Why you see Snail Trail on Solar Panels

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  1. What are Solar Panel Snail Trails?
  2. How are snail trails formed on solar panels?
  3. The Key Reasons Behind The Formation of Snail Trails on solar panels?
  4. What are the impacts of snail trails on solar panels?
  5. How to prevent snail trails on solar panels?


Installing solar panels to power your home is a sustainable long-term investment. This not only helps reduce your utility expenses but also contributes to lowering your carbon footprint, creating a more sustainable ecosystem. However, despite the significant advantages of solar panels in providing clean energy, some issues may affect their efficiency over their lifespan, and one common problem is the occurrence of snail trails.

What are Solar Panel Snail Trails?

Snail trails, often called snail tracks or worm marks, are localized discolored lines that appear on solar panels after extended use. They typically present as dark or brown streaks and are commonly found near busbars, along the edges of the panels, or adjacent to microcracks.

These slender, brownish lines give the impression of snails or worms having moved across the panel's surface, leading to their descriptive names "snail trails" or "worm marks." When these markings cover the entire panel, they can substantially affect its aesthetic appeal.

Usually, the presence of snail trails becomes noticeable on solar panels that have sustained microcracks or similar damage, often months after being subjected to outdoor conditions. Once they appear, these trails tend to be a permanent and visually obvious characteristic of the solar panels.

What are Solar Panel Snail Trails

How are Snail Trails Formed on Solar Panels?

The creation of snail trails on solar panels is a result of complex chemical and physical interactions. Initially, a chemical reaction at the solar panel's busbars sets the stage for snail trail formation. Over time, physical stress contributes to the development of microcracks on the panel's surface, allowing moisture to seep in. This moisture, under the influence of an electric field, ultraviolet radiation, and the panel's operating temperatures, starts a corrosion process.

During this process, the deformation of silver contacts and the encapsulation foil leads to the migration of silver particles onto the EVA foil. This foil, containing chemical elements such as sulfur, phosphorus, and chlorine, undergoes secondary chemical reactions with the silver. The result is the formation of tiny particles, which collectively manifest as the visible snail trails on the solar cells and their encapsulation materials.

Extended exposure of solar panels to harsh outdoor conditions further accelerates this process. The EVA material degrades, emitting carbon dioxide and acetic acid. Oxygen in the air reacts with the silver paste of the panel, forming silver carbonate (4Ag + 2CO2 + O2 → 2Ag2CO3). This compound further reacts with acetic acid in the EVA, producing silver acetate (Ag2CO3 + CH3COOH → CH3COO(Ag) + CO2 + H2O). The silver acetate then deposits on the EVA, presenting as brown lines or snail trails.

Importantly, microcracks play a crucial role in this process. Without these cracks, which allow external elements, particularly moisture, to penetrate, the formation of snail trails is significantly less likely. Therefore, the presence and condition of microcracks are key factors in the emergence of snail trails on solar panels.

The Key Reasons Behind The Formation of Snail Trails on Solar Panels

Snail trails on solar panels often develop after extended exposure to outdoor elements, leading to inquiries about their exact causes. Research has identified that these trails predominantly stem from material defects and the onset of certain chemical processes.

1. Chemical Property Variance: A key factor is the difference in chemical properties between the EVA (ethylene vinyl acetate) foil and the silver contacts on the solar panels. This disparity plays a significant role in the formation of snail trails.

2. EVA Material Degradation: The extent to which the EVA material degrades over time, reflecting its aging and wear, is another crucial element. The degradation process affects the panel's resilience to environmental factors.

3. Backsheet Water Vapor Permeability: The ability of the solar panel's backsheet material to prevent water vapor from penetrating into the panel's interior is also a determinant. Ineffective prevention of moisture ingress can lead to the formation of snail trails.

Often, these material defects become apparent when solar panels are in use, although they can also originate during the manufacturing process, known as ‘manufacturing cosmetic blemishes.’

The chemical processes resulting from these material defects primarily involve corrosion reactions. Snail trails become visible when microcracks on the solar panel surface allow moisture and oxygen to seep in. While not every microcrack leads to the formation of snail trails, there is a significant correlation between the presence of microcracks and the appearance of snail trails in the same areas of a solar cell. Therefore, it can be generally stated that microcracks are the principal catalysts for the development of snail trails on solar panels.

The Key Reasons Behind The Formation of Snail Trails on Solar Panels

Impacts of Snail Trails on Solar Panels

Degradation in Solar Panel Performance: Snail trails primarily affect the performance of solar panels by diminishing light reflection from the surface of the solar cells. This results in lowered efficiency and reduced energy yield. Research on crystalline solar panels with snail trails indicates a potential decrease in power efficiency of up to 9.1%. Additionally, the erosion caused by these trails can damage the solar cells, further impairing the electrical performance of the panel.

Formation of Hot Spots: Beyond affecting light reflection, snail trails can also increase current resistance on the solar panel. This resistance leads to the creation of hot spots, which can have a detrimental impact on the panel's overall performance. These localized areas of intense heat not only reduce energy conversion efficiency but can also compromise the long-term stability and reliability of the panel.

Aesthetic Impact: The appearance of solar panels is crucial for their aesthetic integration into an environment. Snail trails not only compromise the panel's performance but also detract from its visual appeal. Over time, these brown marks can worsen, leading to a significant and lasting negative effect on the appearance of the solar panel and its installation surfaces. This aesthetic degradation can be a concern for residential and commercial settings where the visual aspect of solar installations is important.

Impacts of Snail Trails on Solar Panels

How to Prevent Snail Trails on Solar Panels

Handle Solar Panels with Care to Avoid Microcrack Formation

Proper Installation and Maintenance: It's essential to have solar panels installed by qualified professionals. The mounting frame and support structure should be robust and meet design specifications. Regular inspections and maintenance, including cleaning and checking fasteners, are crucial to prevent microcracks caused by external pressures.

Avoid Excessive Force: During installation and maintenance, care should be taken to avoid applying too much force or pressure, especially near the edges of the solar panels. Gentle handling is key to reducing the risk of mechanical damage.

Suitable Foundation and Support: The foundation and support structure for solar panels must meet the necessary design requirements. They should be capable of withstanding environmental factors like wind, rain, and snow. A sturdy support structure can help mitigate the impact of external forces on the panels.

Click to learn more about microcracks on solar panels:

Choose Solar Panels with Advanced Encapsulation Materials

Selecting the right materials for solar panels is key in preventing the formation of snail trails. Some polymer materials used in solar panels can contribute to the development of snail trails. Hence, choosing the right encapsulation materials is crucial. High-quality, durable materials that can withstand environmental changes are ideal. These materials not only help prevent snail trails but also extend the lifespan of the panels and ensure consistent energy efficiency and output.

For example, Maysun's HJT double glass bifacial solar panels are encapsulated with POE (polyolefin elastomer), a thermoplastic material known for its superior performance and sustainability in solar applications. Its resistance to UV light helps maintain stability under various climatic conditions, thereby prolonging the life of the panels. Being weather-resistant, POE can endure exposure to sun and rain and is well-suited to harsh environments. Additionally, POE is environmentally friendly, aligning with the principles of sustainable development.

Choosing solar panels like Maysun's HJT double glass bifacial models, which utilize POE as the encapsulation material, offers significant benefits in terms of performance, durability, and environmental compatibility. This approach aligns with the broader goals of sustainability and long-term efficiency in solar energy systems.

HJT Solar Panel

The goal of Maysun Solar since 2008 has been to make the best solar panels. Check out our wide range of half-cut, MBB, IBC, HJT, and shingled solar panels, which come in silver, full black, black frame, and glass-glass styles. Beautiful designs and great efficiency make the panels stand out and make any building look better. Maysun Solar is a reliable choice because it has long-standing offices and warehouses and relationships with top installers in many countries. Feel free to get in touch with us if you have any questions about PV or want the most up-to-date quotes on solar panels. We’re happy to help.


Solaradvisor. (2023, April 9). Why do you see snail trails on the surface of solar panels? | SolarTechAdvisor. Solartechadvisor.

Admin. (2023, December 4). Snail trails on solar panels | Just Solar. Just Solar.

Hoffmann, V. (2023, November 23). Unveiling the impact of Snail Trails on PV Modules. Above.

Nicolas, & Nicolas. (2022, October 19). Snail Trail effect: how to prevent your PV module from damage – Eco Green Energy. Eco Green Energy – Building a Greener World.


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