The accumulation of dust on the surface of a photovoltaic module decreases the radiation reaching the solar cell and produces losses in the generated power [21]. Dust reduces the radiation available for the photovoltaic conversion on the solar cell and increases the energy loss of the system. Accumulation of dirt or dust particles on the solar photovoltaic panel surface, such as dust, water, and sand, block or hinder light energy from entering the solar cells [22]. It is a major problem since the materials for light obstruction pose as external resistances which reduce solar photovoltaic efficiency [23]. The dust will surely reduce the absorption capacity of the panel's photovoltaic cells. A single layer of dust is enough to obstruct the passage of light, and this will make the solar cells ineffective. Heavy dust covering the surface of the solar panel will reduce the output of the system [24]. The effect would be more obvious if the PV system consists of more cells or Stand-Alone Photovoltaic (SAPV) systems installed in areas where there will be heavy dust. Due to environmental conditions because of the exposure of surfaces, layers of dust are accumulated. Many other factors, such as the direction of the wind, humidity, etc also influence the deposition of dust [25]. It is preferable to have high wind speeds as they help in driving away from the accumulated dust. P_max, I_max, I_sc, and fill factor (FF) are the most affected performance characteristics by the dust deposits on the PV module surface [26]. Studies have shown that accumulated dust can reduce solar panel performance, but the results have not been clearly quantified [27].

The location of solar panels is important when deciding on the development of a photovoltaic solar system [28]. It is very clear that solar panels should be placed in such a way as to absorb solar radiation during the time when the sun is at its highest as shading supersedes this when it comes to dominance [29]. Shadow effects solar panel performance considerably [30]. Partial shadow or full shadow both affect the amount of solar radiation received by cells. When shaded by a tree branch, building, or module dust, a cell's output declines [31]. The output decreases in proportion to the amount of shading. So, depending on the area of the cell that is shaded, the power-producing capacity of the cell will go down [32]. Hence there will be a drop in the amount of energy output of the Solar PV. The disadvantage of a series connection of cells is that one cell will affect the performance of the whole panel [33]. The same concept is applicable, even in the case when a series of panels are connected in the form of an array [34]. For completely opaque objects like a leaf, the decrease of the cell's current output is proportional to the amount of the cell that is obscured.

Recent studies have shown that research has generally been performed, taking into account the effect of dust and the effect of shadows separately. Still, there is very little literature that discusses the study of dust and the shadows simultaneously. This paper is written to bridge that gap to take into account the broader picture so that the overall performance reduction of the solar PV system can be analyzed. The present work was carried out to experimentally investigate the accumulation of dirt or particles and shadow on the electrical performance of the solar PV panel. This research work is not intended to study the quantitative effect of dust and % of the shadow, which is also the limitation of the study.

The small-scale experimental setup is described in this section. Three sets of experiments were conducted for a 3 W_p power capacity panel manufactured by Tata Solar available in the laboratory for this experimental investigation. Based on the latitude of Thanjavur, the panel was oriented for receiving solar radiation for the maximum number of hours. The specifications of the panel are listed in Tab. 1. A 50 Ω rheostat was connected to the PV module for measuring the IV characteristics. The solar panel was tested in the standard test conditions (STC) corresponding to AM 1.5, 25°C, and 1000 W/m². Experiments using solar panels partially obstructed with shadow and soil dirt were conducted under natural outdoor conditions The block diagram of the experimental setup is shown in Fig. 1. Fig. 2 describes the experimental setup of the cleaned PV module, module with shadow and dust, respectively. Fig. 3 shows the solar panel with and without dust. The whole methodology of the experimental study is presented in Fig. 4.

Digital Multimeter was used to measure the open-circuit voltage and short circuit current of the solar panel with the following specifications: DC Voltage: 0–100 V, DC Current: 0–10 A, Double Display, Brand Name: “Tfpro” was used. A light meter, range 0–50000 lux, brand name: “WE300” was used to determine the lux level. The temperature of the PV module was assessed with the Infra-read thermometer. Air temperature and relative humidity were recorded using a thermo-hygrometer with an accuracy of ±2%.

For the first set of studies, the experiment is performed on a cleaned solar PV panel without any dust. The same set of analyses are repeated with the accumulation of dust and under the influence of shadow. The performance analysis is studied using the various equations given in Eqs. (1)–(4). The effect of dust and shadow was studied based on the percentage reduction in power and efficiency of the solar PV modules. (1)∙ Power output (watts) of the PV module P=VOC∗ISC∗FF (2)∙ Electrical efficiency of PV module η=VOC∗ISC∗FFA∗1000∗100 (3)∙ % Reduction in power=powercleanpanel−powerwithdustpowerwithoutdust∗100 (4)∙ % Reduction in efficiency=ηcleanpanel−ηwithdustηcleanpanel∗100 where,

Voc = Voltage of electricity produced (volts)

Isc = Electrical current produced by the solar PV panel (Ampere)

FF = Fill Factor = 0.75

A = Area of solar panel (cross-section of panel) = 180 ∗ 150 mm²

I = Intensity of solar radiation (W/m²) = 1000 W/m²

The following assumptions were made during the study: (1)

The experiments were done on consecutive days on clear sky days during which the climatic conditions are assumed to be similar.

The experimental investigation was carried out with natural dust (soil) and shadow. Performance parameters such as voltage, current, Electrical power, and Electrical efficiency were compared with and without shadow. Fig. 5 shows the comparison of the current of the cleaned panel, with shadow and dust. The peak voltage of 17.56 V and current of 0.147 A for the cleaned panel and peak voltage when the cells of the panel are shadowed is 10.1 V and 0.06 A at 1:00 pm. It can be observed that there is a drop in the peak voltage level by 0.8 V when the panel is accumulated with dust. It is observed that peak radiation is obtained from the sun at 2:30 pm with a voltage of 17.56 V and 0.147 A for the cleaned panel and maximum voltage when the panel accumulated with the dust is 16.8 V and 0.12 A at 1:00 pm. This effect will further increase if the panel capacity increases and the panel is installed at the location where there will be heavy dust concentration. Fig. 6 shows the comparison of the current of the cleaned panel, with shadow and with dust. Natural dust or sand particles are considered to affect the power output more compared to other types of dust. Shading affects the output generated by the solar panel as it leads to hot spots, which may sometimes lead to permanent damage to solar cells.

Fig. 7 shows the comparison of the power of the clean panel, with dust and with shadow. The power output was decreased to 60% of the maximum power that was obtained without any dust. The power output was decreased to 20% of the output power when compared to the one without dust shadow. The results show that the electrical performance of the panel is significantly affected because of shadow [35].

There was a decrease in efficiency by 6% when compared to the one without any dust. These results are in line with various other studies that have been reported in the literature [36–44].

This can be attributed to the fact that natural dust consists of various materials of various sizes [38]. Due to several irregularities, solar cell efficiency is affected, thereby affecting the overall efficiency of the panel [40]. Similarly, there is a significant decrease in the efficiency of the panel due to the effect of shadow. There was a 9% decrease in maximum efficiency due to the effect of shadow. Although the performance of the clean panel is not affected, the improvement was evident when compared to the one exposed to dust and shadow (Fig. 8). From the above characteristics, it can be realized that the power output and efficiency, which primarily describes the performance analysis of any system, is decreased because of the accumulation of dust [41]. The comparison of the present work with other literature on dust and shadow is listed in Tab. 2.

It shows the importance of the proper maintenance of the PV panel in such a way it is free from dust and shadow to generate maximum power under the given climatic conditions.