Salt is power. It might sound like alchemy, but the energy in places where salty ocean water and freshwater mingle could provide a massive source of renewable power. National Science Foundation-funded researchers have developed an affordable, durable technology that could harness this so-called blue energy. The researchers tested a prototype of the battery, monitoring its energy production while flushing it with alternating hourly exchanges of wastewater effluent from the Palo Alto Regional Water Quality Control Plant and seawater collected nearby from Half Moon Bay. Over 180 cycles, battery materials maintained 97% effectiveness in capturing the salinity gradient energy. The technology could work any place where fresh and saltwater intermix, but wastewater treatment plants offer a particularly valuable case study. Wastewater treatment is energy-intensive, accounting for about three percent of the total U.S. electrical load. The process -- essential to community health -- is also vulnerable to power grid shutdowns. Making wastewater treatment plants energy independent would not only cut electricity use and emissions but also make them immune to blackouts -- a major advantage in places such as California, where recent wildfires have led to large-scale outages.
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