Night-time EL testing leads to a warranty claim on 5,000+ modules
Clean Energy Associates (CEA) · 56.49 MW plant, England
The situation
An operations and maintenance provider saw power losses on a large plant and engaged CEA in 2018 to find the cause.
Background
At this scale a loss of a few percent is a large amount of money every year, but the plant was too big to test module by module with a lab flash tester. The question was which part of the plant, and which defect, to chase.
What was tested, and how that method works
On-site night-time electroluminescence (EL) imaging of about 90% of the plant's modules, out of roughly 180,000, over three months.
EL imaging powers a module in the dark so that healthy cells glow evenly. Cracked or poorly soldered areas stay dark. Doing it at night, on site, avoids shipping modules to a lab and lets very large numbers be imaged.
Our service: Electroluminescence (EL) imaging →What was found
- Cold soldering in about 5% of all modules, along with microcracks.
- At one location of nearly 19 MW, about 80% of modules were affected by cold soldering or microcracks.
How it unfolded
Outcome
The defects were traced back to production, so the manufacturer agreed to a warranty claim and replaced more than 5,000 modules, worth almost EUR 500,000 at market value according to CEA.
Lessons for a plant owner
- Field EL on a large share of modules can supply the evidence a manufacturer claim needs.
- Defects can cluster in one block, so sampling across blocks matters.
- Dark images alone do not give a power loss. They need to be paired with IV readings.
Questions to ask about your own plant
- Do we have EL images from delivery or commissioning to compare against?
- Which blocks have the weakest strings in our own data?
- What does our warranty require as proof of a manufacturing defect?
How we would approach a similar site
We would start with a representative sample of modules, confirm the pattern with IV curve tracing, and document findings so they can support a claim.
Published by the testing company itself. The plant is in England, not India. Source: Clean Energy Associates blog. Summarised in our own words.