Scientists review some of the research behind a technology that could cauterize a growing global drinking water crisis.
A nascent but promising solution to the world’s water scarcity problems could be water purification via the direct solar steam generation technology. But while researchers are well on the path to making this technology practically applicable, the finish line remains a ways away. A new study in Elsevier’s Solar Energy Materials and Solar Cells takes us through a part of this incredible research journey, which involves device design strategies to optimize the steam generation process.
Without drinkable water there is no life. Yet, nearly 1.1 billion people worldwide lack access to fresh water and another 2.4 billion suffer from diseases borne by unclean drinking water. This is because while science has yielded advanced water treatment methods such as membrane distillation and reverse osmosis, these are often difficult to implement in developing countries owing to their high cost and low productivity.
A more nascent technology shows promise as an alternative for such regions of the world: direct solar steam generation (DSSG). DSSG involves harvesting the heat from the sun to convert water into vapor, thereby desalinating it or ridding it of other soluble impurities. The vapor is then cooled and collected as clean water for use.
This is a simple technology, but a key step, evaporation, is presenting roadblocks for its commercialization. With existing technology, evaporation performance has hit the theoretical limit. However, this is not sufficient for practical implementation. Measures to improve device design to minimize solar heat loss before it reaches bulk water, recycle latent heat in the water, absorb and utilize energy from the surroundings as well, and so on, have been taken to improve the evaporation performance beyond the theoretical limit and make this technology viable.
In a new paper published in Solar Energy Materials and Solar Cells, Professor Lei Miao from Shibaura Institute of Technology, Japan, along with colleagues Xiaojiang Mu, Yufei Gu, and Jianhua Zhou from Guilin University of Electronic Technology, China, review strategies formulated in the last two years to surpass this theoretical limit. “Our aim is to summarize the story of the development of new evaporation strategies, point out current deficiencies and challenges, and layout future research directions to hasten the practical application of the DSSG purification technology,” says Prof. Miao.
A pioneering strategy with which this evolutionary saga begins is the volumetric system, which, in lieu of bulk heating, uses a suspension of noble metals or carbon nanoparticles to absorb the sun’s energy, transfer heat to the water surrounding these…