The effect of the full-spectrum characteristics of nanostructure on the PV-TE hybrid system performances within multi-physics coupling process

Abstract

Nanostructured surface is an important way to improve the efficiency of solar energy by absorbing more solar irradiance. However, due the bandgap of semiconductor material, more absorbed irradiance results in more waste heat. As for photovoltaic-thermoelectric (PV-TE) hybrid system, more waste heat reduces the efficiency of PV module due to the increased temperature, but is beneficial for TE module. There are complex and coupling physical processes (near-field optics, photovoltaic conversion, thermoelectric effects, and heat transfer) in the PV-TE hybrid system. Therefore, a multi-physics coupling mathematic model is developed for investigating the effect of full-spectrum characteristics of nanostructure on the PV-TE hybrid system performances. At first, the full-spectrum characteristics of nanostructure is found and summed up. As an example, the II set of the cone nanostructures have two cone nanostructure (Ⅱ-1 cone nanostructure and Ⅱ-2 cone nanostructure) with different dimensions. They have the same average reflectance of the wavelength range from 0.35 μm to 1.1 μm (0.05), however the average reflectance of the wavelength range from 1.1 μm to 2.5 μm (Ra,1.1-2.5) of the Ⅱ-1 cone nanostructure is 74.8% lower than that of the Ⅱ-2 cone nanostructure, which results in that the output power density of the PV-TE hybrid system with the II-2 cone nanostructure being 8.4 W/m2 more than that with the II-1 cone nanostructure when the concentration ratio is 10. Thus, the cone nanostructures with as high Ra,1.1-2.5 as possible are more beneficial for the hybrid system. Then, by optimizing the heat transfer structure of the PV-TE hybrid system, the output power density is increased by 9.1%. At last, through dynamic analysis, it is found that the annual power generation per square meter of the PV-TE hybrid system with II-2 cone nanostructure is about 17 kW·h/m2 greater than that with the II-1 cone nanostructure. As a result, combined with the structural analysis of the cone nanostructure, the bottom diameter should be as short as possible for the cone nanostructure.