FEM-based numerical study for enhanced electrical and thermal effectiveness in photovoltaic thermal systems with attached trapezoidal flow channels

Abstract

Until now, the world has experienced financial crises, except for countries with fuel resources. These nations can easily meet their electrical energy needs using their fuel reserves. Conversely, countries without fuel resources have turned to sustainable energy sources to bridge their electricity gap. Among these sources, the Photovoltaic Thermal (PV/T) system is one such solution. This system generates electrical energy from sunlight; however, its efficiency decreases as its temperature increases due to solar radiation. To address this issue, a flow channel is integrated into the system, allowing a coolant such as nanofluids (NFs) to circulate and reduce its temperature, thereby enhancing electrical efficiency. This study investigates a PV/T system composed of polycrystalline silicon and an absorber on the top, with a trapezoidal flow channel attached below. The research examines the passage of ternary NFs within the flow channel, where the coolant is a water-based fluid mixed with zinc, cobalt, and silver nanomaterials. Assuming laminar and steady-state flow, the numerical simulation is conducted using COMSOL 6.0. The aspect ratio (ar) is defined as the ratio of inlet to outlet heights. A parametric study is conducted by varying the Reynolds number (Re) from 100 to 1200, the nanoparticle volume fraction in the base fluid from 0.03 to 0.15, and the aspect ratio from 0.5 to 1.5. The results indicate that the average cell temperature decreases when the aspect ratio remains constant, regardless of the Reynolds number and nanofluid volume fraction. The increase in electrical efficiency of the PV/T system is primarily dependent on an increase in the Reynolds number. Specifically, the electrical efficiency improves by 21 % when the Reynolds number is increased from 100 to 1200. Furthermore, maintaining an aspect ratio of 0.5 (where the inlet height is half of the outlet height) enhances thermal efficiency at lower Reynolds numbers. More precisely, as the Reynolds number increases from 100 to 1200, the thermal efficiency improves by 60 %.