Indoor Characterization of Solar Concentrator SMALFOC Modules Through Cell-to-Ambient Thermal Resistance Measurements

To evaluate the overheating temperature of solar cells in concentrator photovoltaic (CPV) modules during solar radiation conversion, we propose a method for determining the thermal resistivity between the solar cell and its environment (<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub>) in laboratory conditions at room temperature and in the absence of forced ventilation. The essence of this method is the measurement of the temperature change of the solar cells inside the CPV module under thermal load generated by direct current flow through the solar cell. The change in temperature of the solar cells in CPV modules under thermal load is determined by calculating the voltage difference across the module contacts during fast measurements of the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I–V</i> curve at room temperature and the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I–V</i> curve when the solar cells of the module are heated by direct current. The developed methodology eliminates uncertainties associated with the location of temperature sensors and unstable meteorological conditions. In the present work, this technique is used to study the overheating temperature of solar cells of “Small lenses, Multijunction cells, All from glass, Lamination, Fresnel, Optics, Concentration” design CPV modules varying in materials and thicknesses of heat sinks. In laboratory conditions, we determined the values of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sub> of small CPV modules and full-size CPV modules, containing, respectively, 8 and 128 pairs of Fresnel lens—triple-junction InGaP/InGaAs/Ge solar cells soldered to a metal heat sinks of similar design. Copper or steel was used as materials for the heat sinks.