Engineers have developed a groundbreaking solution to eliminate fluid flow “dead zones” in electrodes used for battery-based seawater desalination, significantly improving the efficiency of the process. The innovative design introduces a physics-driven tapered flow channel within the electrodes, facilitating faster and more effective fluid movement. This new approach has the potential to reduce energy consumption compared to traditional reverse osmosis techniques, offering a more sustainable solution for desalinating seawater.

Desalination has long been a challenge for sustainable water supply solutions, particularly due to the high energy demands of current technologies. The most commonly used method, reverse osmosis, filters salt from seawater by forcing it through a membrane. While effective, this process is both energy-intensive and costly.

In contrast, battery-based desalination uses electricity to remove charged salt ions from the water, a potentially more energy-efficient approach. However, this method has its own hurdle: the water must be pushed through electrodes with small, irregular pores, which has previously limited fluid flow and efficiency. Until now, the lack of structured flow channels within these electrodes has posed a significant barrier to optimizing the process.

Professor Kyle Smith, a mechanical science and engineering expert at the University of Illinois Urbana-Champaign, and his team have developed a solution that addresses this challenge. “Traditional electrodes still require energy to pump fluids through because they do not contain any inherently structured flow channels,” said Smith. “However, by creating channels within the electrodes, we can reduce the energy required to push water through, making the technique more efficient than conventional reverse osmosis.”

The new approach builds on years of research, culminating in a study that demonstrates the first use of electrodes featuring microchannels, known as interdigitated flow fields (IDFFs). The key innovation in Smith’s study is the modification of these flow channels from straight to tapered shapes. The tapered design has shown to improve fluid flow and permeability by two to three times compared to straight channels, drastically enhancing the overall efficiency of the desalination process. These findings, recently published in Electrochimica Acta, present a significant step forward in energy-efficient desalination.

The key issue with traditional electrode designs was the presence of “dead zones”—areas where fluid flow stagnates due to uneven distribution. This results in pressure drops and energy inefficiencies. Smith and his team identified these flow irregularities during earlier experiments with straight channels. To overcome this, they created a library of 28 different straight channel designs to study their conductance and flow behavior, ultimately leading to the development of the tapered channel design.

Graduate student Habib Rahman, who contributed to the study, explained, “Our initial work with straight channels led us to discover dead zones within the electrodes, where we saw pressure drops and nonuniform flow distribution. The tapered channels helped us overcome these challenges by improving the overall flow efficiency.”

While the team faced manufacturing challenges, particularly in the time it takes to mill the channels into the electrodes—an issue that could affect large-scale production—Smith is confident these obstacles can be overcome with further development and optimization.

Beyond its implications for electrochemical desalination, this innovative tapered flow design has far-reaching applications. The same design principles can be applied to any electrochemical device that involves the flow of liquids, such as energy storage devices, fuel cells, electrolysis cells, flow batteries, and even carbon capture or lithium recovery technologies.

“Unlike previous channel-tapering strategies that used ad-hoc designs, our approach offers physics-based guidelines to create uniform flow and minimize pressure drops simultaneously,” said Smith. This method can not only improve desalination but also enhance the performance and efficiency of a wide range of technologies focused on energy conversion and environmental sustainability.

In conclusion, the development of tapered flow channels in electrodes represents a significant breakthrough in desalination technology. By reducing the energy required to push water through electrodes, this innovation offers the potential to make desalination more energy-efficient and cost-effective, providing a promising solution to global water scarcity challenges.

By Impact Lab