Abstract. The paper describes the
modulation method of measuring the thermal impedance of solar cells. Subject to
measurements was the 50-watt solar module from polycrystalline silica with the
surface area 700 × 550 mm2, of idling 23.6 B and current by
operation on loading 2,55 A. The measurements were performed using heating
power varying harmonically and measuring a response - variable component of the junction
temperature. Feature
of the modulation method is the possibility of determination of the components
of thermal resistance connected to construction features of the solar module.
Determination of components of thermal resistance of the solar module is based
on measurement and the subsequent analysis of dependence of thermal impedance
on modulation frequency of the heating power. It is experimentally found
out that the amplitude of the variable component of the junction
temperature mostly does not depend on the value of the heating power. This is explained by «current crowding» ‒ the nonuniform distribution of the
current through the junction and the formation of local regions of heating of
the semiconductor of solar module. The formation of local regions of heating is confirmed by the
experimentally detected thermal resistance component, which
is due to the temperature difference between local heated regions and other
part of semiconductor of solar cell. Formation of local hot regions was confirmed by a sharp thermal
resistance decrease with an increase of the heating current.
Key words: thermal resistance, measurement,
modulation method, solar module, current localization.
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