A solar spectral splitting-based PVT collector with packed transparent tube receiver for co-generation of heat and electricity

Abstract

Combined heating and power (CHP) systems co-generating electrical energy as well as thermal energy is indispensable for modern-day distributed applications. Photovoltaic thermal (PVT) systems are such hybrid co-generation systems. However, in a conventional PVT system, the PV module/cell temperature restricts the thermal output, making these systems unsuitable for various applications. This study offers a novel and resilient design for a spectral beam splitting-powered compound parabolic collector-based PVT system that employs a nanofluid optical filter within borosilicate glass tubes for volumetric absorption. By maximizing the “splitting effect”, the goal of this work is to disrupt the long-standing relationship between the thermal and electrical yield from a PVT collector, i.e., obtaining a higher heat transfer fluid temperature than the PV cell temperature. Several configurations with varying array width-to-receiver tube diameter ratios, i.e. bdo ratios (ranging from 3 to 8) and one, two, and three rows/layers of receiver tubes were evaluated and compared. The optical and thermal performance of the collector designs are compared using metrics such as heat flux distribution, optical efficiency, temperature distribution, receiver efficiency, and splitting ratio. This work determines how the splitting effect dictates the performances of the collector. Through the ray-tracing routine and thermal analysis, it is demonstrated that for certain bdo ratios, the developed collector attained a maximum cumulative temperature rise of >100∘ C using ZnO–water–ethylene glycol nanofluid as the optical filter. Also, the receiver and electrical efficiency of 51.81% and 18.77%, respectively, are achieved. Moreover, the packed borosilicate glass receiver tubes with a bdo ratio of 8 and two receiver rows/layers achieved the so-called “splitting ratio” (ratio of filter fluid temperature to cell temperature; THTFTcell) of >1.6. The studied configurations find their application depending on the extent of the achieved splitting ratio. Based on these findings, it is concluded that the analyzed packed glass tube receiver designs provide a viable new route towards cost-effective and dependable robust PVT collectors for distributed and other applications.