Experimental Investigation of the Effects of Partial Shading on Photovoltaic Cells’ Electrical Parameters

Abstract

The short-circuit current (Isc), the open-circuit voltage (Voc), and the maximum power point (VMPP,IMPP) of monocrystalline and multicrystalline silicon solar cells under three kinds of partial shading patterns have been investigated experimentally. The partial shades are, respectively, the nine shelter locations by 1 cm × 1 cm black card, the six shelter locations by 2 cm × 1 cm black card, and the center shelters with isosceles triangle, circle, square, and two rectangles black cards whose areas are 2 cm2. Firstly, the results show that the partial shading causes disproportional high losses on those parameters of both cells but will have a minimal effect onVoc. Secondly, it is found that those parameters of the monocrystalline cell are less dependent on the shading than that of the multicrystalline cell. Thirdly, it is noted thatIscandIMPPof both cells will be decreasing dramatically as a rectangular black shading card with a long side parallel to cell’s finger, compared with that normal to cell’s finger. Finally, it can be seen that the effects of shading on the electrical parameters of both cells will be suppressed when the border lines of shading match the size of the shaded cell.

Series Connected Photovoltaic Cells—Modelling and Analysis

“…where D I is the diode's (PN-junction) current, s I is the reverse-saturation current, t V is the thermal voltage [28] (equal to 25.9 mV at 300 K), n is the ideality factor [29] that depends on the exact recombination mechanism, and ph I is the maximum generated current (short-circuit current) Several works in the past investigated different models for PV cells [5][6][7][8][9][10][11][12][13]. The interest of the researchers and manufacturers is driven by a need to optimize new technologies and to study their behavior in different contexts and under varying conditions.…”

“…Figure 1 shows the current/voltage (I/V) characteristics of a PV module whose electrical parameters are depicted on the same figure. Several works in the past investigated different models for PV cells [5][6][7][8][9][10][11][12][13]. The interest of the researchers and manufacturers is driven by a need to optimize new technologies and to study their behavior in different contexts and under varying conditions.…”

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.…”