Abstract:
Electroluminescence (EL) is an important tool in photovoltaic
(PV) module quality testing and module degradation assessment.
EL imaging is primarily a qualitative test that allows for cell
cracks and severe damage to be easily identified. Degradation
occurs over the lifetime of a module, so it is essential that EL
images are recorded in a way that is consistent and comparable
to ensure that the degradation is reliably monitored. In order to
be able to compare images taken at different labs and over a
period of years, the test procedure needs to standardised to
ensure that results are comparable. This paper sets out the best
practices for lab EL imaging of modules and on-site imaging
informed by the Technical Specification (IEC TS 60904-
13:2018) and current research. The quality of the EL imaging
results is dependant on the camera used, the test setup factors
such as camera position, number of images per module and light
conditions. Optimum camera focus is essential for sharp images
and a procedure to assist manual focusing is suggested. Five test
setups for modules, cells and module-strings are compared,
either involving a single camera/image setup or multiple
images/cameras. The resolution and sharpness are compared for
each setup. The additional cost and/or time involved in the better
image resolution needs to be weighed up to the importance of
detecting finer defects. If the requirement is to detect major
defects then faster, cheaper systems can be used but in order to
detect fine cracks and defects the additional cameras or longer
testing times are needed.
