Making fresh water when stuck in the middle of the ocean sounds easy enough. All you have to do is let the sun heat the water until it evaporates the salt water. Then, somehow, you have to trap the stream and condense it on a plastic surface to collect the fresh water. This process even sterilizes the water.
While this is something we've all seen done in the movies, it is a lot harder, more inefficient and way too slow to be a practical option for those without clean drinking water. The process described above only yields about one cup of fresh water a day, even when plenty of water is available under eight hours of sunlight.
Researchers from the University of Houston and MIT have created a cheap material that desalinates water quickly and efficiently with solar energy using graphite. Rather than heating the entire surface, the material creates hot spots so that all of the energy goes towards creating a stream.
When the graphite is heated, it pops up like popcorn to make a thin, porous material that looks like a black sponge. This material floats on the water to soak up the sun, with holes that concentrate the solar energy to create hot spots in the graphite.
"It creates steam at a low concentration of solar energy," said engineer Hadi Ghasemi. "So you don't need such expensive optical systems to concentrate the solar energy."
Certain aspects still need to be work out, however. For example, researchers still need to figure out what to do with the salt that clogs the pores of the graphite.
"We want to further reduce the concentration of sunlight needed," said MIT's Gang Chen, the study's lead. "Then the technology wouldn't need fancy tracking technology to keep the sun focused on it."
Such a material would have more applications than providing clean drinking water, which would be a feat in itself. It could also make steam power and help to dry up areas after floods.
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