Imagine a major hailstorm rolls through your area. The next morning, you inspect your solar array and, to your relief, the glass on the modules looks perfectly intact—no shatters, no visible cracks. You assume you’ve dodged a bullet.
But what if the most significant damage is completely invisible?
This scenario is more common than many people think. While modern solar panels are built to be robust, the delicate silicon cells inside can fracture under impact without breaking the top glass. These tiny fractures, known as microcracks, are the hidden culprits behind gradual power loss and long-term module degradation. The problem is, you’d never know they were there just by looking.
The Invisible Threat: What Are Microcracks?
Microcracks are sub-millimeter fissures that form in photovoltaic (PV) cells from mechanical or thermal stress. Think of them as tiny, branching cracks in the very heart of the solar cell—the engine that converts sunlight into electricity.
Why are they so problematic?
- They Disrupt Energy Flow: A crack creates a physical break in the cell, forcing electricity to reroute around it. This process is inefficient and reduces the cell’s overall power output.
- They Create „Dead“ Zones: Large or interconnected cracks can completely isolate parts of a cell, turning them into inactive „dead“ zones that no longer generate power.
- They Worsen Over Time: Daily temperature swings cause the module’s materials to expand and contract. This constant movement can cause small microcracks to grow and spread, accelerating performance degradation over the module’s life.
The challenge is that a module can be riddled with performance-killing microcracks while its surface appears flawless. This is where specialized diagnostic tools become essential.
Simulating Nature’s Fury: How We Test for Hail Resilience
Waiting for a real hailstorm to test a module’s durability is hardly a viable strategy for manufacturers or project developers. To truly understand how a module will perform, we need to bring the storm into the lab.
While industry standards like IEC 61215 set a baseline with 25 mm hailstones, the increasing frequency of extreme weather events worldwide means we need to look beyond these minimums. To gather reliable, repeatable data, we use a highly controlled testing protocol.
At PVTestLab, we use a pneumatic ice ball gun to fire calibrated ice projectiles of a specific mass at precise velocities. This allows us to calculate and control the exact impact energy (measured in Joules) delivered to the module surface. By targeting different areas—the center of a cell, its edge, or over a busbar—we can systematically analyze how different module designs and materials withstand stress.
This methodical approach moves beyond a simple pass/fail, allowing us to build a detailed map of a module’s resilience. But how do we see the damage that occurs on a microscopic level?
Making the Invisible Visible: The Power of EL Imaging
Electroluminescence (EL) imaging is the gold standard for quality control in solar module manufacturing. Think of it as an X-ray for a solar cell.
The process is simple in concept but powerful in application: the solar module is placed in a dark room and a forward current is applied. Healthy, crack-free areas of the silicon cells luminesce, or light up, emitting a faint infrared glow captured by a specialized camera. Areas with microcracks, breaks, or other defects, however, disrupt the electrical current and appear dark.
By taking an EL image after a controlled hail impact, we can see the exact pattern and severity of the resulting cell damage. It’s the critical link between a physical event (hail impact) and its electronic consequence (power loss).
The Proof is in the Picture: Glass Thickness and Damage Correlation
So, what have we learned from combining controlled hail impacts with high-resolution EL imaging? Our research reveals a direct, quantifiable correlation between impact energy, front glass thickness, and the extent of microcrack formation.
We tested modules with three different front glass thicknesses: thin 2.0 mm, standard 2.8 mm, and robust 3.2 mm. The results were striking.
Our tests showed that on modules with thinner 2.0 mm glass, microcracks began to appear with as little as 0.44 Joules of impact energy—the equivalent of a small hailstone traveling at a moderate speed. As the impact energy increased, the cracking became progressively more severe, spreading across the cell in a starburst pattern.
In stark contrast, modules built with a robust 3.2 mm glass front could withstand over 2.27 Joules of energy—more than five times that force—before showing any significant microcracking.
These findings provide invaluable data for anyone involved in designing or deploying solar technology. For engineers, this data is crucial for effective solar module prototyping, helping them select materials that balance cost, weight, and long-term durability. It highlights the importance of our comprehensive material testing services, which validate how components like glass and encapsulants perform under real-world stress.
Why This Matters for Your Solar Project
Understanding the hidden risk of hail damage is critical for ensuring a solar project’s long-term financial viability and energy production.
- For Module Developers: This data proves that material selection is about more than just datasheets; it’s about mechanical reality. Investing in slightly thicker glass or more resilient cell structures can dramatically improve a module’s lifetime performance and bankability in hail-prone regions.
- For Asset Owners: If a plant’s performance dips after a storm, don’t rely on a visual inspection alone. Hidden microcracks could be the root cause. EL imaging provides the ground truth needed for accurate diagnostics and warranty claims.
- For Manufacturers: Insights from this type of testing can drive meaningful improvements. By understanding failure thresholds, manufacturers can fine-tune their bill of materials and processes, leading to better process optimization and a more reliable final product.
Ultimately, this research replaces guesswork with data, allowing for a much more accurate risk assessment.
Frequently Asked Questions (FAQ)
What is electroluminescence (EL) imaging?
EL imaging is a diagnostic technique that reveals hidden defects in solar cells. By passing an electric current through a module in the dark, healthy parts of the cells light up, while cracked or inactive areas remain dark, creating a clear map of the module’s electronic health.
Can microcracks be repaired?
Unfortunately, no. Once a silicon cell is cracked, it cannot be physically repaired. The damage is permanent, which is why preventing it through robust module design and material selection is so important.
Does all hail damage solar panels?
Not necessarily. Damage depends on the kinetic energy of the hailstones—a combination of their size, density, and velocity—and the mechanical resilience of the solar module itself. As our tests show, a module with thicker glass can withstand significantly more impact energy than one with thinner glass.
Is thicker glass always the better choice?
For hail resistance, yes, thicker glass provides demonstrably better protection. However, module design involves trade-offs. Thicker glass adds weight and cost, which must be balanced against the project’s specific environmental risks, structural requirements, and financial model.
From Lab Insights to Real-World Resilience
The threat of hail is a perfect example of why we can’t afford to take module durability for granted. What seems like a minor event can cause significant, invisible damage that silently degrades energy production for years.
By moving beyond simple visual checks and adopting data-driven testing methods like controlled impact analysis and EL imaging, the solar industry can build more resilient, reliable, and profitable projects. Understanding the precise correlation between materials and performance is the first step toward engineering the next generation of solar modules—ones built not just to survive the storm, but to thrive long after it has passed.
Ready to dive deeper into the science of module durability? Explore our full range of prototyping and testing services to see how we help innovators turn concepts into reliable, market-ready products.