Structural Optimum Design Of The Spectral Control Module In Solar Thermophotovoltaic System

The solar thermophotovoltaic（STPV）system can realize the selective absorption and re-emission of solar radiation energy by using spectral control module,which can greatly improve the energy conversion efficiency of photovoltaic cells,and has been widely concerned in the field of photovoltaic conversion.In this paper,we focus on the structural optimum design of the selective absorber and the selective emitter in the spectral control module of STPV system.We use multilayer films and two-dimensional photonic crystals to optimize the performance of the spectral control module.The main conclusions are summarized as follows:The influence of the dielectric film on the reflectivity of the lower layer in multilayer system is discussed.A trap structure with the combination of antireflection layer and enhancing reflection layer is designed.The light energy is gathered in the metal absorption layer between the two layers to obtain higher absorption.The multilayer film structure of W/SiO₂/Ti/HfO₂/SiO₂ which contains the trap structure is designed.It has a high average absorptivity of 91.0%in the range of 0.3-2μm,as a selective absorber,the solar energy collection efficiency of 66.4%can be obtained.The average absorptivity under TE polarization and TM polarization is 80.1%and 81.0%respectively at 60°oblique incidence,which indicate a good performance of wide-angle absorption.Compared with the non trap structure,this structure can effectively improve the absorptivity of the metal absorption layer.HfO₂ and TiO₂ layers are designed on the metal surface of W-based cavity array to construct a two-dimensional heterogeneous photonic crystal structure.The structure realizes the combination of multiple absorption peaks of two groups of cylindrical resonators and antireflection layers,thus obtaining more efficient absorption performance in a wide band.The structure is applied to design the selective absorber and emitter of STPV system.The structure design and performance analysis are carried out by finite element simulation:when it is used as the selective absorber（λ_c=2μm）,it can achieve a high solar collection efficiency of 87.9%with a good performance of wide-angle absorption;when it is used as a selective emitter（λ_c=2.2μm）,it can obtain a spectral thermal emission efficiency as high as 81.6%.Compared with the single dielectric filled structure,the two-dimensional heterogeneous photonic crystal has a significant advantage in the wide spectrum absorption.The trap structure and the two-dimensional heterogeneous photonic crystal designed in this paper have good generality,and are expected to be applied to more research involving spectral selective absorption technology.