Mechanical load testing of solar panels — Beyond certification testing

Mechanical load tests are a commonly-performed stress test where pressure is applied to the front and back sides of solar panels. In this paper we review the motivation for load tests and the different ways of performing them. We then discuss emerging durability concerns and ways in which the load tests can be modified and/or enhanced by combining them with other characterization methods. In particular, we present data from a new tool where the loads are applied by using vacuum and air pressure from the rear side of the panels, thus leaving the front side available for EL and IV characterization with the panels in the bent state. Tightly closed cracks in the cells can be temporarily opened by such a test, thus enabling a prediction of panel degradation in the field were these cracks to open up over time. Based on this predictive crack opening test, we introduce the concept of using a quick load test on each panel in the factory as a quality control tool and potentially as a type of burn-in test to initiate cracks that would certainly form early on during a panel's field life. We examine the stresses seen by the cells under panel load through Finite Element Modeling and demonstrate the importance of constraining the panel motion during testing as it will be constrained when mounted in the field.