Imagine you’re developing a solar module for a massive new project. One installation is set for the sun-drenched plains of West Texas, the other in the rolling hills of southern Germany. Both locations have excellent solar irradiance, but they also share a more destructive trait: a growing risk of severe hailstorms.
Do you specify the same module for both?
If you were only looking at standard certifications, you might. But as recent weather events show, the standard playbook for durability is quickly becoming outdated. In the US „Hail Alley,“ annual damages regularly top billions of dollars. This isn’t just an American problem; a single 2021 storm in Europe caused over €500 million in damages to solar installations, with hailstones larger than 5 cm becoming increasingly frequent.
Relying on a baseline certification for a high-risk environment is like wearing a raincoat in a hurricane. It might meet a minimum requirement, but it won’t keep you safe when the storm hits.
A Solar Module Is More Than Just a Pane of Glass
When we think about protecting a solar module from impact, the front glass is usually the first thing that comes to mind. It’s the first line of defense, and its thickness seems like the most obvious dial to turn. But that view misses the bigger picture.
A solar module isn’t monolithic; it’s a highly engineered composite sandwich. Each layer plays a role in its overall strength and resilience.
Here’s a quick breakdown:
- Glass: The primary shield against the elements.
- Encapsulant (EVA/POE): A polymer layer that bonds everything together, cushions the cells, and provides electrical insulation.
- Solar Cells: The delicate silicon wafers that convert sunlight into electricity.
- Backsheet: The final layer that protects the module from the rear.
The „aha moment“ for many designers is realizing that the bond between these layers, created during the lamination process, is just as critical as the thickness of the glass itself. A module with perfectly laminated, void-free layers can distribute the force of an impact far more effectively than one with thicker glass but a weaker bond.
This synergy between materials and process is the secret to engineering true durability.
The IEC Standard: A Good Start, But Not the Finish Line
The international standard for PV module design, IEC 61215, includes a hail test as part of its Mechanical Stress Tests (MQT 17). In this test, a 25mm (about 1 inch) ice ball is fired at the module at 23 m/s (about 51 mph).
For many years, passing this test was the gold standard.
However, as hail events become more severe, the market is demanding more. The latest revision of the standard, IEC 61215:2021, acknowledges this by allowing tests with larger hailstones (from 35mm up to 55mm), but it doesn’t make this mandatory. This leaves a critical gap: a module can be fully certified yet prove completely inadequate for regions where 45mm hailstones are the new normal.
Relying solely on the standard certification is a bet against Mother Nature—and it’s a bet that gets riskier every year.
How to Engineer for Real-World Impact
So, if the standard isn’t enough, what is? Building a hail-resistant module requires a holistic approach that spans from design to physical validation. It’s about making deliberate choices and then testing them under real-world conditions.
1. Strategic Glass Selection
Simply choosing thicker glass isn’t always the answer. The relationship between glass thickness and hail resistance is complex and non-linear—doubling the thickness doesn’t double the strength. Factors like tempering, chemical strengthening, and anti-reflective coatings all influence how the glass behaves under impact. The right choice is a careful balance of durability, weight, cost, and light transmission.
2. The Critical Role of the Lamination Process
This is where theory meets reality. The lamination cycle—the specific profile of temperature, pressure, and time used to bond the module layers—is arguably the most important and least understood factor in mechanical strength.
An optimized lamination process ensures a perfect, uniform bond. It eliminates microscopic air pockets or areas of poor adhesion that can become catastrophic failure points under impact. This is also where different encapsulants, like EVA and POE, reveal their unique characteristics. Only physical testing can reveal which performs better with your specific module design.
3. The Necessity of Controlled Prototyping
You can run all the computer simulations you want, but nothing reveals the truth like a physical impact test. This is the core of an effective design validation strategy.
Building prototypes allows you to test different combinations of materials and process parameters in a controlled, repeatable environment. The goal isn’t just to pass, but to understand the failure point. Does a 3.2mm sheet of glass from Manufacturer A, combined with a specific POE encapsulant and a faster lamination cycle, outperform a 4.0mm sheet from Manufacturer B?
This is what separates guesswork from certainty. It’s the essential step in solar module prototyping that bridges the gap between a design on paper and a bankable product in the field.
„We often see that a perfectly controlled lamination cycle can improve hail resistance more effectively than simply increasing glass thickness. The data from physical prototypes is what separates assumption from certainty.“ — Patrick Thoma, PV Process Specialist
From Data to Decisions
Validating your design in a dedicated test lab gives you the concrete data needed to make smart, cost-effective decisions. Instead of over-engineering (and over-spending) with thicker glass, you can pinpoint the most efficient combination of materials and processes.
This iterative cycle of building, testing, and analyzing allows you to:
- Compare different suppliers for glass and encapsulants.
- Optimize your lamination recipe for maximum durability.
- Quantify the impact resistance of your final design.
- Confidently enter markets with specific performance requirements.
Effective material testing isn’t an expense; it’s an investment in risk reduction and market readiness.
Frequently Asked Questions (FAQ)
1. What is MQT 17 in the IEC 61215 standard?
MQT 17 refers to the Mechanical Stress Test sequence, which includes tests for static mechanical load, snow load, and hail impact. It’s designed to ensure a module can withstand the common physical stresses it might encounter during its lifetime.
2. Is thicker glass always better for hail resistance?
Not necessarily. While thickness helps, the quality of the glass tempering and, more importantly, the quality of the lamination bond are critical factors. A well-laminated module with 3.2mm glass can sometimes outperform a poorly laminated one with 4.0mm glass.
3. What’s the difference between EVA and POE encapsulants for impact resistance?
Both are polymers used to encapsulate solar cells. POE (Polyolefin Elastomer) generally offers better mechanical stress relaxation and lower water vapor transmission rates, which can contribute to greater long-term durability and impact resistance. However, the ideal choice depends on the specific module design and cost targets, which is why comparative testing is so valuable.
4. How does the lamination process affect durability?
Lamination uses heat and pressure to create a permanent, void-free bond between the module’s layers. An unoptimized process can leave behind bubbles, delamination, or areas of high internal stress. These defects become weak points that can easily fail when struck by hail.
5. Why can’t I just rely on the manufacturer’s spec sheet?
A spec sheet provides certified, baseline performance data, confirming the module passed standard tests. It doesn’t, however, tell you how the module performs beyond the standard or how it will hold up in a specific high-risk environment. For that, you need targeted testing that reflects the real-world conditions your module will face.
Take the Next Step from Design to Durability
Understanding the complex interplay of forces that contribute to module strength is the first step toward building a truly resilient product. The next is to validate your design with real data. By moving beyond baseline standards and embracing a test-driven approach, you can engineer modules that not only survive but thrive in the world’s most demanding environments.
Ready to see how your design holds up under pressure? Explore how a structured solar module prototyping and validation program can give you the certainty you need to innovate with confidence.