Fig. 2. Subcooling and dew harvesting potential enhancement through the radiation shield.

(A) Thermodynamic analysis of the radiation shield and involved heat fluxes. Styrofoam blocks condensation side, consequently ${\stackrel{·}{Q}}_{\text{dew}}=0$. The angular dependence of atmospheric emissivity is represented in blue. (B) Subcooling performance of OPUR, selective emitter with (β = 30°) and without (β = 90°) radiation shield. (C) Theoretical dew harvesting potential. The selective emitter, working collaboratively with the radiation shield, extends the harvesting window by more than 2 hours (t₁ to t₃) and to conditions with RH < 50% and 808 W m⁻² solar irradiation (10-min intervals). (D) Improvement of the state of the art. The selective emitter, collaboratively working with the radiation shield, outperforms existing dew harvesting technologies by a factor 2 to 3 depending on RH.