National Renewable Energy Laboratory(NREL), United States

Reliability and Durability of PV Modules in PV Systems

The long term reliability of photovoltaic (PV) modules is critical to the cost effectiveness and the commercial success of PV. Today most PV modules carry a power warranty of 80% of initial power through 25 years of deployment. Data on long term performance of PV systems indicate that PV modules can survive for 25 years with less than 0.8% per year power loss. To achieve such performance the modules must be 1) designed correctly, 2) fabricated under an adequate quality management system (QMS), 3) shipped/transported to the installation site using an adequately tested method, and 4) installed using installation procedures also under an adequate QMS in a well-designed system. 

There are three organizations that are cooperating to ensure that all four areas are addressed. PVQAT is working on developing improved accelerated stress tests to qualify design and have developed a Guideline for Module Manufacturing QMS. IECRE is developing a conformity assessment system for the PV power systems. IEC bridges the gap between the other 2 by preparing the international standards for use by the IECRE system. This talk will describe how these three groups are providing a system that will help investors balance risk versus cost in design, construction and operation of a PV power system. 


Dr. Wohlgemuth joined the National Renewable Energy Laboratory as Principle Scientist in PV Reliability in 2010. He is responsible for establishing and conducting research programs to improve the reliability and safety of PV modules. Before joining NREL he worked at Solarex/BP Solar for more than 30 years. His PV experience includes cell processing and modeling, Si casting, module materials and reliability, and PV performance and standards. Dr. Wohlgemuth has been an active member of working group 2 (WG2), the module working group within TC-82, the IEC Technical Committee on PV since 1986 and has been convenor of the group for more than 15 years. Dr. Wohlgemuth is a member of the Steering Committee for the PV Module QA Task Force (PVQAT) and he chairs Task Group 3 on Humidity, Temperature and Voltage. Dr. John Wohlgemuth earned a Ph.D. in Solid State Physics from Rensselaer Polytechnic Institute.