Fig. 5. Promoting global safely managed drinking water (SMDW) coverage by solar water evaporation (SWE).

a Four quadrant charts of the annual SMDW yield of the evaporation-condensation-optimized case (Eva.-cond. opt.) concerning the population without SMDW of different income-level countries. b The availability of the SMDW produced by evaporation -optimized case (Eva.-opt.) and Eva.-cond. opt. to the population in need. Doubling Eva.-cond. opt. working area could almost cover the upper potential of the SWE. c The relationship between different investment trends and global SMDW coverage (all the bars represent SMDW coverage, and the dashed lines represent investments).