Journal of Energy Technology is a scientific and professional journal in the field of energy and energy technologies. The first issue of Journal of Energy Technology was launched in November 2008. The founder of the journal is University of Maribor, Faculty of Energy Technology. The journal is intended for domestic and foreign scientific, technical and general public. With the aim of increasing the recognition of the journal, the articles in journal are mainly in English. The journal is issued quarterly in both printed and electronic form. Indexing: The Journal of Energy Technology (JET) is indexed and abstracted in database INSPEC©. Participating University of Maribor Faculties: Faculty of Energy Technology
Radioactive Waste Management Strategy for a New Nuclear Power Plant
An essential early phase of any new nuclear power plant (NPP) project is drafting and preparation of a radioactive waste management strategy. The paper outlines major steps in such strategy presented in a case study approach for new NPP project in Krško (the JEK2 project). The paper includes analyses of options and strategies for radioactive waste (RAW) and spent nuclear fuel (SNF) management. This article presents a proposed management plan for RAW and SNF expected to be produced during operation and decommissioning of JEK2, together with an assessment of anticipated decommissioning and waste management costs. The document further examines the existing financing framework for radioactive waste management in Slovenia, which is legally regulated for current nuclear facilities. A similar approach is planned for JEK2, including the expansion of existing and planned facilities for waste handling and storage. Accordingly, additional financial resources will be required through contributions to the national decommissioning and disposal fund. An analysis was therefore conducted to estimate the scale of additional contributions needed to ensure adequate funding for new NPP project in Krško.
Copyright (c) 2025 University of Maribor, University of Maribor Press https://creativecommons.org/licenses/by/4.0/
Identification and Qualitative Analysis of Liquid Effluents in the Spatial Planning Stage of a New Nuclear Power Plant Project
Planned JEK2 will generate liquid effluents during normal operation, categorized as radioactive and non-radioactive. Radioactive releases will mainly consist of tritium, while other radionuclides will be present only in trace amounts, all below the authorized limits. Non-radioactive effluents, originating from cooling and service water systems, will be treated by filtration, pH adjustment, and biocide neutralization. Thermal load of non-radioactive emissions to the Sava will be minimal to negligible levels, as the cooling tower serves as the heat sink. All effluents from JEK2 will be managed by design through defence in depth: multi-barrier treatment and holdup, controlled storage and release, and comprehensive monitoring under the ALARA principle to keep impacts low and within strict regulatory limits
Systematic Derivation of Clarke and Park Transformations through Vector Representation in Three-Phase Systems
This paper presents a comprehensive mathematical derivation of Clarke and Park transformations from first principles through systematic vector representation. Despite over a century of widespread application in power electronics and motor control, rigorous derivations of these fundamental transformations remain scattered across literature. We address this gap by systematically progressing from three-phase voltage equations in time domain to spatial vector representation in three-dimensional space, then deriving Clarke transformation through geometric projection onto the plane where balanced quantities reside. Subsequently, we derive Park transformation as time-varying rotation of the Clarke frame. The work establishes both amplitude-invariant and power-invariant formulations, explains the geometric significance of the 35.26° angle between coordinate systems, and reveals the mathematical basis for zero-sequence component extraction. This unified treatment bridges the gap between these transformations' ubiquitous practical application and their fundamental mathematical origins.
Copyright (c) 2025 Journal of Energy Technology https://creativecommons.org/licenses/by/4.0
Design and fabrication of a demonstration model for promoting low-carbon energy technologies
This article presents the design, construction, and educational application of a large-scale model representing renewable energy facilities that do not yet exist. The model features a circular layout with a diameter of 2 meters, divided into two halves: the Mokrice Hydropower Plant and a nuclear power plant with an accompanying low- and intermediate-level radioactive waste repository. The Mokrice half highlights key ecological and technical features, including two fish passages and a solar power plant installation, with realistic water effects achieved using epoxy resin. The nuclear half includes a removable low- and intermediate-level radioactive waste repository, allowing viewers to explore storage arrangements via a cross-sectional view. All components were fabricated using FDM 3D printing, assembled, finished with paint and landscaping materials, and mounted on a wooden base with a metal support structure. While the model was not intended to achieve exact technical scaling, it effectively communicates complex energy infrastructures, facilitating public understanding, awareness, and dialogue about low-carbon technologies. The combination of additive manufacturing, interactive features, and detailed landscape representation demonstrates the value of models as tools for education, demonstration, and the promotion of sustainable energy solutions.
Assessment of Harmonic Distortion in School Buildings Equipped with Grid-Connected PV Systems
The integration of photovoltaic systems into power grids can impact power quality, particularly concerning voltage and current harmonics. This study investigates the power quality of a photovoltaic system integrated into the electrical system of an educational facility, focusing on harmonic distortion in both voltage and current. Comprehensive measurements were conducted across three phases and analysed according to the EN 50160 and IEEE 519 Standards. The results demonstrated that, while the voltage quality meets EN 50160 requirements consistently, indicating stable voltage levels, the current measurements revealed significant harmonic distortion. Notably, Phase 2 exhibited Total Harmonic Distortion values substantially above the acceptable limits, with Phase 1 and Phase 3 also showing elevated Total Harmonic Distortion. To address these issues, the study recommends the implementation of advanced harmonic filters and optimisation of inverter technologies. These measures are crucial for enhancing power quality, and ensuring compliance with the industry Standards in high photovoltaic penetration scenarios.
power quality analysis, grid-connected PV systems
Towards Digital Twinning of Electrical Motors – Simulation Models
This paper presents a methodological framework for building a digital shadow of an induction motor based on standardized tests and a two‑axis (dq) simulation model. Tests were carried out according to IEEE Std 112 and IEC 60034‑2‑1 [10, 11]. Parameters of the equivalent circuit were identified and entered into the model. Validation was performed by comparing torque–speed and current–speed curves at 180 V and 220 V, while nominal behavior at 400 V was estimated using the model and voltage scaling. The model was then calibrated to reduce the discrepancy between simulation and measurements and the error was quantified using the root‑mean‑square error (RMSE) and mean absolute percentage error (MAPE). An automated load‑simulation setup that reproduces the torque test is also presented, enabling rapid evaluation of parameter influence. Results show a very good match in the current channel, with larger deviations in the prediction of characteristic torque points, indicating the limitations of linearized parameters and motivating nonlinear model extensions. The approach enables reliable estimates at nominal voltage when direct measurements are not feasible.
Simulation-Based Study of Structural Changes in Electrical Time-Series Signals
This paper addresses the detection of changes in electrical signals typical for industrial and power systems, using statistical indicators. A dedicated MATLAB algorithm was developed to identify change points by tracking shifts in signal behavior and statistical properties. To evaluate the method, synthetic signals were generated through simulation to reproduce common patterns observed in these systems, allowing testing under different operating conditions and varying noise levels. The results demonstrate that the algorithm reliably detects change points across multiple scenarios, showing both flexibility and robustness. This study highlights the value of simulation-based signal generation as a controlled environment for testing detection methods and provides a foundation for future application to more complex real-world electrical signal analysis tasks.
Biomass Gasification Potential for Slovenia’s Green Transition
In 2024, approximately fifty percent of the total kilometers driven by passenger vehicles in Slovenia were attributed to diesel-powered automobiles, underscoring the persistent dependence of the transportation sector on fossil fuels, which are major contributors to greenhouse gas emissions and global warming. Research further substantiates that the transportation sector constitutes the nation's predominant source of greenhouse gas emissions. In this context, e-mobility emerges as a key strategy for Slovenia’s green transition in transportation. Additionally, biomass gasification represents a sustainable and environmentally friendly energy pathway that could support the country in achieving its environmental targets, while promoting the principles of the circular economy.
Consumer Protection in the Electricity Market in the European Union and Slovenia
The article examines consumer protection in the electricity market, focusing on vulnerable customers and the right to emergency supply. At EU level, it outlines the development from the energy legislative packages to Directive (EU) 2019/944, which strengthens consumer rights and requires Member States to define and protect vulnerable groups. In Slovenia, these issues are regulated by Article 33 of the Electricity Supply Act (ZOEE), implemented through the System Operating Instructions (SONDSEE) and the Energy Agency’s act on criteria for ensuring emergency supply. The article applies normative and comparative legal analysis, reviews the Energy Agency’s Annual Reports, and analyzes case law. The findings reveal a gap between regulation and practice, as only one request for emergency supply was approved in Slovenia, in 2019. It proposes clearer criteria, simpler procedures, and more effective consumer information, particularly for vulnerable groups, to ensure the right to emergency supply is realized in practice.
THE IMPACT OF WIND POWER PLANT SIZE ON ECONOMIC VIABILITY AT THE OJSTRICA LOCATION
Wind energy in Slovenia has not yet achieved a significant share in the energy resource mix, due primarily to the limited number of suitable locations and opposition from local communities. Nevertheless, interest in wind power plants is increasing, as they represent significant potential for utilising renewable energy sources. The paper analyses the economic viability of wind farm installation and electricity production at the proposed Ojstrica site in the Dravograd Municipality. Two scenarios were considered, involving wind turbines with capacities of 3.5 MW and 7 MW. Based on wind speed data, turbine power curves, and an electricity selling price of 75 EUR/MWh, the study calculated the maximum investment costs for each turbine type to ensure economic viability under the condition of a net present value (NPV) equal to zero. The results show that the maximum allowable investment is 5.99 million EUR for the 3.5 MW turbine and 15.60 million EUR for the 7 MW turbine.
CHEMICAL ANALYSIS OF THERMALLY AGED CABLES IN NUCLEAR POWER PLANTS
The paper presents findings on the implementation of various mechanical and chemical diagnostic procedures aimed at enhancing the monitoring of cable insulation conditions in Krško Nuclear Power Plant (NEK). This article introduces the advancement of four novel diagnostic testing methodologies for evaluating the mechanical and chemical properties of cable insulation: Indenter Modulus (IM), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TGA) and X-Ray Fluorescence Spectral Analysis (XRF). Experiments were performed on diverse samples of widely used nuclear-qualified cable polymer materials, including Ethylene Propylene Rubber (EPR) and Crosslinked Polyethylene (XLPE), all with a Chlorosulphonated Polyethylene (CSPE) jacket. Samples from various vintages were subjected to additional temperature ageing in many stages, to establish field testing acceptability requirements and assess the remaining lifespan of the polymer insulation. Diagnostic tests were performed and some preliminary results are reported.
ARTIFICIAL INTELLIGENCE -BASED EXERGY ANALYSIS OF AN ABSORPTION COOLING SYSTEM
An artificial intelligence (AI)-based exergy analysis of an absorption cooling system (ACS), utilizing a lithium bromide–water refrigeration cycle, is presented in this paper. The ACS is characterised by the utilisation of the intermediatepressure (IP) extraction steam from the steam turbine for its operation. The exergy analysis of the ACS is detailed, based on AI modelling through a machine learning algorithm, which predicts and optimises the ACS performance. The machine learning algorithm is validated using real process data obtained through ACS measurements via the supervisory control and data acquisition (SCADA) system. The AI results show that the ACS generates 126.71 kW of cooling for district cooling and 279.57 kW of heat, which is used for heating demineralised water. During the analysis period, the ACS consumed an average of 152.86 kW of IP steam, and operated with an average exergy efficiency of 17.3%. The study suggests that the average exergy efficiency of the ACS could be improved by using lower-quality steam, or even hot water, for operation.
ENERGY TRANSITION IN MUNICIPALITIES – A MODEL FOR SUSTAINABLE RENEWABLE ENERGY MANAGEMENT
This study explores optimal strategies for utilizing the electricity generated from already installed PV systems at the local level, aiming to reduce electricity costs and increase revenues through the sale of surplus electricity. Two scenarios are analyzed: (1) individual consumption of the generated electricity within each building and the sale of surplus electricity at the time of production, and (2) collective energy management through a municipal energy enterprise, where surplus electricity is distributed among buildings, and the remaining surplus is sold on the free market. By analyzing existing research and case studies, the study seeks to determine which strategy is more efficient regarding energy efficiency and financial viability, and to propose a model for the collective management of electricity generated from PV systems at the municipal level.
The Krško Nuclear Power Plant (NEK) operates based on a Pressurised Water Reactor (PWR), which utilises three loops for heat transfer: primary, secondary, and tertiary. Heat generation occurs in the primary loop; steam production takes place in the secondary loop; and waste heat is discharged in the tertiary loop. During outages, which occur every 18 months, the secondary systems are exposed to the atmosphere, increasing the risk of corrosion. To prevent this, in 2021, the plant used a chemical solution, Film Forming Amine (FFA), which formed a protective hydrophobic layer on the inner surfaces of the pipelines. In March 2021, during the first use of FFA, deviations were observed in the main feedwater (FW) flow measurements. This affected the reactor power calculations, leading to a 0.4–0.5 % reduction in plant output (approximately 4 MWe). The main feedwater flow is a critical parameter for secondary calorimetric calculations, and has the largest impact on error in the event of deviations. The power reduction was confirmed by comparing various process parameters, including changes in the primary loop temperature differences (ΔT), main steam flow (MS), and generator output vs. condenser vacuum. Since the measurement of the main feedwater flow contributes the most to the uncertainty of primary flow and reactor calorimetric calculations, NEK is focused on improving its accuracy. Developing a numerical model in the computer-based programming environment is proposed as part of further research. This model would enable independent calculations of the main feedwater flow, to reduce the impact of the FFA chemicals on the measurement readout and its associated calculations. The model will be based on thermodynamic equations and algorithms for determining the flow with lower uncertainty than the current system. Using this model, correction factors should be obtained to adjust the current venturi meter readings. Ultimately, this approach will ensure better plant management, reduce energy losses, and increase revenues for NEK and its stakeholders.
Copyright (c) 2024 Journal of Energy Technology
A REVIEW OF ARTIFICIAL INTELLIGENCE IN NUCLEAR POWER PLANTS
Nuclear power plants are recognised as complex systems, where maintenance is critical for ensuring safety and operational stability. Time-based preventive maintenance programmes are employed in most nuclear power plants, relying on periodic inspections to prevent equipment failures. However, this method is considered resource-intensive and not always efficient. An alternative is offered by Artificial Intelligence and condition-based maintenance, which allow early fault detection, reduce unnecessary maintenance tasks, and lower operational costs. The potential of Artificial Intelligence in nuclear power plants is vast, ranging from operational improvements to predictive maintenance. Techniques such as Supervised and Unsupervised Learning are highlighted as essential tools for fault detection, pattern recognition, and predictive modelling. In Supervised Learning, known input-output pairs are used to train models, while Unsupervised Learning is employed to identify hidden patterns in unlabelled data, which is particularly useful in the large, unstructured datasets found commonly in nuclear power plants. The challenges in integrating Artificial Intelligence into nuclear power plant operations shall be noted, including the lack of standardised procedures for selecting and applying algorithms. Despite these challenges, AI-driven tools, including Deep Learning and hybrid models, have shown promising results in fault detection and prediction in nuclear power plants. These advancements support the broader goal of improving safety and operational efficiency. In conclusion, although Artificial Intelligence has not yet been adopted fully across all nuclear power plants, it is seen as a promising advancement for the future of nuclear energy operations. Its implementation enhances fault detection, reduces operational risks, and ensures more reliable energy production.
THEORETICAL AND EXPERIMENTAL INVESTIGATIONS OF A WATER HAMMER IN SAVA RIVER KAPLAN TURBINE HYDROPOWER PLANTS
This paper deals with critical flow regimes that may induce an unacceptable water hammer in the Sava River Kaplan turbine hydropower plants. The rigid water hammer model is introduced first. The computational results are then compared with the results of measurements in two distinct hydropower plants (HPP): (i) The refurbished and upgraded Medvode HPP, and (ii) The newest Brežice HPP. Comparisons of the computed and measured results are examined for normal operating regimes. The water hammer in the two power plants is controlled by appropriate adjustment of the wicket gates and runner blades closing/opening manoeuvres. The agreement between the computed and measured results is reasonable.
ASSESSING THE EFFECTS OF A HYDROPOWER PLANT BASIN ON FISH SPAWNING IN AN UPSTREAM RIVER TRIBUTARY
This paper presents a combined modeling approach to evaluate the ecological effects on the habitat of an upstream tributary of a river with a series of hydropower plants. The influence is investigated of the last planned hydropower plant to be built, which has a large impact on the river ecosystem. The new hydropower plant basin will affect the tributary with hydropeaking in the upstream basin. A simulation was conducted of spawning conditions for two protected fish species. The analysis combined a hydro-morphological model with a fish module that considers the water depth and velocity necessary for fish reproduction. The different river discharge scenarios were simulated, incorporating the hydropeaking effects of the new hydropower plant basin on the upstream tributary. With the new hydropower plant, sustainable measures are planned to prevent the damaging negative impacts that could lead to the degradation of the river ecosystem and the destruction of the existing ecosystem at the river’s confluence. The results indicate that, after the hydropower plant begins operation, the habitat`s suitability will decrease, and the planned sustainable measures will not provide a fully satisfactory solution.
VERIFICATION AND VALIDATION OF STUDENT’S CFD TOOL ON THE VENTURI FLOW CASE
The main goal of this study is to investigate the usability of the CFD software ANSYS Student 2023 R1 for students` scientific research. To carry out this investigation, a comparison was carried out of the analytically calculated flow rates through a standard venturi tube with the results obtained by simulations of the flow in the specified program. Given that it is a student, free version of the program, which comes with certain limitations, proving its usability by performing verification and validation on known geometry would be of great benefit. To ensure comparability, a 3D model of the venturi tube was created in accordance with the ISO 5167 Standard. The flow rate was calculated on that selected geometry of the venturi tube, using the well-known equations of fluid mechanics. The selected geometry of the venturi tube was discretised in the ANSYS Student 2023 program, respecting all CFD rules. Comparison of these two sets of results showed a match within 5%.
HEAVY METAL CONTENT IN VEGETABLE GARDEN SOILS IN RELATION TO THEIR NATURAL BACKGROUND
Heavy metals (HM) are present in soil naturally [1], due to the weathering of the element-rich parent rock and by anthropogenic sources (industry, energy production, agriculture, traffic) [2– 4]. The agricultural sources of increased HM concentrations in soil are HM-containing fertilizers and pesticides. Agricultural soils are often considered polluted, and are therefore subject to soil contamination monitoring for food safety reasons. Allotments are particularly at risk from intensive gardening, the general overuse of fertilizers, soil conditioners, often seen as a means of improving soil quality, in some cases the overuse or misuse of pesticides and, in the past, the use of coal ash. In some cases, landowners are also receiving untested and potentially polluted soils from elsewhere. Therefore, the soils of the vegetable/allotment gardens are generally considered to be ‘highly anthropogenized'. According to Slovenian legislation [5], the HM concentration is considered elevated if the HM concentration in the soil is above the limit immission value (LIV), polluted if it is above the warning immission value (WIV) and critically polluted if it is above the critical immission value (CIV). The HM content was analyzed in the soils of 20 allotment gardens in the village of Legen (Municipality of Slovenj Gradec, Carinthia, Slovenia). The soil samples were dried, ground and sieved in the FEP laboratory, and analyzed ‘by Bureau Veritas Commodities (Canada) using Aqua Regia extraction to determine the 'pseudo-total content' for 37 elements (Ag, Al, As, Au, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, Hg, K, La, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Sc, Se, Sr, Te, Th, Ti, TI, U, V, W, and Zn), 10 of which (in the frames) are considered common HM soil contaminants. The comparison of the HM concentrations in the garden soils with the well-known rich natural geochemical background of the area showed that the values for all the compared metals, except Al, Fe, Ga, Sc, Th and Co, were higher than natural element backgrounds in the Eastern Alps and in Slovenia as a whole. The HM concentrations in the garden soils were within, or slightly above, the natural background values [1], but below the LIV, with the exception of Pb and Zn in four gardens, where the concentrations exceeded the WIV [6]. The garden soils in the Legen village area have been enriched anthropogenically, most likely by the introduction of manure, and, in one case, untested and contaminated soils from elsewhere. Most of the gardens are characteristically oversupplied with the nutrients P and K; the soils are moderately enriched with soil organic matter and have an average acidity of pH 6.7, which means that the soil is neutral.
HEAVY METAL CONTENT IN SOILS OF SELECTED HOP PLANTATIONS IN RELATION TO THEIR NATURAL BACKGROUND
Heavy metals (HM) are present in soil naturally [1], due to weathering of the element-rich parent rock and anthropogenic sources (industry, agriculture, traffic, energy production) [2–4]. The agricultural source of the increased HM concentrations in soil are HM-containing fertilisers and pesticides. Agricultural soils are often considered polluted, and are, therefore, subject to soil contamination monitoring for food safety reasons. Permanent crops are particularly at risk, due to the intensive and traditional (over)use of pesticides and fertilisers. Hop plantations are a special type of economically important permanent crop in the Lower Savinja region. The product, the dried hop cones, is mainly exported. The cultivation of hops requires intensive soil tillage, fertilisation, and, above all, constant protection of the hop plant by usage of pesticides. According to Slovenian legislation [5], the HM concentration is considered elevated if the HM concentration in the soil is above the limit immission value (LIV), polluted if it is above the warning immission value (WIV), and critically polluted if it is above the critical immission value (CIV). The HM content was analysed in the soils of 10 hop plantations in the Lower Savinja region. The soil samples were dried, ground and sieved in the FVO laboratory, and analysed by Bureau Veritas Commodities (Canada) using Aqua Regia extraction to determine the 'pseudo-total content' for 37 elements (Ag, Al, As, Au, B, Ba, Bi, Ca, Cd, Co, Cr, Cu, Fe, Ga, Hg, K, La, Mg, Mn, Mo, Na, Ni, P, Pb, S, Sb, Sc, Se, Sr, Te, Th, Ti, TI, U, V, W, and Zn), 10 of which (in the frames) are considered common HM soil contaminants. The HM concentrations in the soils of the hop plantations were within the natural background values [1] (below the LIV), with the exception of Cd, Cu and Zn, which were above the LIV in some cases. The Cd concentration was elevated in 90 % (it exceeded the LIV). The hop fields were not contaminated with Cd – as the concentration did not exceed the WIV. The Cu concentration was within the natural background values in 20 % of the hop plantations (well below the LIV), 30 % were elevated (exceeded the LIV), while 50 % were polluted with Cu (the Cu exceeded the WIV). The Zn concentration was below the LIV value in 80 % of the hop plantations, 10 % exceeded the LIV value, while 10 % of the hop plantations were considered to be polluted with Zn (the Zn exceeded the WIV value) [6]. As expected, we found that the soils of the hop plantations contained significantly increased, and, in some places, exceeded quantities of Cu and Zn, and in some cases also Cd. Elevated concentrations of HM may also be reflected in other parts of the environment, while the effects on food quality were not detected (i.e., elevated concentrations in beer).
ADDRESSING THE CHALLENGES TO THE INTRODUCTION OF BATTERY ENERGY STORAGE SYSTEMS IN RENEWABLE ENERGY UTILISATION SYSTEMS
The transition to sustainable energy sources is integral to addressing climate change and ensuring long-term environmental resilience. Battery Energy Storage Systems (BESS) play a pivotal role in this transition, by mitigating the intermittency of renewable energy sources such as wind and solar power. However, the widespread deployment of BESS faces significant challenges, including high implementation costs, environmental impacts, grid stability concerns and battery lifecycle management issues. This paper investigates these challenges systematically through a comprehensive literature review methodology, synthesising insights from peerreviewed articles, conference proceedings and technical reports. Common themes and recurring challenges related to BESS implementation are identified and categorised, encompassing technical, economic, regulatory and environmental factors. Furthermore, the effective mitigation strategies and solutions proposed in the literature are analysed and evaluated for their feasibility and applicability. The findings underscore the importance of innovative approaches, such as second-hand battery modules, sustainable production practices, the implementation of advanced operational strategies, and predictive maintenance algorithms, in enhancing the feasibility and efficacy of BESS integration. Additionally, policy incentives and collaborative efforts with utilities and grid operators are highlighted as crucial for promoting grid resilience and reliability. This research contributes to a nuanced understanding of the complexities inherent in advancing sustainable energy infrastructures, and provides valuable insights for policymakers, industry stakeholders, and researchers seeking to address the challenges of BESS deployment in renewable energy utilisation systems.
ENERGY MANAGEMENT IN MICROPROCESSOR-DRIVEN CIRCUIT DESIGN USING SLEEP MODES
The article explores the important significance of sleep mode in the design of microprocessorcentric electronic devices, emphasising energy efficiency, device longevity and environmental sustainability. Sleep mode enables devices to enter low-power states during periods of inactivity, conserving energy and extending battery life. Various levels of sleep modes are examined, ranging from light to deep sleep, each with unique power savings and system responsiveness advantages.1 The article also presents a case study involving an electronic circuit controlling sensors, actuators, LTE, WiFi and a geolocation module, where sleep mode is utilised to optimise power consumption. The system operates at varying activity levels, and the employment of sleep modes such as light sleep, deep sleep and hibernation, results in energy savings exceeding 70%. Light Sleep offers rapid responsiveness with moderate power savings, while Deep Sleep and Hibernate Mode maximise energy efficiency but require longer wake-up times. The design approach emphasises the importance of managing the system components carefully, and transitioning between different power modes to ensure an optimal balance between energy conservation and performance. Finally, the article discusses the broader environmental impact of sleep mode, noting its contribution to reducing devices' energy demands and carbon footprints. By integrating effective sleep mode strategies, designers can create energy-efficient systems that meet both consumer expectations and environmental responsibilities, supporting sustainability efforts in electronic device design.
ANALYSIS OF THE CAPACITY OF LiFePO 4 BATTERIES BASED ON THE RELEASED ELECTRONS
The lithium iron phosphate battery, or LiFePO 4, has been analysed in this article. Initially, a comprehensive overview was provided concerning the properties and chemistry of batteries. Subsequently, the core focus of the research was addressed, which centred on quantifying the number of electrons released per 1 cm2 in 1 second in one cell in the battery during charging. Additionally, comparisons were made, to ascertain whether batteries with capacities lower than the one selected for this study impact the number of electrons released during charging, assuming constant battery voltage, cell surface area and current, or whether the number of released electrons remains unaffected by the capacity variations. The analysis was conducted analytically, and demonstrated transparently using the MATLAB software package.
HARDWARE IN THE LOOP TESTING OF A PROTECTION MONITORING AND DIAGNOSTIC SYSTEM
Protection, automation, and control (PAC) devices are very important for the reliable operation of electric power systems (EPS), which can be improved further by monitoring the PAC devices. One way is to apply a protection monitoring and diagnostic (PMD) system, which was tested using a real-time digital simulator and two numerical protection relays in the hardware in the loop configuration. Furthermore, the communication between the protection relays and the PMD system was also tested, while the EPS faults were simulated in a safe environment on a digital simulator in real-time. When a fault occurs in the EPS, the PMD system performs the fault analysis, and generates a disturbance report within several minutes after the fault. The tested PMD system also gathers all protection relays' settings, thus reducing the workload of protection specialists significantly.
CONFIGURATION OF A FLAT ROOF SOLAR POWER PLANT FOR MAXIMUM ELECTRICITY PRODUCTION
Commercial solar power plants are often installed on larger industrial, warehouse and commercial buildings. Modern prefabricated constructions of such buildings dictate architectural solutions involving flat roofs, which are particularly suitable for the installation of larger solar power plants. This research investigates which configuration of solar module installation and which inclinations are suitable for implementation on a flat roof to achieve maximum annual electricity production. It aims to determine the maximum annual production per unit area and per installed power of the solar modules. The simulation results are conducted for all months of the year, and for the geographic latitude and longitude of the town of Lenart in Slovenia.
CONSERVATION OF FISH MIGRATIONS AT HYDROELECTRIC POWER PLANTS: FISH PASSAGE SYSTEMS AS AN ENVIRONMENTALLY RESPONSIBLE MEASURE
The geostrategic situation in the world is a stark reminder that, for any country seeking to be sovereign, it is essential to strengthen the degree of energy and food self-sufficiency as soon as possible, all the while also ensuring sustainable environmental and social development. In terms of renewable energy sources, Slovenia has the greatest privilege in being able to utilise hydropower and wood biomass for energy uses. The paper discusses the importance of implementing multipurpose and goal-oriented projects such as hydropower plants (HPPs), which fulfil a number of strategies set by the state and local communities. Since every human intervention in the environment has certain impacts, the paper shows how synergistic effects can be created between environmental protection and energy sector development through responsible environmental planning and implementation of the best possible measures, drawing from a practical example of the multipurpose construction project of HPPs on the lower course of the river Sava. The paper addresses the issue of fish migration and barriers in watercourses, presenting the current situation in Slovenia and worldwide. It also examines the success of fish passes at HPP Arto-Blanca, based on several years of monitoring. Such passes enable fish to migrate past hydropower plants, maintain healthy fish populations, preserve genetic diversity, and ensure the connectivity and preservation of the entire aquatic ecosystem. The example of the future Mokrice hydropower plant illustrates the trend and commitments in the planning of such passes in the future.
INFRARED THERMOGRAPHY IN THE DETECTION OF WATER STRESS IN PLANTS
Rastline in zeleni otoki v urbanih območjih so eden od načinov za ublažitev podnebnih sprememb in zmanjšanje povpraševanja po energiji za klimatske naprave. Tako kot ljudje so tudi rastline izpostavljene učinku mestnega toplotnega otoka, ki se kaže v tem, da so temperature zraka v urbanih območjih v povprečju za 2‒5 °C višje kot na podeželju. Poleg tega so rastline izpostavljene vodnemu stresu, ki nastane, ko količina razpoložljive vode presega ali pade pod potrebe rastlin po vodi. Prispevek prikazuje porast povpraševanja po električni energiji s posebnim poudarkom na Hrvaški, Sloveniji in državah s podobno porabo električne energije. Učinki mestnega toplotnega otoka so prikazani z grafično primerjavo iz novejše literature. Infrardeča termografija kot ena od metod za zaznavanje vodnega stresa je pojasnjena s fizikalnim ozadjem zaznavanja dolgovalovnega sevanja in primerjana z digitalno fotografijo blizu infrardečega sevanja. Predstavljeni so vsi možni vidiki detekcije sevanja, ki nastanejo pri termografski analizi. Podan je poseben pregled pomanjkanja vode, njegovi učinki pa so prikazani na primerih višine rastline in velikosti cvetov. Uporaba infrardeče termografije pri zaznavanju pomanjkanja vode je prikazana s termogrami pšenice na suhem polju in po namakanju. Na podlagi predstavljenega so sklepali o možnostih uporabe infrardeče termografije pri detekciji vodnega stresa.
Copyright (c) 2025 Journal of Energy Technology
METHODS FOR RECYCLING PHOTOVOLTAIC MODULES AND ELEMENT RECOVERY PROJECTIONS IN SLOVENIA
This paper aims to present different methods of recycling photovoltaic modules, which were researched by different institutes. Significant importance has been attributed to photovoltaic modules in the Renewable Energy sector, thereby contributing to the global transition towards sustainable energy sources. However, as the lifespan of these modules comes to an end, effective recycling methods will become crucial to minimize the environmental impact and resource depletion. This paper highlights recent advancements in photovoltaic module recycling technologies, focusing on predicting the potential mass of a specific element that could be recovered through recycling in Slovenia, considering the installed capacity of solar power plants, which is approximately 1105 MW. A projection of materials that can be obtained through the recycling process of photovoltaic modules was conducted based on current installed capacity, and it was discovered that up to 2150 tons of silicon and 1025 tons of copper could be obtained by the recycling process. The acquisition of various materials would have a significant role in the production of new photovoltaic modules, thereby enabling sustainable manufacturing and contributing substantially to the circular economy.
ANALYSIS OF AGED CABLES` INSULATION WITH X-RAY FLUORESCENCE SPECTROMETRY
The paper provides an analysis with X-ray fluorescence spectrometry of aged cable samples. The work encompasses a review of the electrical, mechanical and chemical properties, as well as measurement methods for determining those parameters. The analyses are based on physical principles that allow us to assess the condition of the cable insulation. Using the physical properties and measurement results, mathematical models can be formulated to describe the ageing of individual materials in the presence of specific influences. The goal of the paper is to establish the foundation for the development of a measurement method using X-ray spectral analysis. The methodology assumes that the presence of specific elements decreases or increases on the material's surface as it ages. By using a standard indenter modulus test, we can determine reference points for X-ray spectral analysis. Sampling these points on differently degraded cables enables the establishment of criteria for acceptable cable insulation.
CONCEPTUAL TECHNO-ECONOMIC ANALYSIS OF RETROFITTING A 210 MW THERMAL HEAVY-OIL POWER PLANT WITH A MOLTEN SALT THERMAL ENERGY STORAGE SYSTEM FOR RENEWABLE POWER: A CASE ANALYSIS OF TEC NEGOTINO
This study conducts a conceptual techno-economic analysis to explore the possibility of retrofitting a 210 MW thermal heavy-oil power plant, TEC Negotino, with a molten salt thermal energy storage system (a Carnot battery). The proposed approach enables storage of surplus or curtailed renewable electricity on the grid in the form of thermal energy. This initial exploration involves analysing the sensitivity of annual energy yield, load factor, total investment cost, annual O&M cost and levelized cost of a discharging electricity with varying discharging duration, thermal storage capacity and charging duration. The results demonstrate that the most favorable annual roundtrip efficiencies and lowest levelized cost of discharge electricity were obtained for longer discharge duration (in full load hours). This approach of the possibility of repurposing TEC Negotino not only prioritizes the potential for the comprehensive decarbonization of the thermal power plant, but also conserving the majority of jobs within the power plant, making it a sustainable and economically viable initiative.