Self-thermal storage integrated absorber-emitter to stabilize solar thermionic conversion

Abstract

Solar thermionics is an appealing clean solid-state power technology, while it faces one of the major challenges for generating continuous and stable power on account of the temporal intermittency of solar radiation. This paper proposes a novel concept of self-thermal storage integrated absorber-emitter for solar thermionic conversion, which can store excess heat from the sun and generate remarkably stable day-night electricity. A transient 1-D energy transfer model is developed to investigate the impacts of various critical system parameters on the power performance of innovative thermionics. The results revealed that a maximum total energy density of 100.06 kW h/m2 is delivered at a cutoff wavelength of 1300 nm and a concentration ratio of 300. The thermionic power is not sensitive to the variation of solar radiation for low thermal diffusivity of substrate, while a thermionic converter with a high thermal effusivity substrate achieves superior discharge performance at night. A rather constant conversion efficiency of ∼31% is attained, regardless of the seasons, while a significantly lower discharge ratio of 11.69% is recorded in summer. The fluctuating with high intensity of solar radiation on cloudy days prompts a discharge ratio of ∼30% and a conversion efficiency of ∼45%.