The article deals with designing rotor disks of a double-sided axial flux permanent magnet machine, based on their deflection, due to the pull forces between opposite rotor disks, caused by the permanent magnets. Permanent magnets cause the magnetic flux density to flow between the magnets and its size determines the size of the pull force. That is why it is essential to determine the size of the axial component of magnetic flux density in the middle of the clearance between opposite rotor disks in order to calculate the deflection of the rotor disks. The article presents a new method for determining the size of the axial component of magnetic flux density, based on a simplified finite element method and an approximation method as well as modified equations for determining the deflection of rotor disks. The method is used to determine the pull forces between rotor disks and based on the deflection of the disks an optimum rotor disk thickness can be selected in order to reduce the weight of the machine.

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.

This paper represents a development process of the energy concept maps in higher education learning environment, in order to foster new and innovative learning experiences as well as improve the understanding of energy planning, especially from the interdisciplinary perspectives, including energy, environment, spatial planning. Energy concept maps were developed based on sustainable energy action plans to build a common knowledge base. The use of the energy concept maps developed were tested by 24 lecturers and 206 students from six European countries, comprising Slovenia, Croatia, Portugal, Italy, Spain and Malta. The learning processes were evaluated based on self-evaluation of competencies as well as external evaluation of students' knowledge and understanding of energy planning. The evaluation process revealed that participants included in learning activities gained new knowledge and competences in the energy planning and have a better understanding of a relationship between different concepts, subjects, developed a critical thinking, and proved their problem solving ability. Our study acknowledges the efficiency of the learning process in energy planning education by using concept maps.

This article proposes a methodology for the design of double-sided coreless axial flux permanent magnet synchronous machines, which is based on a developed model for calculating the axial component of the magnetic flux density in the middle of the distance between opposite permanent magnets, which also represents the middle of the stator. Values for different geometric parameters represent the input data for the mathematical model in explicit form. The input data are calculated by using a simplified finite element method (FEM), which means that calculations of simplified 3D models are performed. The simplified model consists of two rotor disks with surface-mounted permanent magnets and air between them, instead of stator windings. Such a simplification is possible due to similar values of permeability of the air and copper. For each simplified model of the machine the axial component of the magnetic flux density is analyzed along a line passing through the center of opposite permanent magnets and both rotor disks. Values at the middle of the distance between the opposite permanent magnets are the lowest and are therefore selected for the input data at different stator, rotor disks and permanent magnets (PM) thicknesses. Such input data enable the model to consider the nonlinearity of materials.

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.

This article presents the research on the optimum distance (fictitious air gap) between permanent magnets of the coreless axial flux permanent magnet machine with a double rotor and single stator. Magnetic flux density of the permanent magnets follows the mean flux path between the opposite magnets. The size of the leakage flux depends on the axial distance between the magnets, the distance between adjacent magnets and the back iron of the rotor disks. If the fictitious air gap (clearance between opposite permanent magnets) is too large, the flux path will close through the adjacent magnet and not the opposite one. The article presents the finite element analysis of the magnetic flux density between the permanent magnets mounted on the rotor disks where the fictitious air gap thickness was set as a variable to determine the maximum clearance. Connection between bending (pull) forces of rotor disks and fictitious air gap thickness is also presented with the mechanical stress analysis of rotor disks.