Photovoltaics (PV) is one of the solutions that contributes to the diversification of energy sources and in addition to reasonable integrating into the grid positively affects the energy security and self-sufficiency. The use of photovoltaics for combined use with the aim of eliminating the depreciation of valuable/agriculture land is starting to be a relevant and discussed topic. The paper illustrates a specific case of the integration of photovoltaics for the needs of a parking lot and powering an associated railway station. The designed parking lot type park and ride at the railway station in Nove Kosariska in Slovakia and the related technical and economic analyses in variant scenarios were chosen as a model case of study.

The main role of cable sheath is to protect the cable cores from external degradation factors such as water, moisture, mechanical stress, various types of radiation, etc. Its aim is to ensure trouble-free operation and long service life of cable routes, which currently reaches 40-50 years. The composition and properties of sheathing compounds are modified with various admixtures to improve their resistance to external degradation. In real practice, we often encounter cables placed in environment that is not suitable in terms of their declared properties, which can ultimately lead to their damage and shortening of their predicted service life. This paper presents results from the measurements of dielectric parameters, insulation resistance, dissipation factor and breakdown voltage, and mechanical parameters, tensile strength and elongation at break of the cable sheaths. The samples were commercially produced low-voltage cables made from HFFR blends with and without UV stabilization. The influence of natural environment after two years of natural aging in an unprotected outdoor environment was investigated. We accent that while dielectric properties of insulating polymeric materials applied in the cable structure could be convenient, but already two years long exposure to natural environment influence could threaten with important shortening the lifetime.

The paper is focused on the analysis and detection of faults of photovoltaic (PV) elements, especially PV modules, and their impact on the reliable operation of the photovoltaic system. Brief overview of currently used measurement techniques and methods in photovoltaic diagnostics is introduced. The consequences for the safe and reliable supply of electricity from the PV system were demonstrated on silicon photovoltaic modules by modelled faults and evaluate them using selected diagnostic methods. The influence of respective defects and environmental impact was demonstrated using current-voltage (I-V) curves, impedance spectroscopy and thermography. The aim was not to quantify the deterioration of measured samples, but to demonstrate chosen methods and their potential.

Public lighting networks (PLNs) play a crucial role in urban infrastructure, directly impacting safety and comfort. This paper presents a comprehensive analysis of PLN operation at reduced voltage, considering factors such as voltage drop, line parameters, and component capabilities. A case study demonstrates the feasibility of operating PLNs with a wide voltage range, offering insights into potential benefits and challenges. Overall, the study underscores the potential of innovative operational models to enhance the efficiency and reliability of public lighting networks.

This paper deals with heating system powered by a heat pump. It presents a basic theoretical knowledge and principle of operation. The heat losses of the building and the specific heat flux are calculated on a practical example of a family house. Based on these values, it is further shown how the heat pump performance is designed to provide underfloor heating.

Improving the properties of impregnants used for the windings of electric rotating machines and transformers is still an actual problem that is being dealt with by many scientific institutions looking for more efficient and environmentally friendly materials. The goal is not only to increase the reliability and service life of electrical equipment, but also to optimize the production process and material base, which will lead to a reduction in economic costs. Constantly increasing requirements on the properties of impregnants are met either by introducing completely new impregnants or by modifying the original ones. In both cases, it is necessary to test their properties in order to verify the long-term stability and resistance to degradation effects. This paper presents partial results from testing the resistance of three different impregnants in the cured state to water in terms of investigation of selected dielectric properties.

Building Integrated Photovoltaics (BIPV) is an option which offers renewable energy production and environmental friendly technology in the situation of actually increasing energy demand and threatening climate changes. When building materials are replaced by BIPV, new challenges to be solved appear. We discuss various aspects which are specific in BIPV in comparison with standard ground installed photovoltaics. Results obtained by simulation and experimental measurements related to the BIPV operation are also presented.

The photovoltaic (PV) module is the basic building block of each photovoltaic system. Output power of the PV module and the produced energy strongly depends on the operating conditions. The operating temperature of the device, ambient temperature, solar radiation intensity, humidity, and dustiness can be considered as the most important factors. A significant decrease of delivered power occurs in the case of partial or complete shading of PV module, which comes e.g. from clouds, surrounding buildings, pillars, snow or e.g. from various impurities (bird droppings). This shading brings, in addition to power loss, an associated problem of existence two (or more) power maxima in the P-V curve. Existence of "two knees" on the I-V characteristic can negatively affect the operation of the associated electronics (MPP tracker). No less important problem related to power losses is creation of the hotspots (places of excessive local heating). Shaded part of the module behaves like an electric load and converts electric energy into joule heat. Hotspot affects safety (fire, destruction of equipment) and reliability of electricity supply from PV device. Comprehensively analysis of the negative consequences of the different degree of shading of the PV module parts, as well as the role of bypass diodes following the reliability in power engineering is very useful. Practical experiments on created experimental PV module were confronted with the simulations in MATLAB. Presentation of simulation and results useful for practice are main aim of this paper.

The ampacity (current carrying capacity) of cable routes is an important parameter for assessment the economical and safe supply of electricity. The cables often routed through short segments such as walls, ceilings, fire barriers etc., which have different thermal conductivity than environment of the other parts of cable route. Although, the length of short segments can be negligible in comparison to the entire length of the cable route, their impact on ampacity of the cable route can play a significant role. Experimentally measured results of temperature of a low voltage cable used in building installations passes through wall from wood, aerated concrete block and mineral wool at different current loads are presented in this paper.

Reducing the electricity consumption is a current trend which has an economic, social and environmental impact. Measures which are outlined to increase efficiency are also supported by legislation and could be funded from the national or European funds in EU countries. In Slovakia, there are many establishments, public buildings and households built in past decades where energy is being wasted. Approximately the share one third of the consumed energy in Slovakia belongs to industry. This statistic naturally legitimizes the effort to achieve energy savings in this segment. We choose a body which is in use partially as commercial offices and partially as production facility. The matter was to identify areas with excessive energy consumption and propose appropriate measures to avoid unnecessary losses. The paper presents more aspects of building operation regarding of energy consumption, especially in relation with old buildings with more structural and operational defects and propose some ways of the improvements the energy efficiency. The work also includes experimental data and simplified economy considerations related to the proposed measures. Finally the step model is presented in order to simplify the decision making process. The model is relevant and also applicable generally for the other engineering disciplines.

This work is focused on the results of the development of solar photovoltaic heterostructures which consist of a combination of amorphous silicon carbide (used as emitter), doped crystalline silicon substrate and deposited thin transparent conductive oxide layer. Two types of transparent conductive oxide layers: indium tin oxide and indium zinc oxide were prepared for the investigation. The advantages and benefits of the conductive oxides applied on prepared solar cell structures are described in this paper. The main contribution of the work is the assessment of the impact of a sputtering current applied at transparent conductive oxide deposition on the resulting photovoltaic properties. It was found that all electrical (charge carrier mobility, electrical conductivity, photovoltaic parameters) as well as optical (transmittance) parameters are strongly dependent on the sputtering setup. The analyses were performed on both, prepared photovoltaic heterostructures and transparent conductive oxide layers deposited on the glass using DC and AC measurement and optical techniques. The sputtering conditions were optimized to get the best photovoltaic behaviour.

Amorphous silicon carbide is known as a material resistant except others influences also against radiation. This study investigates the effects of neutron radiation on electric characteristics (I-V characteristic, impedance spectra and obtained dynamic parameters of AC equivalent circuit) of solar cell a-SiC/c-Si heterojunction structure. The heterojunction structure was irradiated using neutrons with neutron fluence 1013 cm-2. Existence of neutron induced structural defects, which could be introduced within semiconductor structure of heterojunction, has been illustrated using DC and AC analysis. The structural defects induced by neutron particles radiation affect mainly trapping mechanism. The process results in the changes of electronic elements included into proposed equivalent circuit.

An important part of the photovoltaic power plants are cable systems. The dielectric properties of cables, reliability and durability depend on quality of production processes, operating conditions and degradation factors, as well. Expected lifetime of cable systems is more than 20-30 years in general. Their failure free operation and long-term stability of properties has a direct impact on the economic return of the investments. According to our experiences the tests in compliance with valid standards are not adequate to verify real life time during operation. Photovoltaic cables intended for use in outdoor applications for the connection between the solar panels and possible connection between panels and inverter were chosen for our experiments. The changes of insulation resistance and breakdown voltage caused by some degradation factors, mainly water, are presented. This research was inspired by real failure in operation.

In this paper theoretical and experimental results are presented relating to the polarization which appears as a consequence of non-uniform temperature spacing in cable insulation. This temperature gradient has both a short term influence and a long term influence. In the brief time the gradient creates mainly a conduction inhomogenity. This means that the conductivity of insulation adjacent to the heated core is higher than conductivity of insulation at outer radius of the cable. After a long time operation the changes of conductivity became massive due to chemical reactions accelerated in the places with higher temperature. All these processes give rise to the interfacial polarization which is created in insulating material with non-zero gradient of conductivity or permittivity. In our work we try to identify the mentioned interfacial polarization in a specimen of commonly used PVC cable. It was found, that the polarization appears at frequencies of the order of a few mHz. Measurement in this scale requires a special apparatus as it is sensitive to any perturbation. Here we are dealing with the problem of separation of polarization part from the conduction part of dielectric data. Following our experiments the best way of date processing is the use of complex modulus formalism. Experiences with interfacial polarization induced by a temperature gradient will be utilized for monitoring the cable properties during a long-term ageing.

Globally, emphasis is placed on increased security in the field of human health protection during the fire. That is, why fire resistant, flame retardant and halogen-free cables are more used in public buildings. Their using can improve fire safety and fire rescue capability. Although, the fire performance is a priority for these cables, we cannot neglect the others important properties of core insulation. Changes of electro physical properties may be related with modifications of insulation in order to limit smoke, fumes and halogen or improve their fire resistance and maintain circuit integrity of vital emergency services (e.g. fire alarm). New insulation materials and cable constructions should be tested for different operating environment and emergency situations. The intention of our experiment was to simulate unexpected events during operation such as flooding of cable systems and water ingress through the open ends of the cables or damaging of the sheath. The paper presents the results of laboratory tests of fire resistant cable insulated cores with different types of flame barrier in case of long-term contact with water.

Modern measurement systems allow the acquisition of dielectric relaxation spectra over a wide range in frequency and temperature with a high accuracy. This paper presents application of low frequency dielectric spectroscopy measurement in purpose of study slow polarisation processes in PVC insulating cable systems.

Power cables with PVC based insulation blends are nowadays still one of the most applied types of cables. Usually, this kind of cables is used for 400 V transmission lines, but also for 6/10 kV voltage level. This paper deals with various degradation mechanisms and factors influencing this kind of cables in service. The analysis of this influence is focused on the feasible change of dielectric and mechanical properties of insulation material.

Photovoltaics is an important and extensive science area offering a lot of industrial and research activities based on sophisticated physical ground. Solar electricity is one of the currently already exploited and rapidly developing renewable energy sources. In this paper we tried to outline simple physical context of light to electricity conversion and present alternatives which are available on the commercial and research level. Of course with regard to limited space, the information provided here is limited.

In this paper theoretical and experimental results are presented relating to the polarization which appears as a consequence of non-uniform temperature spacing in cable insulation. A simple model of the polarization is outlined and analyzed regarding to the influence on the measurable parameters of a cable. The analysis of the dielectric data showed, that the polarization can be identified in the range of very low frequency. The methods of acquiring data in the mentioned range of frequency are also discussed. Additionally the question of separating the data from the polarization and conduction processes is solved. The final results were acquired on a line cord with PVC insulation, where the polarization was generated by heating of two cores. The results proved possibilities of the polarization identification. The only obstacle by these measurements is that they require very long time for reaching a steady state. Reliable results can be expected at frequencies of a few mHz.

Absorption current measurements and very low frequency dielectric measurements were performed to evaluate the insulation properties of halogen free fire retardant cables at various temperatures. Changes of electrical parameters have been used for the cables characterization and comparison. The results of measurements proved a complex character of the dielectric phenomena, which consist of several independent processes with individual response to the temperature changes. In the paper a technique of dielectric measurements and analysis of their results was reviewed with emphasis on the range of very low frequencies. The measured and calculated parameters will be used in the future as a start point for evaluation of the cables ageing.