International PV Module QA forum held in San Francisco on July 15th and 16th 2011.
The International PV Module Quality Assurance (QA) Forum discussed the need for quality assurance and developed an action plan for how to address this. The industry recognized that the current IEC testing standards are designed to test for infant mortality issues not for module life up to 25 years and there needed to be rapid efforts to develop test standards to address this gap. In addition, there needs to be a mechanism for the customer to easily assess the quality control program that the manufacturer uses.
As a result of the QA Forum meeting The PV QA Task Force was formed, including 5 Task Groups:
- Task Group 1: PV QA Guideline for Manufacturing Consistency - (leader Ivan Sinicco, Oerlikon)
- Task Group 2: PV QA Testing for Thermal and mechanical fatigue including vibration - (leader Chris Flueckiger, UL)
- Task Group 3: PV QA Testing for Humidity, temperature, and voltage - (leaders John Wohlgemuth, NREL and Neelkanth Dhere, Florida Solar Energy Research Center)
- Task Group 4: PV QA Testing for Diodes, shading and reverse bias – (leaders Vivek Gade (Jabil) and Paul Robusto (Intertek)
- Task Group 5: PV QA Testing for UV, temperature and humidity - (leader Michael Koehl, Fraunhofer Institute for Solar Energy Systems)
To volunteer for one or more of the Task Groups, individuals could contact the leader directly or request access to the website at http://pvqataskforceqarating.pbworks.com/ or http://pvqataskforcemanufacturingqa.pbworks.com/w/page/42004135/FrontPage.
SEMA will keep our membership informed on the activities of the Task Groups and contribute to them.
Each of the task groups is expected to provide a draft standard by April 2012, which will be submitted to the IEC Technical Committee 82 Working Group 2. These draft standards can then be used by the community while they are being formally adopted as IEC standards.
For the development work in the task groups, there were groups in each of the regions (Americas, Europe and Asia) who would merge their work into an agreed task group report.
The standards were mainly for testing of the modules/panels. Standards could also be developed for the individual materials such as diodes, EVA, backsheet, sealant etc.
Further details on the task group activities are available below:
PV QA Task Force - QA Rating Development
Five Task Groups (with leaders) were formed:
- PV QA Guideline for Manufacturing Consistency - Ivan Sinicco
- Thermal and mechanical fatigue including vibration - Chris Flueckiger
- Humidity, temperature, and voltage - John Wohlgemuth and Neelkanth Dhere
- Diodes, shading and reverse bias - Vivek Gade and Paul Robusto
- UV, temperature and humidity - Michael Koehl
Proposed scope: Failures of cell interconnects and solder bonds have been identified as a key cause of long-term failure of PV modules. The primary stresses affecting the failure rates have been shown to be thermal and mechanical. There is evidence that vibration during transportation and/or caused by wind can contribute. This task group will study how to best induce and quantify these failures.
Proposed scope: Corrosion and charge movement, especially resulting from moisture ingress and electrical bias, can have dramatic effect on PV modules. There are many relevant processes and the interactions between stresses may make testing very difficult. There is also evidence that light can affect the failure rates, but a separate task group has been formed for this; the two will need to coordinate definition of scope.
Proposed scope: There is increasing evidence that shading or other non uniformities in modules puts localized stress that can lead to overheating, and, in some cases, to fires. Not only is this failure a serious safety issue, but there is some evidence that aging modules show increasing non uniformity, implying that this may turn out to be a significant wear out mechanism. The details of the stresses that lead to these failures are not well understood but may be related to shading (and reverse bias operation associated with shading or other situations), high temperatures, and lightning. Thermal cycling may also be important since thermal fatigue failures can cause stress on the diodes.
Proposed scope: Light (especially UV light) can cause changes in modules including solarization of the glass, light-induced degradation in the cells, discoloration, and decrease in adhesion. Unfortunately, application of light in large area is expensive, so a strategy has often been to apply the stresses to a smaller version of a module. This scope is closely related to the scope of the second task group, so will need to be coordinated with them.