More Than 200 Attend NREL/SNL/BNL Photovoltaic Reliability Workshops
March 28, 2017
NREL, Sandia National Laboratories, and Brookhaven National Laboratory partnered to host two coordinated workshops on PV Reliability, which ran from Feb. 28 to March 2. More than 200 technical experts from 100 companies and 18 countries participated. Each organization was required to actively participate through an oral presentation or a poster, resulting in about 40 oral and 100 poster presentations.
Some technical highlights included the following:
- Despite today’s lower costs of modules, published reports suggest that the fraction of modules failing in the field may be steady or decreasing slightly and that the nature of the problems is shifting. For example, reports of encapsulant discoloration for modules deployed in the last 10 years have dropped by about a factor of 3 to 4 relative to historical data, and reports of hot spots have increased by about a factor of 3.
- The increased observations of hot spots may be linked to reduced mechanical strength of the lower-cost modules, as thinner glass and frames are being used to reduce costs. Evidence was presented on how dropping or twisting a module can damage the cells and, in some cases, lead to loss of performance. Although a twist test was routinely applied decades ago, it was discontinued about 15 years ago because all modules passed the test. Today’s larger modules, with thinner cells, glass, and frames, are more likely to be damaged. Extensive discussion was unable to resolve the extent to which the modules should be made robust to rough handling versus the extent to which workers should be trained and/or provided with tools to handle the modules gently.
- Similarly, today’s higher-efficiency solar panels sometimes show increased light-induced degradation. Methods for avoiding this degradation are also being developed, but understanding all of the different effects is complicated by the many different types of solar cells on the market today and by the lack of understanding of the causes of the changes.
- A standardized method of documenting data for accelerated testing of solar panels was presented by CSA Group. The standards community has largely focused on defining pass-fail requirements, but this approach is designed to document how modules respond to extended application of common stress tests. Observed changes in the modules motivate further investigation and/or addition of contract terms and planned system assessments to see if these changes are also observed in the field.
Presentations from the workshops are posted privately for viewing by the workshop participants. The presentations will be packaged for publication, and public posting is anticipated in about six months. Watch for updates on the NREL website.