Measuring outdoor I-V characteristics of PV modules and systems

The cumulative installed capacity of photovoltaics has passed 1 TW, of which about two-thirds were only installed in the past five years. Many of these new installations incorporate novel module and cell designs that have not yet been subjected to long-term in-field characterization. Indoor accelerated stress testing has historically been a valuable methodology to identify fault mechanisms, estimate degradation rates, and to ensure the safety and normal operation of modules in the field. Still, these methodologies deliver an incomplete image of the exact stress mechanisms that photovoltaic systems are subject to outdoors, which vary with location, time of day, and time of year. In this work we review different outdoor methods to measure current-voltage (I-V) characteristics of photovoltaic systems, discuss how the environmental conditions impact those characteristics, and examine alternative methodologies for acquiring light and pseudo I-V characteristics more applicable to larger scale installations. This review also provides an insight into methods useful for real-time monitoring and degradation analysis at the module and string level.