Minireview on Solar Desalination and Hydropower Generation by Water Evaporation: Recent Challenges and Perspectives in Materials Science

Environmental energy harvesting holds great promise for sustainable development of society. Today, there are many kinds of available energy sources, such as hydropower, nuclear energy, thermal power, etc., but all of these suffer from requiring massive infrastructure investment, producing environmental pollution, and/or having the potential to experience catastrophic failure. In this review, we introduce novel methodology for harvesting energy, using evaporation of water from three-dimensional porous media, low-dimensional nanotubes, or microfibrous structures. We can produce fresh water driven by harnessing sunlight and can generate hydroelectric power via water transpiration. The former is driven by nanoscale photothermal heating, which induces rapid evaporation of water, while its bulk remains near room temperature. The latter is coupled with mass transport of water comprising ions that are condensed adjacent to the charged surface of the porous or fibrous media. These proposed schemes are clean, simple, and useful, which can be employed anywhere, because they operate as a result of spontaneous capillary action of water, solar power, or coulombic attraction occurring at the water–solid interface. The low-cost micro- and nanostructured materials presented here are readily available, suitable for securing potable water, and offer ubiquitous, clean, permanent energy sources for self-powered sensor networks and night-time energy harvesters that do not require energy inputs.