This paper presents current research trends and prospects of utilizing additive manufacturing (AM) techniques to manufacture electrical machines. Modern-day machine applications require extraordinary performance parameters such as high power-density, integrated functionalities, improved thermal, mechanical & electromagnetic properties. AM offers a higher degree of design flexibility to achieve these performance parameters, which is impossible to realize through conventional manufacturing techniques. AM has a lot to offer in every aspect of machine fabrication, such that from size/weight reduction to the realization of complex geometric designs. However, some practical limitations of existing AM techniques restrict their utilization in large scale production industry. The introduction of three-dimensional asymmetry in machine design is an aspect that can be exploited most with the prevalent level of research in AM. In order to take one step further towards the enablement of large-scale... [more]

Innovative vehicle concepts have been developed in the past years in the automotive sector, including alternative drive systems such as hybrid and battery electric vehicles, so as to meet the environmental targets and cope with the increasingly stringent emissions regulations. The preferred hybridizing technology is lithium-ion battery, thanks to its high energy density. The optimal integration of battery packs in the vehicle is a challenging task when designing e-mobility concepts. Therefore, this work proposes a conceptual design procedure aimed at optimizing the sizing of hybrid and battery electric vehicles. Particularly, the influence of the cell type, physical disposition and arrangement of the electrical devices is accounted for within a conversion design framework. The optimization is focused on the trade-off between the battery pack capacity and weight. After introducing the main features of electric traction systems and their challenges compared to conventional ones, the rele... [more]

Animal by-products (ABP) can be valorized via anaerobic digestion (AD) for biogas energy generation. The digestate issued from AD process is usually used to fertilize farming land for agricultural activities, which may cause potential sanitary risk to the environment. The European Union (EU) requires that certain ABP be thermally pasteurized in order to minimize this sanitary risk. This process is called hygienization, which can be replaced by alternative nonthermal technologies like pulsed electric field (PEF). In the present study, Enterococcus faecalis ATCC 19433 and Escherichia coli ATCC 25922 were used as indicator bacteria. Their resistance to thermal pasteurization and PEF treatment were characterized. Results show that Ent. faecalis and E. coli are reduced by 5 log10 in less than 1 min during thermal pasteurization at 70 °C. The critical electric field strength was estimated at 18 kV∙cm−1 for Ent. faecalis and 1 kV∙cm−1 for E. coli. “G+” bacteria Ent. faecalis are generally mor... [more]

Considering the intrinsic benefits of power line communications, the long-lasting lifetime of industrial systems and the growth of IoT, PLC technologies will be part of the worldwide industrial landscape for many decades. This paper discusses the history of the G3-PLC technology and current challenges and opportunities identified in real systems. Finally, it introduces recent evolutions within the G3-PLC standard, which bring additional performance and versatility, enhancing the relevance of G3-PLC as a complementary technology to other telecommunication systems in a 5G-driven telecommunication technology landscape.

The aim of this study is to look into the current information surrounding decommissioning and life extension strategies in the offshore wind sector and critically assess them to make informed decisions upon completion of the initial design life in offshore wind farms. This was done through a two-pronged approach by looking into the technical aspects through comprehensive discussions with industrial specialists in the field and also looking into similar but more mature industries such as the Offshore Oil and Gas sector. For the financial side of the assessment, a financial model was constructed to help portray a possible outcome to extend the life for a current offshore wind farm, using the existing data. By employing a techno-economic approach for critical assessment of life extension strategies, this study demonstrates the advantages and disadvantages of each strategy and looks to inform the offshore wind industry the best course of action for current wind farms, depending on their si... [more]

The article presents an analysis of geographical-settlement and legal-planning conditions for the development of Poland’s distributed generation. The choice of this country is important and interesting due to the highly dispersed settlement, which may be a factor stimulating the development of this type of energy systems. For this reason, the analysis can be a model for other countries and regions, indicating ways to analyze and evaluate settlement and planning conditions for the development of renewable and distributed energy. At the same time, Poland is struggling with a severe crisis of spatial planning. By analysing these opportunities and threats, empirical analyses try to indicate regularities in this respect in Poland’s regions in a detailed approach to communes and detailed legal and planning conditions. The conclusions emphasise the usefulness of distributed generation development for peripheral and sparsely populated areas of Europe and other parts of the world and appropriat... [more]

Insufficient environment protection may have serious ecological consequences, resulting in a number of problems in the modern world, many of which are a direct result of human behavior. Therefore, one needs to limit negative ecological effects by consciously shaping environment-related behaviors. The present paper analyzes the declared attitudes of individuals when it comes to taking into consideration pro-environmental factors, including energy, consumption, and waste. We have also studied the social awareness of the socially responsible investment idea, as well as pro-ecological individual behaviors related to private finance. Our survey study, conducted on a representative sample of 1030 Polish respondents, shows that participants’ individual features have little impact on pro-ecological decisions, and that declared pro-ecological attitudes are not reflected in actual behaviors. Polish consumers are still not active enough in making decisions concerning pro-ecological actions, first... [more]

The current transformers with split-core are used for installation in places where it is impossible to install classic current transformers. Moreover, this design allows for any measurement location change, and even switching one current transformer into several different shapes of bars or cables. Power network operators, striving for more accurate current measurements, require producers to provide current transformers with a special accuracy class 0.2S. Therefore, manufacturers and designers try to meet the market requirements and, similarly to non-demountable current transformers, i.e., with a toroidal core, design current transformers with split-core class 0.2S. To meet the high metrological requirements, 3D analyses of electromagnetic fields were performed, taking into account physical phenomena and not approximate analytical models. Two types of cores and four different arrangements of the secondary windings of the measuring current transformers were considered. The magnetic field... [more]

The dynamic characteristics of hydropower unit governing systems considerably influence the stability of hydropower units and the connected power system. The dynamic performances of hydropower units with power regulation mode (PRM) and opening regulation mode (ORM) are different. This paper establishes a detailed linear model of a hydropower unit based on the Phillips−Heffron model. The damping characteristic and stability of two regulation modes with different water inertia time constants TW were analyzed. ORM tended to provide negative damping, while PRM often provided positive damping in the major parts of the frequency range within the normal frequency oscillations when TW was large. Eigenvalue analysis illustrated that PRM has better stability than ORM. To validate the analysis, a simulation under two typical faults WAS conducted based on a nonlinear model of a hydropower unit. The simulation results illustrated that the responses of units with PRM are more stable in terms of impo... [more]

Grid-connected photovoltaic (PV) systems are designed to provide energy to the grid. This energy transfer must fulfil some requirements such as system stability, power quality and reliability. Thus, the aim of this work is to design and control a grid-connected PV system via wireless to guarantee the correct operation of the system. It is crucial to monitor and supervise the system to control and/or detect faults in real time and in a remote way. To do that, the DC/DC converter and the DC/AC converter of the grid-connected PV system are controlled wirelessly, reducing costs in cabling installations. The used control methods are the sliding for the DC/DC converter and the Proportional-Integral (PI) for the inverter. The sliding control is robust, ensures system stability under perturbations, and is proven to work well via wireless. The PI control is simple and effective, proving its validity through wireless too. In addition, the effect of the communications is analysed in both controll... [more]

The paper focuses on problems connected with Environmental Corporate Social responsibility in the energy industry. The objective behind this article is to analyse pro-environment activities within Environmental Corporate Social Responsibility (ECSR) that heating operators carry out, using the example of a Poland-based company called Miejska Energetyka Cieplna Spółka z o.o. with headquarters in Koszalin. In particular, this study focuses on pro-environment activities that the company has been involved in from 2017−2020. The data and information found in this study demonstrate that the company systematically devoted its financial resources to pro-environment efforts in terms of both ISO 14001 maintenance as well as educational/promotional activities. According to the findings, the company has been highly committed to Environmental Corporate social Responsibility issues. The implementation of its strategy in this field can lead to ecological innovation and help establish an effective busi... [more]

This paper presents a method to limit the arc energy and hence the hazard risk category value according to IEEE 1584 by using a system of two oppositely connected multi-sectional thyristor branches. A test circuit for testing the effectiveness of a thyristor arc eliminator was designed and constructed. Arc ignition inside electrical switchgear can be a source of danger for technical personnel. The arc energy calculated according to the algorithms in IEEE 1584 can be significantly reduced by using multi-sectional arc eliminator MSAE. For the actual measuring object, the calculation of the hazardous arc flash zone and the hazard category was carried out for the system not equipped with an arc eliminator, and then the same was performed in a system with an arc eliminator. In parallel, the pressure inside the closed polyvinyl chloride (PVC) electrical box enclosure was measured and then compared with the calculated pressures that could occur during an arc fault. It was found that a Multi-S... [more]

The incorporation of phase change materials (PCM) in buildings has the potential to enhance the thermal efficiency of buildings, reduce energy cost, shift peak load, and eventually reduce air pollution and mitigate global warming. However, the initial capital cost of PCM is still high, and thus the establishment of a control strategy has become essential to optimize its use in buildings in an effort to lower investment costs. In this paper, an extensive review has been made with regard to various control strategies applied to PCM-enhanced buildings, such as ON/OFF control, conventional control methods (classical control, optimal, adaptive, and predictive control) and intelligent controls. The advantages and disadvantages of each control strategy are evaluated. The paper further discusses the opportunities and challenges associated with the design of PCM-enhanced buildings in combination with control strategies.

Climate changes necessitate measures to reduce greenhouse gas emissions (GHG). The European Union’s climate and energy policy places particular emphasis on the development of renewable energy, considered to be the primary mean in achieving the climate neutrality goal by 2050. Having in mind the aforementioned, the study was conducted to determine time delay in the development of renewable energy sources between the Visegrad Group (V4) countries and Germany, considered the most advanced country in developing renewable energy and having the greatest impact on shaping European Union climate and energy policy. The time delay econometric method was used in four of its variants. The research results show that, despite the existence of support mechanisms, the development of renewable energy sources (RES) in the V4 countries has a high mutual correlation. There is a hight correlation between RES penetration in energy mix and UE goals of the climate and energy policy until 2020. At the same tim... [more]

The European Union aims to reduce Greenhouse Gas (GHG) emissions by 55% before 2030 compared to 1990 as a reference year. One of the main contributions to GHG emissions comes from the household sector. This paper shows that the household sector, when organised into a form of prosumer microgrids, including renewable sources for electric, heating and cooling energy supply, can be efficiently decarbonised. This paper investigates one hypothetical prosumer microgrid with the model RES2GEO (Renewable Energy Sources to Geothermal). The aim is to integrate a carbon-free photovoltaic electricity source and a shallow geothermal reservoir as a heat source and heat sink during the heating and cooling season. A total of four cases have been evaluated for the Zagreb City location. The results represent a balance of both thermal and electric energy flows within the microgrid, as well as thermal recuperation of the reservoir. The levelised cost of energy for all cases, based on a 20-year modelling ho... [more]

This paper presents an analysis of methods to increase the efficiency of heat transfer in heat exchangers. The scope of the research included analysis of efficiency optimization using the example of two tubular heat exchanger structures most often used in industry. The obtained efficiency of heat recovery from the ground of the examined exchangers was over 90%, enabling the reduction of emissions of the heating systems of buildings. The paper presents the results of tests of two types of heat pipes using R134A, R404A, and R407C working agents. The paper also presents the results of experimental tests using the R410A working medium. The results included in the study will also enable the effective use of land as a heat store.

With the increasing depth of coal mining, the quantitative evaluation of the degree of geological structure development is becoming increasingly important for the control of mine water hazards in coal mining areas. Understanding the complexity of geological structure development can improve the safety and efficiency of coal production. At present, various evaluation indicators of the geological structure development cannot fully reflect the complexity of faults and folds, and the evaluation process is usually affected by subjective human factors. In this paper, the fractal dimension from fractal theory is used as the evaluation indicator to quantitatively analyze and evaluate the complexity of fault and fold structure in the mining area. To verify the evaluation results, the mathematical geology method is applied in an analysis of the trend surface of fault and fold networks. The results indicate that the fractal dimension can be applied for the quantitative analysis and evaluation of... [more]

Within the current context of energy transition, the first step to assure cost-efficient and reliable grid operations is the use of adequate planning tools. These tools must evaluate the real needs for reinforcing, replacing and incorporating new network assets considering not only technical and regulatory aspects but also the operational benefits that distributed energy resources (DER) may provide. With this purpose, this paper presents a novel methodology for the analysis and the advanced planning of the active distribution networks in the context of smart grids. The main contributions of the proposed methodology are the following: to incorporate the real capabilities of DER proactively to the planning and operation of distribution networks; to appropriately use the data available in current smart grids; and to promote the efficient use of network capacity in distribution level (efficiency decisions of its users, grid assets in service, access conditions, etc.) through potential oper... [more]

New guidelines set by international organizations for refrigeration companies cause that natural working fluids such as carbon dioxide are increasingly used in new refrigeration systems. Carbon dioxide (R-744) is used in freezing, cooling, or air conditioning installations, in which the cooling load fluctuates hourly. To adapt the cooling capacity of the evaporator to the current cooling load of the cooled space, a number of control elements are used. The paper proposes a new method of regulating the cooling capacity for a one-stage refrigeration cycle with the R-744 refrigerant and an internal heat exchanger (IHX). The proposed method involves using an additional evaporator and combines the possibility of regulating the cooling capacity with the possibility of energy efficiency ratio (EER) improvement. The energy analysis of the proposed method of regulating the cooling capacity was performed and the results were compared with the control method. The control method was using the compr... [more]

To assist in light weighting of electric vehicles by improving the volumetric and gravimetric energy density and the structural performance of the battery pack, a modelling methodology based on a macro finite element model of a pouch cell has been developed. This model treats the core cell structure as a homogeneous orthotropic honeycomb block with the pouch material being defined as an orthotropic fabric with compressive stress elimination. The model considers five compression and bending load cases simultaneously and allows a level of element discretisation that is computationally efficient and appropriate for inclusion in full vehicle and sub-system simulations. The methodology is scalable in that it can be applied to a range of chemistries, external geometries and internal cell constructions. When considering stacks of cells, the model is predictive for both lateral compression and three-point bend, but further work is required to improve the confined compression response.

Energy efficiency in the building industry is related to the amount of energy that can be saved through thermal improvement. Therefore, it is important to determine the energy saving potential of the buildings to be thermally upgraded in order to check whether the set targets for the amount of energy saved will be reached after the implementation of corrective measures. In real residential buildings, when starting to make energy calculations, one can often encounter the problem of incomplete architectural documentation and inaccurate data characterizing the object in terms of thermal (thermal resistance of partitions) and usable (number of inhabitants). Therefore, there is a need to search for methods that will be suitable for quick technical analysis of measures taken to improve energy efficiency in existing buildings. The aim of this work was to test the usefulness of the type Takagi-Sugeno fuzzy models of inference model for predicting the energy efficiency of actual residential bui... [more]

Power converters in wind turbines exhibit frequent failures, the causes of which have remained unexplained for years. Field-experience based research has revealed that power- and thermal-cycling induced fatigue effects in power electronics do not contribute significantly to the field failures observed. Instead, clear seasonal failure patterns point to environmental influences, in particular to humidity, as a critical stressor and likely driver of converter failure. In addition to the electrical operating conditions, it is therefore important to also identify and characterize the climatic conditions that power converters in wind turbines are exposed to, both as a contribution to root-cause analysis and as a basis for the derivation of suitable test procedures for reliability qualification of components and systems. This paper summarizes the results of field-measurement campaigns in 31 wind turbines of seven different manufacturers spread over three continents. The temperature and humidi... [more]

Data-driven diagnosis methods for faults of proton exchange membrane fuel cell (PEMFC) systems can diagnose faults through the state variable data collected during the operation of the PEMFC system. However, the state variable data collected from the PEMFC system during the stack switching between different operating points can easily cause false alarms, such that the practical value of the diagnosis system is reduced. To overcome this problem, a fault diagnosis method for PEMFC systems based on steady-state identification is proposed in this paper. The support vector data description (SVDD) and relevance vector machine (RVM) optimized by the artificial bee colony (ABC) are used for the steady-state identification and fault diagnosis. The density-based spatial clustering of applications with noise (DBSCAN) and linear least squares fitting (LLSF) are used to identify the abnormal data in datasets and estimate change rates of the system state variables respectively. The proposed method c... [more]

In many circles, brown coal continues to be viewed as a cheap source of energy, resulting in numerous investments in new opencast brown coal mines. Such a perception of brown coal energy is only possible if the external costs associated with mining and burning coal are not considered. In past studies, external cost analysis has focused on the external costs of coal burning and associated emissions. This paper focuses on the extraction phase and assesses the external costs to agriculture associated with the resulting depression cone. This paper discusses the difficulties researchers face in estimating agricultural losses resulting from the development of a depression cone due to opencast mineral extraction. In the case of brown coal, the impacts are of a geological, natural-climatic, agricultural-productive, temporal, and spatial nature and result from a multiplicity of interacting factors. Then, a methodology for counting external costs in crop production was proposed. The next section... [more]

The methodologies for calculating exhaust emissions and fuel consumption, which are given in the normative documents, do not take into account the fact that vehicles equipped with liquefied petroleum gas (LPG) or compressed natural gas (CNG) systems are fueled with petrol after a cold start. When calculating exhaust emissions and fuel consumption of LPG or CNG-powered vehicles, it is assumed that they result from the combustion of gaseous fuel only. This simplification leads to an incorrect determination of the emissions and fuel consumption values, as the formulas for calculating these values differ depending on the fuel type. This article presents the results of tests aimed at checking how that factor affects the value of emissions and fuel consumption calculated in the driving cycles used in the type-approval tests. In order to estimate the error resulting from this simplification, the tests of exhaust emissions and fuel consumption of a vehicle equipped with an LPG system were carr... [more]