Gravity Assisted Heat Pipe With Strong Marangoni Fluid for Waste Heat Management of Single and Dual Junction Solar Cells

Abstract

This study investigates the cooling of single and multijunction solar cells with an inclined, gravityassisted heat pipe, containing a 0.05 M 2propanol/water mixture that exhibits strong concentration Marangoni effects. Heat pipe solar collector system thermal behavior was investigated theoretically and semiempirically through experimentation of varying input heat loads from attached stripheaters to simulate waste heat generation of singlejunction monocrystalline silicon (Si), and dualjunction GaInP/GaAs photovoltaic (PV) solar cells. Several liquid charge ratios were investigated to determine an optimal working fluid volume that reduces the evaporator superheat while enhancing the vaporization transport heat flux. Results showed that a 45% liquid charge, with a critical heat flux of 114.8 W/cm2, was capable of achieving the lowest superheat levels, with a system inclination of 37 deg. Solar cell semiconductor theory was used to evaluate the effects of increasing temperature and solar concentration on cell performance. Results showed that a combined PV/heat pipe system had a 1.7% higher electrical efficiency, with a concentration ratio 132 suns higher than the standalone system. The dualjunction system also exhibited enhanced performance at elevated system temperatures with a 2.1% greater electrical efficiency, at an operational concentration level 560 suns higher than a standalone system.