Feb
11
A Battery That Desalinates Water
February 11, 2016 | Leave a Comment
University of Illinois at Urbana-Champaign researchers show a technology that charges batteries for electronic devices could provide fresh water from seawater. Electricity running through a salt water-filled battery draws the salt ions out of the water.
Smith said, “We are developing a device that will use the materials in batteries to take salt out of water with the smallest amount of energy that we can. One thing I’m excited about is that by publishing this paper, we’re introducing a new type of device to the battery community and to the desalination community.”
Interest in water desalination technology has risen as water needs have grown, particularly in drought-stricken areas. But technical hurdles and the enormous amounts of energy required have prevented wide-scale implementation. The most-used method, reverse osmosis, pushes water through a membrane that keeps out the salt, a costly and energy-intensive process. By contrast, the battery method uses electricity to draw charged salt ions out of the water.
The researchers were inspired by sodium ion batteries, which contain salt water. Batteries have two chambers, a positive electrode and a negative electrode, with a separator in between that the ions can flow across. When the battery discharges, the sodium and chloride ions – the two elements of salt – are drawn to one chamber, leaving desalinated water in the other.
In a normal battery, the ions diffuse back when the current flows the other direction. The Illinois researchers had to find a way to keep the salt out of the now-pure water.
“In a conventional battery, the separator allows salt to diffuse from the positive electrode into the negative electrode,” Smith said. “That limits how much salt depletion can occur. We put a membrane that blocks sodium between the two electrodes, so we could keep it out of the side that’s desalinated.”
The battery approach holds several advantages over reverse osmosis. The battery device can be small or large, adapting to different applications, while reverse osmosis plants must be very large to be efficient and cost effective, Smith said. The pressure required to pump the water through is much less, since it’s simply flowing the water over the electrodes instead of forcing it through a membrane. This translates to much smaller energy needs, close to the very minimum required by nature, which in turn translates to lower costs. In addition, the rate of water flowing through it can be adjusted more easily than other types of desalination technologies that require more complex plumbing.
Smith and Dmello conducted a modeling study to see how their device might perform with salt concentrations as high as seawater, and found that it could recover an estimated 80% of desalinated water. Their simulations don’t account for other contaminants in the water, however, so they are working toward running experiments with real seawater.
“We believe there’s a lot of promise,” Smith said. “There’s a lot of work that’s gone on in developing new materials for sodium ion batteries. We hope our work could spur researchers in that area to investigate new materials for desalination. We’re excited to see what kind of doors this might open.”
Its sounds like a great idea for producing fresh water. But it isn’t looking like the system will also be a rechargeable battery any more. The prospect to produce a lot more fresh water has great attraction in many parts of the world. Many of those place are not exactly supplied with low cost power to run desalination. This system may well offer a much lower cost to fresh water production and save a lot of energy where desalination is already underway.
Keep going guys, there is more market and need out there than you might think if the operating costs are low.
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