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.
Request an EL testing scope
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
