researchers at the a. james clark school of engineering at the university of maryland (college park, md.) have devised a novel solution to the global problem of water scarcity, creating a suite of solar steam generation devices from wood.
this new research could help minimize the world's water shortage.
according to a report from the university, the engineers were inspired by the way that water is carried from the roots of trees to small pores on the underside of leaves. the researchers created a method for water to be transported through wood and be purified for consumption.
“picture a bowl of unpurified water sitting in a sunny spot,” the article explained. “on top of it floats a small block of wood about two inches by two inches. the side of the block facing up is darkened, to catch the sun's rays.
“as the sun heats the wood, the water below is drawn up through the wood’s natural channels. the hot dark surface evaporates the water, which can be condensed and distilled off. the salt or other contaminants are too heavy to evaporate, so they stay below.”
the engineers have explored various options to optimize the performance of the water purifiers, including the addition of carbon nanotubes or metal nanoparticles on one side of the wood to heat the water on the inside.
another design carbonizes the top layer of the wood to create a dark surface and turned the wood so the porous channels would be running up and down, just as they would in a tree.’
“by the same measure used to test solar cells’ efficiency, the team measured how efficient the solar steam generation devices are,” the article continued. “the most efficient device was the burned-top wood, with 87% efficiency at ten suns of light. it was also the least expensive to produce, coming in at only $1 per square meter.”
with more than 1 billion people worldwide struggling to find safe drinking water, the researchers are hopeful that this new technology could provide an efficient, cost-effective, and environmentally-friendly alternative to solve the water crisis.
the latest research was published in advanced materials. the abstract stated:
“solar steam generation with subsequent steam recondensation has been regarded as one of the most promising techniques to utilize the abundant solar energy and sea water or other unpurified water through water purification, desalination, and distillation.
“although tremendous efforts have been dedicated to developing high-efficiency solar steam generation devices, challenges remain in terms of the relatively low efficiency, complicated fabrications, high cost, and inability to scale up.
“here, inspired by the water transpiration behavior of trees, the use of carbon nanotube (cnt)-modified flexible wood membrane (f-wood/cnts) is demonstrated as a flexible, portable, recyclable, and efficient solar steam generation device for low-cost and scalable solar steam generation applications.
“benefitting from the unique structural merits of the f-wood/cnts membrane—a black cnt-coated hair-like surface with excellent light absorbability, wood matrix with low thermal conductivity, hierarchical micro- and nanochannels for water pumping and escaping, solar steam generation device based on the f-wood/cnts membrane demonstrates a high efficiency of 81% at 10 kw cm−2, representing one of the highest values ever-reported.
“the nature-inspired design concept in this study is straightforward and easily scalable, representing one of the most promising solutions for renewable and portable solar energy generation and other related phase-change applications.”