Photo-thermo-electric modeling of photon-enhanced thermionic emission with concentrated solar power

Abstract

Photon-enhanced thermionic emission (PETE) is an advanced technology that combines both the photoelectric and the thermionic effects synergistically into a single device for direct electricity generation. However, its industrial-level application is still missing partly due to the lack of advanced models to analyze its operating characteristics and to understand the synergistic mechanism. Herein, we develop a numerical model of PETE by fully considering the optical, the electrical and the thermodynamic aspects with one-dimensional steady-state continuity equations of carriers in the semiconductor cathode. A hybrid PETE-Stirling cycle system is also proposed to yield an output power density of 162.65 kW/m 2 with 32.8% conversion efficiency. The PETE conversion efficiency keeps ∼20% with the optimal electron affinity increases from 0.5 to 1.14 eV as solar concentration ratio varies from 100 to 500. The cathode thickness should be optimized by considering both solar absorption and photon enhancement, where the thickness range of 0.78–1.52 μm is obtained for 50–500 suns. The interelectrode gap is also found to significantly affect the PETE performance by regulating both the space-charge effect and near-field radiation, where the range of 0.5–2 μm is recommended. This work can serve as a foundation to understand the working mechanism of PETE converters and provide guidelines for the performance evaluation. • Numerical models are developed for photon-enhanced thermionic emission converters. • Coupled effects of optical, electrical and thermodynamic fields are fully considered. • Characteristics of the converter for various scenarios are analyzed in detail. • A hybrid system is proposed with a 162.65 kW/m 2 power density and a 32.8% efficiency.