Steam Generators ‘Grown’ on Natural Materials could Help Solve Looming Fresh Water Crisis

Discovering new and more efficient methods of harvesting fresh water from non-potable sources is becoming more and more relevant as the world’s population keeps growing.

And even though scientists are well aware of how to purify water in theory, the challenge is to find ways of doing it sustainably and on the cheap energy-wise.

One promising contender – a pioneering method of solar-driven distillation (SDD) – has recently been developed by researchers from the University of Chicago’s Pritzker School of Engineering and the UC-affiliated Argonne National Laboratory.

The research team’s goal was to come up with an easy way to fabricate solar steam generators (an alternative name for SDD) – which are currently mostly relegated to the lab – at relatively low cost.

In order to be useful, systems designed for generating steam by harvesting sunlight must be buoyant in water, capable of absorbing a broad spectrum of light and efficiently converting it to heat, and be able to transfer heat to water.

Writing in a paper out in the journal Advanced Materials Interfaces, the researchers claim to have developed just such a system, thereby solving the problem of transferring heat to water faced by previous techniques which lacked a porous structure.

Water desalination could become much more streamlined in the future, phasing out such large and complex desalination plants as the one pictured above. Image: Mark Neyman via, CC BY-SA 3.0

“Most existing methods cannot be easily engineered to produce steam-generating devices with both arbitrary control over the shape and high photothermal efficiency,” said lead author on the study Zijing Xia who’s currently a graduate student at Pritzker Molecular Engineering.

The key to success here was the use of a porphyrin covalent organic framework (or POF) – a newly discovered class of materials capable of growing uniformly on the surface of many different materials and providing high performance for water evaporation.

According to Xia, the most promising outcome of the study is the POF’s ability to grow on the surface of membranes, fabrics, sponges, and wood – the latter showing roughly 80 per cent light-to-steam conversion efficiency.

This capacity of the material could have an obvious advantage when implementing solar-based desalination in different parts of the world using native materials.

“POF-based interface engineering design shows promise for large-scale purification methods, and it could also be used for desalination, wastewater treatment and beyond,” claimed Xia.



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