Update on the International PV QA Task Force

By Sarah Kurtz, NREL

The status of the PV QA Task Force was reviewed at the IEC TC82, Working Group 2 Meeting in Oslo, Norway in October 2012.

A proposal for how to organize a rating system was presented and discussed.   The rating system is designed to provide comparative test results reflecting the long term reliability of silicon modules in multiple climates and use conditions.  Module designs must be tested to IEC 61215 first before evaluation in the rating system.  The description will include:

Part 1 – Defines overall test sequence
Part 2 – Defines mechanical and thermal cycling tests
Part 3 – Defines UV/weathering test
Part 4 – Define test to demonstrate improved durability to hot and dry climates and roof top installations
Part 5 - Define test to demonstrate improved durability to hot and humid climates

Testing of thin-film and CPV modules will be addressed separately.  Attendees felt the thin film and crystalline rating systems should be comparable.  The draft will be sent out for comments and the first draft of Part 1 will be submitted to IEC as a New Work Item in about a month.

Task Groups Reports

Group 1 – QA Guidelines

The four global regions are merging the separate drafts of a QA guideline designed to ensure companies are following a quality system based on ISO 9001-2008.  The merged document is planned to be submitted to ISO in January, 2013.  In parallel, discussions are ongoing with IEC about how IEC can better aid in guiding quality control.

Group 2 – Thermal Cycle & Vibration:

Failures of cell interconnects and solder bonds have been identified as key causes of long term failure in modules.  Ongoing testing to verify proposed test sequence to be provided in May 2013.

Group 3 – Humidity, Temperature & Voltage:

In order to determine whether testing is needed beyond 1000 h of damp heat, this group is trying to determine if failure modes seen in damp heat >2000 h are observed in the field or if products that passed 1000 h damp heat are showing failures.

The Japanese task group is focused on polymer material and outdoor exposure to determine the degradation mechanism that needs to be simulated. 

A committee draft for a test for Potential Induced Degradation, IEC 62804 will be submitted in the near future. A round robin is in progress for testing based on draft to show repeatability between labs and show sample size of two is sufficient to give meaningful results. 

Group 4 – Diodes, Hot Spots & Reverse Bias

This group is exploring the benefit of various bypass diode testing including extended test time, reverse bias testing and surge test to simulate electrostatic discharge failures.

Group 5 – UV

This group is working to quantify real UV loads in different locations, to compare the effects of different UV sources (Fluorescence, Metal Halide, Xenon) on glass/encapsulant/backsheet laminates with different materials and discussing whether to do sequential or simultaneous testing and when to test the entire module versus when to use Mini-modules or materials testing.

Group 7 – Wind Load

Leader has resigned and a new leader is sought, so no progress was reported.

Group 8 - Thin Film Group

First meeting was 09/25/2012; Initial task is to review crystalline Si work and determine if the same failure modes apply to thin film modules.  Next meeting will be in February 2013.

Group 9- CPV to be discussed at WG7 meeting

A survey is in progress to identify the most important wear out mechanisms.

About the PV QA Task Force

The goal of the PV QA Task Force is to define a concept for creation of standards that allow stakeholders to quickly assess a module's ability to withstand regional stresses, thereby reducing risk and adding confidence for those developing products, designing incentive programs, and determining private investments.  For more information, visit http://www.nrel.gov/ce/ipvmqa_forum/index.cfm

Resources:

Proceedings from Photovoltaic Module Reliability Workshop 2012 - February 28–March 1, 2012