Imagine a sprawling solar farm, its panels glistening under the sun as they generate clean energy. Everything looks perfect. But years down the line, performance begins to dip. The culprit isn’t the solar cells or the glass—it’s the failure of a tiny, often-overlooked component: the seal protecting the module’s edge.
This is far from a hypothetical scenario. For one of the most popular and cost-effective designs, the glass-backsheet bifacial module, the integrity of the edge seal is critical to its long-term survival. So, what’s the best way to protect it?
We put two common methods to the test—a flexible edge tape and a liquid potting compound—to find out. The results might surprise you.
The Rise of Glass-Backsheet Modules and a New Challenge
Glass-backsheet bifacial modules have become a popular choice in the solar industry. They combine a sturdy glass front with a lightweight, transparent polymer backsheet, allowing them to capture sunlight from both sides while remaining cheaper and lighter than traditional glass-glass designs.
But this design has an Achilles‘ heel: the exposed edge where the glass, encapsulant, and backsheet meet. Over time, this junction becomes a direct pathway for moisture, oxygen, and pollutants to creep inside the module. If this happens, it can lead to corrosion, delamination (where the layers start peeling apart), and a significant drop in power output.
To prevent this degradation, manufacturers must seal this vulnerable edge. The question is, with what?
Sealing the Deal: Two Common Approaches to Edge Protection
Two primary methods compete for the job of edge protection:
Edge Tape
Think of this as a high-tech, industrial-strength adhesive strip. This pre-formed strip is applied directly to the module’s edge. Its clean and simple application makes it an attractive option for high-volume manufacturing. The tape relies on a strong adhesive bond to the glass and backsheet to create a physical barrier.
Potting Compound
This liquid sealant, typically a silicone or polyurethane, is dispensed along the module’s edge. It then cures, or hardens, to form a solid, durable, and seamless seal. Its liquid nature allows it to fill microscopic gaps, but its application requires more precision to ensure a consistent and even coating.
On paper, both sound like viable solutions. But how do they hold up after years of simulated sun, heat, and humidity?
Putting Sealants to the Test: A Real-World Durability Study
To get a definitive answer, we brought both methods into our lab. We prepared two sets of identical glass-backsheet bifacial modules: one sealed with a leading brand of edge tape, the other protected with a two-component potting compound.
Our goal was to simulate decades of harsh environmental exposure in a condensed timeframe. We placed the modules in a climatic chamber for a Damp Heat (DH) test, subjecting them to a punishing 1,000 hours at a constant 85°C (185°F) and 85% relative humidity—a standard industry stress test designed to accelerate aging and reveal long-term failure modes.
Initial Observations
Even before the test began, we noted one key difference. Applying the potting compound, while effective, resulted in a slightly uneven finish—a practical manufacturing challenge that requires precise process control to overcome.
The Aftermath: Clear Evidence of Failure
After 1,000 hours, we inspected the modules. The difference was dramatic.
The modules sealed with edge tape showed significant and widespread delamination. The tape had started to peel away from the backsheet, allowing moisture to penetrate the module’s internal layers. The bond had clearly failed.
In stark contrast, the modules sealed with the potting compound showed no visible signs of degradation. The seal remained completely intact, with no delamination or moisture ingress. It looked almost exactly as it did before the test.
Why Did the Edge Tape Fail? A Deeper Look at the Science
The Damp Heat test didn’t just weaken the tape’s adhesive; it broke down the fundamental bond holding it to the module. Here’s what happened:
- Failure of Adhesion: Edge tape relies solely on adhesion—the force that makes two separate surfaces stick together. The intense heat and humidity weakened this adhesive bond between the tape and the polymer backsheet, causing it to peel away.
- A Robust Chemical Bond: The potting compound, on the other hand, forms a much stronger and more integrated seal. As it cures, it creates a chemical bond with both the glass and the backsheet. It doesn’t just stick to the module; it becomes part of it. This cohesive, cross-linked structure is far more resistant to the stresses of heat and moisture.
This experiment highlights the importance of material compatibility—a core focus of our prototyping and module development process. Simply applying a barrier isn’t enough; that barrier must form a lasting, resilient bond with the materials it is meant to protect.
Key Takeaways for Module Designers and Manufacturers
This head-to-head comparison offers several crucial insights for anyone involved in producing or purchasing solar modules:
- The edge seal is not a minor detail. For glass-backsheet modules, it is a mission-critical component directly linked to the product’s long-term reliability and bankability. A failure here can compromise the entire module.
- Potting compounds offer superior durability. In harsh, humid conditions, a properly applied potting compound provides a significantly more robust and durable barrier against moisture ingress than edge tape.
- Process control is everything. Although the potting compound was the clear winner in durability, its uneven application is a reminder that the best material is only as good as the process used to apply it. Precision and consistency are key.
- Testing reveals the truth. Specification sheets don’t tell the whole story. Rigorous material testing and lamination trials under accelerated aging conditions are the only way to truly validate the long-term performance of critical components like sealants.
Frequently Asked Questions (FAQ)
What is a glass-backsheet bifacial module?
It’s a type of solar panel with a glass front and a transparent polymer material (a backsheet) on the back. This design allows it to capture reflected sunlight from the ground, boosting energy production. It’s often lighter and less expensive than modules with glass on both sides.
What causes delamination in solar modules?
Delamination is the separation of the bonded layers inside a solar module (e.g., glass, encapsulant, cells, backsheet). It’s primarily caused by the breakdown of adhesive bonds due to factors like moisture ingress, extreme temperature cycles, and UV radiation.
Is potting compound always better than edge tape?
In our accelerated life testing for glass-backsheet module durability, the potting compound provided a vastly superior seal. However, any material’s performance depends on its quality, the module design, and the precision of the application process. For this critical application, it proved to be the more reliable solution.
How long does a 1,000-hour Damp Heat test simulate in real-world conditions?
There isn’t a direct one-to-one conversion, such as 1,000 hours equaling 20 years. Instead, accelerated tests like this create extreme stress to reveal potential failure modes that might otherwise take many years to appear in the field. Passing the test provides a high degree of confidence in a module’s long-term durability.
From Lab Insights to Production Reality
Choosing the right edge sealant is more than a material choice—it’s a strategic decision that directly impacts the long-term performance and profitability of a solar asset. As our test shows, what seems like a small detail can be the difference between a reliable 25-year power source and a premature failure.
Understanding these nuances of material science is the first step. The next is applying this knowledge to create more durable and reliable products. Whether you are developing a next-generation module or qualifying new materials, real-world performance data is your most valuable asset.
Discover how our full-scale process optimization and training capabilities help bridge the gap between innovative research and reliable mass production.