Photothermal structural fluid behaviors of PV ETFE cushion roof in summer: Numerical analysis using three dimensional multiphysics model
Abstract PV ETFE cushion roof combines transparent ETFE films and flexible photovoltaics, making it possible to harvest both electricity and heat from solar energy simultaneously. However, high temperature caused by solar radiation remarkably affects the mechanical behaviors of ETFE foils and converting efficiency of PV due to their thermal sensitivity. To tackle this issue, it is critical to understand the photothermal structural fluid performance of PV ETFE cushion. Due to the difficulty to measure by experiment, this paper presents a three dimensional mathematical model considering heat structure fluid couplings to conduct numerical analysis. Time dependent analysis and dynamic boundary conditions are applied to study the behaviors which are difficult to observe in experiment. Results explain how photothermal structural fluid properties vary in a typical summer day from 9:00 to 17:00. Incident solar radiation and PV modules are two main factors that affect the temperature distribution of the cushion roof and the circulation of internal air. Eight groups of air circulation are found inside cushion chambers during simulating period. Air pressure is mainly determined by average temperature rather than local air flow and uneven heat distribution. It is also found that the worst structural case occurs on the upper layer at noon in terms of structural safety factor. Structural safety of PV ETFE cushion roof in typical summer days can be guaranteed. These results can be applied further to improve and optimize the design of PV ETFE cushion roof.