The defects your eyes can’t see. The origin your OEM can’t dispute.
Electroluminescence (EL) testing makes the invisible visible: microcracks, broken cells, soldering faults and PID that no visual inspection can find. Sinovoltaics performs EL imaging on-site - without dismounting a single module - and analyses every image with SELMA, our EL platform that compares each module against its factory EL image, per serial number
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What is field EL testing?
Field EL testing applies a current to installed PV modules and captures their infrared emission with specialised cameras, producing X-ray-like images that reveal microcracks, cell breakage, soldering faults and degradation invisible to the eye - without removing modules from the racking. On-site EL testing of PV power plants is the reference method for solar panel microcrack detection - performed without removing modules from the racking.
How we test:
- Nighttime EL - the reference method: full-resolution imaging in darkness, modules in place, plant production unaffected
- Daylight EL - filtered imaging for campaigns where night work is restricted
- Tripod, rig and elevated imaging - matched to site layout: fixed-tilt, tracker or rooftop
- Sampling or 100% coverage - statistical AQL sampling for routine checks, full coverage for claims and acceptance disputes
Deliverables: per-module EL report with defect classification, serial-number mapping, severity grading, and - where a factory baseline exists - origin assignment per defect.
The SELMA difference: every image has a twin
Any competent inspector can photograph a microcrack. The question that decides warranty claims is: when did it happen?
Since 2009, Sinovoltaics has captured 100% factory EL images for more than 25 GW of client modules. SELMA links every field image to the factory image of the same serial number and to any on-arrival image in between. A crack visible in the field but absent at the factory and on arrival is installation damage. Present on arrival but absent at the factory: transport. Present at the factory: manufacturing - and claimable.
That timeline turns an argument into a settlement. No field-only inspector can produce it.
If we didn’t inspect your modules at the factory, your first field EL campaign becomes the baseline - and every later campaign trends against it.
What EL testing finds
| Defect | EL signature | Typical origin |
|---|---|---|
| Microcracks | Dark lines/branches across cells | Manufacturing, transport, handling, installation |
| Cell breakage / isolated areas | Dark inactive regions | Mechanical stress, hail |
| Soldering & interconnect faults | Dark fingers, busbar shadows | Manufacturing |
| PID | Darkened cells, checkerboard patterns | Operation (voltage stress) |
| LeTID / UVID | Uniform emission loss | Cell technology / operation |
| Edge ribbon cracks | Dark edges near frame | Newer cell formats; grows in transport & installation |
When you need EL testing
- Modules arrived on site: on-arrival verification before installation
- After hail, storm or site incidents: hidden damage assessment for insurance
- Underperformance without visible cause: root cause analysis
- Before warranty expiry: claim-ready evidence while rights still stand
- Annually, as part of the Annual Plant Health Program - trended year-on-year
