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Scientists Use Solar Energy To Transform Seawater Into Drinking Water

Earth is a planet covered in water. Yet amazingly, less than three percent of that water is drinkable freshwater. Of that three percent, around 68 percent of our freshwater is completely inaccessible to humans, locked within icecaps and glaciers. As the climate continues to change and droughts become more common, scientists are seeking ways to access more water from oceans, where 97 percent of our planet's water resides.

It has been possible, for some time, to extract drinkable water from seawater. But the only two processes for doing so were sorely inefficient, using far too much energy. But now, thanks to a breakthrough in the process known as distillation, scientists are able to collect drinkable water from the ocean via solar power. This breakthrough couldn't have come at a better time, considering that climate change has caused droughts to become more common in recent years. 

Prior to recent findings, seawater could only be "made into" fresh water via distillation or membrane distillation. Regular distillation involved boiling salt water and collecting the steam, then processing that steam through a condensing coil. The heat needed to boil the water consumed a large amount of energy, making the process inefficient. 

In membrane distillation, hot and cold ocean water was pushed through a porous membrane, and the vapor from the process was collected. This used only slightly less electrical energy than regular distillation. The inefficiency of these processes meant that their usefulness was limited. Freshwater could not be extracted on a large enough scale to meet the demands of an increasingly water-starved population. 

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But now, according to the findings of a federally-funded study at Rice University, it is possible to extract freshwater from seawater using a process called "nanophotonics-enabled solar membrane distillation" technology, or NESMD. As its name suggests, this process is powered entirely by solar energy. Using nanotechnology, NESMD converts sunlight into the heat needed to produce water vapor via membrane distillation. This seemingly small change could have a huge impact on the widespread use of distillation, and make a significant global impact, according to Rice University researcher and water treatment expert, Qilin Li. 

As Li explains in a statement on their research, "Direct solar desalination could be a game changer for some of the estimated 1 billion people who lack access to clean drinking water. This off-grid technology is capable of providing sufficient clean water for family use in a compact footprint, and it can be scaled up to provide water for larger communities."

As Li points out, one important aspect of this new technology is how easy it is to reproduce. Because it utilizes the same type of membranes already used in membrane distillation, NESMD could be easily integrated into at least a few of the more than 18,000 water desalination plants currently operating around the world. Her research team has already developed a system which utilizes a small membrane panel in the distillation process, that could be replicated for use anywhere. 

“You could assemble these together, just as you would the panels in a solar farm,” Li continues. “Depending on the water production rate you need, you could calculate how much membrane area you would need. For example, if you need 20 liters per hour, and the panels produce 6 liters per hour per square meter, you would order a little over 3 square meters of panels.” 

It seems likely that, if such technology were to become widely available, water desalination plants would jump at the chance to install it, considering that energy costs account for half of the total expense of their operation.

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