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Outdoor photoluminescence imaging of photovoltaic modules with sunlight excitation
Author(s) -
Bhoopathy Raghavi,
Kunz Oliver,
Juhl Mattias,
Trupke Thorsten,
Hameiri Ziv
Publication year - 2018
Publication title -
progress in photovoltaics: research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.286
H-Index - 131
eISSN - 1099-159X
pISSN - 1062-7995
DOI - 10.1002/pip.2946
Subject(s) - photovoltaic system , photoluminescence , biasing , signal (programming language) , optoelectronics , diode , solar cell , computer science , sunlight , materials science , excitation , open circuit voltage , voltage , optics , electrical engineering , physics , engineering , programming language
To operate photovoltaic power plants at maximum capacity, it is desirable to identify cell or module failures in the field at the earliest possible stage. Currently used field inspection methods cannot detect many of the electronic defects that can be revealed with luminescence‐based techniques. In this work, photoluminescence images are acquired using the sun as the sole illumination source by separating the weak luminescence signal from the much stronger ambient sunlight signal. This is done by using an appropriate choice of optical filtering and modulation of the cells' bias between the normal operating point and open circuit condition. The switching is achieved by periodically changing the optical generation rate of at least one cell within the module. This changes the biasing condition of all other cells that are connected to the same bypass diode. This method has the advantage that it can deliver high quality images revealing electrical defects in individual cells and entire modules, without requiring any changes to the electrical connections of the photovoltaic system.