1. IoT-based off-grid solar power supply : design, implementation, and case study of energy consumption control using forecasted solar irradiationMarijan Španer, Mitja Truntič, Darko Hercog, 2025, izvirni znanstveni članek Opis: This article presents the development and implementation of an IoT-enabled, off-grid solar power supply prototype designed to power a range of electrical devices. The developed system comprises a Photovoltaic panel, a Maximum Power Point Tracking (MPPT) charger, a 2.5 kWh/24 V high-performance LiFePO4 battery bank with a Battery Management System, an embedded controller with IoT connectivity, and DC/DC and DC/AC converters. The PV panel serves as the primary energy source, with the MPPT controller optimizing battery charging, while the DC/DC and DC/AC converters supply power to the connected electrical devices. The article includes a case study of a developed platform for powering an information and advertising system. The system features a predictive energy management algorithm, which optimizes the appliance operation based on daily solar irradiance forecasts and real-time battery State-of-Charge monitoring. The IoT-enabled controller obtains solar irradiance forecasts from an online meteorological service via API calls and uses these data to estimate energy availability for the next day. Using this prediction, the system schedules and prioritizes the operations of connected electrical devices dynamically to optimize the performance and prevent critical battery discharge. The IoT-based controller is equipped with both Wi-Fi and an LTE modem, enabling communication with online services via wireless or cellular networks.
Ključne besede: energy consumption control, forecasted solar irradiation, power management, off-grid power supply, photovoltaic, solar, IoT, LTE, Wi-Fi, ESP32
Objavljeno v DKUM: 14.11.2025; Ogledov: 0; Prenosov: 8
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2. Dynamic modeling and experimental validation of the photovoltaic/thermal systemKlemen Sredenšek, Eva Simonič, Klemen Deželak, Marko Bizjak, Niko Lukač, Sebastijan Seme, 2025, izvirni znanstveni članek Opis: The aim of this paper is to present a novel and comprehensive methodology for the dynamic modeling and experimental validation of a photovoltaic/thermal system. The dynamic model is divided into thermal and electrical subsystems, encompassing the photovoltaic/ thermal module and the thermal energy storage. The thermal subsystem of both the photovoltaic/thermal module and the thermal energy storage is described by a one-dimensional dynamic model of heat transfer mechanisms and optical losses, while the electrical subsystem is presented as an electrical equivalent circuit of double diode solar cell. Model validation was conducted on a modern experimental photovoltaic/thermal system over an extended operational period at a five-minute resolution, with validation days classified as sunny, cloudy, or overcast based on weather conditions, thereby demonstrating an applied approach. The results demonstrate the lowest deviation values reported to date, confirmed using six quantitative indicators. The added value of the proposed methodology, not previously addressed in the literature, lies in the following contributions: (i) comprehensive modeling of the entire photovoltaic/thermal system, (ii) accurate consideration of optical losses in the photovoltaic/thermal module, and (iii) long-term experimental validation. Overall, the proposed methodology provides a reliable and efficient framework for PV/T system design, optimization, and long-term performance assessment.
Ključne besede: photovoltaic/thermal system, thermal energy storage, dynamic modeling, experimental validation, heat transfer mechanism, temperature, electrical power
Objavljeno v DKUM: 10.11.2025; Ogledov: 0; Prenosov: 13
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3. Research on the modelling and analysis of the penetration of renewable sources and storage into electrical networksEva Simonič, Sebastijan Seme, Klemen Sredenšek, 2025, izvirni znanstveni članek Opis: To address the growing integration of renewable energy sources and storage systems into distribution networks, there is a need for effective tools that can assess the impact of these technologies on grid performance. This paper investigates the impact of integrating residential rooftop photovoltaic (PV) systems and battery energy storage systems (BESSs) into low-voltage (LV) distribution networks. A stochastic approach, using the Monte Carlo method, is applied to randomly place PV systems across the network, generating multiple scenarios for power flow simulations in MATLAB Simulink R2024b. The method incorporates real-world consumer load data and grid topology, representing a novel approach in simulating distribution network behaviour accurately. The novelty of this paper lies in its ability to combine stochastic PV placement with real-world load data, providing a more realistic representation of network conditions. The simulation results revealed that widespread PV deployment can lead to overvoltage issues, but the integration of BESSs alongside PV systems mitigates these problems significantly. The findings of this paper offer valuable insights for Distribution Network Operators, aiding in the development of strategies for optimal PV and BESS integration to enhance grid performance.
Ključne besede: photovoltaic system, battery energy storage system, low-voltage distribution network, Monte Carlo method, power flow
Objavljeno v DKUM: 03.11.2025; Ogledov: 0; Prenosov: 13
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4. Solar irradiance stability factorsBorut Jereb, 2024, izvirni znanstveni članek Opis: In the field of renewable energies, the logistical intricacies of production, as well as the use and storage of photovoltaic energy, have become critical issues. In addition to sheer quantity, the stability of this type of energy is a crucial factor in ensuring the reliability and consistency of power generation. This paper defines Solar Irradiance Stability Factors (SISFs) as indicators complementing electricity production. When planning solar energy production in each geographical area, both the quantity and stability of solar irradiance are necessary for exploitation and determining the quality of solar irradiance. While the average production of solar energy per unit area in each time interval is a widely used parameter in daily practice, the observation of the amplitude of solar irradiance and its influence on energy production in the observed time interval is currently still rare. The SISFs defined in this article are new metrics that mainly depend on the meteorological variability in an area, and the observed time intervals should be in the range of seconds, minutes, or even hours. Larger time
intervals are not helpful for the stability of solar irradiance in energy production and logistics from the source to the destination. They provide a complementary and more accurate measure of how suitable a particular geographical area is for producing solar energy.
Ključne besede: solar irradiance, stability metrics, photovoltaic energy, meteorological variability, geographical area
Objavljeno v DKUM: 23.09.2024; Ogledov: 0; Prenosov: 48
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5. Comparative analysis of batteries for photovoltaic systems : bachelor's thesisKristina Gočanin, 2023, diplomsko delo Opis: Renewable energies represent unlimited power sources that are significantly reducing greenhouse emissions. The possibilities and advantages of abundantly available solar energy are immense. However, some challenges are preventing solar energy from reaching its full potential regarding its efficiency and energy storage. Therefore, the main focus of this thesis is on electrochemical storage systems. The aim is to compare the currently leading technology – Li-ion battery to the most recent breakthrough in storage systems – the solid-state battery. The thesis includes a comparative analysis of the mentioned technologies, as well as the theoretical part that introduces solar energy and photovoltaic systems with their main components.
Ključne besede: photovoltaic system, energy storage, analysis, Li-ion battery, solid-state battery
Objavljeno v DKUM: 30.01.2024; Ogledov: 457; Prenosov: 57
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7. Simplified method for analyzing the availability of rooftop photovoltaic potentialPrimož Mavsar, Klemen Sredenšek, Bojan Štumberger, Miralem Hadžiselimović, Sebastijan Seme, 2019, izvirni znanstveni članek Opis: This paper presents a new simplified method for analyzing the availability of photovoltaic potential on roofs. Photovoltaic systems on roofs are widespread as they represent a sustainable and safe investment and, therefore, a means of energy self-suffciency. With the growth of photovoltaic systems, it is also crucial to correctly evaluate their global effciency. Thus, this paper presents a comparison between known methods for estimating the photovoltaic potential (as physical, geographic and technical contributions) on a roof and proposes a new simplified method, that takes into account the economic potential of a building that already has installed a photovoltaic system. The measured values of generated electricity of the photovoltaic system were compared with calculated photovoltaic potential. In general, the annual physical, geographic, technical and economic potentials were 1273.7, 1253.8, 14.2 MWh, and 279.1 Wh, respectively. The analysis of all four potentials is essential for further understanding of the sustainable and safe investment in photovoltaic systems.
Ključne besede: photovoltaic system, rooftop photovoltaic potential, economic potential, light detection and ranging, LiDAR
Objavljeno v DKUM: 05.12.2023; Ogledov: 386; Prenosov: 34
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8. Analysis of photovoltaic system with battery storage in winter periodJan Lokar, Peter Virtič, 2019, objavljeni znanstveni prispevek na konferenci Opis: Energy sources as a solar, wind and water energy are used in production of electrical energy. Their biggest advantage is that they are renewable and they are sustainable. On the other hand, production from renewable energy sources is limited by environmental conditions. Production of photovoltaic systems are dependent on solar radiation, temperature, incidence angle, shadowing and other variable quantities. That is why designing of photovoltaic system is complex. In this paper a photovoltaic system production analysis and consumption analysis in residential house are presented. With real measured data the consumption and production are compared and energy balance equations, battery charge and discharge model are defined and behaviour of battery storage system through the one day are analysed. In addition, the reactive energy production and consumption are also analysed.
Ključne besede: photovoltaic system, battery storage
Objavljeno v DKUM: 05.12.2023; Ogledov: 266; Prenosov: 20
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9. Efficiency of laser-shaped photovoltaic cellsEwa Korzeniewska, Mariusz Tomczyk, Łukasz Pietrzak, Miralem Hadžiselimović, Bojan Štumberger, Klemen Sredenšek, Sebastijan Seme, 2020, izvirni znanstveni članek Opis: The main aim of this paper is to analyze the influence of laser shaping of the photovoltaic cell based on its efficiency. The authors described both process of the monocrystalline photovoltaic cell manufacturing, its efficiency, and the possibilities of usage in architecture and the process of creating the photovoltaic cells of unconventional shapes by using laser technology. A method for cutting photovoltaic cells using a fiber laser was presented as well as the parameters of the laser cutting process. The described method allows cutting the massively produced silicon cells according to the predetermined trajectory. Using the proposed process parameters, satisfactory cutting edge quality, and negligible impact of the laser beam on changes in the structure of the photovoltaic cell active layers were achieved. In each cycle of structure cutting, only a small part of the material is removed (from 1 to 2 mikro), and depending on the thickness, the process is repeated from 50 to 300 times. It has been shown that the efficiency of the modified cells depends on the ratio of their surface area to the laser cutting line.
Ključne besede: photovoltaic cells, efficiency, photovoltaic cell modification, laser modification, silicon cells
Objavljeno v DKUM: 15.11.2023; Ogledov: 389; Prenosov: 35
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10. Solar photovoltaic tracking systems for electricity generation : a reviewSebastijan Seme, Bojan Štumberger, Miralem Hadžiselimović, Klemen Sredenšek, 2020, pregledni znanstveni članek Opis: This paper presents a thorough review of state-of-the-art research and literature in the field of photovoltaic tracking systems for the production of electrical energy. A review of the literature is performed mainly for the field of solar photovoltaic tracking systems, which gives this paper the necessary foundation. Solar systems can be roughly divided into three fields: the generation of thermal energy (solar collectors), the generation of electrical energy (photovoltaic systems), and the generation of electrical energy/thermal energy (hybrid systems). The development of photovoltaic systems began in the mid-19th century, followed shortly by research in the field of tracking systems. With the development of tracking systems, di%erent types of tracking systems, drives, designs, and tracking strategies were also defined. This paper presents a comprehensive overview of photovoltaic tracking systems, as well as the latest studies that have been done in recent years. The review will be supplemented with a factual presentation of the tracking systems used at the Institute of Energy Technology of the University of Maribor.
Ključne besede: solar energy, photovoltaic tracking system, tracking strategies, drive system, degree of freedom
Objavljeno v DKUM: 15.11.2023; Ogledov: 436; Prenosov: 48
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