Fig. 4. Energy balance analysis in STD systems.
Energy balance analysis is performed in four different steady-state STD configurations: (A) a nonselective absorber with a finite bulk solution volume with perfect thermal insulation, (B) a selective absorber with a finite bulk solution volume with perfect thermal insulation, (C) a selective absorber with an infinite bulk solution volume and no wick, and (D) a selective absorber with an infinite bulk solution volume and wick. For each scenario, the energy flux and temperature of the absorber as a function of the solar absorptivity (α) of the absorber are also plotted next to the schematic of each STD configuration. In each plot, the total incoming solar flux is 1000 W m−2, and it is equal to the sum of the unabsorbed solar flux (orange region), the radiative heat loss (red region), the convective heat loss (purple region), the heat loss to water (brown region), and the energy consumption for evaporation (blue region). The dashed black curve represents the average temperature of the absorber.