The Solar America Board for Codes and Standards (Solar ABCs) has recently published a report, “Accelerated Lifetime Testing of Photovoltaic Modules,” that provides a literature review and associated analysis of photovoltaic (PV) field failures, degradation mechanisms and statistics, and available accelerated testing (AT) methodologies. The Photovoltaic Reliability Laboratory at Arizona State University (ASU-PRL) wrote the report and the authors collected and systematically analyzed the major sources of literature on PV module reliability and durability. The report and one-page summary can be found at: http://www.solarabcs.org/acceleratedtesting
The anticipated lifetime of PV modules spans several decades, and construction materials and design are constantly changing in an effort to reach the module power price of $0.5 per watt and to reduce the levelized cost of energy to about 6 to 8 cents per kilowatt-hour. More than 94% of installed modules around the world were manufactured within the last five years and may incorporate new construction materials. Stakeholders cannot wait for decades to identify the failure modes and mechanisms of these new modules. The purpose of AT is to assess the reliability and durability of products by inducing failures and degradation in a short period of time using accelerated test conditions much more severe than actual field operating conditions while replicating the actual field failure mechanisms. This report communicates and emphasizes the importance of AT for assessing the reliability (failures) and durability (degradation) issues related to the lifetime of PV modules in the field.
This report does not attempt to develop a new AT methodology or to select an existing AT methodology, but rather provides a literature review and analysis of field failures, degradation, and available AT methodologies. Based on this review report and the other published literature, research teams can develop AT protocols that could be converted into an accelerated comparative testing and/or lifetime testing protocol/standard by one or more standards developing organizations or international/national industry organizations.
Concerns about PV modules underperforming (durability) or becoming obsolete prematurely (reliability) are major barriers to PV diffusion and project financing. Accelerated testing is a way to assess the reliability and durability of PV products by inducing failures and degradation in a short period of time. It accomplishes this by using accelerated test conditions much more severe than actual field operating conditions while replicating the actual field failure mechanisms. The detailed literature review and analysis in this report resulted in a number of observations about the current and future state of accelerated testing for PV modules. A few of these observations include:
Based on the detailed literature review and analysis in this report, much of the information needed to develop accelerated testing protocols for comparative and lifetime testing of PV modules is available from a number of sources.
The review of an extensive list of field failure and degradation modes indicates that the design, packaging, and construction of PV modules as well as the field environment in which they operate dictate their failure and degradation modes and mechanisms.
There is a great need to develop a database of climate-specific technology-sensitive wear-out failures in old (10-30 years) PV power plants that have similar or identical construction characteristics as those of the current generation modules.
There is little or no detailed physical and statistical modeling effort reported in the public literature, so this report attempts to present a background and detailed analysis on the physical and statistical models relevant to PV modules.
This literature review and analysis suggests a need for the development of a climatic-specific, technology-agnostic comparative rating system and lifetime rating system.
About Solar ABCs
The Solar ABCs is a collaborative effort among experts to formally gather and prioritize input from the broad spectrum of solar photovoltaic stakeholders including policy makers, manufacturers, installers, and consumers resulting in coordinated recommendations to codes and standards making bodies for existing and new solar technologies. The U.S. Department of Energy funds Solar ABCs as part of its commitment to facilitate widespread adoption of safe, reliable and cost-effective solar technologies. For more information, visit www.solarabcs.org.