Professor in Engineering Kyle Smith and his team developed a new desalination device last month that removes salt from water. The device uses a special design to move fluids quickly and use less energy.
The inspiration for the design came from managing the distribution of the electrode material used for fluid flow. The goal was to increase fluid flow in contact with the device to reduce and minimize energy use.
This led to the team modeling the use of heat transfer fins. Fins are flat structures that maximize the heat transfer from a system and the surface area of the structure. The increased surface area is key, as any flowing fluid introduced then comes into contact with more of the device.
“I realized after learning from those analyses that the flow distribution is, in general, highly non-uniform when you use straight channels,” Smith said. “You get a dead zone in the middle between these channels if the channels are straight. And if they’re really long, I can basically find a solution to the system of equations that forces the flow distribution to be uniform.”
By making the distribution of fluid flow uniform, the device would ideally save energy while desalinating water. This is done by reducing the pressure pumped to over 100 times less than current reverse osmosis techniques. This allows fuel cells, flow batteries and electrolysis cells to use less energy for the same output.
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“For electromechanical systems that use flow, which a desalination device is certainly a type of, that means that there’s less energy input that needs to go in in order to get a certain amount of desalinated water produced or a certain amount of power delivered,” Smith said. “So it just means more efficient energy conversion.”
The team’s design saves more energy than the current desalination standard, reverse osmosis, on a small level. Reverse osmosis is a desalination technique that first filters the water from organic substances and separates it into a brine and a freshwater stream, then dilutes the brine stream so that less salt is returned to the ecosystem.
“And you may say: Why small scale,” Smith said. “Large-scale reverse osmosis uses additional energy recovery mechanisms that small-scale systems aren’t outfitted for.”
More specifically, the device reduces the amount of pressure by using electrical energy output to recirculate the water.
“But part of the reason that we still consume energy that is similar in magnitude to reverse osmosis is because, when we operate our device, we recirculate the water through our electrodes,” Smith said. “So it’s a small pressure, but since we have to recirculate it many times, that’s a lot of flow. So the energy consumption is essentially proportional to that flow rate and the pressure.”
Some of the applications for the device include improving efficiency for fuel and electrolysis cells, as well as providing fresh water to troops. According to Smith, these applications are important for organizations, such as the Navy, to conserve energy.
“This project is currently funded by the Navy,” Smith said. “And the Navy is interested in water desalination because basically all their troops need water, and the more fuel that they need to bring along to sustain generators that would run desalination processes means the more encumbered they are on the battlefield or wherever they’re at.”
The future of this device involves scaling up its design with larger materials for use in bigger environments, such as larger energy storage.
“I want to implement this technology in other application spaces, and we’re actively pursuing opportunities for that right now,” Smith said. “And the application spaces, this is beyond just desalination, energy storage and conversion, which includes fuel cells, flow batteries, electrolysis cells, things of that sort.”
Additionally, Smith hopes that although the desalinated water production output is low, the device could be used for applications such as providing clean drinking water for a home or filtering the brine released from fossil fuel extraction processes.
“Brine itself can be an environmental hazard, and so it actually costs something to dispose of that material, and it presents issues with the environment,” Smith said. “So if you were to do desalination in some way, particularly use desalination that produces minimal liquid discharge; as a result, minimal waste, you could help to alleviate that problem.”
