EL vs. PL - Two paths to PV module quality inspection
EL vs. PL for PV modules: A concise comparison of daylight photoluminescence and electroluminescence for detecting microcracks, shunts, and degradation.
Hail Damage Inspection
Why EL after hail?
Making invisible hail damage visible – in the installed condition
After hail, microcracks can locally interrupt current flow in cells – often without an immediate measurable loss of yield. With EL inspection, these defects become visible as dark lines/areas. Our DaySy method also works in daylight – without night-time measurements.
You can find more about the method on our page on electroluminescence inspection, as well as on patents and the drone-based development project ELFI.
Early detection of cell cracks & micro-damage
EL reveals even the smallest cracks before power losses or hotspots become apparent during operation.
Objectively & reproducibly documented
You receive clear image documentation for each inspected module – ideal for comparison, verification, and quality assurance.
Daylight measurement (DaySy)
We measure in daylight – simplifying scheduling and making inspections especially efficient in urban environments.
Insurance-relevant expert report
On request, we prepare an evaluation with damage categories and recommended actions (e.g., replacement/continued operation).
Typical damage patterns
What happens after hail – and what does EL show?
After hail, visual inspection or thermography is often insufficient: hidden cell cracks remain invisible but can lead to hotspots, power loss, or module failure in the long term. EL makes these patterns visible and enables a well-founded decision.
Hidden cell cracks (invisible)
Microcracks in solar cells that are usually not visible from the outside – but appear clearly as lines/segments in EL.
Visible damage
Glass breakage, impacts, frame deformation, or delamination can be identified visually – EL additionally helps with cell-level assessment.
Damage attribution & patterns
Certain crack patterns can provide clues about the cause of damage – important for insurance assessment.
Roof inspection by drone
Using a drone eliminates the need for scaffolding or lifts – significantly speeding up the inspection.
Hail inspection in 5 steps
Step 1: Initial contact & assessment
You describe the hail event, location, and symptoms (e.g., visible glass damage, yield loss, anomalies). We briefly clarify the objective (quality / insurance), accessibility, and electrical connection.
Step 2: Inventory & documentation
You send us photos, system documentation, and – if available – the string layout. For EL, a suitable power connection is required; PL can be performed without an external power source.
Step 3: Quotation & insurance coordination
We prepare a quotation based on system size and inspection strategy (sampling vs. comprehensive). If insurance is involved, we provide the necessary information for approval and commissioning.
Step 4: On-site EL measurement
We connect the strings and capture luminescence images of the modules – in the installed condition, in daylight.
Step 5: Evaluation & report
We categorize the findings, document the location/type of defects, and provide recommendations (replacement/continued operation/further tests). The report can be prepared in an insurance-ready format on request.
Hail EL FAQs
FAQ on hail damage inspection for PV systems
The most important questions about invisible hail damage, EL diagnostics, and documentation for insurers & operators.
Why is a visual inspection often not sufficient after hail?
Hail can cause microcracks in solar cells without visible damage to glass or frame. These hidden defects can later lead to hotspots, power loss, or accelerated degradation. EL makes such cell cracks directly visible.
When should I carry out an EL inspection after a hailstorm?
Ideally shortly after the event – especially if visible damage is present, the system was exposed to hail, or the cause is unclear. Early EL images facilitate reliable assessment and documentation.
How does electroluminescence (EL) work in daylight?
During EL, modules are electrically energized and emit near-infrared light (invisible to the human eye). Our DaySy method enables imaging even in daylight using special optics/filters and measurement strategies – without night-time work.
Does EL help with insurance claims?
EL images provide objective, documentable evidence of cell cracks and defect patterns. On request, we prepare a report with damage categories and recommendations that often serves as a basis for further steps.
Does the entire system need to be inspected 100%?
Not always. Depending on the situation, sampling may be sufficient (e.g., low risk), or a comprehensive inspection may be required (e.g., visible glass damage or high event intensity). We recommend the appropriate strategy after initial assessment.
What information helps to get a quick quotation?
Helpful information includes:
- Location & date of the hail event
- System size (kWp), module type & year of installation
- Photos (modules, roof access)
- String layout (if available)
- Notes on glass breakage/yield anomalies
Experienced hail – and unsure?
Send us key details & photos – we’ll get back to you promptly with a suitable inspection strategy.
Discover more insights in our blog
See all blog entries »Our blog features a wide range of posts on photovoltaic topics. Take a look and stay informed.
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