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Axial flux permanent magnet machines have garnered significant attention in recent years due to their numerous advantages in various applications, including electric vehicles, wind turbines, and robotics. However, one of the critical challenges associated with these machines is the presence of cogging torque, which can hinder their efficiency and performance. This review article provides a comprehensive overview of the state-of-the-art techniques employed for cogging torque reduction in Axial Flux Permanent Magnet Machines. Different techniques are described, encompassing geometric optimization, magnet placement, and skewing methods. Firstly, the significance of Axial Flux Permanent Magnet Machines is described, as well as the issue of the cogging torque. In the methods section, a review of the strategies for the reduction of cogging torque is described from various articles, and finally, in the discussion section, a list of actions is presented for cogging torque reduction for different topologies. The novelty of the study is that it combines strategies for cogging torque reduction in a single article. [ABSTRACT FROM AUTHOR]

This paper presents an analysis of energy production in a pilot building located in Slovenia, which is a typical residential house with an installed photovoltaic (PV) system and pilot battery storage system. Energy management system gathers data from smart meters every 15 min. As the pilot building location is in central Europe, complete energy self-sufficiency cannot be provided. The most problematic period of energy production with photovoltaic systems is winter. Solar radiation during the winter is much lower than in the summer and sometimes snow covers photovoltaic panels and disables energy production. Energy production and energy consumption are analyzed for one year. This study shows that complete self-sufficiency can be achieved by supplementing photovoltaic systems with hydrogen fuel cells. The amount of hydrogen, which would suffice for complete self-sufficiency for the whole period, is calculated according to the analyzed data. A synergy between photovoltaic system and hydrogen fuel cells is a step forward to complete self-sufficiency with renewable energy sources. The share of self-sufficiency of a hybrid PV fuel cell system would be 62.13%, meaning that there is no possibility for complete self-sufficiency from the pilot system. The shortage of hydrogen is 144.24 kg for one year and for achieving complete energy self-sufficiency, PV system should be bigger. A hybrid system with photovoltaic system, battery storage system and hydrogen fuel cells can be a solution for complete self-sufficiency. From an economic point of view, such systems are accessible for commercial use. The initial investment is relatively high, because of the high cost of the hydrogen storage tank. • Hybrid PV/hydrogen fuel cell system with batteries can provide energy self-sufficiency. • Batteries in hybrid PV/fuel cell system optimize hydrogen consumption. • Surplus of PV production can be converted into hydrogen with electrolysis. [ABSTRACT FROM AUTHOR]

Abstract Energy for society is an important element globally. Policy discussions in relation to climate change, suggest a transition from fossil-carbon-based systems to those based primarily upon renewable sources. The authors of this paper focused on a technical approach that can help to make that transition, namely pilot photovoltaic net metering installation for a business-residential entity in Slovenia, including its environmental perspectives. Results of the pilot photovoltaic net metering system installation revealed that the most cost effective solution is a photovoltaic installation with peak power of 6 kW, producing excess energy during the daytime. This has demonstrated that, with a proper planning, an optimum balance between energy production and consumption can be reached, and achieving a minimum price per kWh of the system. Regarding the environmental performance of the system, the results indicated that the most significant environmental impacts during its life cycle are related to global warming followed by human toxicity and terrestrial eco-toxicity. Photovoltaic net metering represents an option for producing and consuming cleaner energy, compared to conventional generation and usage, lowering the total price of the electrical energy (including fees and taxes) in comparison with the market purchases. This case study suggested that employing photovoltaic net metering in Slovenia is a reasonable option from the financial and environmental points of view, especially in the event of future increases of electricity price. Highlights • A new technical solution for PV net metering and its environmental performance. • PV net metering is an option of cleaner energy production and consumption. • Developed solution could be further utilized by the smart communities and cities. [ABSTRACT FROM AUTHOR]

The article deals with numerical analysis of a double sided coreless axial flux permanent magnet machine with two rotor disks and a coreless stator. Coreless stator represents copper windings which are held together by epoxy raisin, therefore a special focus has to be given to the stator temperature. In this article a numerical analysis is presented, which is based on the copper losses, namely the I2R product, where the resistance of the copper windings was both calculated as well as measured in the prototype machine. [ABSTRACT FROM AUTHOR]

This paper presents a torque analysis of an axial flux permanent magnet synchronous machine (AFPMSM) based on analytical analysis of magnetic field. The proposed method for torque analysis requires less computational time and is more flexible than finite element method (FEM). This is important advantage, especially for the early stages of the design process. Torque measurements on prototype AFPMSM confirm the validity of the torque analysis method. [ABSTRACT FROM AUTHOR]

This paper presents the analytical analysis of magnetic field, and back electromotive force (back EMF) calculation in an axial flux permanent magnet synchronous generator (AFPMSG) without stator core. For the verification, the numerical analysis [finite element method (FEM)] of magnetic field is accomplished and comparison between analytical and numerical solution of magnetic field is presented. Both analytical and numerical solutions are obtained via magnetic vector potential, respectively. This paper also presents the comparison between analytical solution and numerical (FEM) solution of back EMF using Faraday's law. The verifications show that good agreement between analytical and numerical solution of magnetic field and back EMF is obtained. The validity of the proposed analytical method is additionally confirmed with measurements of back EMF on prototype AFPMSG with coreless stator. [ABSTRACT FROM AUTHOR]

This paper deals with the use of solar energy, heat pumps, and solar system-heat pump combinations for domestic water heating. The testing of solar tiles, flat plate collectors as an autonomous system, as well as flat plate collector-heat pump and solar tile-heat pump combinations, are presented. Black-coloured water absorbs solar radiation flows through solar tiles made of transparent polymethyl methacrylate (CH2C(CH3)COOCH3). At the same time, solar tiles are used as a roof covering and as a solar radiation collector. Hot water from solar tiles or a flat plate collector is directed to the heat pump, which increases the temperature of water entering the boiler heating coil. The heat of water heated in solar tiles or in flat plate collectors serves as a source of energy for the heat pump. Since the goal was realistically evaluate the efficiency of solar tiles in comparison with the flat plate collector, extensive measurements of both systems under identical condition were carried out. The experiments were carried out in rainy, cloudy, and clear weather. [ABSTRACT FROM AUTHOR]

Heavy duty vehicles (HDVs), such as those used for winter services (e.g. snow plowing), are responsible for around 25% of CO 2 emissions caused by road transportation, which is also a challenge of energy resources. In this paper an optimization approach developed for the fleet management of winter services is presented, which was also evaluated in city of Maribor, Slovenia. The algorithm used is based on a mathematical graph theory, specifically on a solution to the Chinese postman problem, using two types of optimization: 1) optimization of the entire plan of the winter service and 2) optimization of the completed part of the planned service. The winter service includes plowing and a salting process that requires refilling the salt reservoirs on the vehicles. In our real-world case only one base was available for refilling the salt reservoirs, so two additional optimization approaches were evaluated: a) optimization of the traversals of plans starting form a single base and b) using proposed three additional recharge bases distributed across the city and recharging at the closest base when needed. The results of the optimization suggested a reduction of route length by 28.3% when executing the entire plan. When considering a redistribution of the salting material at three other locations, our estimation has showed that additional savings up to 9.8% could be achieved regarding to the selection of those locations. Less routes traveled consequently leads to a reduction of resource usage (diesel) and lower CO 2 emissions. When executing 15 plans in a single winter service campaign, 210 L less diesel was used, resulting in 1.362 t less CO 2 emissions per campaign, representing a reduction of 30%. Our model was initially based on real-life snow plowing processes and their statistics; where possible we used real-life data to configure the model, such as the salting material, loading times, the quantity of salting material distributed per km, the characteristics of the plowing vehicle, etc. Due to the heavy conditions during the execution of planned winter services, plans sometimes had to be readjusted on the go. Combining optimization with custom software for real-time execution, planning and service monitoring, assisted from the cloud, provided even more deterministic cost and environmental management, and gave further opportunity for optimization processes. [ABSTRACT FROM AUTHOR]

Abstract: The paper proposes a new method for determining force characteristics of an electromagnetic brake (EMB) by using co-energy considering only the main flux linkage. The co-energy is calculated by integrating the flux linkages in terms of exciting currents. The flux linkage depends on exciting current and on the variable air-gap thickness. The characteristics of flux linkages are determined numerically using finite-element method (FEM). Using flux linkage characteristics, the current and air-gap thickness-dependent co-energy characteristics of the EMB can be determined in the entire range of operation. Considering the co-energy variation caused by the air-gap thickness variation, the attractive force characteristics can be obtained. The paper presents a detailed description of the proposed method for determination of force characteristics of an EMB using co-energy considering only the main flux linkage. The procedure for determining force characteristics of an EMB using co-energy considering only the main flux linkage of an EMB has not been described yet. The results presented in this paper are used as a part of the EMB magnetically nonlinear dynamic model for the reaction time prediction. [Copyright &y& Elsevier]

• Examining user load profiles is a major task of future energy management strategies. • Advanced classification algorithms provide new insights into energy usage patterns. • We propose a network-based framework for the aggregation of specific users. • The proposed data-driven approach eases robust pattern discoveries in load profiles. Understanding energy consumption patterns in the residential sector is of paramount importance for the design of new energy management strategies that are based on innovative information and communication technologies. Smart metering provides considerable opportunities in this respect and allows for the assessment of household characteristics, behaviors and routines that drive household electricity loads. However, the handling of vast quantities of data delivered by smart metering systems requires advanced data analytics technologies and pattern detection algorithms. For the improvement of load forecasting strategies, a good user aggregation and classification is necessary. In the present paper we address this issue and propose a novel technique for data aggregation that was inspired by network science principles. We operate with a dataset of 1 year hourly measured electricity consumption data of 2201 users. The weekly and annual user load profiles are considered separately. Based on the load time series, we construct functional energy consumption networks and extract the minimum spanning tree. Subgroups with similar consumption curves are then objectively identified by means of a community detection algorithm. The proposed methodology is purely data-driven and facilitates an efficient aggregation of users, reduces heterogeneity, eases the study of the relation with environmental factors such as temperature, and is developed to efficiently handle large datasets in an unbiased manner. [ABSTRACT FROM AUTHOR]

Abstract Potential-induced degradation (PID) of photovoltaic (PV) modules is one of the most severe types of degradation, where power losses on system level may even exceed 30%. The PID process depends on the strength of the electric field, the temperature, the relative humidity, conductive soiling, time and the PV module materials. For p-type cells, it has been established that the decrease of the shunt resistance, due to migration of sodium ions across the n/p junction is the root cause of the degradation. On the other hand, it has recently been confirmed for n-type cells that the PID occurs due to an increase in recombination as charges are driven to the anti-reflection (AR) coating/emitter interface. In this paper, we present the comparison between PID of p-type and n-type crystalline silicon (c-Si) solar cells and their progression of PID. The time evolution of PID is studied by light and dark I-V curve measurements, electroluminescence images and progressions of the one- and two-diode equivalent model parameters, viz. photocurrent, 1st and 2nd diode reverse saturation currents, 1st and 2nd diode ideality factors, shunt resistance and series resistance. Highlights • Migration of sodium ions across the n/p junction is the root cause of degradation. • Side by side comparison between PID of p-type and n-type modules. • Progression of the photocurrent can be well described with exponential fit equation. [ABSTRACT FROM AUTHOR]

Since the publication of the Brundtland Report, production processes and consumption patterns towards sustainability have improved. This Special Volume Section of the Journal of Cleaner Production focuses on sustainable consumption and production (SCP), and identifies further challenges and provides solutions related to resource efficiency (ReE), sustainable water systems, sustainable management, cleaner production (CP), and sustainable urban development. In order to better understand the state of the SCP issues globally, existing policy directions have been explored within this paper, as well as six newly emerged sustainability terms, which have been integrated into the existing terminology classification to better describe and understand sustainable development concepts. In this Special Volume Section, the authors have demonstrated many valuable theoretical and practical contributions to the aspects of SCP, including a number of practical examples of achieving sustainability in companies, such as using bottom-up and a top-down approaches or by implementing theoretical models. There are also examples of achieving eco-efficiency in water systems (including urban), further requiring economic incentives and governmental support, and practical experiences, providing in-situ data and evidence of impacts of measures on processes and systems regarding resource efficiency, cleaner production, and also considering life cycle assessment (LCA). The examples of SCP research and development in the fields of ReE presented in this section of the SV indicate that existing production and service processes in companies and social (urban) environment could be more sustainable, using a holistic approach to the SCP and achieving global policy recommendations. [ABSTRACT FROM AUTHOR]

The performance comparison of three- and single-phase line-start interior permanent magnet synchronous motors (LSIPMSMs) and induction motors (IMs) with equal squirrel-cage design and symmetric four-pole stator windings is presented. The finite element method was employed in analysis of steady-state synchronous performance of LSIPMSMs. A magnetically linear lumped parameter model was employed in analysis of line-starting performance of LSIPMSMs, where the electrical and also the mechanical subsystems were considered. The procedure which was used for the LSIPMSM design was validated by comparison of calculation and measurement results. The performance of three- and single-phase LSIPMSMs and IMs with equal squirrel-cage design was directly compared and evaluated, thus emphasizing impacts of the permanent magnet breaking torque and reluctance breaking torque on the LSIPMSM performance in the asynchronous operation region. [ABSTRACT FROM AUTHOR]

The paper presents a finite-element method-based design and analysis of interior permanent magnet synchronous motor with flux barriers (IPMSMFB). Various parameters of IPMSMFB rotor structure were taken into account at determination of a suitable rotor construction. On the basis of FEM analysis the rotor of IPMSMFB with three-flux barriers was built. Output torque capability and flux weakening performance of IPMSMFB were compared with performances of conventional interior permanent magnet synchronous motor (IPMSM), having the same rotor geometrical dimensions and the same stator construction. The predicted performance of conventional IPMSM and IPMSMFB was confirmed with the measurements over a wide-speed range of constant output power operation. [ABSTRACT FROM AUTHOR]

The line-starting performance and synchronization capability of a line-start interior permanent magnet synchronous motor (LSIPMSM) has to be evaluated by considering different loads and different values of supply voltages, which requires the usage of a reliable dynamic model. In this work the parameters of a magnetically linear lumped parameter LSIPMSM dynamic model were determined by the differential evolution (DE). The optimization objective was the best possible agreement between the measured and by the model calculated time-behavior of model variables. Parameters determined by the DE are used in the LSIPMSM dynamic model, improving agreement between measured and calculated responses of currents and motor speed. [ABSTRACT FROM AUTHOR]