Engineers have discovered a way to eliminate the fluid flow “dead zones” that affect the electrodes used in battery-operated seawater desalination systems. This innovative approach utilizes a tapered flow channel design based on physics principles, allowing liquids to move swiftly and efficiently, potentially using less energy than the energy-intensive reverse osmosis methods in common use today.
Engineers have discovered a method to remove the fluid flow “dead zones” that negatively impact the electrodes utilized in battery-powered seawater desalination. This new approach employs a physics-informed tapered flow channel design within the electrodes, facilitating faster and more efficient fluid movement, which may require less energy compared to conventional reverse osmosis techniques.
Significant technical challenges have hindered the widespread adoption of desalination technologies. The most prevalent technique, reverse osmosis, forces water through a membrane to separate salt, but this process is both expensive and high in energy consumption. In contrast, battery-based desalination relies on electricity to extract charged salt ions from the water while still demanding energy to drive the water through electrodes that possess tiny, irregularly shaped pore spaces.
“Conventional electrodes necessitate energy to push fluids through because they lack any structured flow channels,” explained Kyle Smith, a mechanical science and engineering professor at the University of Illinois Urbana-Champaign who led the research. “However, by integrating channels within the electrodes, this method could require less energy to push the water through and ultimately prove more efficient than the existing reverse osmosis processes.”
Smith’s technique for battery-based desalination builds on years of modeling and research by his team at Illinois, culminating in a recent study that showcased the first utilization of electrodes featuring tiny microchannels known as interdigitated flow fields (IDFFs).
The latest research incorporates IDFFs into electrodes as well, but with a tapered channel design instead of a straight one. This modification significantly boosts fluid flow—or permeability—by two to three times compared to straight channels. The results are documented in the journal Electrochimica Acta.
“Our early investigations into straight channels in electrodes led us to identify dead zones where we observed pressure drops and uneven flow distribution,” said Habib Rahman, a graduate student at Illinois. “To address this issue, we developed a library of 28 distinct straight channels to analyze conductance and flow variations, ultimately leading to the incorporation of this channel-tapering approach.”
During their experiments, Smith and Rahman encountered some manufacturing obstacles, particularly regarding the production time required to mill the channels into the electrodes, a concern for any large-scale manufacturing scenario. However, Smith expressed optimism that these challenges could be surmounted.
“In addition to its influence on electrochemical desalination, our channel-tapering theory and design principles can be applied to any electrochemical device that involves fluid flow, including those used for energy conversion and environmental applications such as fuel cells, electrolysis cells, flow batteries, carbon capture devices, and lithium recovery systems,” Smith stated. “Unlike previous channel-tapering methods that employed arbitrary designs, our approach offers physics-based design guidelines aimed at ensuring uniform flow and reducing pressure drops concurrently.”
This research was funded by the Office of Naval Research. Smith, Rahman, and their co-authors Irwin Loud IV, Vu Do, and Abdul Hamid have pending patents under U.S. patent applications 17/980,017, 17/980,023, and 63/743,995.
Smith also has associations with the material science and engineering department and the Beckman Institute for Advanced Science and Technology.
