Photovoltaic Systems
Radin Ahmadi; Ali Sarreshtehdari
Abstract
Photovoltaic (PV) panels experience efficiency losses from elevated operating temperatures, particularly in high-insolation regions where overheating reduces power output and module lifespan. This issue is exacerbated in arid climates like Iran, where abundant solar resources coincide with extreme heat, ...
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Photovoltaic (PV) panels experience efficiency losses from elevated operating temperatures, particularly in high-insolation regions where overheating reduces power output and module lifespan. This issue is exacerbated in arid climates like Iran, where abundant solar resources coincide with extreme heat, emphasizing the need for cost-effective passive cooling. Prior research focuses on active cooling or wind-assisted methods, overlooking natural convection under stagnant conditions and the use of commercially available materials. To address these gaps, this study evaluates the thermal and electrical benefits of repurposing industrial aluminum profiles as heat sinks for PV panels, offering a sustainable solution using off-the-shelf components without custom fabrication. Experiments used a controlled laboratory setup with a monocrystalline PV panel under 1000 W/m² irradiation and zero wind speed. Three aluminum profiles, varying in mass and geometry, were attached to the panel's rear and compared to an uncooled reference. Measurements included time-dependent surface temperatures, power outputs and thermal imaging, with uncertainty analysis for reliability. Findings indicated time-dependent effects: during the initial heating phase (0-30 minutes), heat sinks reduced temperatures (up to 2.56°C for the heaviest model) and increased power (up to 1.65%). In the stabilization phase (30-60 minutes), temperatures exceeded the reference (by 0.25-1.57°C), causing slight power drops (0.67-1.24%). Heavier profiles delayed stabilization but risked hot air entrapment. These time-dependent effects underscore the potential of aluminum heat sinks for modest PV performance improvements in zero-wind conditions, albeit with trade-offs in long-term stability. These findings emphasize the importance of geometry selection for enhancing natural convection efficiency in stagnant-air PV applications.
Solar Thermal Engineering
Seyed Younes Afshoon; Rouzbeh Shafaghat; Mofid Gorji Bandpy
Abstract
This paper investigates the melting behavior of phase-change material (PCM) in an evacuated tube solar collector. The outer tube was made of borosilicate glass with a diameter of 60 mm, and the inner tube was made of copper with a diameter of 10 mm and length of 1500 mm. The heat transfer problem in ...
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This paper investigates the melting behavior of phase-change material (PCM) in an evacuated tube solar collector. The outer tube was made of borosilicate glass with a diameter of 60 mm, and the inner tube was made of copper with a diameter of 10 mm and length of 1500 mm. The heat transfer problem in heat pipe was investigated in four cases: finless, full fin, half fin, and third fin. The fins were cut from a 35 mm diameter copper tube and installed concentrically with the outer tube. The inner space between the absorber tube and the heat pipe was filled with stearic acid as the PCM. The numerical simulation was conducted using the Ansys Fluent 2022 for the laminar incompressible Newtonian fluid flow in the transient state via the enthalpy-porosity model. The initial temperature of PCM was 27°C, and liquid fraction was zero at the beginning of the simulation. After validating the numerical results with experimental ones, the collector performance was evaluated by considering the four temperatures of 68, 72, 76, and 80°C for the fin and heat pipe at three different times t = 22, 55, and 110 s. The results showed that by increasing the fin area in three cases of third fin, half fin, and full fin, the melting and storage time of PCM were reduced by 6%, 44%, and 87%, respectively. Also, as the Estefan number increased from 0.007 to 0.05, 0.09, and 0.13, the process of PCM melting decreased by 75%, 85%, and 92%, respectively.
