The cooling effect of polycrystalline type PV panels using perforated aluminum plates

A study has been conducted to improve the efficiency of Polycrystalline type PV panels. This research was conducted at the Energy Technology Research Laboratory, Engineering Faculty, Sriwijaya University, South Sumatra, Indonesia. The disadvantage of PV panel, when receiving solar radiation, it will increase the temperature of the PV panel but decrease the efficiency. This study uses a perforated aluminum plate with hole diameter of 2.5 mm. The plate is placed behind the PV panel. The dimensions of the plate are 960 mm x 600 mm x 20 mm and the number of holes of 1457. The specifications of PV panels are 1020 mm x 670 mm x 30 mm, Polycrystalline type PV panels, maximum power of 100 WP. The results showed that the PV panels given a perforated aluminum plate cooling had higher efficiency than those not given perforated plate cooling.


Introduction
PV panels have the potential to be developed as energy conversion equipment. These PV panels are able to convert solar energy into electrical energy for countries that have a hot climate all year round. Indonesia is one country that has this potential. South Sumatra Province is one of the regions in Indonesia that has this energy source. Although, this province is a storehouse of energy storage for the country of Indonesia, but the energy reserves taken today are still fossil-based (oil, coal, and gas). This type of energy decreases because it takes a long time to produce this energy again. Therefore, it is time to reduce the use of fossil energy and switch to using this abundant and environmentally friendly source of solar energy. Furthermore, the Indonesian government has made policies to increase the use of new and renewable energy, one of which is the use of solar energy to produce electricity for households, street lights, and traffic signs along the road. In fact, solar energy is one source of energy that can be used as electricity generation and to support transportation and industry.
Based on research results that increasing the temperature of the PV panel will reduce its efficiency [10] have research on perforated plates and PV panels. The results show that increasing the air mass flow rate using a fan can increase the PV panel cooling. It has been investigated cooling using a fan so that the temperature of the PV panel decreases and can increase the efficiency of the PV panel [11].
The use of PV panels is to produce electricity for household equipment, vehicles, to drive a pump for irrigation needs, etc. Some of these PV panel [12] consists of PV panel research to produce electricity for Air Conditioning equipment for preserve of agricultural products. Furthermore, Abdul Hadi N K et.al., 2018 [13] on thermal storage uses Phase Change Materials (PCM), in which the PV panel serves as a medium for receiving solar radiation and this system is used to produce a freezer. Adejuyigbe S. B. et.al, 2013 [14] utilize PV panels to conduct electricity for office equipment. Bhattacharjee B. et.al., 2019 [15] utilize PV panels to drive water a pump, and water is used for agricultural and household needs.
In this paper, the problem of PV panel efficiency has been reviewed again when PV panels reserve solar radiation and high temperatures as previous researchers have done. Cooling media used in the form of perforated plates made of aluminum without using a fan to suck hot air or cooling with free convection heat transfer. The perforated aluminum plate is placed at the below of the PV panel. The PV panel used is 100 Wp type Polycrystalline. This research is a continuation of the initial research that has been done but the power of PV panel used is still small, namely 8 Wp Polycrystalline type [16].

Experimental Procedure
Pollycritalline type PV panel mounted cooling media on the below to reduce the temperature of the panel. The cooling media used is perforated plates. This cooling media is made from aluminum. Figure 1 shows the structure of PV panels and perforated plates.
The PV panel tested consisted of 2 units, namely one unit without cooling media and one unit installed with cooling media in the form of perforated aluminum plates. In addition, some additional equipment was used in this test, such as solar charge control (SCC), batteries, and cables. Measuring instruments used consist of temperature measuring devices using K type thermocouple wire, measuring wind speed using anemometer, and measuring solar radiation intensity using pyranometer equipment, measuring electric current using current meters, and measuring voltage using voltage meters.

Figure 1. Structure of PV panels and perforated plates being tested
The specifications of the PV panels and the cooling media are explained in Table 1.    Figure 3. Comparison between PV panel surface temperature using perforated plate cooler (T1), PV panel surface temperature without cooler (T2) and solar radiation on February 4, 2020 As shown by the data taken in the field in Figure 3, the surface temperature of PV panels that do not use perforated aluminum plates (T2) is higher than the surface temperatures of PV panels that are cooled with perforated aluminum plates (T1). Likewise, in Figure 4 the opposite occurs, the tendency of the surface temperature under the PV panel not to use perforated aluminum plate (T2-2) is lower than the surface temperature below the panel which uses perforated aluminum plate cooler (T1-2). This event is interesting to study because the power produced by PV panels that use perforated aluminum plate cooler (P1) has higher compared to PV panels that do not use perforated aluminum plate cooler (P2) as shown in Figure Figure 4. Comparison between the below surface temperature of the PV panel using perforated plate cooler (T1-2) and without perforated plate cooler (T2-2) on 4 February 2020  The intensity of the sun or solar radiation (IR, W/m 2 ) that comes to the surface of the PV panel (Ap, m 2 ) will effect the current (I, Ampere) and voltage (V, Volt) that produce by a PV panel. The efficiency of the PV panel (h) is reduced if the intensity of the sun is high as shown in the equation (1). The results of the efficiency calculation are shown in table 2 for Sunny weather conditions, namely January 21, 2020; February 4, 2020; and February 05, 2020.
(1) High average solar radiation has resulted in low PV panel efficiency, so cooling media is needed below the PV panel. Installation of perforated aluminum plate cooling media has increased the efficiency of 100 Wp Polycrystalline PV panels. This perforated aluminum plate media has been useful to increase the efficiency of PV panels. In addition, how to make it simple, inexpensive, and easy to install.

Conclusion
A study has been carried out for 100 Wp Polycrystalline PV panels. The PV panel used consists of 2 units, each with a perforated aluminum plate cooler and without a perforated aluminum plate cooler. The diameter of this plate under study is 2.5 mm. Some concluding observations from the investigation are given below.
PV panels that use perforated aluminum plate cooler are better due to an increase in current and voltage output of PV panels compared to without perforated aluminum plate cooler.
The higher solar radiation received by the PV panel will increase the surface temperature of the PV panel but decrease the efficiency of the PV panel. For this reason, a cooling media is needed below the PV panel.