A new project kicked off this July as researchers across four institutions joined forces with local start-up companies, consultants, and coastal utilities to explore how a process that occurs naturally every minute along North Carolina’s coast may be harnessed for sustainable energy.

The process in question is the mixing of salt and fresh water in North Carolina’s sounds and estuaries. In order to develop technology and assess the feasibility of implementing such technology along North Carolina’s coast, researchers from North Carolina State University, the University of North Carolina at Chapel Hill, the Coastal Studies Institute, and East Carolina University are collaborating on a three-year project funded by the UNC Research Opportunities Initiative (ROI).

Co-principal investigator Orlando Coronell, PhD, Assistant Professor of Environmental Sciences and Engineering at the Gillings School of Public Health at UNC, describes the premise in terms of the more familiar process of desalinization. During electrodialysis, he explains, you apply electricity to a membrane to remove ions, the components of salt, from water. Then you end up with two compartments: one with a very high ion concentration and one of fresh water. Desalinating water uses electricity. But, you can also run the process backwards: by starting with two compartments with very different salt concentrations, you can use reverse electrodialysis to generate electricity as the ions move across the membranes from the saltier side to the less salty side. Of course, Coronell notes, “first you have the concept theoretically of why it could work, but then you still have to get all the components of the technology to work.”

Co-principal investigator Doug Call, PhD, Assistant Professor of Civil, Construction, and Environmental Engineering at NC State, agrees that getting those components, particularly the membranes, to work efficiently will be one of the challenges of getting reverse electrodialysis energy from the lab to the market. Another important focus of this project is to survey natural water from North Carolina’s coast to determine where optimal salinity gradients are located and to evaluate the effect of water quality on the system. Initial experiments will be done in the lab. A small laboratory set-up, Call says “may be the size of a tea cup, and a larger one might be more like a Big Gulp.” Ultimately, though, the goal is to attract industrial interest and build a larger-scale system along the coast.


Fresh water meets salt water in North Carolina’s estuaries, providing a natural laboratory where scientists will explore how power generation from salinity gradients might work in NC. Image credit: NASA satellite imagery via www.terraprints.com.


Reverse electrodialysis differs from other green energy alternatives in that the same technology can be used not only to generate electricity but also to store electricity (similar to a battery) and to clean up wastewater by harnessing the power of bacteria with a microbial fuel cell. “Typically when you look at an energy technology like a wind turbine or solar panel,” explains Call, “you get one function from it: electricity. But here, we have a technology that can provide multiple benefits in one platform. We want to better understand the economics of this system.” Perhaps because reverse electrodialysis has three benefits, the effective cost of each kilowatt of electricity may be lower.

The ability to store energy by setting up a high salinity gradient is of particular interest to Coronell. He explains that energy storage is a novel and important application of this type of technology. “We’re not talking about powering a cell phone,” he explains; this technology is more appropriate for “grid-scale application.” He also notes that because of the ability to store energy, reverse electrodialysis could be used in conjunction with other green energy technology such as solar and wind to continue providing electricity even at off-peak times.

In order to understand the wider ranging effects of reverse electrodialysis, Call and Coronell have teamed up with economists and environmental scientists. Together, they hope to achieve what Call refers to as the overarching goal of this project: “to get a sense of the impact this technology could have on North Carolina’s energy and environmental sectors.”

You can read more about this project and meet some of the other members of the research team on ECU’s website. You can also check out the UNC Research Opportunities Initiative to see more game-changing research being done in North Carolina.

Peer edited by Lindsay Walton & Kelly Jones

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