Size optimization of nanoparticle and stability analysis of nanofluids for spectral beam splitting hybrid PV/T system

Abstract

Spectral beam splitting hybrid PV/T system is a promising way to utilize effectively full spectrum solar energy for power and high-grade heat cogeneration. Heat medium liquid with nanoparticles (NPs) exhibits great potential in solar photothermal applications considering where using NPs to selectively absorb and transmit solar spectrum enables more efficient PV/T system. The paper begins with an introduction to the finite-difference-time-domain (FDTD) method system to analyze the full spectrum solar optical properties of SiO2 and TiO2 NPs. Moreover, taking spectral response of monocrystal silicon solar cells as example, the degree of appropriateness (DOA) was proposed to evaluate the response degree of NPs to specific bands of sunlight and optimize particle size. We suspend SiO2 and TiO2 NPs in Deionized water (DI) by two-step method to filter out the ideal spectrum for generating electricity from monocrystal silicon solar cells. The effects of ultrasonic time, ultrasonic power, and NPs/dispersants mass fraction ratios (MFR) on the stability of SiO2/water and TiO2/water nanofluids (NFs) were experimentally investigated based on static precipitation and absorbance methods. The results show that the optical properties are sensitive to the particle size of NPs and the extinction power increase with the increase of particle size. The particle size of TiO2 NPs in the range of 20-200 nm can regulate the position of extinction peak over a wide extent of 300-400 nm. The DOA of SiO2 and TiO2 NPs with particle size of 20 nm is the largest, which are 94.21% and 97.45%, respectively. The stability of SiO2/water and TiO2/water NFs is the best when Sodium Hexametaphosphate (SHMP) is added as dispersant. And the optimal MFR of NPs and SHMP is 1:1. The 0.05wt% SiO2/water NFs prepared has high stability at 250 W ultrasonic power and 50 min ultrasonic time. Moreover, the good stabilization of 0.01wt% TiO2/water NFs is achieved at 200 W ultrasonic power and 50 min ultrasonic time.