Assessing the Reliability of PV Modules

Imagine that you’re a solar PV module manufacturer whose company has invested many years in refining your product’s quality and durability. With so many new products constantly entering the market, each with a claim to rival your own, how do you differentiate your module in the marketplace? Or say you are one of these manufacturers of a new product: you know your product has great potential, but with so much existing competition and so few opportunities for comprehensive testing of your module versus your competitors’, how can your product gain marketplace and investment acceptance as a durable option for PV projects?

When manufacturers need to generate this quantitative data, some existing tests – which have been very successful in reducing the early field failure rate – do not apear to provide the opportunity to quantitatively compare products due to the tests’ simple pass/fail methodology. Ad hoc assessments by engineering firms and consultants are most often based on inspections of factory quality assurance (QA) systems, rather than on much-needed field or accelerated lifetime test data.

The Fraunhofer Institute for Solar Energy Systems (ISE) in Freiburg, Germany, and the Fraunhofer Center for Sustainable Energy Systems in the US, with advanced indoor and outdoor testing capabilities in Cambridge, Massachusetts and Albuquerque, New Mexico, have begun to address this challenge with the PV Module Durability Initiative (PVDI).

PVDI has three components: a state-of-the-art accelerated test protocol, a research and development programme, and an educational and outreach component.

The six-month accelerated test protocol (PVDI 2012) was developed by Fraunhofer researchers and included the participation of industry experts and other research institutions. It expands on the current knowledge of important failure modes for flat-plate PV modules, using a combination of stress factors already used in the IEC certification test with extended durations, additional stress factors, and combined stresses. Most importantly, the test protocol includes measurement of important module performance parameters throughout the programme, allowing insights into degradation behaviour and trends.

The R&D programme serves to continuously improve the test protocol and to validate it with long-term field data, quantifying the link between test protocol results and actual field durability, supported by field data. With education and outreach efforts, Fraunhofer will inform PV supply chain stakeholders about the potential and limitations of accelerated lifetime testing, as well as providing data to inform the durability engineering community.

The test data generated from PVDI is of great interest for PV module manufacturers, their customers, and the renewable finance industry. Recognising manufacturers’ desire for confidentiality, a detailed test report with failure mode analysis for each module is available to the programme participant only; a comprehensive test report for all modules is available to all participants; and a summary test report with the high level rankings of the modules will be available to the general public.

The first round of PVDI testing started early this year, and the first test data is expected to be published at the beginning of the third quarter 2012. Additional rounds of tests are already in preparation.

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