In this paper, local parallel resistances of solar cells are determined by using thermal imaging analysis data. The electrical measurement and thermal infrared measurement were done for twenty unused and non-encapsulated crystalline cells. The bulk resistance of each cell, i.e. a combination of series resistance and shunt resistance, is determined by its IV characteristic at standard test condition and IV characteristic in the dark. The thermal IR images of r. In this paper, local parallel resistances of solar cells are determined by using thermal imaging analysis data. The electrical measurement and thermal infrared measurement were done for twenty unused and non-encapsulated crystalline cells. The bulk resistance of each cell, i.e. a combination of series resistance and shunt resistance, is determined by its IV characteristic at standard test condition and IV characteristic in the dark. The thermal IR images of reverse biased solar cells are captured under dark conditions. Each cell is vertically hung in the temperature controlled chamber. The electrical–thermal model of a solar cell is proposed and its result is published for the first time. Based on a bulk electrical resistance of each cell, the four approaches to estimate local parallel resistance are presented. From the experimental results, it is found that the effective local parallel resistances calculated by thermal imaging analysis are correlated and comparable with measured resistance of the whole cells. For the best case, the resistance obtained from the local resistance measurements differs from the electrical bulk resistance less than 2%.••Single crystalline solar cellLocal parallel resistanceNon-encapsulatedThermal image analysisSolar cell or photovoltaic (PV) module is technically characterized by current–voltage measurement (IV characteristic) either under illumination (according to IEC60904-1) or in the dark. The parameters measured typically consist of series resistance, parallel resistance, a combination of the shunt resistance and diode resistance. Those parameters consider the bulk parameters of the whole cell,,,. However, the non-uniformity or inhomogeneity and hot spot heating of the cell cannot be revealed or calculated from the IV characteristic measurement. Hot spot heating occurs in a solar cell module when the operating current exceeds the reduced short-circuit current (Isc) of a shadowed or damaged cell or group of cells.There are various methods which can be used for detecting failure of a PV module or a cell in the literature. The methods including the infrared images (IR), Lock in thermography (LIT), Resonance ultrasonic vibrations (RUV) technique, Electroluminescence (EL) and photoluminescence (PL) have been reviewed in Ref. The infrared image is used for determining the hottest cell of the module under illumination as the temperature of material is related to infrared radiation emissivity of material in the IEC61215:2005 standard. The areas with higher temperature are called hot spots. The lock-in thermography method (LIT) is also non-destructive and can be used in finding lateral power l. IR thermograph of each reverse biased cell has 320 pixels × 240 pixels. Each pixel exhibits the temperature of the constituent cell surface defined by that pixel area. This paper presents four approaches to estimate the equivalent cell temperature of the whole cell in which there is different temperature distribution. This inhomogeneity or non-unif. IV characteristics of 20 single crystalline solar cells (10 cm × 10 cm, c-Si cells) were measured both in the dark and under illumination at standard test condition (STC). The IV characteristics were measured according to IEC60904-1, irradiance at 1000 W/m2, AM 1.5G and cell temperature of 25 °C. The IV characteristics measurements of the illuminated cells were performed by the Pasan Sun simulator 3b, AAA class according to IEC60904-9.In the dark experiments, the air temperature of the 0.3 m × 0.3 m × 0.3 m chamber was maintained at 25 °C. All chamber walls were painted black. Fig. 4 illustrates a schematic diagram of the experimental setup. After reverse biasing a cell for 600 s, allowing the steady-state cell temperature to be reached, infrared images were taken. The infrared images are obtained by a high quality image portable IR camera (Thermo Tracer TH770 of NEC San-ei Instruments, Ltd.). Each picture has 320 pixels × 240 pixels. One pixel can represent a temperature ranging from −20 to 100 °C with resolution 0.1 °C. The Viewer Software TH78-719 was used to download thermal images from the internal memory to a PC. A programmable current source (KEITHLEY Model 224) supplied a reverse bias at 100 mA to the cells. It is equal to current density 1 mA/cm2. Three temperature values (mid cell surface temperature, air temperature and wall temperature), current and voltage of cells are recorded b.
