Large-scale testing and simulation of nanofabricated thermionic energy converters

Thermionic energy converters are a potential technology for efficient, direct, and compact heat-to-electricity conversion with no moving parts. We discuss the testing and simulation of devices for thermionic conversion which incorporate a nanofabricated electrostatic lensing system to mitigate space charge. In order to achieve high performance, these devices must minimize loss of the vacuum electrons to the electrostatic grids, which requires precise modeling of electron emission and absorption. We demonstrate the use of a large experimental dataset, encompassing a variety of grid geometries and operating conditions, to validate and improve our model. Specifically, we show that including effects such as dielectric charging provides statistically significant improvements in agreement between experiments and kinetic particle-in-cell simulations. We then use these models to improve device performance, exemplifying the value of experimental validation.