Evaluating the IEC 61215 Ed.3 NMOT procedure against the existing NOCT procedure with PV modules in a side-by-side configuration

Nominal operating cell temperature (NOCT) is a simple parameter to distinguish the thermal performance of one PV module design from another. Recently, the National Renewable Energy Laboratory (NREL) participated in NOCT round-robin testing designed to quantify the reproducibility of NOCT values between eight different test laboratories. This work expands on the round-robin testing by further examining NOCT results produced at NREL. Heat transfer modeling suggests that similarly constructed/packaged modules should not have the widely varying NOCT values that are publicly reported. In order to test this premise, a side-by-side NOCT comparison is presented for three glass/silicon/plastic modules that represent the extreme range of reported NOCT values. A glass/silicon/glass module is also included in the side-by-side comparison to gauge the impact of changing a packaging parameter. Working group 2 of the International Electrotechnical Commission Technical Committee 82 has recently drafted a replacement for NOCT that is titled “Nominal Module Operating Temperature” (NMOT). With this change in progress, NREL data are also used to compare NOCT to NMOT.