Any comments are welcome on the discussion page including additional resources/papers/links etc. Papers can be added to relevant sections if done in chronological order with all citation information and short synopsis or abstract. Thank You.
highlights the effects of shading locations and surface temperature on power output
partial shading >> increased surface temp.
Partial shading from sources >> bird droppings, leaves, and shadows
67% shaded ratio (worst case) >> 99.6°C surface temp.
Experimental setup:
solar simulator with iodine-tungsten lamps, a data measurement system, and a solar PV system
18 thermocouples to measure temp on front and back of PV module
black cardboard to simulate partial shading at various ratios (25%, 33%, 50%, 67%, 75%, and 100%)
Ambient temp 20°C
irradience @ 1100 W/m²
Shaded Locations
Seven locations on the solar PV panel:
upper-right
right
bottom
middle
top
left
lower-left
seven different shading ratios, including no shading and full shading
Technique for Order Preference by Similarity to Ideal Solution (TOPSIS)
was employed to evaluate the experimental results
ranks the potential reduction of energy output and fire risk
helps in identifying the optimal shading scenarios that minimize energy loss and risk
higher scores indicating better performance
Surface Temperature and Energy Output Performance
The temperature of the middle cell (No. 17) rises initially and stabilizes under different shaded ratios.
The average temperature during the last 400 seconds of stabilization is used for analysis
Short circuit current decreases with increasing shaded ratios, while open circuit voltage shows minimal change
Shaded cells consistently exhibit higher temperatures than unshaded cells
maximum temperatures occurring at different shaded ratios depending on the cell's location
The upper right cell >> reaches a peak temperature of 99.6°C at a 67% shaded ratio, exceeding the melting point of polyethylene vinylacetate (EVA) at 85°C
shaded middle cell >> 92.9% ↓ power output >> only 2.2 W
shaded middle cell (completely shaded) >> 88.2% reduction in short-circuit current
the highest fire risk is associated with the top cell (No. 22) at 25 %, 67 %, and 100 % shadded ratio
Relationship Between Temperature and Power Dissipation
nonlinear relationship between temperature rise at shaded cells and power drop of solar PV panels is explored, indicating a complex interaction
The temperature rise at shaded cells increases with power drop initially but decreases after reaching a certain threshold due to bypass diode activation
Relationship between temperature rise and power drop >> (ΔT = 2.79ΔP - 0.08ΔP², R² = 0.844)
Experimental and numerical study of solar cell performance under different shading conditions[2]
highlights the effects of shading on key performance parameters and proposing a method for predicting performance under irregular shading
Key performance parameters >> open circuit voltage, short circuit current, and maximum output power
Shading significantly reduces short circuit current and maximum output power >> a linear decrease as shading ratio increases
Voc >> a slight decline, while series resistance (Rs) increases exponentially, indicating its critical role in power loss
An equivalent transformation method is proposed to predict performance under various shading conditions, achieving relative deviations in key parameters below 3%
Experimental Setup and Methodology
Shading was simulated using black opaque material to cover portions of the solar cell
Newport solar simulator provided stable illumination at 1000 W/m² with less than 2% irradiance inhomogeneity
The single-diode model serves as the equivalent circuit for solar cells >> a photocurrent source, a diode, equivalent shunt resistance, and equivalent series resistance
Localized shading creates regions with different illumination intensities, affecting photocurrent and series resistance
Relative Power Losses in Shaded Conditions
Power losses categories >> finger shading, busbar shading, emitter region shading, contact resistance, and resistances of fingers and busbars
accounts for the impact of series resistance on the operating voltage at maximum output power
Numerical simulations using COMSOL Multiphysics were compared with experimental data to evaluate model accuracy
The maximum output power's relative deviation under various shading conditions was found to be within 3.922%, indicating high reliability of the model
Performance of Solar Cells Under Shading Conditions
Voc decreases slightly with increased shading; at 50% shading, it drops by approximately 3%
Isc decreases linearly with shading, with a slope of -0.187; at 50% shading, it decreases by about 49%
Pmax decreases linearly, with a slope of -0.100; at 50% shading, it drops by around 50%
Rs increases exponentially with shading; at 50% shading, it rises by approximately 32%
The shading ratio significantly impacts the generation and collection of photogenerated carriers, leading to reduced output power
10% shading ratio>> relative power losses are 9.79% (x-axis) and 9.19% (y-axis)
30% shading ratio >> losses increase to 27.42% (x-axis) and 27.60% (y-axis)
50% shading ration >> losses are 46.03% (x-axis) and 46.01% (y-axis)
Major contributors to power losses include contact resistance, finger resistance, and busbar resistance, with busbar resistance being the most significant
Performance Under Regular Shading Scenarios
Experimental validation shows relative deviations of 0.152% for Voc, 0.275% for Isc, and 2.432% for Pmax
Performance Under Irregular Shading Scenarios
A leaf with a shading area of 1232 mm² results in a shading ratio of 19.3%
relative deviations for key performance parameters below 3%
The maximum deviation for Pmax is only 2.199%, indicating high predictive accuracy
Irregular shading >> asymmetric voltage distribution and increased ohmic losses, contributing to efficiency degradation
Impacts of shadow conditions on solar PV array performance: A full-scale experimental and empirical study[3]
reduced power gen >> empirical studies revealing a decrease of up to 90% in power generation capacity when a solar cell is fully obstructed
⅔ of the modules are shaded>> Isc drops by 20-25% >> Voc drops by 25-30%
The study developed an empirical model indicating that power generation efficiency is negatively related to the 3/2 power of the shadow area
highlights the need for further studies on the impact of various shadow conditions on solar PV systems
The experimental platform consisted of a full-size PV array with 30 modules arranged in 3 rows and 10 columns
Black opaque cardboard was used to create controlled shading conditions, allowing for systematic analysis of direct, diffuse, and total irradiance effects.
The study measured output characteristics using an IV curve tester
Isc demonstrated a linear decrease with increasing shadow area, aiding in fault detection for PV power plants
Voc remained relatively stable under small shadow conditions but showed significant drops when larger areas were shaded
suggest that monitoring Voc can help estimate shadow coverage in PV arrays, particularly under large-area shading scenarios
η dropped to about 4% for East-3 and 6% for East-7 when two cells were shaded, with further decreases as shading increased
When half of the PV modules were shaded, η fell to approximately 45%, deviating from the theoretical 50% due to increased surface temperature
As shadow area increases from 0% to 15%, η of East-7 and East-9 shows only slight decreases due to minimal obstruction
Initial sharp drops in efficiency for East-1 and East-5 are attributed to calculation issues; beyond 5% shadow, all modules exhibit similar efficiency decline patterns
Photovoltaic System Performance Under Partial Shading Conditions: Insight into the Roles of Bypass Diode Numbers and Inverter Efficiency Curve[4]
A practical solution to mitigate hotspot formation >> bypass diodes
No of bypass diode ↑ >> enhances PV system performance but alters the global maximum power points, shifting their voltage locations and power magnitudes, consequently resulting in a change in the operating points in the efficiency curve of the inverters >> which may increase thermal stress due to sustained forward-biased operation
investigates 3 inverters with different efficiency characteristics in terms of loading and input voltage
also module configurations with different numbers of bypass diodes
additional factors >> ambient temperature, inverter loading ratio by varying the number of series-connected PV modules, and shading intensity
different cases are simulated using a Simscape/Simulink-based circuit model with random irradiance samples
a 125 kWp grid-connected PV system at the University of Brasília demonstrates a stable performance ratio of 78% using a 50 kW inverter
A case study for the northern regions of Thailand reports that the selected inverter can operate at maximum efficiency for irradiances greater than 350 W/m2 for three different PV module types
In another study conducted in five different regions in Corsica and seven different regions in Bulgaria, it is emphasized that the PV array should be oversized by 30% or undersized by 30% depending on the selected inverter
Evaluating the Effectiveness of Photovoltaic Systems: A Comparison of Microinverters and Conventional Non-Optimized Solutions[5]
The conventional series, parallel, series-parallel (SP), and total cross-tied (TCT) configurations suffer significant mismatch losses under partial shading condition
The power output of a PV array is decreased by partial shading because it causes mismatch loss inside the string of traditional series–parallel configurations
conventional solutions: maximum power point tracking (MPPT) [2], bypass diodes [3], and optimized array designs, like series–parallel, cross-tied, bridge-link, or honeycomb configurations[7]
Critical evaluation and review of partial shading mitigation methods for grid-connected PV system using hardware solutions: The module-level and array-level approaches[8]
The review encompasses module-level solutions like micro-inverters, power optimizers, and energy recovery circuits
Building Integrated Photovoltaics (BIPV) face significant energy yield reductions due to partial shading, primarily caused by nearby structures and environmental factors
Partial shading can cause up to 50% power loss with only 9% shading
Advanced MPPT techniques include metaheuristic algorithms like differential evolution and particle swarm optimization
These methods aim to optimize point-by-point searches to locate the global peak power point
Micro-Inverter Technology Overview
Micro-inverters connect directly to individual modules, allowing independent energy extraction and reducing the risk of system-wide failures
utilize simple MPPT algorithms like perturb and observe (P&O) due to their ability to handle single peak P-V curves
Commercial micro-inverters are available with power ratings typically between 240-300 W, exhibiting peak conversion efficiencies of 94-96%
micro-inverters can be classified into two categories: the isolated (utilizing transformer) and the non-isolated (utilizing boost converter) topologies
the micro-inverter (and also power optimizer) needs to consume power continuously in order to sustain its operation
Micro-inverter is an effective solution for systems which require the modules to be distributed within the plant, or be arranged in multiple orientations due to limited mounting space
faulty modules within a system do not affect the power generating capabilities of the rest. These features make micro-inverter an excellent option for BIPV applications. Another major advantage of micro-inverter system is in its upgradability.
faulty modules within a system do not affect the power generating capabilities of the rest. These features make micro-inverter an excellent option for BIPV applications. Another major advantage of micro-inverter system is in its upgradability.
Shading Scenarios and Their Impact
Seven shading scenarios >>from light to heavy shading
since the modules do not forma string, the possibility for a hotspot vanishes.
Micro-inverters offer flexibility and efficiency in partial shading scenario
Micro-inverters allow distributed installation and operate autonomously, minimizing shading effects
Most string inverters exceed 95% efficiency, while micro-inverters range from 93-96%
Shading variability can lead to energy yield improvements of 1.5-20.3% for micro-inverters
A typical 6.2 kW residential system with micro-inverters costs $3.06 per watt, compared to $2.64 per watt for string inverters with optimizers
Micro-inverters often come with a 25-year warranty
Micro-inverter market growth is projected at a CAGR of 17.3% from 2019 to 2025, targeting $5.6 billion in sales
In terms of energy gain, micro-inverter energy gain is 1.8% higher than string inverter system
Optimal control of grid-connected microgrid PV-based source under partially shaded conditions[9]
When the PV array modules are exposed to non-uniform irradiation, its power-voltage (PeV) characteristics exhibit multiple peaks. The highest peak is called the global maximum point and the others are the local maximum points.
Review Mitigation Methods of Partial Shading Condition for PV System[10]
6kW residential PV system are thoroughly evaluated
most of the microinverter manufacturers are now providing a standard 25-year warranty [5, 6, 9, 10].
The inverter is generally considered to be the most failure prone component in the PV energy system [11, 19]
results show that the string inverter is responsible for 43% of failures and 36% of energy loss [19]
Under the light (7% shading), moderate (15-19%), and heavy shading 25%, the microinverter generation was 3.7%, 7.8%, and 12.3%, respectively, higher than the string inverter.
Performance and economical comparison between micro-inverter and string inverter in a 5, 1 kWp residential PV-system in Colombia[12]
The location selected is the Engineering building (Block 19) of Antioquia University in Medellin, Colombia. >> The array modeled has 20 modules>> 5.1 kWp
without shading condition, the micro-inverters improve the performance ratio in 5.9 %
with partial shading condition the improvement on the performance ratio reaches 8%. Nevertheless, it is necessary 7.5% less initial capital to install the PV system using string inverter.
↑Y. Song, L. Huang, Y. Wang, Y. Du, Z. Song, Q. Dong, X. Zhao, J. Qi, G. Zhang, W. Li, L. Shi, Energy performance and fire risk of solar PV panels under partial shading: An experimental study, Renewable Energy 246 (2025) 122910. https://doi.org/10.1016/j.renene.2025.122910.
↑Y. Lu, J. Wang, P. Liu, R. Rafee, S. Rashidi, G. Li, Experimental and numerical study of solar cell performance under different shading conditions, Solar Energy 296 (2025) 113599. https://doi.org/10.1016/j.solener.2025.113599.
↑Z. Song, L. Huang, Q. Dong, G. Zhang, M.Y.L. Chew, S. Setunge, L. Shi, Impacts of shadow conditions on solar PV array performance: A full-scale experimental and empirical study, Energy 320 (2025) 135219. https://doi.org/10.1016/j.energy.2025.135219.
↑H.G. Sezgin-Ugranlı, Photovoltaic System Performance Under Partial Shading Conditions: Insight into the Roles of Bypass Diode Numbers and Inverter Efficiency Curve, Sustainability 17 (2025) 4626. https://doi.org/10.3390/su17104626.
↑C. Ortiz, M. Parada, Evaluating the Effectiveness of Photovoltaic Systems: A Comparison of Microinverters and Conventional Non-Optimized Solutions, E3S Web Conf. 629 (2025) 06004. https://doi.org/10.1051/e3sconf/202562906004.
↑M.A. Raza, S. Zahra, S. Raza, M.R. Altimania, M. Hassan, H.M. Munir, I. Zaitsev, V. Kuchanskyy, Mitigating the Impact of Partial Shading Conditions on Photovoltaic Arrays Through Modified Bridge-Linked Configuration, Sustainability 17 (2025) 1263. https://doi.org/10.3390/su17031263.
↑T. Alves, J.P. N. Torres, R.A. Marques Lameirinhas, C.A. F. Fernandes, Different Techniques to Mitigate Partial Shading in Photovoltaic Panels, Energies 14 (2021) 3863. https://doi.org/10.3390/en14133863.
↑I.M. Mehedi, Z. Salam, M.Z. Ramli, V.J. Chin, H. Bassi, M.J.H. Rawa, M.P. Abdullah, Critical evaluation and review of partial shading mitigation methods for grid-connected PV system using hardware solutions: The module-level and array-level approaches, Renewable and Sustainable Energy Reviews 146 (2021) 111138. https://doi.org/10.1016/j.rser.2021.111138.
↑A. Guichi, S. Mekhilef, E.M. Berkouk, A. Talha, Optimal control of grid-connected microgrid PV-based source under partially shaded conditions, Energy 230 (2021) 120649. https://doi.org/10.1016/j.energy.2021.120649.
↑A.A. Al-Samawi, A.S. Alkhafaji, A.S. Atiyah, H. Trabelsi, Review Mitigation Methods of Partial Shading Condition for PV System, in: 2024 21st International Multi-Conference on Systems, Signals & Devices (SSD), 2024: pp. 401–410. https://doi.org/10.1109/SSD61670.2024.10549153.
↑S. Harb, M. Kedia, H. Zhang, R.S. Balog, Microinverter and string inverter grid-connected photovoltaic system — A comprehensive study, in: 2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), 2013: pp. 2885–2890. https://doi.org/10.1109/PVSC.2013.6745072.
↑O.A. Arráez-Cancelliere, N. Muñoz-Galeano, J.M. Lopez-Lezama, Performance and economical comparison between micro-inverter and string inverter in a 5, 1 kWp residential PV-system in Colombia, in: 2017 IEEE Workshop on Power Electronics and Power Quality Applications (PEPQA), 2017: pp. 1–5. https://doi.org/10.1109/PEPQA.2017.7981678.
