Safety Analysis of Solar Module under Partial Shading

Abstract

Hot spot often occurs in a module when the qualities of solar cells mismatch and bypass diodes are proved to be an efficient alternative to reduce the effect of hot spot. However, these principles choosing a diode are based on the parameters of bypass diodes and PV cells without consideration of the maximum heating power of the shaded cell, which may cause serious consequences. On this basis, this paper presents a new approach to investigate partially shaded cells in different numbers of PV cells and different shading scenarios, including inhomogeneous illumination among solar cells and incomplete shading in one cell, which innovatively combines the same cells or divides one affected cell into many small single cells and then combines the same ones, and analyzes the shaded cell. The results indicate that the maximum power dissipation of the shaded cell occurs at short-circuit conditions. With the number of solar cells increasing, the shaded cell transfers from generating power to dissipating power and there is a maximum point of power dissipation in different shading situations that may lead to severe hot spot. Adding up the heat converted from solar energy, the heating power can be higher. In this case, some improvements about bypass diodes are proposed to reduce hot spot.

Effect of Industrial Dust Deposition on Photovoltaic Module Performance: Experimental Measurements in the Tropical Region

“…Reduction in PV module performance highly depends on particle size and surface density of dust deposited over the modules [24]. Deposition of dust on a panel influences the solar cell to heat up whereby affected cells will act as a resistance to the generated current; this tendency may lead to substantial degradation of conversion efficiency and even to formation of a hot spot that can ultimately damage the PV module [25,26]. Due to minimal interparticle distance between fine particles, a small amount of solar radiation can pass through; therefore, it reduces more performance efficiency of a module compared with the larger particles [27,28].…”

On the Link between the Operating Point and the Temperature Distribution in PV Arrays Working under Mismatching Conditions

“…This is a general result. In the absence of mismatching conditions, the working of the PV system in the MPP is preferable for a two-fold reason: the maximization of the extracted power and the minimization of the aging effects that are, without exceptions, all intensified with the increase of the PV cell operating temperature [1][2][3][4][5][6]. A number of additional experimental characterizations confirming the above statement have also been carried out in different days and in different ambient operating conditions as concerns the irradiance level and the ambient temperature.…”

“…A similar analysis has been carried out by artificially creating a mismatching condition as shown in Figure 6. It is well known that in PV systems, mismatching can be due to partial shading, shadows of neighboring objects, dirtiness, bird droppings, leaves, snow, clouds, different orientation angles of modules of the PV field, soiling, manufacturing tolerances, or ageing [1][2][3][4][5][6]. In particular, mismatching due to moving clouds and also to other possible moving bodies is characterized by both relatively fast dynamics (short duration) and also a relatively low degree of nonuniformity as concerns cell operating conditions.…”

“…It is well known that, in photovoltaic (PV) systems, mismatching due to partial shading, shadows of neighboring objects, dirtiness, clouds, different orientation angles of modules of the PV field, soiling, manufacturing tolerances, or ageing can cause reduced reliability and significant losses in the energy yield [1][2][3][4][5][6]. Even with the commonly used bypass diodes, mismatched cells may become reverse biased [7] and dissipate power, leading to dangerous localized heating phenomena called hot spots that in turn may cause accelerated ageing or even the damage of the cells.…”

Mismatch Based Diagnosis of PV Fields Relying on Monitored String Currents

“…Otherwise, references could be achieved by exploiting real-time data on weather conditions. In such a case, very reliable parameters and accurate modeling of the solar field structure would be needed [20]; special cases like architectural shadows [21,22] could not be recognized.…”