for complex residential roofs. For two-stage PV MICs, high step-up DC-DC converters are required to boost the low PV module voltage to a higher voltage, in order to suit the DC bus voltage requirements of grid-tied inverters. Thus, to support researchers interested in developing DC-DC power conversion for PV microinverters, this paper classifies the DC-DC converters according to their operational and constructive characteristics and presents some elementary voltage-boosting techniques to aid in analyzing and understanding more complex topologies. Finally, high step-up DC-DC converters based on magnetic coupling and switched capacitor widely cited by important works related to PV applications are presented, with their principles of operation an... [more]

Building energy waste has become one of the major challenges confronting the world today, so specifications and targets for building energy efficiency have been put forward in countries around the world in recent years. The schematic design stage matters a lot for building energy efficiency, while most architects nowadays are less likely to make energy efficiency design decisions in this stage due to the lack of necessary means and methods for analysis. An integrated multi-objective multivariate framework for optimization analysis is proposed for the schematic design stage in the paper. Here, the design parameters of the building morphology and the design parameters of the building envelope are integrated for analysis, and an integrated performance prediction model is established for low-rise and medium-rise residential buildings. Then, a comparison of the performance indicators of low-rise and medium-rise residential buildings under five typical urban climatic conditions is carried ou... [more]

The worldwide transformation from fossil fuels to sustainable energy sources will increase the demand for biomass. However, the ash content of many available biomass sources exceeds the limits of national standards. In this study, short-rotation coppice willow biomass was hydrothermally treated at 150, 170 and 185 °C. The higher heating value increased by 2.6% from x¯ = 19,279 J × g−1 to x¯ = 19,793 J × g−1 at 185 °C treatment temperature. The mean ash content was reduced by 53% from x¯ = 1.97% to x¯ = 0.93% at 170 °C treatment temperature, which was below the limit for category TW1b of the European pellet standard for thermally treated biomass. The nitrogen, sulfur and cadmium concentrations were reduced below the limits for category TW1b of the European biomass pellet standard (N: from 0.52% to 0.34%, limit at 0.5%; S: from 0.051% to 0.024%, limit at 0.04%; Cd: from 0.83 mg × kg−1 to 0.37 mg × kg−1, limit at 0.5 mg × kg−1). The highest reduction rates were sampled for phosphor (80−84... [more]

Hotels emit large amounts of CO2 when providing services. Carbon neutrality objectives and the growth of homestays have forced hotel managers to pay more attention to carbon reduction. First, this paper adopted the input−output method to calculate hotel CO2 emissions. It was found that the amount of CO2 emissions in the hotel industry decreased from the year of 2016 to 2018, and there are structural differences in the CO2 emissions of the hotel industry in China. Furthermore, this paper adopted the three-stage SBM-DEA model to evaluate hotel CO2 emission efficiency in 30 provinces in China. The results show that CO2 emission efficiency increased significantly when environmental factors were eliminated. A close observation of different regions shows that the eastern region has a higher CO2 emission efficiency than the western and middle regions. The emergence of homestays has led to increased input slacks in the labor and energy consumption of hotels, which has a negative effect on effi... [more]

In the era of globalization and rapid economic growth, affecting most world economies, increased production and consumption are leading to higher levels of energy production and consumption. The growing demand for energy means that energy resources from conventional sources are not sufficient; moreover, its production generates high costs and contributes to the emission of greenhouse gases and waste. In view of the above, many countries have opted to implement an energy transformation. The energy transition allows the transition from an energy system based on conventional fuels to an energy system based mainly on renewable energy (RE) and low-emission sources. In the EU, the development of a “green economy” has become a strategic goal in the fight against climate change. The development of RE offers the possibility to improve the energy security of a given country and the entire EU. New, innovative technologies of RE also increase the attractiveness and competitiveness of the economies... [more]

Renewable energy has a crucial role in facing climate change. One promising strategy is the creation of energy communities that require active involvement from a bottom-up perspective. Their implementation is difficult, as they currently rely on local policies, community readiness, and technological availability. The objective of this paper is to provide a qualitative overview of energy community concepts and strategies at the European level. The aim is to identify common approaches that are framing the development of energy communities, and to understand the most successful steps leading to their creation and growth. To achieve this objective, a threefold methodology is provided: (1) an updated review on policies dealing with energy communities at the European and Italian level; (2) a qualitative overview of European-funded projects under the Horizon 2020 work program; and (3) a qualitative overview of some of the most successful existing energy communities in Europe. The results outl... [more]