Electroluminescence (EL) Testing for Solar Panel Damage Assessment
Multifamily Property Solar Power Installations the Midwest
See the Damage You Can’t See—At the Cell Level
When severe weather impacts a solar project, the most serious damage is often hidden. Microcracks and internal cell failures can reduce output, accelerate degradation, and complicate insurance decisions—without leaving obvious visual signs.
Wolf River Electric provides advanced Electroluminescence (EL) Testing to reveal internal damage within installed solar modules. Our services support solar asset owners, customers, and insurance stakeholders by delivering clear, objective insight to guide repair, replacement, and claim decisions.
Why EL Testing Matters for Solar Assets
Hail, windborne debris, handling, and manufacturing defects can all create microcracks and cell-level failures that:
- Don’t show up in a visual inspection
- May not be obvious in basic performance data
- Can grow over time into serious production and safety issues
Industry data shows that hail alone has driven hundreds of millions of dollars in insured losses for solar projects in recent years, especially in states like Texas, Minnesota, and other hail-prone regions.
EL testing lets us see inside the module structure and pinpoint:
- Where damage exists
- What type of damage it is
- What likely caused it (weather, manufacturing, or handling)
That level of clarity is critical when you’re dealing with multimillion-dollar assets and complex insurance or warranty responsibilities.
Hail, windborne debris, transportation, and handling can all create cell-level damage that:
- Is not visible during standard visual inspections
- May not immediately appear in basic performance data
- Can worsen over time, leading to production loss and safety concerns
In hail-prone regions such as Texas, Minnesota, and the Midwest, severe weather has resulted in hundreds of millions of dollars in insured solar losses in recent years. Understanding whether damage exists—and what likely caused it—is critical when managing high-value assets and insurance or warranty responsibilities.
EL testing allows us to identify:
- Where internal damage exists
- What type of damage is present
- Whether the damage is consistent with weather, handling, or degradation
What Is Electroluminescence (EL) Testing?
Electroluminescence testing is a non-destructive diagnostic method that acts like an infrared X-ray for solar cells.
Using specialized field equipment, we:
- Apply a controlled electrical current to selected module strings
- Capture high-resolution images using short-wave infrared (SWIR) cameras
- Analyze emission patterns to highlight cell-level defects
Healthy cells emit uniform light in EL images. Cracked or compromised cells appear as dark regions or fracture patterns, allowing us to assess the internal condition of each module with precision.
Types of Issues EL Testing Can Detect
- X-shaped or “crow’s feet” patterns from rear-side impacts
- Extensive microcracking from hail even when glass appears intact
- Localized cell shattering that may not yet show as obvious power loss
- V-shaped cracks and dark regions near busbars often linked to soldering issues
- Repeating blotchy patterns that can indicate cell processing contamination
- Cracks from improper lifting or flexing during installation
- Damage caused by dragging modules or swinging connectors impacting the rear of the panel
- Early-stage cell failures and stress points that may predict future power loss
- Non-uniformities across strings or blocks that suggest systemic issues
EL Applications
Inject current via clipping to wires, probing pads, chuck busbar probing, or multiplexed probing of arrays of thin-film cells
Electroluminescence testing benefits solar asset owners, commercial customers, and insurance stakeholders who need a clear and objective view of module condition. It is especially valuable after hail or severe weather, during underperformance investigations, or when there is uncertainty about the cause and extent of damage. EL testing provides evidence that supports decisions about repair, replacement, monitoring, and insurance claims by revealing internal damage patterns that cannot be confirmed through visual inspection alone.
Wolf River Electric begins by reviewing the site layout, event history, and performance concerns to understand the situation and the questions that need to be answered. A sampling strategy is then developed to balance confidence and cost, with additional focus placed on high risk or visibly impacted areas when appropriate. EL imaging is performed in the field, typically at night, using specialized infrared equipment. The captured images are analyzed by experienced professionals who classify defect types, assess severity, and correlate findings to system layout. The final deliverable is a clear, defensible report that supports owners, insurers, and stakeholders in making informed decisions.
EL testing is one of the most effective tools for identifying microcracks and internal cell fractures, especially when damage is not visible and has not yet produced obvious thermal hotspots. While infrared imaging is excellent for identifying active hotspots and thermal anomalies, EL testing can detect internal damage earlier in the failure timeline. UV fluorescence testing is strong for identifying material and encapsulant degradation, but EL provides deeper insight into cell level damage and electrical integrity. For many sites, EL testing offers the strongest diagnostic value when combined with visual inspection and infrared testing to create a complete picture of module condition.
UV fluorescence testing helps reveal early stage module degradation that may not appear in performance monitoring or visual inspection. Customers should care because issues such as moisture intrusion, encapsulant degradation, and seal integrity failures can silently reduce long term reliability and may eventually lead to underperformance or premature failure. UVF testing provides objective documentation that supports maintenance planning, warranty evaluation, and insurance discussions, especially when the goal is to understand long term module health rather than only identifying current electrical failures.
Wolf River Electric uses UV fluorescence inspection strictly for field diagnostics and maintenance related evaluations of installed solar assets. UVF is especially useful when investigating long term degradation, environmental stress exposure, moisture intrusion, seal integrity issues, or unexplained performance concerns. Wolf River Electric does not provide manufacturing support, quality control services for production, or research and development work. Our focus is independent inspection and condition assessment of existing systems.
UVF is highly effective for detecting material related degradation such as encapsulant changes, moisture pathways, delamination, and aging effects within the module layers. However, UVF does not detect every type of defect. Cell level cracking and internal electrical issues are often better evaluated using EL testing. Because solar module failure can involve multiple mechanisms, UVF is often best used as part of a broader diagnostic approach that may include EL imaging, infrared scans, and electrical testing depending on the nature of the concern.
No. UVF testing is non destructive and non invasive. It does not require disassembling the module or removing it from the array. The inspection is performed externally using ultraviolet excitation and imaging equipment, allowing the module to remain installed and intact while still revealing degradation signatures within the module materials.
UVF is used on solar modules because it can reveal degradation and material failures that are not always visible through electrical testing or infrared scans. It is especially helpful for identifying encapsulant discoloration, moisture intrusion patterns, backsheet and seal integrity issues, delamination, and aging effects that can reduce long term module reliability. UVF can also highlight early stage changes that may precede hotspots or electrical failure, making it valuable for preventive maintenance and warranty evaluation.
UV Fluorescence testing is a diagnostic imaging method that uses ultraviolet light to excite certain polymers within a solar module, causing them to fluoresce. The resulting fluorescence patterns are captured with specialized imaging equipment and can reveal material degradation, moisture pathways, seal integrity issues, and aging effects. UVF is a non destructive technique that provides insight into module health beyond what is visible during standard inspections.
Yes. EL and PL testing can be used for both residential and commercial solar, but it is more common on commercial and utility scale projects because the asset value and scale justify deeper diagnostics. Residential EL or PL testing is most often performed after hail events, storm impacts, or when a homeowner experiences unexplained underperformance and needs objective evidence of damage or defects.
Wolf River Electric emphasizes quality testing because solar modules can suffer internal damage or degradation without showing visible signs. Hidden defects often worsen over time and can lead to long term production losses, safety risks, and expensive replacements if not identified early. Advanced diagnostic testing provides clearer evidence of what is actually happening inside the modules and supports accurate decision making for asset owners and insurers. For large systems, even a small defect percentage can become a major financial issue, which is why evidence based diagnostics matter.
No. Most solar installers do not offer EL or PL testing because it requires specialized equipment, nighttime field deployment capability, controlled energization procedures, and expert interpretation. EL and PL testing are considered advanced diagnostic tools rather than standard installation services. Wolf River Electric provides these services specifically to support asset owners, customers, and insurance professionals who need objective and defensible evaluations.
EL and PL testing benefit solar systems by identifying hidden module damage that can reduce output and reliability over time. This helps owners address issues before they become widespread failures, improves confidence in repair and replacement decisions, and provides stronger documentation for insurance claims or warranty discussions. EL and PL testing can also explain underperformance that cannot be diagnosed through standard monitoring or visual inspection alone.
EL and PL testing can detect microcracks, fractured cells, inactive regions, stress damage from handling or installation, and patterns consistent with storm impacts such as hail. These tests can also reveal early stage cell failures and non uniform defect patterns that may indicate broader reliability concerns. Because these issues are often invisible externally, EL and PL provide a deeper view into cell level health and integrity.
EL testing applies a controlled electrical current to solar modules and captures infrared images of cell emission patterns. PL testing uses light excitation to trigger cell level emission and capture similar diagnostic images. In both methods, healthy cells show consistent emission while damaged cells show dark regions, fractures, and irregular patterns. These tests allow experts to assess internal module health at the cell level and identify defects that are not visible through conventional inspection methods.
EL and PL testing are advanced diagnostic imaging methods used to evaluate the internal health of solar cells and modules. Wolf River Electric uses EL and PL because they provide highly detailed insight into damage and defects that cannot be seen through visual inspection, basic electrical testing, or performance monitoring. These tools support storm damage assessment, underperformance investigation, and insurance or warranty evaluations by providing objective evidence of internal module condition and likely damage mechanisms.
Ready to See What Your Panels Are Hiding?
If your solar project has been hit by severe weather, is underperforming, or is heading into a critical financial milestone, Electroluminescence Testing can provide the clarity you need to move forward.
Contact Wolf River Electric today to discuss:
- Site size and location
- Recent events or performance concerns
- Your goals (insurance, warranty, O&M optimization, or due diligence)
We’ll design an EL testing program tailored to your project, your risks, and your budget—so you can make decisions based on data, not guesswork.
