The global population growth and an ever-increasing need for energy due to the introduction of modern technologies are attracting greater attention (Qasim et al., 2020). Traditional electricity generation technologies, powered by fossil-based energies, are featured by high operating costs, high energy consumption, and destructive environmental effects such as climate change, ozone depletion, and greenhouse warming (Kumar et al., 2020). Therefore, to satisfy energy sustainability necessities and abate negative environmental impacts, clean and renewable energy technologies such as wind, wave, solar, tidal, geothermal, and biomass are seeing increased demand. Solar energy is the most widely used and widely recognized renewable energy source because of its cleanliness, ease of access, sustainability, and limitless potential (Xu et al., 2021). Photovoltaic (PV) technology is now one of the most appealing alternatives for increasing the percentage of renewable energy utilized, with the potential to meet about 5% of global power consumption by 2030 and 11% by 2050. Although PV technology has a tremendous perspective, it has been hampered by its low conversion efficiency due to its elevated working temperature (Ali, 2020). As a result, to sustain a powerful electrical performance of the PV systems, it is necessary to employ an adequate cooling strategy to reduce its temperature, hence extending its lifespan. Many studies have documented a variety of thermal regulation technologies, which may be divided into two categories: passive and active cooling. Active cooling, as opposed to passive cooling, is dependent on an exterior source to maintain the fluid stream and improve heat transmission. Generally, it is more powerful than a passive scheme, but it is less cost-competent (Tan et al., 2017).
Phase-changing material (PCM) technologies have received significant interest between researchers, primarily due to its advantages over sensible heat storage materials such as higher energy density, its capability of storing/releasing much amount of heat with small temperature variations (isothermal nature), compactness, lower heat loss, and lower weight per unit of storage capacity. Therefore, many academics have recently focused on the merging of PV and PCM. For instance, (Waqas and Ji, 2017) explained the effects of employing PCM-packed transferrable shutters fixed at PV rear on its performance under meteorological conditions of Islamabad, Pakistan. Shutters unlocked during nocturnal hours, thereby giving a solution for PCM’s partial solidification problem in the evening. PCMs with Tm = 30 °C and Tm = 35 °C demonstrated the greatest performance in January and June respectively. (Elarga et al., 2016) studied through numerical simulation the comparative performance of PV systems in double skin facades with and without PCM. Two types of paraffin wax are considered, i.e. RT55 was employed for a warm environment of Abu Dhabi whereas RT42 was employed for a cold environment of Helsinki and Venice. PCM thermally regulated PV temperature by maximum reduction of 17, 20, and 10 °C, leading to electricity yield improvement of 6, 8, and 5% for Abu Dhabi, Helsinki, and Venice respectively. (Browne et al., 2016) inspected the effects of using palmitic acid/capric mixture as PCM material on the electrical performance of photovoltaic thermal PV/T configuration through outdoor experiments. Circulation of water through the heat exchanger embedded in the PV/T system was done using a thermosyphon closed-loop flow approach. The results exhibited that utilization of PCM with PV/T system contributed to more than 5 °C reductions in cell temperature as opposed to that of PV/T system in the absence of PCM. (Su et al., 2017) examined the impacts of varying the thickness and the position of the PCM on the effectiveness of air-based PV/T-PCM system. It was found that the upper PCM position exhibited overall superior performance of nearly 62% higher efficiency in comparison with the lower PCM position. Also, adding 3.4 cm thickness of PCM to the PV/T system gave the optimum performance with a peak PV-temperature reduction of 7.6 °C, leading to 10.7% greater overall efficiency than air-based PV/T without PCM. (Khanna et al., 2018) optimized the depth of the PCM for the thermal regulation of PV panels in several operating conditions (wind velocity, ambient temperature, solar intensity levels, and melting temperature of PCM). The findings indicated that increasing the wind azimuth angle from 0° to 90°, rising the optimal depth of the PCM layer from 3.8 cm to 5.2 cm for 4.9 kWh/m2/day solar intensity. While, at the same level of solar intensity, rising the wind velocity from 1 m/s to 4 m/s, reducing the optimal depth of the PCM layer from 4.6 cm to 3.5 cm.
Despite its widespread use, PCM suffers from a severe flaw: weak thermal conductivity, which limits the efficiency of heat transfer throughout charging and discharging processes (Duan, 2021). Several techniques for heat transfer augmentation inside PCMs were accomplished by many researchers to overcome such a limitation including embedded fins, dispersion of high conductive nanoparticles, using heat pipes (HP), porous structures, encapsulation, and multiple PCMs (Xu et al., 2018). (Huang et al., 2011) explained through indoor experimentations the effectiveness of inserting fins inside a container filled with RT27 and RT35 as PCM for thermal regulation of PV modules. With increasing fins number, convection inside PCM was augmented and the time needed for complete melting was shortened. As opposed to the PV-only module, a maximum reduction (i.e. 21 °C) in PV temperature for the PV-PCM system is observed. (Biwole et al., 2013) explained through CFD simulation the transient performance of PV module incorporated with finned-PCM (RT25) container fixed at PV-module rear. The results revealed that the operating temperature of the PV panel in the absence of PCM touched 40 °C after 5 min and it retained on rising further whereas using PCM maintained the PV temperature down for 80 min at 40° regulating the temperature escalation. (Rajvikram et al., 2019) proposed including an aluminum sheet above the PCM layer to act as a heat spreader. They reported that the average temperature of the cooled panel declined by 10.3 °C, leading to a 24.4% improvement in electrical performance. (Sopian et al., 2020) experimentally studied in outdoor conditions the comparative performance assessment of different designs of PV/T system namely water-based PV/T, water-based PV/T with PCM, and nanofluid-based PV/T with nano-PCM based on energy and exergy methodologies. The maximum thermal energy, thermal efficiency, and electrical exergy gained for nanofluid-based PV/T with the nano-PCM system are 13 kW, 71%, and 75.25, respectively. (Nehari et al., 2016a) numerically investigated the influence of changing fin lengths embedded in PCM (RT25) to get the optimum fin length. Heat dissipation from PCM is improved due to the presence of fins inside PCM, resulting in better PV cooling. The simulation findings revealed that fin lengths of 25, 30, and 35 mm were the most efficient in impeding PV-temperature escalation. In another study by the same authors (Nehari et al., 2016b), the influence of tilt angle on the effectiveness of PV system with finned PCM (RT25) at module rear for its temperature regulating is performed. They concluded that at tilt angles lesser than 45o, PCM was powerful because of convection dominance.
However, amongst all previous enhancement approaches, one of the most thermally efficient approaches is inserting metal porous foams in PCMs because of its many desirable properties, such as a high surface area/volume ratio, low weight, and large porosity, and high thermal conductivity. Metal foams accelerate heat transfer by expanding the surface exposed between the working fluid (PCM) and the heat source (absorber plate), resulting in improved heat transfer capability at the expense of a little reduction in heat storage capacity (Hajjar et al., 2020). As a result, several experimental and computational studies have previously demonstrated the effectiveness of embedding porous metal material inside PCMs (Chen et al., 2021), (Zheng et al., 2018), (Zhao et al., 2010), (Ghahremannezhad et al., 2020), (Dinesh and Bhattacharya, 2020), (Mancin et al., 2015), etc. They discovered that using metal porous structures improves temperature uniformity and also shortens the time required for PCM to melt. In another investigation, heat transmission of PCM-porous hybrid was observed to be 10 times higher than unmodified PCM (Duan and Li, 2021). Nevertheless, limited studies have been conducted to improve the thermal behavior of PCM by employing porous structures for PV module heat dissipation (Ahmadi et al., 2021). Temperature regulation of low concentration photovoltaic system (LCPV) comprising V-trough concentrator using paraffin wax (Tm = 56 °C) with metal turnings was experimentally evaluated by (Maiti et al., 2011). By using the PCM composite, the PV temperature could be reduced up to 61 °C and 64 °C for outdoor and indoor experiment conditions. Also, the tested system achieved about 55% more output power compared to the non-cooled system. (Shastry and Arunachala, 2020) studied through outdoor experiments the thermal performance improvement of PCM for thermal regulation of PV system by incorporating aluminum metal matrix. The largest enhancement of 8.5% in electrical efficiency is attainable with using the proposed system compared to 3.6% for PCM-based PV/T without metal matrix, as a result of temperature drop of 11.2% and 7.8% respectively. Another solution for addressing the traditional drawback of PCM’s poor thermal conductivity, (Luo et al., 2017) proposed a paraffin-based graphite composite having a high thermal conductivity of (7.58 W/mK) for thermal regulation of solar panels. PV temperature declined by 24 °C in the proposed system, was retained for a long time. The maximum improvement attained in electrical performance was 12.5%. Recently, (Ahmadi et al., 2021) have conducted indoor experiments to examine the performance of PV panels passively and actively cooled by carbon foam embedded in PCM and passing water underneath PV, respectively, under a broad range of solar irradiance. The findings indicate that using PCM-composite as a passive cooling approach declined the PV- temperature by 6.9%, which enhanced the PV electrical efficiency by 13.9%. Furthermore, it was stated that the energy efficiency of the tested system with active cooling enhanced up to 81.6%.
Previously published research has shown that inserting metallic porous media in PCMs enhanced the heat transfer efficiency of PCMs, allowing for more powerful temperature control of photovoltaic panels and the bulk of the majority of these investigations used numerical simulations. Although there are few studies on experimental exams, most of them were conducted in indoor situations, which may provide data that are insufficiently dependable to fully examine system performance, It is critical to do more research in outside environments.Accordingly, the key objective of the present work is to experimentally examine the performance enhancement of PV using an aluminum foam matrix (AFM) embedded in PCM, under hot climate conditions of Benha city, Egypt, located at (latitude 30.466° North and longitude 31.185° East). Three alternative instances were tested outdoors: PV/PCM-AMF, PV/PCM, and PV. A comparison of the three PV systems is established based on the PV cells temperature, paraffin temperature, power yield and electrical efficiency. In addition, the current study's important results are compared to those of comparable systems in the literature.