Development of a Visual Inspection Checklist 

for Evaluation of Fielded PV Module Condition

Corinne E. Packard1, 2*, John H. Wohlgemuth1, Sarah R. Kurtz1

1National Center for Photovoltaics, National Renewable Energy Laboratory, Golden, CO USA 2Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden, CO USA *

Corresponding Author: cpackard@mines.edu

ABSTRACT

A visual inspection checklist for the evaluation of fielded photovoltaic (PV) modules has been developed to facilitate collection of data

describing the field performance of PV modules. The proposed inspection checklist consists of 14 sections, each documenting the

appearance or properties of a part of the module. This tool has been evaluated through the inspection of over 60 PV modules produced

by more than 20 manufacturers and fielded at two different sites for varying periods of time. Aggregated data from a single data collection

tool such as this checklist has the potential to enable longitudinal studies of module condition over time, technology evolution, and field

location for the enhancement of module reliability models.

ACKNOWLEDGEMENTS

This work was supported by the U.S. Department of Energy under Contract No. DE-AC36-08GO28308 with the National Renewable Energy Laboratory. We also acknowledge the contributions of

Ulrike Jahn (TÜV Rheinland Immissionsschutz und Energiesysteme GmbH, Germany), Karl Berger (Austrian Institute of Technology), Thomas Friesen (Scuola Universitaria Professionale della

Svizzera Italiana), and Marc Koentges (Institut fuer Solarenergieforschung GmbH Hameln/Emmerthal) (Lead of IEA PVPS Task 13 Subtask 3.2) in developing the format and content of the

checklist. Special thanks are also due to Cassius McChesney of Arizona Public Service for providing access to modules that were deployed there.

OVERVIEW OF VISUAL INSPECTION CHECKLIST

• Uses IEC/UL standard terminology

• Attempts to balance collection of sufficient detail for failure mode 

evaluation against minimizing recording time per module

• Consists of 14 sections- based on module component

• Additional detail can be found in the full NREL report

DESCRIPTION OF TEST FACILITIES

Photovoltaic modules from 2 sites served as the principle testbeds for the

development of the inspection checklist, supplemented with the experience and

knowledge of other professionals (identified in the Acknowledgements). Modules

from Site 1 were inspected on location at the APS STAR Center ® (Arizona Public

Services Solar Test and Research Center) in Tempe, Arizona USA. Modules from

Site 2 were shipped from the field site at the Solar Energy Center (SEC) in New

Delhi, India* to NREL for evaluation.

In all, more than 60 modules

were inspected, representing

more than 20 manufacturers.

In addition to covering a broad

range of technologies and

manufacturers, these modules

experienced different exposure

times in the field: modules were

fielded between 1-12+ years at Site

1 and 1-10 years at Site 2*.

VISUAL INSPECTION CHECKLIST

• Composed of 14 sections

• Sections 1-2: field site, system configuration, and module identification

• Sections 3-13: individual module components, starting from the back and

ending at the front of the module

• Section 14: locations of electronic records (I-V curves, infrared images, etc.)

• Detailed instructions are given in the full report for each part of the

checklist to reduce ambiguity and variation in survey responses

• Required and optional tools:

• a tape measure with centimeter and millimeter gradations, a pen or other

recording implement, and any personal protective equipment required by the

facility (required)

• a digital camera, an I-V curve tracer, and an infrared camera (optional)

• A full visual evaluation can be completed in approximately 8 minutes

by a pair of experienced inspectors, though this can be reduced

significantly for data sets consisting of a large number of similar modules

or by the use of the abbreviated inspection list.

PRELIMINARY RESULTS

No discoloration

Discoloration over Center Of Cells

Discoloration 

over whole cell

Absorber delamination

EXAMPLES

Chips >10, module edge

Section 3: Rear side glass

Section 9: Frameless Edge Seal

Section 12: Silicon (mono or multi) module

Section 13: Thin film module

Most frequently observed issues at Sites 1 & 2

If visually observable defects can be correlated or conclusively linked with the

measured electrical performance degradation rates, visual inspection may provide a

relatively low impact method for assessing which PV installations may be more likely

to see accelerated degradation based on the frequency and types of defects that

develop.

We have not yet developed a large enough database to make conclusive statements

about climate-zone dependent degradation but a preliminary analysis illustrates the

types of data that become available through visual inspection.

*O. S. Sastry, et al., "Degradation in performance ratio and yields of exposed modules under arid conditions,"

in 26th European Photovoltaic Solar Energy Conference and Exhibition, Hamburg, Germany, 2011.

FUTURE

• Availability of the checklist, a data collection spreadsheet, and NREL report with

detailed instructions for using the checklist

• Availability of a database for compiling user-submitted field data

Please contact Corinne Packard if you are interested 

in participating in data collection

36

NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC. 

Presented at the PV Module Reliability Workshop, 28 February - 2 March 2012, Golden, Colorado • NREL/PO-5200-54568