Determining how many years a solar panel will last can take, well, years. Intended to function for 25 years or more, solar panels must be made to withstand the elements. In some cases, panels continue working well after their planned operational lifetime. Nowhere is this more evident than on the sunny hillside in Golden, Colorado, where the National Renewable Energy Laboratory (NREL) operates the Outdoor Test Facility (OTF).
The OTF continues to run tests on photovoltaic (PV) panels made by companies still very much interested in the outcome. The OTF is equipped to perform accelerated testing on PV panels, which discovers problems in their design or in the materials used, said Dirk Jordan, a physicist who is a senior engineer at NREL. However, it is difficult to make long-term performance and degradation predictions for different environments with accelerated testing only. Multi-year outdoor testing is used to complement and validate accelerated testing. That is critical feedback to give to the manufacturer. Jordan studies the long-term performance of PV systems and analyzes the physics and chemistry of changes. For further information see the IDTechEx report on Energy Harvesting Microwatt to Gigawatt: Opportunities 2020-2040.