Experimental observations in mismatch losses in monofacial and bifacial PV generators

Abstract

AbstractMismatch losses ( ) in PV arrays have been experimentally investigated by observing the dispersion in the operating voltage of the individual modules under normal operating conditions, that is, with the inverter delivering energy to the grid, and by assuming that in the absence of mismatch, all the modules will have the same operating voltage which are equal to the observed average. For that, a quadratic relationship between relative power and relative voltage deviations derived from the power‐voltage curve of the modules is required. This has been carried out in two different PV generators: a 5.1 kWp with monofacial multicrystalline BSF modules installed in March 2013 and a 6.6 kWp with bifacial monocrystalline PERC modules, installed in May 2019. The respective coefficient of variation of the STC power is 1.6% and 0.3%. This decrease reflects the improvement between these two PV technologies and translates into a reduction in the component derived from intrinsic differences in the constitution of the module, from 0.09% to 0.01%, following theoretical considerations. The component due to the non‐uniformity of rear irradiance in the bifacial PV array is deduced by comparing its functioning with and without the rear side of the modules covered by opaque canvas and results in about 0.2–0.4%, which represents half of the total observed . The difference between these components and the total observed is attributed to differences in the module operating temperature. The aging of the monofacial PV array translates into an increase in at a ratio of 0.04% per year.