Fig. 6: Comparison of different desalination technologies.

The energy consumed per unit volume of yield, or specific energy consumption (SEC), is plotted against the concentration drop for different desalination technologies: reverse osmosis (RO), multi-stage flash (MSF) and multi-effect distillation (MED), electrodialysis (ED), adsorption, capacitive deionisation (CDI), novel solar-driven desalination (NSD), e.g. interfacial evaporation and contactless steam generation, membrane distillation (MD), and the thermodiffusive desalination (TDD) technology proposed in this work. Corresponding sources are indexed and listed in Supplementary Table 4. For some technologies, SEC is dependent on the feedwater salinity and the yield salinity. The vertical black dashed line indicates a concentration drop from seawater to freshwater. The thermal-driven desalination methods are captured by the mauve circle. SEC of different technologies vary vastly and the thermal-driven desalination technologies generally have a much higher energy consumption. For TDD, the presented SEC data is based on multi-pass TDU experiment. A heat flux of 232 W (Supplementary Method 8) was used and the yield was 0.3 L h⁻¹. Under this condition, SEC is calculated as \({{{{{{{\rm{SEC}}}}}}}}=0.232\,{{{{{{{\rm{kWh}}}}}}}}/0.3\,{{{{{{{\rm{L}}}}}}}}=773\,{{{{{{{{\rm{kWh}}}}}}}}}\,{{{{{{{{\rm{m}}}}}}}}}^{-3}\). However, when only considering the electrical energy usage, \({{{{{{{{\rm{SEC}}}}}}}}}_{{{{{{{{\rm{e}}}}}}}}}\), its value drops to nearly 0. SEC data is not available for the adsorption-based desalination.