Microcracks: A Full Guide

Microcracks (or Microfractures) are a common problem in solar modules and are difficult to detect with the naked eye. So, it is important to know how to identify and correct them. This article explains the causes of microcracks in solar panels, how they are detected, their effects and which types of solar panels are less likely to produce them.

What are microcracks?

Microcracks in solar panels are tiny fractures or fissures that can arise in the photovoltaic cells or the protective layers of the solar panel structure. These fractures are often microscopic and undetectable to the naked eye. However, they play a crucial role in influencing the overall performance and lifespan of solar panels.

This issue is a relatively common defect in crystalline silicon photovoltaic modules. Because of the characteristics of their own crystalline structure, crystalline silicon modules are very prone to cracking.

Microfractures can affect solar panel performance, leading to power loss, a much shorter lifespan, or even the cessation of energy production from the entire solar panel.

Causes of Microcracks in Solar Panels

The causes of microcracks can be diverse and multifaceted:

Manufacturing defects:

Improper handling, poor material selection, or quality control failures create an environment in which vulnerabilities are introduced. These vulnerabilities, arising from the manufacturing phase, become potential catalysts for the initiation and propagation of microcracks within the solar panel structure. Attention to detail, proper staff training, and strict adherence to quality control protocols are essential throughout the manufacturing process. This helps minimize the risk of microcrack formation.

Mechanical stress

Mechanical stress is a major factor causing microcrack formation in solar panels. It can be categorized into several phases: transportation, installation, and exposure to external environmental factors.

A comprehensive approach to minimizing the risk of microcrack formation in solar panels involves understanding and mitigating mechanical stress. This includes various stages, from transportation to installation, and operation.

By taking into account both internal handling practices and external environmental factors, the overall reliability and performance of solar panels can be improved.

Transportation

During transportation, mechanical stress can significantly affect solar panels, particularly packaging, storage, and handling practices in the supply chain. Improper packaging or storage procedures can subject solar panels to excessive pressure, which can cause microfracture formation. Wrong transportation methods, such as rough handling or incorrect stacking, can subject solar panels to vibration and impact. This can cause mechanical stress and an increased risk of microcrack formation.

Installation

Installation-induced mechanical stress is also a critical concern for solar panels. Practices like improper stacking, resting equipment on panels, accidental bumps, and installation on uneven surfaces can create localized pressure points. These pressure points can lead to the formation of microcracks.

Dragging panels during transport can introduce friction-induced stresses. Improper transport techniques, such as using only one person or sitting on the edge of the module, can result in uneven forces. These practices can compromise the efficiency and longevity of solar panels. So, it is crucial to follow careful handling and installation procedures to mitigate mechanical stress and ensure optimal performance.

Environmental factors

During the long-term operation of solar panels, external environmental factors can impose significant mechanical stress. These factors include weather-related stresses like wind, heavy snowfall, hail, and extreme temperature variations. This situation, when persistent over time, can contribute to the cumulative development of microcracks.

Thermal Cycles

Thermal cycles, resulting from daily and seasonal fluctuations in temperature, are a key factor contributing to the development of microcracks in solar panels. .The constant expansion and contraction of materials within solar panels are influenced by varying sunlight and weather conditions. This creates favourable conditions for the initiation and propagation of microcracks over extended periods of exposure.

The repetitive stress caused by thermal cycles highlights the importance of considering temperature variations. Solar panel design, manufacturing, and installation processes must account for these variations to improve durability and longevity.

What damage can microcracks cause?

Increased electrical resistance and thermal damage

Microcracks can lead to increased electrical resistance, raising temperatures and creating hotspots. This escalation of thermal damage further contributes to the overall deterioration of the affected solar cell. In some cases, microfractures can propagate and cause circuit isolation of a significant area of ​​an individual cell. This insulation can cause reverse polarization, inducing high temperatures in the connected section of the cell.

As temperatures rise, there is a risk of causing permanent damage, not only by decreasing power output. Also, in extreme cases, this situation leads to catastrophic failures. For example, glass breakage or, a fire because of the intense heat generated by a reverse polarized cell.

Reduced power output

Increased electrical resistance leads to decreased power generation, causing a decrease in the overall efficiency of the solar panel.

Crack propagation and module failure

If microcracks extend in length, they can develop into larger cracks. So, this can stop or terminate the power production of the entire module. This result makes replacement necessary and significantly affects the overall lifespan of the solar panel.

To mitigate these damaging effects, early detection through regular inspections is essential.

How to detect microcracks?

Detecting microcracks in solar panels is a critical process to ensure optimal performance and long life. There are several inspection methods to suit different situations during the installation and operation phases.

In practice, professionals can choose to employ these inspection methods individually or in combination. This depends on the specific requirements and circumstances of the solar panel system. It is imperative to employ trained experts, especially when using advanced technical equipment. So, you can ensure accurate detection and analysis of microcracks. Regular monitoring and a thorough approach contribute significantly to the overall reliability and longevity of the solar power system.

ELCD (Electroluminescence Crack Detection):

Electroluminescence works on the principle of generating light when an electric current is applied to a material. In the solar cell field, EL is applied to visualize and identify defects that are not easily visible using alternative methods. EL testing is particularly effective in detecting microcracks, broken cells, and other internal defects in solar cells. This method provides direct insight into the structural integrity of cells. So, uncovers hidden problems that may escape detection using other testing methods.

ELCD (Electroluminescence Crack Detection) uses electroluminescence to effectively detect microcracks in solar panels. The application of an electric current activates electroluminescent materials. So, this produces a visible light that is altered by microcracks, making them visually detectable. This non-destructive method is crucial for quality control during manufacturing and preventative maintenance.

Best used during installation and operation, photoluminescence imaging identifies microcracks that affect photovoltaic conversion efficiency. This technique integrates seamlessly into periodic maintenance routines to maintain efficiency.

Infrared Imaging

Infrared (IR) imaging captures the thermal radiation emitted by an object. This allows for the identification of temperature variations indicative of defects or irregularities.

IR technology is widely used for thermal inspections in solar cells. These inspections help detect overheating, identify faulty components, and detect irregularities in both solar cells and photovoltaic modules. This technique is especially effective in identifying problems related to electrical connections, such as loose or damaged cables.

Visual Inspection and Microscopic Examination:

Most applicable during installation and routine maintenance, visual inspection and microscopic examination involve direct observation and detailed structural scrutiny. This practical approach effectively identifies visible cracks on solar panel surfaces.

Curve Scanning Method (I-V)

For PV panels that have been installed and connected to an intelligent monitoring platform, the curve scanning function (I-V) can be used to quickly scan and classify PV panels with micro cracks.

If the scan results in an abnormal I-V curve (dotted line), cracks in damaged cells or blocked currents are likely.

Advantages:

1. This solution can identify a variety of faults in PV modules.

2. The response time is fast, the investigation can be completed in just 5 minutes.

3. No professional equipment or personnel are needed (save costs).

Choosing the Right Solar Panels to Reduce Microcracks

Microcracks are a common challenge in solar panels. However, innovative technologies like HJT and IBC have significantly reduced their impact on performance. Here’s why they are more resistant to microcracks

HJT Solar Panels:

• N-Type Monocrystalline Silicon Substrate: HJT solar cells employ an N-type monocrystalline silicon substrate known for its high purity and uniformity. Compared to polycrystalline silicon, the monocrystalline structure is more compact and consistent, which helps reduce microcracks caused by stress concentration.
• Undoped amorphous silicon layer: A layer of undoped amorphous silicon is deposited on the monocrystalline silicon substrate. This layer serves as a “buffer layer.” So, this layer enhances the cell’s elasticity and protection. It is particularly beneficial when the cell is subjected to physical stress. For example, in the case of bending or pressure during transportation and installation.
• Full half-cell processing method: HJT solar panels employ a unique full half-cell processing technique. This technique entirely prevents shear damage to the solar cells.
• Lower manufacturing temperature: Compared to traditional crystalline silicon solar cells, HJT cells are manufactured at lower temperatures. This results in less thermal stress on the materials during production.
• Optimized overall structure: The overall structure of HJT cells is optimized during design and manufacturing. This optimization improves their resistance to physical stresses. For example, the edges and corners of the cells are designed to be smoother, reducing stress concentration points.
• Ultra-Multi-Busbar Design: HJT panels utilize a design with narrower busbars. This design reduces the amount of silver paste required. So, it minimizes shading effects and shortens current transmission distances. On the other hand, this feature enhances the electrical performance of the panels. Besides, it minimizes current loss resulting from microcracks, damaged busbars, and fractures. This ultimately improves panel reliability and extends their lifespan.
• Increased Mechanical Strength: The various design and manufacturing optimizations mentioned above improve the overall mechanical strength of HJT solar cells. This increased strength helps maintain cell integrity during transportation and installation, reducing the risk of microcracks.

For example, the company Meyer Burger manufactures solar panels with HJT technology

IBC Solar Panels:

Solar panels with IBC (Interdigitated Back Contact) technology are an advanced type of photovoltaic panel. Unlike traditional panels, these panels have their electrical contacts on the back of the solar cells, rather than on the front.

This design prevents tensile damage and detachment. Such damage is typically caused by the thermal expansion and contraction of the front welding strip under high-temperature stress. This feature ensures consistent and stable energy generation from the solar panels. It also mitigates the adverse effects of thermal variations on the panel’s integrity.