SOLAR DESALINATION

In many settings where freshwater resources or water supply infrastructure are inadequate, fossil energy costs may be high whereas solar energy is abundant. Further, in the industrialized world, government policies increasingly emphasize the replacement of fossil energy by renewable, low-carbon energy, and so water scarce regions are considering solar-driven desalination systems as a supplement to existing freshwater supplies. Even in regions where petroleum resources are copious, solar-driven desalination is attractive as a means of conserving fossil fuel resources and limiting the carbon footprint of desalination. Finally, in settings that are remote and ‘off-the-grid,” a solar driven desalination system may be more economical than alternatives such as trucked-in water or desalination driven by diesel-generated electricity. This article reviews various technologies that couple thermal or electrical solar energy to thermal or membrane based desalination systems. Basic principles of desalination are reviewed. Solar stills and humidification-dehumidification desalination systems are discussed. Membrane distillation technology is reviewed. Current designs for solar coproduction of water and electricity are considered. Finally, photovoltaic driven reverse osmosis and electrodialysis are reviewed. The article concludes by summarizing the prospects for cost efficient solar desalination.