Impact of tilt angle, dust deposition, and humidity on potential induced degradation and electrical performance of crystalline silicon photovoltaic modules: an experimental study

Introduction. Photovoltaic (PV) modules constitute the backbone of renewable energy systems, yet their performance is compromised by degradation mechanisms, particularly potential induced degradation (PID), which causes rapid power losses through ionic migration under high voltage stress, creating p...

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Дата:2026
Автори: Khammassi, Z., Jeridi, A., Khaterchi, H., Zaafouri, A.
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Мова:Англійська
Опубліковано: National Technical University "Kharkiv Polytechnic Institute" and Аnatolii Pidhornyi Institute of Power Machines and Systems of NAS of Ukraine 2026
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Electrical Engineering & Electromechanics
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author Khammassi, Z.
Jeridi, A.
Khaterchi, H.
Zaafouri, A.
author_facet Khammassi, Z.
Jeridi, A.
Khaterchi, H.
Zaafouri, A.
author_institution_txt_mv [ { "author": "Z. Khammassi", "institution": "University of Tunis" }, { "author": "A. Jeridi", "institution": "University of Tunis" }, { "author": "H. Khaterchi", "institution": "University of Tunis" }, { "author": "A. Zaafouri", "institution": "University of Tunis" } ]
author_sort Khammassi, Z.
baseUrl_str http://eie.khpi.edu.ua/oai
collection OJS
datestamp_date 2026-07-01T21:42:56Z
description Introduction. Photovoltaic (PV) modules constitute the backbone of renewable energy systems, yet their performance is compromised by degradation mechanisms, particularly potential induced degradation (PID), which causes rapid power losses through ionic migration under high voltage stress, creating parasitic shunts that reduce shunt resistance Rsh and energy output. Problem. Although the influence of moisture and temperature has been widely investigated, the combined contribution of operational and environmental factors such as dust soiling remains insufficiently clarified. Goal. This work assesses dust as a contributor to potential induced degradation focusing on the combined effects of tilt angle, dust exposure and dust-moisture interaction on insulation integrity and degradation susceptibility. Methodology. A comparative experimental study was conducted on 3 identical crystalline-silicon PV modules without bypass diodes, installed at tilt angles of 20°, 30° and 40°. A controlled and uniform layer of sandy dust (maximum particle size about 150 μm) was deposited on the front surface. Insulation resistance between the frame and the front glass was measured at three locations (bottom, middle and top) under dry conditions and then at relative humidity above 80 %. The modules were subsequently subjected to a DC electrical stress of 1 kV, followed by cleaning. Electrical performance was evaluated under identical irradiance and temperature conditions using current-voltage (I-V) and power-voltage (P-V) characterization to extract the fill factor (FF) and Rsh. Results. Lower tilt angles (20°) promoted non-uniform dust accumulation, reducing insulation resistance and increasing leakage currents. High humidity intensified these effects, creating localized PID-prone regions. Post-cleaning, modules at 20° exhibited significantly lower FF and Rsh compared to 40°, indicating persistent degradation and incomplete recovery. Scientific novelty. This work establishes dust as an active PID initiator rather than merely an optical attenuator, uniquely examining coupled effects of tilt angle and dust-moisture interaction on PID susceptibility through moisture-assisted surface conduction pathways. Practical value. Appropriate tilt-angle selection and cleaning strategies are essential to preserve insulation integrity, limit leakage currents, mitigate degradation risk and maintain PV performance in dusty and humid environments. References 38, tables 6, figures 19.
doi_str_mv 10.20998/2074-272X.2026.4.08
first_indexed 2026-07-02T01:00:17Z
format Article
fulltext Electrical Engineering & Electromechanics, 2026, no. 4 55 © Z. Khammassi, A. Jeridi, H. Khaterchi, A. Zaafouri UDC 621.383.51:621.311.243 https://doi.org/10.20998/2074-272X.2026.4.08 Z. Khammassi, A. Jeridi, H. Khaterchi, A. Zaafouri Impact of tilt angle, dust deposition, and humidity on potential induced degradation and electrical performance of crystalline silicon photovoltaic modules: an experimental study Introduction. Photovoltaic (PV) modules constitute the backbone of renewable energy systems, yet their performance is compromised by degradation mechanisms, particularly potential induced degradation (PID), which causes rapid power losses through ionic migration under high voltage stress, creating parasitic shunts that reduce shunt resistance Rsh and energy output. Problem. Although the influence of moisture and temperature has been widely investigated, the combined contribution of operational and environmental factors such as dust soiling remains insufficiently clarified. Goal. This work assesses dust as a contributor to potential induced degradation focusing on the combined effects of tilt angle, dust exposure and dust-moisture interaction on insulation integrity and degradation susceptibility. Methodology. A comparative experimental study was conducted on 3 identical crystalline-silicon PV modules without bypass diodes, installed at tilt angles of 20°, 30° and 40°. A controlled and uniform layer of sandy dust (maximum particle size about 150 μm) was deposited on the front surface. Insulation resistance between the frame and the front glass was measured at three locations (bottom, middle and top) under dry conditions and then at relative humidity above 80 %. The modules were subsequently subjected to a DC electrical stress of 1 kV, followed by cleaning. Electrical performance was evaluated under identical irradiance and temperature conditions using current-voltage (I-V) and power-voltage (P-V) characterization to extract the fill factor (FF) and Rsh. Results. Lower tilt angles (20°) promoted non-uniform dust accumulation, reducing insulation resistance and increasing leakage currents. High humidity intensified these effects, creating localized PID-prone regions. Post-cleaning, modules at 20° exhibited significantly lower FF and Rsh compared to 40°, indicating persistent degradation and incomplete recovery. Scientific novelty. This work establishes dust as an active PID initiator rather than merely an optical attenuator, uniquely examining coupled effects of tilt angle and dust-moisture interaction on PID susceptibility through moisture-assisted surface conduction pathways. Practical value. Appropriate tilt-angle selection and cleaning strategies are essential to preserve insulation integrity, limit leakage currents, mitigate degradation risk and maintain PV performance in dusty and humid environments. References 38, tables 6, figures 19. Key words: photovoltaic performance, potential-induced degradation, tilt angle, dust deposition. Вступ. Фотоелектричні (PV) модулі є основою систем відновлюваної енергетики, проте їхня ефективність знижується внаслідок деградаційних процесів, зокрема потенціально-індукованої деградації (PID), яка спричиняє швидкі втрати потужності через міграцію іонів під дією високовольтного електричного поля, утворення паразитних шунтів, зменшення шунтового опору Rsh та зниження енергетичної продуктивності. Проблема. Незважаючи на те, що вплив вологи та температури досліджено достатньо широко, сумарний вплив експлуатаційних і навколишніх факторів, зокрема забруднення пилом, залишається недостатньо вивченим. Мета. Оцінити вплив пилу як чинника потенціально-індукованої деградації з урахуванням сумісної дії кута нахилу, пилового забруднення та взаємодії пилу з вологою на цілісність ізоляції та схильність до деградації. Методика. Проведено порівняльне експериментальне дослідження трьох однакових кремнієвих PV модулів без обвідних діодів, встановлених під кутами нахилу 20°, 30° та 40°. На фронтальну поверхню наносився контрольований рівномірний шар піщаного пилу з максимальним розміром частинок близько 150 мкм. Опір ізоляції між рамою та фронтальним склом вимірювали у трьох точках (нижня, середня та верхня частини) спочатку в сухих умовах, а потім при відносній вологості понад 80 %. Після цього модулі піддавали дії постійної напруги 1 кВ, а далі виконували очищення поверхні. Електричні характеристики оцінювали за однакових умов освітленості та температури шляхом аналізу вольт-амперних (I–V) та вольт-потужних (P–V) характеристик із визначенням коефіцієнта заповнення (FF) та шунтового опору Rsh. Результати. Менші кути нахилу (20°) сприяли нерівномірному накопиченню пилу, що призводило до зниження опору ізоляції та збільшення струмів витоку. Висока вологість посилювала ці ефекти, формуючи локальні області, схильні до PID. Після очищення модулі з кутом нахилу 20° демонстрували значно нижчі значення FF та Rsh порівняно з модулями з кутом 40°, що свідчить про стійку деградацію та неповне відновлення характеристик. Наукова новизна. У роботі пил розглядається не лише як оптичний послаблювач випромінювання, а як активний чинник ініціювання PID. Уперше детально досліджено сумісний вплив кута нахилу та взаємодії пилу з вологою на схильність до PID через поверхневі провідні шляхи, утворені за участю вологи. Практична значимість. Правильний вибір кута нахилу та стратегій очищення є важливими для збереження цілісності ізоляції, обмеження струмів витоку, зменшення ризику деградації та підтримання ефективної роботи PV модулів у запилених і вологих умовах. Бібл. 38, табл. 6, рис. 19. Ключові слова: фотоелектричні характеристики, потенціально-індукована деградація, кут нахилу, осадження пилу. Introduction. The current global energy and environmental context is characterized by an ever- increasing demand for primary energy sources. Despite significant advances in renewable energy deployment, fossil fuels still account for the majority share of the global energy portfolio [1]. According to the International Energy Agency, global energy consumption could increase by up to 45 % between 2022 and 2030, driven mainly by population growth and rapid industrialization in developing countries. This upward trend is expected to further elevate carbon dioxide (CO2) emissions, the principal greenhouse gas released from fossil fuel combustion, which is a major contributor to global warming and climate change. These environmental impacts directly threaten key sectors such as agriculture and water resources [2–5]. To mitigate these challenges, it is imperative to accelerate the transition towards sustainable, renewable, and economically viable energy alternatives. Renewable energy systems, including solar, photovoltaic (PV), wind, hydropower, biomass and geothermal sources, offer promising pathways to meet this goal. Among these, PV technology has emerged as one of the most reliable and cost-effective solutions for sustainable electricity generation. The global solar PV market is experiencing rapid growth in support of the energy transition and the rising demand for clean electricity. As of 2024, global PV capacity has reached 1.6 TW up from 1.2 TW in 2022, with most of it installed over the past twelve years. China and the USA are leading this expansion, achieving record growth in 2023. The market is expected to continue expanding, fueled by high-efficiency modules, decreasing costs, and emerging applications such as hydrogen production and water desalination [6–8]. The main part of a solar system is the module. A good PV module retains more than 80 % of its power output for many years, which is why manufacturers guarantee reliable operation for over 25 years. However, PV systems can lose performance and lifespan due to defects and environmental factors. Production, transport, installation and weather conditions are major causes of damage. Understanding these issues and improving quality control are key to ensuring long-term reliability The IEC 61215-1:2021 56 Electrical Engineering & Electromechanics, 2026, no. 4 standard requires accelerated tests to validate the robustness and long-term reliability of PV modules under outdoor conditions [9, 10]. Despite their widespread global adoption as efficient renewable energy sources, PV systems still face several persistent technical challenges. Faults may occur at the PV generator level, such as hot spots and microcracks, as reported in [11], or at the power-conversion stage (inverter/converter), as discussed in [12]. In addition, dust accumulation (soiling) reduces the transmittance of the incident radiation and degrades conversion efficiency, particularly in arid regions. Numerous recent studies have investigated the impact of dust on PV system performance under different climates, installation configurations, and cleaning approaches, highlighting the need for advanced predictive models and optimized maintenance strategies [13]. For instance, in a year-long study conducted in Jeddah, researchers evaluated the impact of tilt angle on dust accumulation. Results showed that, after 6 months without rain, flat panels lost over 80 % of their power, while panels tilted at 45° performed best. Over the entire year, a 25° tilt angle offered the best energy yield, demonstrating the importance of angle optimization for dusty environments [14]. Another study focusing on panel layout found that tilt angle, height, and wind direction influence dust deposition patterns, with the first row of panels collecting more dust. Adequate spacing between panels can help mitigate this effect [15]. Similarly, tests in Krakow revealed that low-tilt panels accumulate more dust. Interestingly, light rain may worsen dust buildup, whereas heavy rain (>38 mm/h) can effectively clean the surface [16]. In China, microanalytical assessments across nine cities confirmed that dust-related efficiency losses range from 4.5 % to over 7 % annually, depending on the panel tilt. This study also provided predictive models to improve cleaning schedules and tilt optimization [17]. The situation is further illustrated by field tests in Pakistan, where 6 weeks of dust exposure led to a 15–25 % drop in panel efficiency, with higher temperatures and dust densities amplifying losses [18]. In addition, simulations showed that wind speeds above 5 m/s help reduce dust buildup, while horizontal surfaces (e.g., 23° tilt) attract more deposition. Wind direction, however, had limited influence on the accumulation rate [19]. A study in Sohar, Oman, examined the composition of dust – mainly sand (65 %), followed by cement, gypsum, and industrial ash. The impact of these particles varied: while some affected voltage more than current, materials like cement and ash caused the most significant power losses [20]. From a modeling perspective, another study confirmed that dust particle size and tilt angle directly influence accumulation. Particles around 150 μm resulted in the highest deposition. An empirical model was developed to predict power loss based on tilt angle, supporting better design and maintenance [21]. Importantly, dust does not only impact optical properties. It can also increase the surface conductivity of PV modules— especially under high temperatures—leading to a rise in leakage currents and a higher risk of potential induced degradation (PID). In extreme cases, conductivity rose by 118 %, causing a 3.48 % drop in activation energy and jeopardizing long-term system reliability [22]. PID has been identified across all PV technologies and in nearly every operational climate, although its occurrence remains relatively infrequent. When it does occur, however, it can lead to severe performance losses within a short period, making it a key factor in accelerating degradation, particularly in newer module generations. PID can cause severe power losses in P-type silicon PV modules, with up to 53 % reduction after one year, confirmed by voltage shifts and imaging. It results mainly from leakage currents, with power drops reaching 18.7 % in just 96 hours, as shown by changes in I–V curves and EL images. These effects pose real challenges for operators and highlight practical ways to detect PID in the field [23, 24]. Various studies highlight the significant impact of PID on mono- and multi-crystalline silicon modules, with power losses reaching nearly 19 % after just 96 h of continuous stress. These investigations deepen the understanding of the physical mechanisms involved, propose evaluation methodologies, identify mitigation strategies, and explore recovery solutions depending on environmental conditions [25]. In parallel, other research [26–28] focuses on common defects found in PV modules, such as cell cracks and hot spots, whose detection and monitoring help improve system reliability and extend service life. In the context of the rapid expansion of large- scale PV plants, designers seek to maximize profitability while minimizing investment and operational costs. One widely adopted approach is to increase the voltage of PV strings by connecting more modules in series. This configuration reduces ohmic losses in the wiring and optimizes costs by decreasing the number of cables, connectors, junction boxes, and inverters required. As a result, system voltage levels have gradually increased from 600 V in the 1990s to around 1  kV by 2010, with the current industry standard trending toward 1.5 kV and research exploring even higher levels. Since it was first documented in 2010, PID has been extensively investigated to clarify its underlying mechanisms and to develop suitable mitigation measures. Its relevance has grown considerably in recent years due to its potential to cause severe module failures under specific conditions [29, 30]. Additional studies [31] have analyzed the recombination behavior of PID-affected modules and assessed the mismatch losses caused by performance differences between degraded and unaffected modules. The shading- induced mismatch effect, which can amplify such losses, is addressed in reference [32]. PID has direct implications for maximum power point (MPP) tracking techniques, as discussed in [33, 34]. An experimental study compares two identical PV modules, with one exposed to voltage stress to observe changes in insulation and leakage resistance. The results show that higher voltage and humidity accelerate the decrease in insulation resistance and Rsh, which increases PID effects and makes maximum power extraction more difficult [35]. In addition to field observations, numerical approaches have been used to better understand and predict soiling behavior. Dust deposition reduces optical transmittance and, consequently, power output and module lifetime; discrete element modeling further indicates that the tilt angle strongly governs particle accumulation, while wind speeds above 5 m/s tend to remove deposits, and wind direction has only a minor influence. The deposited mass also increases with exposure time, and simulations show good agreement with transmittance-based measurements, with an average deviation of about 3.41 % [36]. However, few studies have analyzed the combined impact of dust, module tilt angle, and dry or humid environmental conditions on the performance of PV modules. Electrical Engineering & Electromechanics, 2026, no. 4 57 Goal. This work assesses dust as a contributor to potential induced degradation, focusing on the combined effects of tilt angle, dust exposure, and dust–moisture interaction on insulation integrity and degradation susceptibility. For this reason, an experimental methodology was designed to evaluate PID in PV modules subjected to dust deposition under controlled conditions representative of real outdoor environments. Three identical PV modules, installed at tilt angles of 20°, 30° and 40° and without bypass diodes, were selected to investigate the combined effects of inclination and soiling on Rsh Dust samples were collected from a desert area near PV installations in Tunisia. The collected material, characterized by an average particle size of approximately 150 µm, was applied using a controlled-deposition system to ensure a uniform dust layer across each module surface. Two environmental conditions were considered: dry and humid. Insulation resistance measurements were performed at constant temperature by applying a DC voltage up to 1 kV using an insulation tester. The same voltage levels were used to impose a controlled electrical stress on the modules in order to reproduce high-potential PID-inducing conditions. Following the stress application, the I–V characteristics of each module were recorded, and the corresponding Rsh values were extracted for comparative analysis. Methods. Modeling of PV string elements. A PV cell is the elementary building block of a solar module. It intercepts solar irradiance and converts it into electrical energy via the PV effect, behaving essentially like a current source. Under illumination, the cell can deliver a relatively high current – depending on its size and format (M2, M4, G1, M6 or half-cell) – but only a small voltage, typically about 0.4–0.6 V, which limits the power of a single cell. To obtain practical power levels, many cells are interconnected in series and/or in parallel and then encapsulated together to form a PV module. Among the various PV cell architectures, passivated emitter and rear cell (PERC) technology has taken the lead in recent years, progressively replacing the older back surface field (BSF) design. Regarding PV cell technologies, the BSF cell (Fig. 1), was the standard industrial solution up to around 2015. It is based on p-type crystalline silicon and features a highly doped rear side, most commonly realized with aluminum (Al-BSF), to limit charge-carrier recombination. A thin aluminum layer is deposited by screen printing and then fired so that part of the aluminum diffuses into the silicon, forming a p+ region that creates an internal electric field. This field pushes minority carriers (electrons) away from the rear surface, reduces recombination losses, and enhances the open-circuit voltage, enabling typical efficiencies of about 17 % in mass production and up to roughly 19 % in laboratory cells. Despite its robustness and straightforward fabrication, BSF technology has been overtaken by more advanced concepts such as PERC, HJT and TOPCon, which achieve higher efficiencies and superior outdoor performance. N‐Doped Silicon  P‐Doped Silicon  Dopé p+   (Al‐BSF)1E 2E 11 23 4 5 6 23 4 5 6 A A Section A‐A P‐Type Cell  C ‐ Si Back Surface Field (BSF) cell 1 - Front Contact 2 - Anti-Reflextion Passivation layer SiNx 3 - N-Type Silicon layer (emitter) 4 - P-type silicon bulk 5 - Back surface field 6 - Rear Contact by Al Fig. 1. Architectural model of a BSF solar cell Since around 2015, PERC technology (Fig. 2) has progressively replaced traditional BSF cells thanks to its more efficient rear-side passivation and resulting gain in efficiency. Still relying on crystalline silicon (mono- or multicrystalline), a PERC cell maintains a strongly doped aluminum rear surface, but adds one or more passivation layers together with a back reflector to further suppress carrier recombination and improve light trapping. Localized rear contacts are used to optimize the extraction of charge carriers. This architecture effectively reduces electrical losses and delivers higher conversion efficiencies, with a particular advantage under low irradiance or elevated operating temperatures, where standard cells typically suffer from increased rear-side heating. The passivation layers, most commonly aluminum oxide (Al2O3), silicon nitride (SiNx), or combinations of dielectric films, serve to protect the silicon surface, limit defect-related recombination, and support stable performance over the module’s lifetime. 3E A A B B 11 23 4 5 6 2E 7 8 Section A‐A Dopé N (P) Dopé P   (B) 4 6 7 8 23 Section  B‐B Dopé N (P) Dopé P   (B) Dopé p+   (Al‐BSF)1E 2E 4 5 6 23 P‐Type Cell  C ‐ Si Passivated Emitter Rear Contact (PERC) cell 1 - Front Contact 2 - Anti-Reflextion Passivation layer 3 - N-Type Silicon layer 4 - P-type silicon bulk 5 – Local Back surface field 6 – Aluminium Rear Contact 7 – Al₂O₃ Passivating layer 8 – SiNx Capping layer Fig. 2. Architectural model of a PERC solar cell Al2O3 is widely used in PERC cells to passivate the rear side: it neutralizes surface defects (chemical passivation) and creates an internal electric field that repels electrons, reducing recombination and increasing the open- circuit voltage (Voc) and short-circuit current (Isc). A SiNx layer is often added on top to serve as an anti-reflective coating, an additional passivation layer, and a protective barrier, further improving the module’s efficiency, durability and light reflectivity. In this work, with reference to the previously discussed technologies, which rely on the presence of 2 junctions each generating a distinct electric field, we have chosen to adopt a two-diode mathematical model to more accurately reflect the real operating behavior of these cells. This more advanced approach, compared to the single-diode model, uses 7 parameters to describe their electrical performance in detail. These include the photocurrent (Iph), which is generated by incident irradiance (G, W/m2), directly proportional to light intensity and affected by temperature (T, K), as well as 2 saturation currents (I01 and I02) that account for recombination losses in the main junction and in the quasi- neutral regions, respectively. The ideality factors (n1, n2) characterize the dominant transport mechanisms for each diode. Additionally, the model includes a series resistance (Rs), which accounts for ohmic losses occurring in the contacts, metal fingers, the metal-semiconductor interface, as well as the interconnections between multiple PV cells; and a Rsh that models leakage currents resulting from defects or irregularities within the cell. Rs RshD2D1 Iph ID2 IshID1 G : Solar Irradiation Ipv Vpv Load Fig. 3. Mathematical model of a PV cell 58 Electrical Engineering & Electromechanics, 2026, no. 4 The current (Ipv) and voltage (Vpv) delivered by the cell depend on the characteristics of the connected load. Referring to the equivalent model (Fig. 3) and applying Kirchhoff’s current law, the equation describing the (I-V) relationship of the PV cell can be written as:  shDDphpv IIIII  21 , (1) where Ipv is the output current of the double diode model; Iph is the photocurrent. Equations (2) – (4) respectively define the currents through the 2 diodes, ID1 and ID2, and the current flowing through the shunt resistor Ish:                 1exp 1 011 t pvspv D Vn IRV II ; (2)                 1exp 2 022 t pvspv D Vn IRV II ; (3)   shpvspvsh RIRVI  ; (4) qkTVt  , (5) where the thermal voltage Vt of the diode is determined using the Boltzmann constant k; q is the electron charge; T is the operating temperature of the cell. The saturation current is influenced by temperature, the surface area of the diode (and thus the PV cell), and the properties of the junction. It varies exponentially with temperature and can be represented as:                          opref g ref op sc TTkn qE T T II 11 exp 1 3 01 ; (6)                          opref g ref op sc TTkn qE T T II 11 exp 2 3 02 ; (7)    0G G TTkII refopiscph  , (8) where Isc is the PV cell’s short-circuit current; T represents its actual operating temperature; Tref is the reference temperature used for performance comparison; Eg is the optical bandgap of the cell material; n1, n2 are the diode ideality factors, which generally lies between 1 and 2; Top is the absolute temperature; I01, I02 are the diode’s saturation currents; ki is the temperature coefficient related to the short-circuit current; G0 is the irradiance under standard test conditions (STC), whereas G is the actual irradiance under real operating conditions [37]. PV module is a device designed to capture solar radiation and convert it into electrical energy through the PV effect; his based characteristics as shown in Table 1. It is one of the key components of a PV system. The module is composed of an array of identical PV cells, interconnected in series and/or in parallel in order to achieve the desired electrical characteristics: voltage, current and fill factor (FF). To obtain a sufficiently high voltage at the module terminals, the cells are generally connected in series, which increases the overall voltage and reduces ohmic losses. However, when the number of series-connected cells is large, partial or total shading of a single cell, or any change in its electrical characteristics, leads to a reduction in the current it can deliver. The affected cell then becomes reverse-biased, causing local overheating and the formation of hot spots, which may damage the cells and degrade the operation of the module. The integration of bypass diodes is therefore essential to mitigate these phenomena. Moreover, PV cells represent only one part of the laminated structure of the module. This structure also includes the packaging (protective glass, encapsulant and backsheet), the internal circuitry (electrodes, ribbons and interconnections), bypass diodes, junction boxes, the mechanical frame, as well as cables and connectors. All of these elements contribute to the overall reliability and durability of the PV module. Table 1 Example of characteristics of a PV module Characteristics Value Maximum power Pmax, W 165 Open-circuit voltage Voc, V 23.45 Short-circuit current Isc, A 8.8 Voltage at maximum power Vmpp, V 19.4 Current at maximum power Impp, A 8.51 Maximum system voltage V, V 1000 Temperature coefficient for power Pmax, % –0.45 Number of cells connected in series Ns, cellules 36 Diode quality factor 1.3 Series resistance Rs, Ω 0.15 Parallel resistance Rsh, Ω 120 Optical band gap of the material Eg, eV 1.1 PID in PV systems. In PV systems, modules are typically connected in series to reach the voltage range required by the inverter, which results in high voltage levels within the DC string. Under these conditions, the DC-side configuration (grounding scheme, insulation level and protection devices), as well as correct, standards- compliant grounding, become critical parameters to ensure safe and stable operation of the installation. Grounding all accessible metallic parts, especially PV module frames, is essential to dissipate leakage currents, reduce the risk of electric shock and insulation faults, and lower the likelihood of degradation phenomena such as transient overvoltage or certain accelerated aging mechanisms, thereby directly improving the long-term reliability of the system. Moreover, depending on the inverter technology (with or without an isolation transformer) and the selected grounding scheme, a significant potential difference may develop between the metallic frame and the PV cells. This electrical stress promotes PID, which accelerates array aging and leads to performance losses. Transformerless inverters, which provide no galvanic isolation between the DC and AC sides, commonly operate with a floating DC grounding scheme. This approach is cost-effective and widely used, particularly in humid climates; however, the lack of a defined reference potential can allow a negative bias to build up along the PV string. This bias drives PID through the gradual accumulation of charges at the cell surface and within the encapsulant, disturbing the internal electric field and causing a progressive, and sometimes irreversible, reduction in conversion efficiency and energy yield. By contrast, positive pole grounding using a transformer-based inverter provides galvanic isolation, but it is seldom adopted because it can worsen PID by imposing a high negative voltage on the modules located at the end of the string, increasing their vulnerability. Finally, negative pole grounding (also with a transformer-based inverter), as shown in Fig. 4, keeps the PV cells at a positive potential with respect to the frame, thereby mitigating PID-related stress and enhancing long-term module reliability. Nevertheless, the sustained positive bias can increase Electrical Engineering & Electromechanics, 2026, no. 4 59 susceptibility to corrosion in coastal or highly humid environments, which is why this configuration is generally preferred in dry or moderately humid sites. DC AC GRID  CONNECTED Isolated InverterPV array Transformer Pv+ Pv‐ Fig. 4. Grounding topology for the negative pole of the PV string The main cause of PID is the high voltage between the solar cells and the glass surface at the front of the module. PID directly impacts the core of power generation, the PV cells, by increasing the leakage current. In this context, leakage current is defined as the portion of the current that flows from the base to the emitter while bypassing the external load. This mechanism is illustrated in Fig. 5, 6, which shows the various leakage paths within the module as functions of its tilt (or incidence) angle and the thickness of the dust layer accumulated on its surface. For analytical purposes, the total leakage current can be decomposed into five distinct components. First, the current may escape through the sodalime glass and the water molecules present on its surface (I1). Second, it may flow through the dust layer deposited on the module (I5). Third, leakage can occur due to electrons or ions located on the front surface of the cell (I2). Fourth, the current can pass through the ethylene-vinyl acetate (EVA) encapsulation layer (I3). Finally, fifth, part of the current may leak through the rear contact, thereby completing the circuit (I4). Fig. 5. Leakage current caused by the PID effect SiNx (Anti-reflective coatin) Cell N-Doped Silicon P-Doped Silicon Dopé p+ (Al-BSF) Rear contact by Al 4 4 Detail 1 Grounding systemVPID VCell 1 dust deposition 3 VPV Fig. 6. Cross-sectional modeling of a PV module To analyze PID at both the cell and module levels for a tilted PV generator (defined by its incidence angle) exposed to dust soiling, a voltage-divider circuit is employed. The underlying assumption is that the magnitude of the electric field within the SiNx layer plays a decisive role in the initiation and progression of PID. As shown in Fig. 6, four resistors are connected in series to represent the main leakage-current path: the dust layer (1), the glass (2), the encapsulation sheet (3), and the SiNx anti-reflection coating on the solar cell (4). The voltage drop across the SiNx layer can then be estimated using the model shown in Fig. 7: PID SolingGlassPolySiNx SiNx SiNx V RRRR R V    , (9) where VPID is the potential difference between the front glass of the module and the surface of the encapsulated silicon cells; VSiNx is the voltage across the SiNx passivation layer; RSiNx, RPoly, RGlass, Rsoiling are the resistances of the SiNx layer, the polymer encapsulant (EVA), the glass and any deposited dust layer, respectively. Glass and polymer layers exhibit high bulk resistivity, whereas the SiNx film is comparatively more conductive. This stack configuration redistributes the electric field and limits the voltage drop across the SiNx layer, thereby reducing the susceptibility to PID. The encapsulation materials surrounding the PV cells provide thermal stability, protection against moisture, resistance to UV-induced aging, and electrical insulation between internal components. An increase in the overall resistive path decreases the leakage current for a given applied potential, which in turn limits the surface potential of the solar cells and mitigates PID effects. Consequently, the resistance measured between the PV cell and the module frame constitutes a key diagnostic parameter for PID in PV systems, as deviations from nominal values indicate insulation degradation and emerging faults. VPID N‐Doped Silicon RGla ss RPolymer foil R SiNx Ant i- refle ct ive c oating IL IL VSiNx VPoly VGla ss Rsoil ing VSoil ing Fig. 7. Model representing the voltage drop in the SiNx passivation layer PID modeling. Several studies have investigated the impact of PID on PV modules operated at different bias voltages (750 V, 500 V and 250 V) under fixed environmental conditions of 70 °C and 100 g/m3 humidity. The results indicate that the temporal evolution of degradation can be described by an exponential law: the loss in performance is initially rapid, then progressively slows down. After a certain exposure time, the PID- induced degradation rate becomes very small, approaching a quasi-steady state. This behavior can be modeled as ]1[)( tePIDtPID    , (10) where PIDPID t    lim , (11) where t is the PID stress duration; PID∞ is the asymptotic (maximum) degradation level reached by a PV module for very long exposure times; τ is the corresponding time constant. 60 Electrical Engineering & Electromechanics, 2026, no. 4 The quantity PID∞ increases with the applied bias voltage (e.g., 250 V, 500 V, 750 V). The parameter τ the rate at which the degradation approaches this limit and is governed by both the intrinsic PID robustness of the module materials and the prevailing environmental conditions. A PID-resistant module is associated with a larger τ and therefore requires longer stress duration to reach PID∞, whereas a PID-sensitive module exhibits a smaller τ and attains PID∞ over a shorter time. On the basis of extensive experimental data, a compact predictive model was derived to quantify the influence of operating and environmental parameters on PID. The leakage current was shown to scale with the square of the operating voltage (module-to-ground potential) and to be proportional to the square of both the module service time and the relative humidity. In addition, the leakage current follows an Arrhenius-type temperature dependence with an activation energy of 0.94 eV. In the equivalent PV cell circuit, this leakage path is represented by the Rsh, whose evolution is fitted by the relation given in (12) [38]: 2226 deg 90700 exp107 1 t RT RHV R avg op sh,            , (12) where Rsh,deg is the degraded Rsh value; Vop is the operating voltage of the panel (panel-to-ground voltage); RH is the relative humidity; R is the gas constant; Tavg is the average temperature; t is the time. The degraded Rsh is influenced not only by the cell location relative to the metallic frame, where PID becomes more severe near the frame, especially at the module corners, but also, to a large extent, by dust soiling. The module tilt angle governs how much dust settles on the front surface; at certain inclinations, deposits can become heavier and more uneven, creating locally more conductive regions and additional leakage pathways. This non-uniform soiling can intensify leakage currents and the electric-field stress at critical interfaces, thereby increasing both the likelihood and the severity of PID and accelerating the overall performance loss of the PV module (Fig. 8). Fig. 8. Representation of dust deposition and its distribution on a PV module The dust accumulation on the front surface of a PV module is modeled by a surface density of deposited particles σd(t, φ) [g/m2], which depends on the exposure time t and the module tilt angle φ d(t, ) = rd0f()t, (13) where rd0 is the nominal dust deposition rate on a horizontal surface (gꞏm−2ꞏday−1); f(φ) is the angle- dependent correction factor. Assuming that dust particles fall vertically under gravity, the effective collecting area is the projection of the module on a horizontal plane. If S0 denotes the actual area of the module, the projected area Sproj on which dust accumulates is Sproj = S0cos. (14) Under this assumption, a first-order approximation for the angular correction factor is therefore f()  cos. (15) At the bottom of the PV module, the impact of PID is most pronounced due to dust accumulation, which is promoted by the tilt angle: particles slide along the surface and pile up at the lower frame bar, where they accumulate. This impact gradually decreases toward the top of the PV module. Accordingly, the following equation defines a normalization factor that weights the severity of PID as a function of the position of a PV cell in the module with respect to its lower edge. L and l denote the width and the height of the PV module, respectively. The horizontal coordinate x  [0, L] is measured from the left edge, and the vertical coordinate y  [0, l] is measured from the bottom edge. Since dust accumulation and PID effects are more pronounced near the lower corners of the module, where particles tend to pile up along the frame edges, the spatial dependence of the PID severity can be modeled by a two-dimensional, dimensionless normalization factor F(x, y, θ) defined as:                          L x eyxF l y ky   2 ).( cos1,, , (16) where ky > 0 controls the vertical decay of the PID impact and 0    1 enhances the contribution of the lateral edges. In this formulation, F(x, y, θ) attains its maximum value at the lower corners (x, y) = (0, 0) and (L, 0), while it decreases both toward the top of the module and toward the central region along the bottom edge. The local PID can be expressed as: D(x, y) = DmaxF(x, y, θ), (17) where Dmax is the maximum degradation level at the lower corners of the PV module. Rsh,deg(x, y) = Rsh,degF(x, y, θ). (17) Experimental study. This experimental study focuses on comparing the performance of three identical small-scale PV modules mounted on the same supporting structure, each tilted at a different angle of 20°, 30° and 40° (Fig. 9), to ensure the reliability of the results and minimize the influence of environmental factors, all measurements are carried out under stable weather conditions, with uniform irradiance and a constant temperature. P3 P1 P2 P3 P1 P2 P3 P1 P2 Module 1Module 2Module 3 C CC Fig. 9 Structure comprising 3 small-scale PV modules mounted at respective inclination angles of 20°, 30° and 40° The modules were carefully selected because they are not equipped with bypass diodes. This specific design feature makes their electrical behavior comparable to that of a single PV cell, thereby enabling a more accurate and direct investigation of internal phenomena, particularly those associated with the shunt (parallel) resistance. In order to evaluate the Rsh and establish a correlation between the experimental conditions (tilt angle and degree of soiling) and the observed variations in electrical performance, a uniform layer of fine sand dust was deposited on the glass surface of the modules using a horizontal deposition apparatus designed to ensure an even distribution over the horizontal surface normal to the vertical (Fig. 10). Electrical Engineering & Electromechanics, 2026, no. 4 61 This procedure is intended to reproduce realistic environmental soiling conditions, which may affect the electrical characteristics and the conversion efficiency of the modules as a function of their tilt angle. After the sand dust deposition (Fig. 11), it was observed that the PV module tilted at 20° had the highest amount of deposited dust, followed by the one at 30°. In contrast, the module tilted at 40° showed a significantly lower dust accumulation compared to the other two. Device designed to uniformly deposit sand dust on the  modules, which are exposed at different tilt angles. Megohmmeter:  A  measuring  instrument  used  to  determine insulation resistance. A computer, equipped with  dedicated  software,  enables  the  extraction  of  measurement reports. Fig. 10. An experimental test bench (a vertical dust deposition device was used to uniformly distribute fine sand particles over the front surface of the PV modules) Fig. 11. Distribution of fine sand deposits on 3 PV modules tilted at 20°, 30° and 40° To ensure a consistent and representative comparison, Fig. 12 depicts the experimental setup adopted for insulation-resistance measurements. Junction box Aluminum frame P1 P2 P3 R1 R R2 Fig. 12. Selected measurement points on the module (P1, P2, P3) and insulation resistances to be measured (R1, R2, R) Three measurement locations (P1, P2, P3) are selected on the front glass surface of each module along a vertical axis, corresponding to the lower, central and upper regions to capture potential spatial non-uniformities associated with dust deposition and moisture. Point P1, located near the lower frame, represents the area most susceptible to gravitational accumulation of contaminants, whereas P2 and P3 correspond to generally less soiled regions. The lower- right corner of the metallic frame is used as the common reference for all frame-related measurements to ensure data consistency. Using an insulation tester at different applied voltages, three resistances are determined: R1 – between the positive terminal (representing the front surface of the PV cells) and the aluminum frame; R2 – between the frame and each surface point Pi; and R – between the positive terminal and each of the 3 points P1, P2, P3. This methodology enables quantification of the spatial distribution of insulation performance and assessment of the combined effects of tilt angle, environmental conditions (dry versus humid), and imposed electrical stress, particularly with respect to PID- like phenomena and shunt-resistance degradation. Measurements and results. Three curves in Fig. 13–15 show an excerpt of the measurements carried out on Module 1, tilted at 20°, under dry conditions. They correspond to the insulation resistance measured between the module frame and the selected surface points, denoted respectively P1, P2, P3. V R R, M V, V Fig. 13. Dry-state insulation resistance (frame-front surface) at P1 of Module 1 tilted at 20°, under 1000 VDC V R R, M V, V Fig. 14. Dry-state insulation resistance (frame-front surface) at P2 of Module 1 tilted at 20°, under 1000 VDC V R R, M V, V Fig. 15. Dry-state insulation resistance (frame-front surface) at P3 of Module 1 tilted at 20°, under 1000 VDC Figure 16 shows that the insulation resistance measured between the frame and the lower point on the front surface P1 is significantly lower than the value obtained at the central point P2. A decrease in resistance is also observed at the upper point P3, which can be explained by its proximity to the frame in the upper part of the module. In addition, the low tilt angle promotes dust deposition over a large portion of the surface, thereby further accentuating the overall reduction in insulation resistance. Table 2 summarizes dry-state insulation resistance measurements (GΩ) between the module frame and the glass-surface points Pi (P1, P2, P3) for 3 PV modules tilted at 20°, 30° and 40° and tested at 500 V and 1000 V, revealing a clear dependence on both tilt angle and surface 62 Electrical Engineering & Electromechanics, 2026, no. 4 condition: the 20° module M1 exhibits consistently very low resistances (≈ 0.017–0.08 GΩ), indicative of severely degraded insulation, whereas the 30° module M2 shows intermediate values (≈ 0.3–0.9 GΩ) and the 40° module M3 reaches very high levels exceeding 40 GΩ, reflecting a substantially improved insulation state at higher tilt. Fig. 16. Dry-state insulation resistance (frame-front surface) at P1, P2, P3 of Module 1 tilted at 20°, under 500 V and 1000 V This behavior is consistent with enhanced dust retention at low tilt angles, which limits natural particle removal, promotes surface leakage paths, and leads to non- uniform contamination characterized by heavier deposition near the lower frame and a progressively cleaner upper region, as evidenced by the spatial trend where P1 (most soiled area) systematically yields the lowest resistance, P2 intermediate values, and P3 the highest (up to 45 GΩ for M3 at 500 V); additionally, increasing the test voltage from 500 V to 1000 V produces a slight reduction in measured resistance, most noticeable for M3, consistent with field- enhanced surface conduction, although this voltage effect remains secondary compared with the dominant influence of tilt angle and contamination distribution. Table 2 Isolation resistance values under dry conditions measured between the module frame and each Pi point on the glass surface Insulation resistance, GΩ Dry environment Voltage, V Pi M1 θ=20° M2 θ=30° M3 θ=40° P1 0.032 0.3 1.34 P2 0.019 0.7 27.36 500 P3 0.08 0.9 45 P1 0.035 0.3 0.92 P2 0.017 0.7 22.75 1000 P3 0.07 0.8 40 Measurements could not be extended above 100 V because the insulation resistance dropped to very low levels, leading to saturation of the measuring instrument. As shown in Table 3, the wet-condition insulation resistance (GΩ) measured between the module frame and the glass-surface points P1, P2, P3 for modules tilted at 20°, 30° and 40° is substantially lower than that obtained under dry conditions, confirming the strong influence of moisture on surface leakage. At P1, the resistance evolution remains broadly comparable to the dry-case behavior, which can be attributed to heavy soiling in the lower part of the module caused by gravitational dust accumulation, whereas at locations with lower deposit density, humidity becomes the dominant factor by facilitating leakage pathways and further degrading insulation integrity. Among the tested configurations, the 20° module M1 exhibits the most severe degradation, with resistances collapsing to approximately 0.001 GΩ at P2 and P3, suggesting the formation of quasi-continuous conductive films on the glass; the 30° module M2 shows higher yet still strongly reduced values, particularly at P2 (0.01 GΩ), indicating increased sensitivity to locally contaminated regions. In contrast, the 40° module M3 maintains the highest insulation levels (about 1.1–1.2 GΩ at P1 and P3), although a noticeable decrease persists at P2 (0.03 GΩ), and the overall spatial pattern highlights pronounced non-uniformity under humid conditions, with P2 and P3 emerging as the most critical zones, likely due to localized moisture retention combined with deposits (dust/salts) that enhance water adsorption and ionic conduction; nevertheless, increasing tilt remains beneficial by limiting water stagnation and improving natural drainage, which explains the comparatively better performance of the 40° module. Table 3 Isolation resistance values under dump conditions measured between the module frame and each Pi point on the glass surface Insulation resistance, GΩ Dry environment Voltage, V Pi M1 θ=20° M2 θ=30° M3 θ=40° P1 0.085 0.46 1.2 P2 0.001 0.01 0.03 100 P3 0.001 0.81 1.1 After applying an identical PID-type electrical stress imposed by the measuring instrument and cleaning the front surfaces, electrical measurements were carried out under controlled laboratory conditions: the modules were installed at a uniform tilt angle of 30°, exposed to the same irradiance level, and maintained at a stabilized temperature of 30 °C; their I–V and P–V characteristics were then recorded, as shown in the following figures. The tests were performed on modules whose specifications are summarized in Table 4. Table 4 Specifications of the test modules employed in the experiments Pmax, W 10 Voc, V 20.5 Tolerance, % 5 Isc, A 0.59 Vmp, V 18 Vmax, V 750 Imp, A 0.55 Size, cm 34518018 Test condition 1000 W/m2 AM1.5 25°C Figure 17 shows that the relatively pronounced slope of the I–V curve and the MPP location suggest increased internal losses (higher series resistance and/or degraded Rsh, which is consistent with performance degradation potentially associated with soiling and/or PID-type electrical stress. Ipv, mA Ppv, W Vpv, V Fig. 17. I–V and P–V characteristics of module 1 (pre-inclined at θ=20°), measured after cleaning and reinstallation at 30° under uniform irradiance and temperature conditions Figure 18 indicates that the low-voltage region of the I–V curve exhibits reduced leakage, pointing to a higher Rsh compared with the 20°-tilted module. The lack of an early current roll-off and the more nearly rectangular I–V shape are consistent with fewer parasitic Electrical Engineering & Electromechanics, 2026, no. 4 63 conductive pathways. This trend agrees with the 30° tilt configuration, which limits dust accumulation, thereby lowering surface conduction and mitigating PID-related stress, ultimately leading to a higher maximum power and improved operational stability. Ipv, mA Ppv, W Vpv, V Fig. 18. I–V and P–V characteristics of module 2 (pre-inclined at θ=30°), measured after cleaning and reinstallation at 30° under uniform irradiance and temperature conditions Figure 19 shows that the very smooth I–V profile at low voltages reflects minimized leakage currents, suggesting a high Rsh with limited degradation compared with the 20° and 30° modules. The absence of an early current drop and the reduced slope near the origin confirm that parasitic conductive paths on the module surface are strongly mitigated. This improvement is consistent with a 40° tilt angle, which promotes natural self-cleaning of the glass, limits dust accumulation, and reduces surface conduction and PID-type effects. Consequently, the module achieves a higher maximum power and exhibits more stable and better overall electrical performance. Ipv, mA Ppv, W Vpv, V Fig. 19. I–V and P–V characteristics of module 3 (pre-inclined at θ=20°), measured after cleaning and reinstallation at 40° under uniform irradiance and temperature conditions Experimental performance evaluation of the three modules: characterization and comparison. To experimentally evaluate these 3 identical PV modules, we first determine the degradation rate and corresponding Rsh for each module. Table 5 indicates that the FF is a sensitive indicator of module degradation, increasing from 30.5 % for M1 (20°) to 45 % for M2 (30°) and 57 % for M3 (40°), while remaining far below the STC reference value (76 %), which reflects increased internal losses and a more pronounced shunt-resistance deterioration, particularly at low tilt angles. In this study, degradation is assessed relative to the FF value. Furthermore, to simplify the analysis of thermal influence, it is assumed that the temperature coefficients associated with voltages are identical, βVoc ≈ βVmpp, and similarly, that the temperature coefficients associated with currents are identical, αIsc ≈ αImpp. This assumption allows for estimating variations in maximum power point parameters using the conventional coefficients provided for Voc and Isc, while maintaining consistency with the manufacturer’s specifications. Table 5 Comparative analysis of electrical performance following stress application using FF as a degradation indicator M1, θ=20° M2, θ=30° M3, θ=40° Factory status STC Voc, V 21.3 20.6 20.7 20.5 Isc, A 0.37 0.374 0.397 0.59 Pmax, W 2.41 3.58 4.747 10 Pth.max, W 7.88 7.70 8.22 12.1 FF, % 30.5 45 57 76 Thus, the degradation of modules 1, 2 and 3 relative to the reference module, denoted respectively as D1/R, D2/R and D3/R, can be defined as: %1001 max max        RM iM FF FF iD , (19) where i = (1/R, 2/R, 3/R). So D1/R = 25 %, D2/R = 40 % and D3/R = 59 %. The results confirm that increasing the tilt angle mitigates soiling, reduces leakage currents and PID-related effects, and therefore helps preserve the module’s electrical performance. The degradation of a PV module can be quantified by comparing its measured electrical parameters with the reference values provided by the manufacturer under STC, particularly the FF. In this study, degradation is assessed relative to FF value. Furthermore, to simplify the analysis of thermal influence, it is assumed that the temperature coefficients associated with voltages are identical, βVoc ≈ βVmpp, and similarly, that the temperature coefficients associated with currents are identical, αIsc ≈ αImpp. This assumption allows for estimating variations in maximum power point parameters using the conventional coefficients provided for Voc and Isc, while maintaining consistency with the manufacturer’s specifications. Therefore, the degradation of modules 1, 2 and 3 relative to the reference module can be defined by the equations denoted as D1/R, D2/R and D3/R, respectively. By identification, the Rsh is associated with the slope of the I–V characteristic of the module in the region to the left of the maximum power point (low-voltage region). It can therefore be estimated from the derivative dI/dV evaluated in this domain, as indicated as: I  Isc – V / Rsh. (20) As shown in Table 6, Rsh of module M1 (θ = 20°), which was subjected to the highest level of sand-dust deposition, is Rsh1 ≈ 121 Ω. This value is significantly lower than those of the other modules: Rsh2 = 337 Ω for module M2 (θ = 30°) and Rsh3 = 733 Ω for module M3 (θ = 40°). Since Rsh represents the resistance of the parallel paths through which leakage current can flow when a voltage is applied between the module frame and the PV cell, this reduction in Rsh confirms that the amount of dust deposited on the modules is a key factor promoting PID. Furthermore, the data shows that the severity of this degradation is inversely proportional to the tilt angle of each module during the soiling exposure. Table 6 Determination of the Rsh of PV modules through analysis of their I–V characteristic curves M1, θ=20° M2, θ=30° M3, θ=40° Isc, A (I, V) Isc, A (I, V) Isc, A (I, V) 0.37 (0.338, 3.9) 0.374 (0.358, 5.4) 0.397 (0.391, 4.4) Rsh = 121 Ω Rsh = 337 Ω Rsh = 733 Ω 64 Electrical Engineering & Electromechanics, 2026, no. 4 Discussion. The objective of this experimental work was to analyze the influence of the tilt angle on the initial dust accumulation and its consequences on the electrical integrity of PV modules subjected to potential-induced voltage bias stress. More specifically, this work investigates how differential particle deposition, governed by module inclination, modulates the severity of performance degradation induced by applying an electrical potential between the frame and the output terminals. The methodology was based on the use of three identical PV modules, initially positioned at distinct tilt angles (20°, 30°, 40°) before being subjected to a controlled, vertical deposition of sand dust. An insulation resistance test, applying a voltage from 100 V to 1 kV, was subsequently used to impose identical electrical stress on each sample. Following a thorough cleaning, I–V characterization was performed under standardized laboratory conditions (30° tilt, uniform irradiance and temperature) to evaluate the residual impact on performance. The main results reveal a clear differential degradation. The module pre-inclined at 20° exhibited the most degraded FF and the highest power loss. Conversely, the module initially at 40° showed the least degradation and an FF closest to its original condition, while the module at 30° occupied an intermediate position. This systematic correlation between a lower initial tilt angle and increased degradation suggests a multi-step causal mechanism. Interpretation of these observations leads to the following proposed scenario. First, the tilt angle during deposition directly conditions the mass and adhesion of the dust layer. A shallow angle (20°) maximizes the capture surface for vertically sedimenting particles, leading to greater accumulation. A steeper angle (40°) conversely promotes particle shedding and reduces retention. Second, this contamination layer, potentially conductive in the presence of residual humidity, compromises the surface insulation properties. It establishes parasitic conduction paths between the active cells and the grounded frame. Consequently, the most soiled module (20°) likely presented the lowest insulation resistance prior to the high-voltage test. During this test, the leakage current density and the local electric field intensity across the contaminant layer were therefore maximal for this sample. This amplified electrical stress likely caused irreversible degradation of the dielectric materials (encapsulant, backsheet) and critical interfaces. Third, this degradation subsequently manifests as a permanent reduction in the FF after cleaning. The decrease in FF is a characteristic indicator of altered internal electrical parameters, primarily a drop in Rsh due to the creation of internal micro-shunts. The complete causal chain can therefore be summarized as follows: a low initial angle leads to increased dust accumulation, which reduces surface insulation resistance, a condition that amplifies the electrical stress during the HV test; this stress, in turn, causes permanent internal degradation (such as a decrease in Rsh and a reduction in FF. In conclusion, this study demonstrates that the tilt angle of a PV module not only modulates the temporary optical losses due to soiling but also critically influences its susceptibility to permanent electrical degradation. A shallow tilt angle, by promoting heavier dust accumulation, can precipitate a reduction in surface insulation. When coupled with high-voltage events, such as during testing, under storm conditions, or in humid environments, this can lead to irreversible performance deterioration. These findings underscore the importance, for the long-term durability of installations in dusty environments, of considering steeper tilt angles where feasible and adopting proactive cleaning strategies. Such measures are essential to mitigate both immediate energy yield losses and the long-term risk of performance failure. Conclusions. This study shows that the initial tilt angle of a PV module affects not only soiling-related optical losses, but also its susceptibility to long-term electrical degradation (PID), especially under humid conditions and high-voltage stress. Tests on 3 identical modules (20°, 30°, 40°) with controlled dust deposition, insulation-resistance mapping (dry/humid), and DC stress up to 1 kV, followed by standardized I–V and P–V measurements, revealed a clear tilt dependence: the 20° module suffered the strongest degradation (FF and Rsh drop), the 40° module the weakest, and the 30° module an intermediate response. This trend is explained by higher and more uneven dust accumulation at low tilt, which lowers surface insulation, increases leakage, and intensifies local electric stress, leading to irreversible dielectric damage and shunt- path formation. Results indicate that the glass–frame region is a critical leakage pathway due to the coupling between the front glass, the grounded metallic frame, and the dust layer (potentially made more conductive by moisture), which can exacerbate PID severity, especially at low tilt angles. From a practical standpoint, these findings support the adoption of steeper installation angles where feasible and preventive cleaning strategies to preserve insulation integrity, limit leakage, mitigate PID risk, and enhance the long-term durability of PV systems operating in dusty (and humid) environments. The study will be extended to additional tilt angles, soiling levels, and exposure durations to identify critical thresholds and strengthen the relationships between soiling, insulation integrity, and electrical losses (FF, Rsh). 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Electrical Engineering & Electromechanics, 2026, no. 3, pp. 55-65. doi: https://doi.org/10.20998/2074-272X.2026.4.08
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spelling eiekhpieduua-article-3493462026-07-01T21:42:56Z Impact of tilt angle, dust deposition, and humidity on potential induced degradation and electrical performance of crystalline silicon photovoltaic modules: an experimental study Impact of tilt angle, dust deposition, and humidity on potential induced degradation and electrical performance of crystalline silicon photovoltaic modules: an experimental study Khammassi, Z. Jeridi, A. Khaterchi, H. Zaafouri, A. photovoltaic performance potential-induced degradation tilt angle dust deposition фотоелектричні характеристики потенціально-індукована деградація кут нахилу осадження пилу Introduction. Photovoltaic (PV) modules constitute the backbone of renewable energy systems, yet their performance is compromised by degradation mechanisms, particularly potential induced degradation (PID), which causes rapid power losses through ionic migration under high voltage stress, creating parasitic shunts that reduce shunt resistance Rsh and energy output. Problem. Although the influence of moisture and temperature has been widely investigated, the combined contribution of operational and environmental factors such as dust soiling remains insufficiently clarified. Goal. This work assesses dust as a contributor to potential induced degradation focusing on the combined effects of tilt angle, dust exposure and dust-moisture interaction on insulation integrity and degradation susceptibility. Methodology. A comparative experimental study was conducted on 3 identical crystalline-silicon PV modules without bypass diodes, installed at tilt angles of 20°, 30° and 40°. A controlled and uniform layer of sandy dust (maximum particle size about 150 μm) was deposited on the front surface. Insulation resistance between the frame and the front glass was measured at three locations (bottom, middle and top) under dry conditions and then at relative humidity above 80 %. The modules were subsequently subjected to a DC electrical stress of 1 kV, followed by cleaning. Electrical performance was evaluated under identical irradiance and temperature conditions using current-voltage (I-V) and power-voltage (P-V) characterization to extract the fill factor (FF) and Rsh. Results. Lower tilt angles (20°) promoted non-uniform dust accumulation, reducing insulation resistance and increasing leakage currents. High humidity intensified these effects, creating localized PID-prone regions. Post-cleaning, modules at 20° exhibited significantly lower FF and Rsh compared to 40°, indicating persistent degradation and incomplete recovery. Scientific novelty. This work establishes dust as an active PID initiator rather than merely an optical attenuator, uniquely examining coupled effects of tilt angle and dust-moisture interaction on PID susceptibility through moisture-assisted surface conduction pathways. Practical value. Appropriate tilt-angle selection and cleaning strategies are essential to preserve insulation integrity, limit leakage currents, mitigate degradation risk and maintain PV performance in dusty and humid environments. References 38, tables 6, figures 19. Вступ. Фотоелектричні (PV) модулі є основою систем відновлюваної енергетики, проте їхня ефективність знижується внаслідок деградаційних процесів, зокрема потенціально-індукованої деградації (PID), яка спричиняє швидкі втрати потужності через міграцію іонів під дією високовольтного електричного поля, утворення паразитних шунтів, зменшення шунтового опору Rsh та зниження енергетичної продуктивності. Проблема. Незважаючи на те, що вплив вологи та температури досліджено достатньо широко, сумарний вплив експлуатаційних і навколишніх факторів, зокрема забруднення пилом, залишається недостатньо вивченим. Мета. Оцінити вплив пилу як чинника потенціально-індукованої деградації з урахуванням сумісної дії кута нахилу, пилового забруднення та взаємодії пилу з вологою на цілісність ізоляції та схильність до деградації. Методика. Проведено порівняльне експериментальне дослідження трьох однакових кремнієвих PV модулів без обвідних діодів, встановлених під кутами нахилу 20°, 30° та 40°. На фронтальну поверхню наносився контрольований рівномірний шар піщаного пилу з максимальним розміром частинок близько 150 мкм. Опір ізоляції між рамою та фронтальним склом вимірювали у трьох точках (нижня, середня та верхня частини) спочатку в сухих умовах, а потім при відносній вологості понад 80 %. Після цього модулі піддавали дії постійної напруги 1 кВ, а далі виконували очищення поверхні. Електричні характеристики оцінювали за однакових умов освітленості та температури шляхом аналізу вольт-амперних (I–V) та вольт-потужних (P–V) характеристик із визначенням коефіцієнта заповнення (FF) та шунтового опору Rsh. Результати. Менші кути нахилу (20°) сприяли нерівномірному накопиченню пилу, що призводило до зниження опору ізоляції та збільшення струмів витоку. Висока вологість посилювала ці ефекти, формуючи локальні області, схильні до PID. Після очищення модулі з кутом нахилу 20° демонстрували значно нижчі значення FF та Rsh порівняно з модулями з кутом 40°, що свідчить про стійку деградацію та неповне відновлення характеристик. Наукова новизна. У роботі пил розглядається не лише як оптичний послаблювач випромінювання, а як активний чинник ініціювання PID. Уперше детально досліджено сумісний вплив кута нахилу та взаємодії пилу з вологою на схильність до PID через поверхневі провідні шляхи, утворені за участю вологи. Практична значимість. Правильний вибір кута нахилу та стратегій очищення є важливими для збереження цілісності ізоляції, обмеження струмів витоку, зменшення ризику деградації та підтримання ефективної роботи PV модулів у запилених і вологих умовах. Бібл. 38, табл. 6, рис. 19. National Technical University "Kharkiv Polytechnic Institute" and Аnatolii Pidhornyi Institute of Power Machines and Systems of NAS of Ukraine 2026-07-02 Article Article application/pdf https://eie.khpi.edu.ua/article/view/349346 10.20998/2074-272X.2026.4.08 Electrical Engineering & Electromechanics; No. 4 (2026); 55-65 Электротехника и Электромеханика; № 4 (2026); 55-65 Електротехніка і Електромеханіка; № 4 (2026); 55-65 2309-3404 2074-272X en https://eie.khpi.edu.ua/article/view/349346/351645 Copyright (c) 2026 Z. Khammassi, A. Jeridi, H. Khaterchi, A. Zaafouri http://creativecommons.org/licenses/by-nc/4.0
spellingShingle photovoltaic performance
potential-induced degradation
tilt angle
dust deposition
Khammassi, Z.
Jeridi, A.
Khaterchi, H.
Zaafouri, A.
Impact of tilt angle, dust deposition, and humidity on potential induced degradation and electrical performance of crystalline silicon photovoltaic modules: an experimental study
title Impact of tilt angle, dust deposition, and humidity on potential induced degradation and electrical performance of crystalline silicon photovoltaic modules: an experimental study
title_alt Impact of tilt angle, dust deposition, and humidity on potential induced degradation and electrical performance of crystalline silicon photovoltaic modules: an experimental study
title_full Impact of tilt angle, dust deposition, and humidity on potential induced degradation and electrical performance of crystalline silicon photovoltaic modules: an experimental study
title_fullStr Impact of tilt angle, dust deposition, and humidity on potential induced degradation and electrical performance of crystalline silicon photovoltaic modules: an experimental study
title_full_unstemmed Impact of tilt angle, dust deposition, and humidity on potential induced degradation and electrical performance of crystalline silicon photovoltaic modules: an experimental study
title_short Impact of tilt angle, dust deposition, and humidity on potential induced degradation and electrical performance of crystalline silicon photovoltaic modules: an experimental study
title_sort impact of tilt angle, dust deposition, and humidity on potential induced degradation and electrical performance of crystalline silicon photovoltaic modules: an experimental study
topic photovoltaic performance
potential-induced degradation
tilt angle
dust deposition
topic_facet photovoltaic performance
potential-induced degradation
tilt angle
dust deposition
фотоелектричні характеристики
потенціально-індукована деградація
кут нахилу
осадження пилу
url https://eie.khpi.edu.ua/article/view/349346
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AT khaterchih impactoftiltangledustdepositionandhumidityonpotentialinduceddegradationandelectricalperformanceofcrystallinesiliconphotovoltaicmodulesanexperimentalstudy
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