A project team led by Sandia National Labs, with partners at Arizona State and TUV Rheinland, has applied a suite of accelerated life tests to module-level power electronics (MLPE) devices to predict their reliability and durability in the field. A subset of the DOE’s Physics of Reliability: Evaluating Design Insights for Component Technologies in Solar (PREDICTS), this project has tested 140 MLPE units from five different manufacturers in four types of tests: damp heat, thermal cycling, static temperature (85, 100, and 125 degrees Celsius), and grid transients.
Of 10 powered devices used in damp heat testing, 2 failed at 1240-1550 hours and 2 failed at 4369-4876 hours. The remaining 6 units were still operating at full power-handling levels even after 5380 hours of the damp heat test. A wealth of historical usage data exists for damp heat degradation and failure rate differences of modules; a lack of historical usage data for MLPEs has hindered data comparison, until now. Comparing data from PVs and MLPEs is useful because they have similar usage environments and design-life expectations. Based on historical testing data, most PV modules fail or degrade significantly (>10%) before 3,000 hours of damp-heat accelerated testing (shown, left). That MLPE units have degraded significantly less than modules with fewer failures after 3,000+ hours of testing indicates that these devices may outlive their attached PV modules in the field under normal usage conditions.
In thermal cycling testing, only one of the 10 powered units failed through 836 thermal cycles. Units showed efficiency degradations <10% after more than 800 thermal cycles. This result compares favorably with PV module failure and degradation during long-term thermal cycle testing, reinforcing the robustness of MLPEs in the field.