Abstract
Technologies for solar steam generation with high performance can help solving critical societal issues such as water desalination or sterilization, especially in developing countries. Very recently, we have witnessed a rapidly growing interest in the scientific community proposing sunlight absorbers for direct conversion of liquid water into steam. While those solutions can possibly be of interest from the perspective of the involved novel materials, in this study we intend to demonstrate that efficient steam generation by solar source is mainly due to a combination of efficient solar absorption, capillary water feeding and narrow gap evaporation process, which can also be achieved through common materials. To this end, we report both numerical and experimental evidence that advanced nano-structured materials are not strictly necessary for performing sunlight driven water-to-vapor conversion at high efficiency (i.e. ≥85%) and relatively low optical concentration (≈10 suns). Coherently with the principles of frugal innovation, those results unveil that solar steam generation for desalination or sterilization purposes may be efficiently obtained by a clever selection and assembly of widespread and inexpensive materials.
Highlights
Developing sustainable technologies is fundamental for mitigating the anthropogenic impact on environment[1]: global warming and clean water scarcity are progressively impacting our economies and societies[2,3,4]
To the strategy suggested by Ghasemi et al.[18] and other authors thereafter[19,27,28,38,41,43,44,45,46,47], solar steam generation is here enhanced by the concurrent action of three phenomena: (i) heat confinement in the evaporative region; (ii) capillary action to distribute water in a narrow gap (iii) effective thermal insulation around the evaporative region
The efficiency of traditional solar distillation techniques has been significantly enhanced by concentrating the solar radiation solely at the water-air interface, in order to reduce the heat losses due to bulk heating of water in the non-evaporative regions
Summary
Developing sustainable technologies is fundamental for mitigating the anthropogenic impact on environment[1]: global warming and clean water scarcity are progressively impacting our economies and societies[2,3,4]. Several filtration or distillation processes have been developed for the generation of fresh water from either brackish or sea water Most of these processes are highly energy intensive and powered by fossil fuels[7], whereas more sustainable alternatives have been recently investigated to couple clean water generation with renewable energy[8]. Several recent studies aimed to gather solar radiation solely at the water-air interface, in order to localize the temperature increase in the evaporative region achieving a more energy-efficient solar steam generation[27]. This strategy has been implemented thanks to nanoparticle suspensions or microporous structures
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