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# Experimental study to asses The Impact of cracks on the Performance of Photovoltaic Modules

hassen ayed chraiga, Zaher Khantouch, Othman Jeddi

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hassen ayed chraiga, Zaher Khantouch, Othman Jeddi. Experimental study to asses The Impact of cracks on the Performance of Photovoltaic Modules. International Conference on Engineering Science, Oct 2024, sfax, Tunisia. hal-04734157

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https://hal.science/hal-04734157v1

Submitted on 13 Oct 2024

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# Experimental study to assess The Impact of cracks on the Performance of Photovoltaic Modules

Hassen Ayed Chraiga ¹,*, Zaher Khantouch ², Othman Jeddi ¹

¹,² High Institute of Technology Study, Mechanical Department, Tozeur, Tunisia B.P:2100 road to Nefta, Tozeur, Tunisia

**Abstract** This work explores the field of photovoltaic energy, focusing on the diagnosis and maintenance of photovoltaic fields. It covers the context of fault diagnosis, analysis and prevention on the yield affected by these faults, the use of measurement and diagnostic equipment such as the I-V curve tracer (IVCT), leading to conditional preventive maintenance to detect anomalies, and the impact of faults that will gradually increase on panel performance. for this purpose, this study has determined the effect of cracks on the yield of a panel or a series of panels, these effects will appear on the I-V or P-V curves from which we will determine the percentages of active surfaces of the cracked cells.

**Keywords:** solar energy; photovoltaics; maintenance, diagnostics, I-V curve tracer,

<figure><img src="image_2.png" /><figcaption>Graphical abstract</figcaption></figure>
## INTRODUCTION

Photovoltaic modules (PV) are expected to have a life time of more than 20 years under various environmental conditions like temperature changes, wind load, snow and many other factors. Such loads induce mechanical stresses into the components of the PV module, especially into the crystalline solar cell [1]. The resulting cracks in silicon solar cells reduce the power output of the PV modules [2]. The amount of this degradation is usually relatively small, if measured directly after the crack initiation.

Among the methods used to determine the malfunction of a photovoltaic module is the I-V curve tracer method.

by a simple knowledge of the analysis of the curves of these types cited above we can easily deduce the residual anomaly in the system on which we are carrying out the study. although this method does not make it possible to identify the shape of the crack parallel, perpendicular or multi directional compared to busbars such as electroluminescence method, but it always remains a complementary and reliable tool in the diagnosis of faults.

There are a statistical analysis tools that have been deployed in PV applications. However, Kajari-Schröder et al [3] used a statistical local distribution analysis in identifying the type of cracks in a PV module. the main contribution of this work is the Development of a graphical approach that can help to draw up a maintenance plan intervention plan in the shortest possible time, so that this study can be followed by one of the statistical methods used to quantify long- and short-term damage values.

Then as we are mentioned above an I-V and P-V curves will be investigated and analyzed to confirm the inappropriate shape of these curves.

## MATERIAL AND METHODS

to quantify the cracked zones of a photovoltaic panel, a methodology has been developed as shown in figure 1, this methodology consists of three phases: image capture, image processing and image analysis. this

this methodology focuses on the systematic execution of these phases, so that many modules can be analyzed in a relatively short time.
<figure><img src="image_3.png" /><figcaption>Figure 1: Methodology</figcaption></figure>

the use of I-v curve tracer (IVCT) in the field of solar panels offers several major advantages for optimizing performance and maintaining installations [4]. Firstly, it enables early detection of faults, such as defective solar cells, poor connections, faulty bypass diodes, insulation problems, and physical damage to panels. These faults can lead to loss of energy production [5], fire hazards and premature panel degradation. Early detection of these problems enables them to be remedied quickly, optimizing plant performance and extending its lifespan. This technique, highlight the role in verifying the quality of new and existing solar installations. It ensures that solar panels are installed correctly and operate as expected. thanks to these many advantages, (IVCT) method is proving to be an indispensable tool for the efficient management of photovoltaic fields.

for sufficient curve tracer, the irradiance of solar radiation must be at least 600 w/m². for satisfactory results, an irradiance of 700 w/m² is recommended. irradiance is the instantaneous power received by a surface, expressed in kw/m². It is measured by a pyranometer (for global solar irradiance) or a pyrheliometer (for direct solar irradiance) [6]. It is highly dependent on location and local climatic conditions. Low outside temperatures can also improve (IVTC) measure.

Today, (IVCT) enables a digital recording of all measured parameters of the analyzed object.
**instruments used in experimental setup.**

To find out the effects of solar panel defects on their output, we used the following
devices:

I-v curve tracer (1500Vcurve tracer)

<figure><img src="image_4.png" /><figcaption>Image1: SOLAR I-V curve tracer</figcaption></figure>

The SOLAR I-V curve tracer (image1) is an I-V (current-voltage) curve plotter used to test the performance of solar panels and photovoltaic systems its role is to Evaluate solar panel performance, detect faults in photovoltaic modules, ensure panels are operating at optimum efficiency and checking that panels comply with technical specifications.

I-V tracer curve can determine the performance under real-life conditions. It works by applying a variable load to the solar panels and measuring the resulting voltage and current it contains a digital display of measured parameters with Ability to measure up to 1500V.

pyranometer and thermometer
<figure><img src="image_5.png" /><figcaption>**Image2: SOLAR-02**</figcaption></figure>

The SOLAR-02 (image2) is a portable device that combines the functions of a pyranometer and a thermometer to measure solar irradiance in (w/m²) and ambient temperature in degree Celsius. It contains a Digital display to show readings, Buttons for navigation and configuration. It uses sensors to measure the intensity of incident solar radiation (irradiance) and the ambient temperature. These measurements are crucial for assessing the operating conditions of photovoltaic systems., these measures will be recorded and stored Functionality for recording and storing measurement data.

*Reference cell sensor*

<figure><img src="image_6.png" /><figcaption>**Image3: HT304N, reference cell**</figcaption></figure>

The HT304N (image3) is a reference cell sensor used to measure solar irradiance and temperature of photovoltaic modules its role is to Measure solar irradiance (in W/m²), Measure solar cell temperature in degree Celsius. It contains reference cells
that simulate the characteristics of solar cells by measuring the voltage and current of these reference cells, it can determine sunlight and temperature conditions, providing accurate data for solar panel performance analysis.

## Electrical model and analysis

This electrical model of the PV module is based on the commonly used single diode model (SDM) of a solar cell shown in Figure 3.

of a solar cell shown in Figure 1. It consists of a current source, a diode, a series resistor (Rs) and a resistor Rsh. The current source representing $I_{ph}$ is proportional to solar irradiance in the plane of the array. The diode and Rsh represent the loss of charge carriers generated by light due to recombination.

Rs and Rsh are the parasitic resistances representing the ohmic loss in the solar cell. I and V are the solar cell output current and voltage respectively.

The mathematical expression of I for SDM of the solar cell can be written as shown in Eq. (1).

<figure><img src="image_7.png" /><figcaption>Figure 2: Flow regimes and governing equations.</figcaption></figure>

$$I = I_{ph} - I_{d} \left( e^{\frac{V+IR_{s}}{nsV_{t}}} - 1 \right) - \left( \frac{V+IR_{s}}{R_{sh}} \right) \quad (1.)$$

where $I_{ph}$ is the photo-generated current at STC, $I_{d}$ is the dark saturation current at STC, Rs is the module series resistance, Rsh is the panel parallel resistance, ns is the number of series cells in the pv module and Vt is the thermal voltage and it can be defined based on:

$$V_{t} = \frac{AKT}{q} \quad (2.)$$
Where A the diode ideality factor, K is Boltzmann's constant and q is the charge of the electron.

## Performance losses

The aim of this part of the procedure was to assess the performance of the analyzed PVmodule. According to [7], the power output correlates directly with the extent of cracking in the PV module. Thus, once the percentages of surface area affected by cracks had been identified, the performance of the PV panel could be calculated using the following expression

$$ \eta = \frac{P_{Nom} - P_{STC}}{P_{Nom}} \quad (3) $$

where:

P<sub>Nom</sub> refers to the maximum power output under standard test conditions (STC), and P<sub>STC</sub> represents the measured power output of the tested panel under standard test condition calculated as follows:

$$ P_{STC} = A.I_{MaxSTC} \cdot U_{MaxSTC} \quad (4) $$

where A denotes the active Pv area percentage within the panel.
calculated power loss is then used for calculation of poison factor.

$$ \varphi = \frac{\text{Total power loss}}{\text{Mean panel output}} \quad (.5) $$

Poison factor $\varphi$ gives an information of how much the total power output of PV system is reduced when the output of one module or more modules are reduced [8]. It is the relationship that is between the array power loss and the failed panels normal power output which shows performed to see the differences between different defects and scenarios.

Means panel output will be deduced from maximum PV systems power for the nominal case and the number of panels.

$$ \text{Means panel output} = P_{\text{Nom}}/N_{\text{panel}} \quad (.6) $$

the percentages of surface area affected by cracks had been identified, the performance of the PV panel could be calculated using the following expression

## RESULTS AND DISCUSSION

In the experimental part, three installations with a multidirectional cracked panels will be studied in order to determine the effect of this defect in these case studies.

### Case study1

We mounted a solar panel on an inclined support structure as mentioned in (image4) allowing optimum exposure to sunlight. Next to the panel, measuring instruments are used to evaluate the system's performance. Among them, an I-V (current-voltage) curve tracer is connected to the panel to analyze the relationship between the current produced and the voltage generated, detecting any deviation from the expected characteristic curves. A pyranometer and thermometer are also used to measure solar irradiance and ambient temperature, providing essential data for assessing the environmental conditions affecting panel performance [9]. This configuration enables the results obtained to be compared with the technical specifications of the photovoltaic modules, thus identifying any faults or malfunctions. This precise diagnosis is crucial to ensuring that the photovoltaic
system operates at its optimum output, ensuring efficient and reliable solar energy production.

<figure><img src="image_8.png" /><figcaption>**Image3:** Experimental set-up with cracked solar panel and measuring instruments</figcaption></figure>

## Analysis of I-V and P-V curves

We carry out the test on this panel using the solar I-V device, which gives the following values under different conditions, as shown in (table1)

<table><caption>**Table 1:** Comparison of cracked panel parameters under different conditions</caption><thead><tr><th></th><th>Nominal<br>Condition</th><th>Standard<br>Condition</th><th>OPC</th></tr></thead><tbody><tr><td>Meas: ISO106<br>Date:10/05/2024</td><td></td><td></td><td></td></tr><tr><td>Irradiance(w/m²)</td><td>1000 w/m²</td><td>1000 w/m²</td><td>970 w/m²</td></tr><tr><td>Température</td><td>25°C</td><td>25°C</td><td>50°C</td></tr><tr><td>Voc</td><td>43.2V</td><td>40.4V</td><td>38V</td></tr><tr><td>Vmpp</td><td>34.1</td><td>36.3</td><td>35.7</td></tr><tr><td>Isc</td><td>2.99A</td><td>2.6A</td><td>2.6A</td></tr><tr><td>Impp</td><td>2.86</td><td>2.52</td><td>2.52</td></tr><tr><td>Pmax</td><td>100W</td><td>40W</td><td>30W</td></tr><tr><td>FF (%)</td><td>77</td><td>39</td><td>37</td></tr></tbody></table>
<table><tr><td>Alpha(%) /°C)</td><td>0.0590</td></tr><tr><td>Beta(%) /°C)</td><td>-0.332</td></tr><tr><td>Tol+ (%)</td><td>3</td></tr><tr><td>String module</td><td>1</td></tr></table>

The following curves (figure2-3) show the effect of cracks on current and power.

<figure><img src="image_9.png" /><figcaption>**Figure 3:** I-V curves for cracked panels under different conditions</figcaption></figure>

The nominal I-V curve (I) (figure3) shows ideal performance, with almost constant current up to a high voltage point (V), after which the current drops off rapidly. And the maximum current is around 3 A, and the maximum voltage is around 43 V. But under standard test conditions, the impact in variation of serial resistance $R_S$ and the shunt resistance $R_{SH}$ is clear, the I-V curve shows a progressive decrease in current with increasing voltage. And maximum current is around 2.6A, and maximum voltage is reduced performance by around 3V.
vertex points A, B, C and D represent the abrupt variations in the I-V curve during panel testing. the cracked cell accelerates recombination, while the cell mentioned is assumed to be non-functional, triggering the bypass diode.

<figure><img src="image_10.png" /><figcaption>**Figure 4:** P-V curves for cracked panels under different conditions</figcaption></figure>

The nominal P-V curve (III) shows a high-power peak (around 100 W) before dropping off rapidly. And the P-V curve under standard test conditions (IV) shows a much lower power peak (around 40 W). The P-V curve under operational conditions (V) shows an even more reduced performance, with a power peak around 30 W.

We conclude that visible cracks on the solar panel reduce the active surface and can cause hot spots, increasing series resistances and decreasing efficiency, and material degradation over time can lead to reduced conductivity and current losses. Variations in temperature, irradiance and shading over the cracked area can affect actual panel performance compared with standard test conditions.

## Case study 2
We've mounted a visibly damaged solar panel (image5) with surface fractures. This type of damage can affect solar cells, reducing their efficiency and creating hot spots. Analyzing the performance curves of a solar panel is essential for understanding the impact of physical defects, such as ruptures, on its operation.

<figure><img src="image_11.png" /><figcaption>**Image5:** The damage is clearly visible on the cell (3/10), the rupture takes on a spiral shape around the damaged cell.</figcaption></figure>

We carry out the test on this panel using the solar I-V device, which gives the following values under different conditions, as shown in the following (table2) The following curves show the effect of this type of cracks on electrical parameters.

<table><caption>**Table 2:** Comparison of cracked panel parameters under different conditions</caption><thead><tr><th></th><th>Normal Condition</th><th>Standard Condition</th><th>OPC</th></tr></thead><tbody><tr><td>Meas: ISOPA106 Date:10/05/2024</td><td></td><td></td><td></td></tr><tr><td>Irradiance(w/m²)</td><td>1000 w/m²</td><td>1000 w/m²</td><td>946 w/m²</td></tr><tr><td>Température(°C)</td><td>25</td><td>25</td><td>50</td></tr><tr><td>Voc (V)</td><td>43.2</td><td>40.41</td><td>36.24</td></tr><tr><td>Vmpp (V)</td><td>34.6</td><td>32.53</td><td>29.33</td></tr><tr><td>Isc (A)</td><td>2.99</td><td>2.51</td><td>2.52</td></tr><tr><td>Imp (A)</td><td>2.89</td><td>1.22</td><td>1.14</td></tr><tr><td>Pmax (W)</td><td>100</td><td>39.81</td><td>33.57</td></tr><tr><td>FF (%)</td><td>77</td><td>39</td><td>37</td></tr></tbody></table>
<table><tr><td>Alpha(%) /°C)</td><td>0.0601</td></tr><tr><td>Beta(%) /°C)</td><td>-0.36</td></tr><tr><td>Tol+ (%)</td><td>3</td></tr><tr><td>String module</td><td>1</td></tr></table>

The I-V (current-voltage) (figure4) and P-V (power-voltage) (figure5) curves

<figure><img src="image_12.png" /><figcaption>Figure 6: I-V curves for cracked panels under different conditions</figcaption></figure>

The I-V curves clearly show a decrease in solar panel performance with a large break from nominal conditions. from the A vertex onwards, the curve has an alectoria shape, indicating a high degree of independence between current and voltage. Breakage in the cells is a major cause of this reduced performance, affecting both current and generated power. Visible breakage on the solar panel reduces the active surface area and can cause hot spots, increasing series resistance and lowering efficiency.
<figure><img src="image_13.png" /><figcaption>**Figure 6:** P-V curves for cracked panels under different conditions</figcaption></figure>

The nominal P-V curve (III) shows a high-power peak (approx. 100 W) before dropping off rapidly.

The P-V curve under standard test conditions (IV) shows a much lower peak power (around 35 W).

The P-V curve under operational conditions (V) shows an even lower performance, with a power peak around 30 W.

## Case study 3

Two similar solar panels have been installed in series (image6), one defective and the other in good condition, so that the electric current flows through each panel in series. This method is often used to increase system voltage. However, when a cell is broken or damaged, this can adversely affect the performance of the whole system.

Broken boards, missing parts or other signs of damage.
The readability of their contents is likely to be reduced, making information partially or totally inaccessible.

<figure><img src="image_14.png" /><figcaption>Image5: Two similar solar panels installed in series</figcaption></figure>

The test was carried out on this installation using the solar I-V device, which gives the following curves under different conditions(figure6), as shown in the following figures.

<figure><img src="image_15.png" /><figcaption>Figure 6: I-V curves for cracked panels under different conditions</figcaption></figure>

<table>
  <tr>
    <td>Table 3: Comparison of cracked panel parameters under different conditions</td>
  </tr>
</table>
<table><thead><tr><th></th><th>Normal Condition</th><th>Standard Condition</th><th>OPC</th></tr></thead><tbody><tr><td>Meas: ISOPA106 Date:20/05/2024</td><td></td><td></td><td></td></tr><tr><td>Irradiance(w/m²)</td><td>1000 w/m²</td><td>1000 w/m²</td><td>953 w/m²</td></tr><tr><td>Température(°C)</td><td>25</td><td>25</td><td>50</td></tr><tr><td>Voc (V)</td><td>45</td><td>44.41</td><td>38.22</td></tr><tr><td>Vmpp (V)</td><td>40</td><td>41.2</td><td>14.19</td></tr><tr><td>Isc (A)</td><td>7.93</td><td>7.55</td><td>7.64</td></tr><tr><td>Impp (A)</td><td>7.5</td><td>6.92</td><td>6.71</td></tr><tr><td>Pmax (W)</td><td>135</td><td>75</td><td>95.22</td></tr><tr><td>FF (%)</td><td>76</td><td>42</td><td>33</td></tr><tr><td>Alpha(%/°C)</td><td></td><td>0.0601</td><td></td></tr><tr><td>Beta(%/°C)</td><td></td><td>-0.45</td><td></td></tr><tr><td>Tol+ (%)</td><td></td><td>3</td><td></td></tr><tr><td>String module</td><td></td><td>1</td><td></td></tr></tbody></table>

The STC I-V curve (II) starts at around 7.55 A at a voltage close to 0 V. The curve remains constant up to around 18 V (point A), indicating that the panel is capable of delivering a near-constant current up to this point.

Above 18 V, the current drops sharply to around 3.5 A (point B), reaching an open circuit voltage Voc equal to 22.4 V. The plateau in the curve indicates good performance under ideal conditions. However, the abrupt drop in current at higher voltages shows that the panel is rapidly reaching its capacity limits. This drop affects overall performance, as the damaged panel limits the total current in the series.
<figure><img src="image_16.png" /><figcaption>Figure 7: P-V curves for cracked panels under different conditions
Power increases with voltage, peaking at around 135 W at a voltage close to 37 V (V<sub>mpp</sub>).</figcaption></figure>

After this point, power decreases rapidly. And the P-V curve in STC condition (IV) shows that maximum power is slightly lower (~75 W) and is reached at a slightly lower voltage (~21 V) this significant drop in current at mid-course (~24-28 V), indicating increased internal resistance due to the cracks and affects overall performance, as the damaged panel limits the total current in the series.

Our conclusion Analysis of the I-V and P-V curves shows that the damaged panel has a significant impact on overall system performance. Cracks increase internal resistance, reducing available current and voltage, thus limiting the maximum power generated by the system. Real-life operating conditions exacerbate these effects, resulting in nominal performance below standard test conditions.

comparative study

<table><caption>**Table 4:** Comparing the three cases</caption><thead><tr><th></th><th>P<sub>Nom</sub><br>(W)</th><th>P<sub>STC</sub><br>(W)</th><th>η<br>(%)</th><th>Active surface<br>A (%)</th><th>Poison factor<br>φ</th></tr></thead><tbody><tr><td>Case 1</td><td>100</td><td>40</td><td>60</td><td>31</td><td>0.6</td></tr><tr><td>Case 2</td><td>100</td><td>39.81</td><td>60.19</td><td>30.8</td><td>0.602</td></tr><tr><td>Case3</td><td>135</td><td>75</td><td>44.44</td><td>21</td><td>0.88</td></tr></tbody></table>
in the table above (table13), we can see that the yield of cracked panels alone (cases1 and 2) is of the order of 60% is greater than that of a set of panels containing a module with cracks, its yield is of the order of 45% so the poison factor supports this idea by presenting a greater coefficient for the third case of 88% on the other hand for cases 1 and 2 this coefficient is of the order of 60%, which justifies the effect of the negative impact of the insertion of a cracked panel on the whole of the modules of installation and the effect of fall of yield will be accentuated with the increase in number of modules.

## CONCLUSION

In this work the diagnosis and control of faults in photovoltaic installations were discussed, underscoring the importance of regular maintenance and anomaly detection methods to ensure optimum performance. Cracking faults and their impact on photovoltaic systems were identified, providing a better understanding of the challenges involved in operating solar fields.

In conclusion, this work contributes to a better understanding of photovoltaic technologies and fault management methods, providing a solid foundation for improving the efficiency and reliability of solar systems. The growth of photovoltaic energy, supported by ongoing research and technological innovation, is essential to achieving energy sustainability goals.

## CONFLICT OF INTEREST

NONE

## ACKNOWLEDGEMENT

NONE

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