Enhancing a Simple Water-Based Photovoltaic-Thermal (PVT) Solar Collector Using CFD Analysis

Abstract

Photovoltaics thermal collectors are gaining more attention due to their promising potential to pave the way for the penetration of solar energy in modern day power generation technologies. PVTs’ flexibility, manufacturability, high efficiency, and multi-output nature inspired many innovative designs and design improvements available in the literature. PVT solar collectors conventionally attach PV cell(s) to a solar thermal collector to simultaneously generate electrical and thermal energies from the same solar input. The advantages of PVTs are twofold. First, extraction of the generated heat from the PV cells to be utilized in end-user applications, most often space heating or direct hot water (DHW). Second, maintaining the PV cells at a reasonable operating temperature, which reflects on the cells’ conversion efficiency and longevity. This study aims to design a PVT system and optimize its operation to maximize overall efficiencies using a zero-dimensional model along with a detailed Computational Fluid Dynamics (CFD) analysis of the thermal collector. The PVT performance can be investigated by determining its thermal and electrical characteristics. The approach taken in this study to analyze the PVT collector is separated into two main sections, energy and exergy analyses in which the thermal, electrical and overall efficiencies are evaluated. The zero-dimensional model involves controlling heat convection of the PV to study the trade-off between high water outlet temperature and electrical conversion efficiency. A detailed CFD analysis is conducted to evaluate the performance of a workable design for the PVT hybrid system. Then, the CFD analysis is used to calculate the overall convection heat transfer for a PVT system. By applying the mathematical model, the effect of flow rate and the inlet temperature on the energy and exergy efficiency has been tested. It was observed that the overall efficiency and exergy of the PVT increase as the mass flow rate increased. This study demonstrated that, the optimum inlet water temperature to maximize the overall exergy generated by the system at any operating conditions can be achieved. Nevertheless, the performance of the PVT was tested at different thermal conductivity and collector geometries to see the effect on the overall exergy and energy efficiency.