  Energy harvesting from sun and outer space using thermoradiative devices
(TRD), despite being promising renewable energy sources, are limited only to
daytime and nighttime period, respectively. A system with 24-hour continuous
energy generation remains an open question thus far. Here, we propose a
TRD-based power generator that harvests solar energy via concentrated solar
irradiation during daytime and via thermal infrared emission towards the outer
space at nighttime, thus achieving the much sought-after 24-hour electrical
power generation. We develop a rigorous thermodynamical model to investigate
the performance characteristics, parametric optimum design, and the role of
various energy loss mechanisms. Our model predicts that the TRD-based system
yields a peak efficiency of 12.6\% at daytime and a maximum power density of
10.8 Wm$^{-2}$ at nighttime, thus significantly outperforming the state-of-art
record-setting thermoelectric generator. These findings reveal the potential of
TRD towards 24-hour electricity generation and future renewable energy
technology.
