The compressed air electric ratio (CAER) describes the ratio of the real electric power demand to the nominal mechanical power of an air compressor. The CAER is an important indicator as the electric power demand of air compressors varies throughout its operation dependent on compressor technology, pressure ratio, and free air delivery. The nameplate power of the compressor drive motor is not sufficient for evaluating the electric power demand; therefore, the CAER plays an important role in assessing the electric operating power demand. In this paper, results from measurements of fixed speed and variable speed (VFD) compressors are presented with the analysis of key influencing factors of the CAER. The data show that the pressure ratio of operating pressure to the maximum design outlet pressure has the largest impact on the CAER. For VFD compressors, the CAER is represented as a linear function dependent on the respective load. Fixed and variable speed compressors’ CAERs are always dep... [more]

This article focuses on the possibility of using an innovative drilling method for the implementation of underground works, especially where there is no physical possibility of using large working machines. Work on a model carried out under the INDIRES project is discussed. A design of a drilling tool equipped with the proposed technology is presented. The solution in question makes it possible to increase the efficiency of the drilling process, which is confirmed by computer simulations. Also, introductory tests of a drilling process supported by torsional vibration generated by an electromagnetic torque generator provided in the KOMAG laboratory facility show the reduction of the drilling time by almost two-fold. In our opinion, adding torsional vibration acting on the plane of a drilled wall that equals natural frequencies of the drilled material represents a promising new technology for drilling. The presented work constitutes the basis for the development of the proposed technolog... [more]

Real-Time Digital Simulation (RTDS) is a powerful tool in modeling and analyzing electrical and drive systems because it provides an efficient and accurate process. There are several hardware devices for this type of simulation; however, their high costs have led to the increasing use of more affordable and reconfigurable technologies. In this context, many logic blocks and storage elements make the Field Programmable Gate Array (FPGA) an ideal device to perform RTDS. This work proposes a technique to embed a real-time digital simulator in an FPGA through Hardware Description Language (HDL) since it provides liberty in the architecture choice and no dependency on commercial ready-made hardware−software packages. The approach proposed focuses on system design developing with expression tree graph, synthesizing and verifying, prioritizing the performance and design accuracy concerning area and power consumption. Thus, the result acquisition occurs at a time step considered in real-time.... [more]

This paper presents a two-dimensional implementation of the high-order penalized vortex in cell method applied to solve the flow past an airfoil with a vortex trapping cavity operating under moderate Reynolds number. The purpose of this article is to investigate the fundamentals of the vortex trapping cavity. The first part of the paper treats with the numerical implementation of the method and high-order schemes incorporated into the algorithm. Poisson, stream-velocity, advection, and diffusion equations were solved. The derivation, finite difference formulation, Lagrangian particle remeshing procedure, and accuracy tests were shown. Flow past complex geometries was possible through the penalization method. A procedure description for preparing geometry data was included. The entire methodology was tested with flow past impulsively started cylinder for three Reynolds numbers: 550, 3000, 9500. Drag coefficient, streamlines, and vorticity contours were checked against results obtained b... [more]

Wide bandgap (Eg) perovskite solar cells (PSCs) are emerging as the preferred choice for top cells in a tandem architecture with crystalline silicon solar cells. Among the wide bandgap perovskites, a mixed cation mixed halide composition containing CsyFA1-yPbI3−xBrx is a popular choice because the presence of bromine widens the bandgap and addition of cesium stabilizes the crystal structure. These perovskite layers are commonly fabricated using one-step spin coating technique; however, sequential spin coating followed by dip coating has been successful in offering better control over the crystallization process for low bandgap absorber layers. In this paper, the fabrication of a Cs0.2FA0.8PbI3−xBrx perovskite absorber layer using the sequential deposition route is reported. The concentration of bromine was varied in the range 0 ≤ x ≤ 1 and optical, structural, and morphological properties of the films were studied. As the concentration was increased, the perovskite showed better crysta... [more]

The present work proposes a Monte Carlo Simulation (MCS) to obtain availability projections for Hydroelectric Power Plants (HPP), based mainly on regulatory aspects involving the Availability Factor (AFA). The main purpose of the simulation is to generate scenarios to obtain statistics for risk analysis and decision-making in relation to the HPP. The proposed methodology consists of two steps, firstly, the optimization of the maintenance schedule of the hydroelectric plant is carried out, in order to allocate the mandatory maintenance in the simulation horizon. Then, for the MCS, scenarios of forced shutdowns of the Generating Units (GU) will be generated, which directly influence the operation and, consequently, the availability of the HPP. The scenarios will be inserted into an operation optimization model, which considers the impact of forced shutdown samples on the MCS. The proposed modeling was applied using real data from the Santo Antônio HPP, which is one of the largest hydroel... [more]

This article deals with the major challenge of electric vehicle charging infrastructure in urban areas—installing as many fast charging stations as necessary and using them as efficiently as possible, while considering grid level power limitations. A smart fast charging station with four vehicle access points and an intelligent load management algorithm based on the combined charging system interface is presented. The shortcomings of present implementations of the combined charging system communication protocol are identified and discussed. Practical experiments and simulations of different charging scenarios validate the concept and show that the concept can increase the utilization time and the supplied energy by a factor of 2.4 compared to typical charging station installations.

An innovative method was proposed to facilitate the analyses of meteorological conditions and selected air pollution indices’ influence on visibility, air quality index and mortality. The constructed calculation algorithm is dedicated to simulating the visibility in a single episode, first of all. It was derived after applying logistic regression methodology. It should be stressed that eight visibility thresholds (Vis) were adopted in order to build proper classification models with a number of relevant advantages. At first, there exists the possibility to analyze the impact of independent variables on visibility with the consideration of its’ real variability. Secondly, through the application of the Monte Carlo method and the assumed classification algorithms, it was made possible to model the number of days during a precipitation and no-precipitation periods in a yearly cycle, on which the visibility ranged practically: Vis < 8; Vis = 8−12 km, Vis = 12−16 km, Vis = 16−20 km, Vis = 2... [more]

In this paper, the uneven air stream distribution problem of individual cyclones is studied in the multi-cyclones of intake air filters in special vehicles’ engines. This problem increases in multi-cyclones, in which several dozen cyclones have a common dust trap from which the collected dust is continuously removed by ejection suction. The aim of this study is the recognition of the theoretical and experimental possibility of reducing the streams’ unevenness, which should result in an efficiency increase in multi-cyclone separation. The methods that led to obtaining a relative stream uniformity from the suction of individual cyclones was analyzed. The method for creating equal pressure drops between the suction streams in the channels was used to achieve this goal. For this purpose, the internal structure of the multi-cyclone settler was changed. The multi-cyclone settling tank space was divided by vertical partitions into independent segments. The settling tank segment was then divid... [more]

Schism is the new normal for the bioeconomy concept. Since its proliferation in governments, the concept has been adapted to fit national or regional exigencies. Earlier this century the knowledge-based bioeconomy (KBBE) in Europe was seen as a technical and knowledge fix in the evolving sustainability landscape. At the OECD, the concept was further honed by imagining a future where biotechnologies contribute significantly to economic growth and development. Countries started to make national bioeconomy strategies. Some countries have diverged and made the bioeconomy both much larger and more general, involving a wide variety of sectors, such as industry, energy, healthcare, agriculture, aquaculture, forestry and fishing. Whatever the approach, what seems to be consistent is the need to reconcile environmental, social and economic sustainability. This paper attempts to establish one schism that could have ramifications for the future development of the bioeconomy. Some countries, inclu... [more]

Thanks to the allocation methods, i.e., the division of the total GHG emissions between each of the products generated in the production of biofuels, it is possible to reduce the emissions of these gases by up to 35% in relation to the production and combustion of fuels derived from crude oil. As part of this study, the biodiesel production process was analyzed in terms of greenhouse gas (GHG) emissions. On the basis of the obtained results, the key factors influencing the emissions level of the biodiesel production process were identified. In order to assess the sensitivity of the results of the adopted allocation method, this study included calculations of GHG emissions with an allocation method based on mass, energy, and financial shares. The article reviews recent advances that have the potential to enable a sustainable energy transition, a green economy, and carbon neutrality in the biofuels sector. The paper shows that the technology used for the production of biodiesel is of gre... [more]

With the increasing use of renewable energy, the energy flexibility of buildings becomes increasingly important regarding grid support. Therefore, there is a need to describe this flexibility in a concise manner. For the characterization of building energy flexibility, flexibility factors can be used. The comparison of a selection of existing flexibility factors shows that they are not easy to use or understand for designers and users. A simplification is necessary. The aim of this study is to introduce a flexibility classification that is easy to understand and shows in an easy way if a building already uses the lowest energy cost level or if further improvement is possible. The classification expresses the annual energy costs in colored classes: green (class A) for lowest up to red (class D) for highest level. Basically, the flexibility classes can be derived for any metric of interest, in this paper examples are shown for energy costs and CO2eq emissions. The results given are based... [more]

The non-structural model of a heat exchanger network randomly selects a position of a node on hot and cold streams to generate a heat exchanger and an existing heat exchanger to participate in the evolution. Despite the model being more random and flexible, this selection method cannot easily find a good solution. In addition, the heat exchangers participating in the evolution might not be involved in all streams in each evolutionary process. A stream that does not participate in the evolution will have no significance to the current iteration. Therefore, many iterations are required to make each stream participate in the evolution, which limits the evolution efficiency of the optimization algorithm. In view of this shortcoming, this study proposes a participatory evolutionary strategy for streams based on hot streams. The proposed strategy reorders the existing heat exchangers on hot and cold streams and takes the corresponding measures to ensure that a heat exchanger is selected for... [more]

This article presents studies related to the driving and control of the switched reluctance generator in order to enhance its efficiency. This type of electrical machine is an option for wind energy conversion systems, favoring the generation of electricity in distributed generation systems and contributing positively to loads without access to the main grid. The studies developed in this paper verify the possibility of controlling the output voltage of the switched reluctance generator in parallel with an efficiency tracking technique acting on the switching angles of the power converter. Simulation and experimental results are presented in order to verify the feasibility of implementing this technique to enhance the efficiency of the generator.

Energy systems require technological changes towards climate neutrality. In Poland, where the power system is dominated by outdated coal-fired power plants, efforts to minimize the environmental impact are associated with high costs. Therefore, optimal paths for the development of the energy sector should be sought in order to achieve ambitious long-term strategic goals, while minimizing the negative impact on the consumers’ home budget. A methodology and a model for the development of the electricity and heat generation structure were developed and implemented in market allocation (MARKAL) modelling framework. Two scenarios were presented, i.e., business as usual (BAU) and withdrawal from coal (WFC) scenarios. The calculations showed a significant role of nuclear energy and offshore wind power in the pursuit of climate neutrality of electricity generation. In the BAU scenario, the model proposes to stay with coal technologies using carbon capture and storage systems. Withdrawal from c... [more]

Polish organic agriculture has faced rapid growth in the recent two decades. Nevertheless, one may observe considerable discrepancies in organic agriculture development in specific regions of Poland. Therefore, it is necessary to recognize the key conditions for this development and its spatial differentiation. Since the relationship between organic farming and the natural environment has a fundamental meaning in this production system, it is crucial to study the development determinants of environmental characters. Thus the paper aims to identify the level of organic farming development in Polish districts and to investigate multidimensional relations between this level and selected environmental conditions. In order to identify the range and direction of those multidimensional relations between the discussed phenomena, canonical analysis was applied. Within the conducted study, proprietary synthetic measures were constructed (using the TOPSIS—Technique for Order of Preference by Simi... [more]

The design and construction of tanks used for the carriage of dangerous liquid materials fall within strict standards (i.e., EN13094:2015, R111). According to these standards, their supporting structures (Ss), used for the mounting of the tank on the freight vehicle, need to be able to sustain the developed stresses. Optimizing the number of supporting structures can lead to more efficient tank designs that allow the tank to transport more liquid material and need less time to be manufactured. In the present paper, the effect of the reduction of the number of supporting structures in (a) the structural integrity of the tank construction, (b) its dynamic behavior and (c) the load-sharing of the tank to the axles of the freight vehicle is investigated using the finite element (FE) method. As a case study a box-shaped tank mounted on a four-axle freight vehicle with a technical permissible maximum laden mass of 35 tn, five Ss are used. Four FE models with a decreasing number of Ss were bu... [more]

As the hydrogen market is projected to grow in the next decades, the development of more efficient and better-performing polymer electrolyte membrane fuel cells (PEMFCs) is certainly needed. Water management is one of the main issues faced by these devices and is strictly related to the employment of fluorinated materials in the gas diffusion medium (GDM). Fluorine-based polymers are added as hydrophobic agents for gas diffusion layers (GDL) or in the ink composition of microporous layers (MPL), with the goal of reducing the risk of membrane dehydration and cell flooding. In this review, the state of the art of fluorinated polymers for fuel cells is presented. The most common ones are polytetrafluoroethylene (PTFE) and fluorinated ethylene propylene (FEP), however, other compounds such as PFA, PVDF, PFPE, and CF4 have been studied and reported. The effects of these materials on device performances are analyzed and described. Particular attention is dedicated to the influence of polymer... [more]

The thermal performance of a large-format (52.3 Ah) Li-ion pouch battery with an n-octadecane PCM was investigated. A simplified 1D model was employed to estimate the transient thermal behavior. Two design parameters, the thickness and the thermal conductivity of the PCM, were considered. A 0.5 mm thick n-octadecane PCM integrated with aluminum foam reduced the battery temperature to 34.3 °C and 50.7 °C at the end stage of discharging under 3C and 5C discharge rates, respectively. The 1D results compared to the 3D results were able to predict the temperature dissipation by the PCM method at the end of discharging. The 1D approach clearly produced reliable results in predicting the thermal behavior of the PCM cooling and was superior in practical applications with its low cost and time consumption. A 3D CFD simulation was able to describe the detailed temperature uniformity in the cell, which is an important factor in the design and evaluation of a battery cooling system.

Thermal energy storage (TES) system plays an essential role in the utilization and exploitation of renewable energy sources. Over the last two decades, single-tank thermocline technology has received much attention due to its high cost-effectiveness compared to the conventional two-tank storage systems. The present paper focuses on clarifying the performance indicators and the effects of different influencing factors for the thermocline TES systems. We collect the various performance indicators used in the existing literature, and classify them into three categories: (1) ones directly reflecting the quantity or quality of the stored thermal energy; (2) ones describing the thermal stratification level of the hot and cold regions; (3) ones characterizing the thermo-hydrodynamic features within the thermocline tanks. The detailed analyses on these three categories of indicators are conducted. Moreover, the relevant influencing factors, including injecting flow rate of heat transfer fluid,... [more]

Saving energy and looking for alternative energy sources are both elements of energy efficiency management, which is still a significant challenge for many companies around the world. Unfortunately, energy efficiency in companies is often equated only with thermo-modernization or the replacement of lighting. However, one of the most important methods of improving energy use in manufacturing companies may be the modernization of the machine park. Therefore, the main purpose of the paper was to investigate the activities of enterprises in the field of the modernization of machines and the impact of this on the actual improvement of energy efficiency. The modernization of machines in production plants is understood as adapting new parts to the old device or rebuilding the machine in such a way that it can cooperate with its new subassemblies. Companies usually decide to modernize the machinery fleet, bearing in mind the benefits of production efficiency, and they do not always combine thi... [more]

According to United Nations data, half of the world’s population lives in cities and forecasts indicate that by the middle of the 21st century, this percentage will have increased to 65%. The increase in the urban population favors the creation of a network of interactions that entails a series of material and energy flows. These cause environmental impacts that affect the quality of life of citizens and the environment as a whole. According to data from the International Energy Agency, cities occupy 3% of the planet’s surface and are responsible for 67% of global energy consumption. The effects caused by this consumption, as well as its impact on the depletion of resources, make it necessary to carry out an exhaustive study of renewable energies and new energy saving systems. This Special Issue aims to present new advances and developments in renewable energy and energy saving systems that allow cities to evolve in a sustainable way.

Electric and hybrid-electric aircraft propulsion are rapidly revolutionising mobility technologies. Air travel has become a major focus point with respect to reducing greenhouse gas emissions. The electrification of aircraft components can bring several benefits such as reduced mass, environmental impact, fuel consumption, increased reliability and quicker failure resolution. Propulsion, actuation and power generation are the three key areas of focus in more electric aircraft technologies, due to the increasing demand for power-dense, efficient and fault-tolerant flight components. The necessity of having environmentally friendly aircraft systems has promoted the aerospace industry to use electrically powered drive systems, rather than the conventional mechanical, pneumatic or hydraulic systems. In this context, this paper reviews the current state of art and future advances in more electric technologies, in conjunction with a number of industrially relevant discussions. In this study,... [more]

The location of smart sustainable city multi-floor manufacturing (CMFM) directly in the residential area of a megapolis reduces the delivery time of goods to consumers, has a favorable effect on urban traffic and the environment, and contributes to the rational use of land resources. An important factor in the transformation of a smart city is the development of CMFM clusters and their city logistics nodes (CLNs); the key elements of the logistics system of a megapolis. The primary goal of this study was to examine the role of the CLN4.0, as a lead sustainability and smart service provider of a CMFM cluster within the Industry 4.0 paradigm, as well as its value in the system of logistics facilities and networks of a megalopolis. This paper presents an innovative model of a CLN4.0 under supply uncertainty using a material flow analysis (MFA) methodology, which allows for specific parameters of throughput capacity within the CMFM cluster and the management of supply chains (SCs) under un... [more]

The indoor air quality (IAQ) of severely polluted toilets is associated with the transmission of diseases. Computational fluid dynamics (CFD) methods and experimental measurements were used to analyze the diffusion characteristics of pollutants. This study investigated the diffusion characteristics and normalized concentration of ammonia and hydrogen sulfide pollutants under three ventilation systems—mixing ventilation (MV), personalized ventilation (PV), and impinging jet ventilation (IJV)—in a public toilet. The mean age of air (MAA) and air exchange efficiency (AEE) were also analyzed in our study. The results show that the MV scheme has a poor removal effect on pollutants compared with PV and IJV. IJV has advantages in reducing the normalized concentration of pollutants and improving the IAQ. Increasing the number of air changes per hour (ACH) may lead to a longer MAA and reduced air exchange efficiency. Choosing an appropriate number of air changes is very important to improve the... [more]