Effect of Spray Angle and Flow Rate on Improving PV Panel Performance: Experimental and Theoretical Study

ABSTRACT


INTRODUCTION
In Iraq, most of energy sources depend on fossil fuel (oil and gas) sources. Less than 5% of produced energy is contributed from renewable energy. Due solar systems' ability to function in various environments, many assessments of their behavior have been conducted; the findings have revealed that only 15% of solar sun can be converted to electricity, with the remainder being lost as heat (Teo et al, 2012). Because the efficiency of photovoltaic solar cells drops as the temperature rises (Dubey et al, 2013), cooling them is necessary to improve performance. For solar cells, this leads in a 0.4 percent /°C loss in electrical power output and a 0.5 percent /°C reduction in electrical yield. Electrical efficiency in solar systems may often be rise by lowering module temperature. Furthermore, several cooling systems that use water as a coolant have been examined in (Abdolzadeh et al, 2009) and (Zhu et al, 2014), with a 10-20 percent rise in output power attained. In addition to the cooling solutions mentioned above, hybrid PV-other-mal energy systems can improve total PV module efficiency. Many experimental and numerical investigations have been conducted to increase the performance of PV modules. (Neyer et al, 2014) & (Chandrasekar et al, 2014) and (Nada et al, 2018) are a few examples. This paper describes a newly built experimental setup for analyzing the effect of water spraying on PV panel performance when the front side of the panel is cooled. Two elements were altered to get the best electrical efficiency and output. To minimize water usage during the cooling process, the number of nozzles has been reduced. The research aims to use the best water spray cooling approach to improve the solar system's electrical efficiency. According to the literature assessment, rising solar system efficiency is linked to increased water use. In this article, a fresh attempt was made to improve the solar panel's electrical efficiency while lowering water use.

METHODOLOGY Experimental Rig
The experimental setup was created to analyze the influence of water cooling on the performance of a PV panel. Experiments were conducted to examine how cooling affects the PV system's performance. As seen in Figure 1. An 250W PV panel with an effective surface of 1.64 m2 was used to create a particular system. Table 1 lists the properties of the module. The pipe and its nozzles are designed uniquely to prevent shadowing. With PV panels, shade is a major concern, as shading just one cell can drastically lower output power. The sun irradiation was measured during the tests using an SPM-1116SD pyrometer. A MIT-367 infrared thermosmeter with a 2°C precision, a digital thermos-meter and a flow rate meter were also included in the system.

Measurements Device
A data-logger was used to record the voltage and temperature of solar panels automatically. Four sensors (Copper constantan thermocouples) were fixed on the surface panel to measure its surface temperature. On the other hand, they connected to the logger and adjusted frequently to record data. To connect data logger with PV modules, two resistances were connected between Logger and modules to decrease the volt. On the other side the logger was connected with PC using USB cable as shown in the schematic diagram in Figure (2). The logger operates with low voltage-less than 5 V, so according to the manual of the logger, the resistances Rs and Rsp were used to adjust the voltage, VPV of logger and the diode was used to protect the circuit. The value of voltage VPV was calculated using the following Equations:

Measurement Error Analysis
The estimated measure-ment error for the measuring equipment is mentioned in this section. See table 2. Table  2 shows the measurement inaccuracy of each piece of equipment.
Where: RS and RSP are series and parallel resistance (Ohm)respectively.

Analytical Model
Water spray cooling is more effective than other ways of water cooling for PV modules. Water spray cooling's cleaning role is vital in eliminating dust from various solar power plants, in addition to providing effective heat transmission. As a result, spray cooling all components of the PV module has the primary purpose of maximizing heat loss to the environment while decreasing surface temperatures to increase electric power production. The heat input into the surface is (Du et al, 2013). Q solar = α .E.A m (9) where α : absorptivity coefficient. (QC), (QR) and(QE) Convection ,radiation and evaporative heat loss all contribute to the total heat loss (Qloss) in this test. Eq. 10 may be used to compute overall PV module heat loss, which includes the all loss indicated above: Q loss =Qc+QR+QE (10) The loss convection in a PV panel may be estimated as (Harry et al, 2O21): Where QC,B=h back Am(T module back -T air back (12) QC,F=h front .Am(T module fron t -T airfront ) (13) Total radiation heat loss is estimated using Eq. 14, QR= Q R,F + Q R,B ` (14) where radiation heat loss is determined using (Singh, 2O20) QR =σAm.F12 (T 4 1 -T 4 2) (15) Both sides of the module may be determined using Equation 15. where V: max. voltage, I: max. current, E: is the pyrometer-measured solar irradiance, and A: constant module effective area (Yun et al, 2007).

Effect water spray cooling system
The working PV panel temperature was reduced because evaporation and the cool-ing impact of water spraying. The ambient and water temperatures were 30 to 40 degrees Celsius and 16.5 degrees Celsius, respectively. The highest PV temperature occurs for the non-cooled -panel, as illustrated in Figures 7 and 8, and it is 64°C (average of observed surface temperature) before and after cooling, as measured by an infrared thermometer. Different portions of the PV panel's front surface were measured, but the average quantity is shown in the graphs below. Cooling resulted in a 40-degree drop in temperature.

RESULTS AND DISCUSSION Solar Irradiation
In Iraq, the spray cooling test was applied. The temperature in the surrounding region ranged from 30 to 40 degrees Celsius during the testing. All of the trials were carried out in July to obtain the best and maximum irradiation.

Figure 8: Panel Temperature with Spray Angles at Cooling
The influence of nozzles on the spacing between PV panels on performance The distance between the nozzles and the PV panel is one of the parameters that affects the efficiency of the solar panel. The distance between the nozzles and the PV panel (Z) was changed between 10 and 50 cm in five different modes, as shown in Figure9.

Effect Spray Angle on Performance
After cooling at a 20° angle, the highest power & efficiency were 78.09 W and 12.03 percent, respectively. Electrical Because of the pressure loss at each nozzle, the rate of flow in varying numbers of nozzles is not proportionate. When compared to non-cooling mode, the efficiency and power rose 17.28 percent and 12 W, respectively, while the number of nozzles was reduced to nine. In addition, as compared to a non-cooled PV panel, the electrical efficiency of 7, 5, and 3 nozzles increased by 14 percent, 11.87 percent, and 9.2 percent, respectively. see Figure 13.
perspectives. Furthermore, reducing the distance between the nozzles and the PV panel boosts efficiency and power. The Min. distance achieves the highest increase, according to the statistics. The water flow rate affects the electrical efficiency of a PV panel. According to the experiment's results, dropping the flow rate from 80 to 20 l/h reduces water use by 45 %. When compared to the steady state, the On-Off cooling system reduced water use while simultaneously lowering electrical efficiency and output power by roughly 10%. The highest gain in PV panel electrical efficiency relative to non-cooled mode was 24.22 percent, and it occurred at steady water cooling with Z/L= 0.9 at angle 20°, which are the nozzles to panel distance and angle, that are the lowest. Future study will focus on the water spraying system's economic approach. Electrical efficiency increased by 11.89 percent when the angle was changed to 30 degrees. After cooling the PV panel by 45°, the overall gain in electrical efficiency was 13.95 percent. In compared to the other five angles, the 50° angle of cooling exhibited the smallest gain in total efficiency -power after cooling. as shown in Figure 11.

Effect different number of nozzles on performance
Despite the fact that the water flow rate in this study was around 80 l/h, which is lower than other similar spray cooling methods in (Abdolzadeh et al, 2009) reducing the number of nozzles can also help to minimize water consumption and water flow rate. Because one of the most important parameters in heat transfer is water flow rate, increasing or decreasing the number of nozzles has an effect on the heat transfer coefficient and hence the heat transfer rate. Some of the nozzles were removed in this research to cut down on water usage. The cooling of water sprays in four different modes (9, 7, 5, and 3) was investigated. As shown in Figure 12.

CONCLUSIONS
In this study, provide a new technique for improving the performance of PV panels. According to the study, water cooling increases panel performance. The outcomes of article support the idea that lowering cooling spray angle enhances efficiency and power. The lowest angle (20 degrees) produces the best outcomes compared to other