A nanotechnology-enabled rechargeable battery, which uses freshwater and seawater to create electricity, has been developed by researchers at the United States-based Stanford University. The battery employs the difference in salinity between the fresh and saltwater to generate a current. Yi Cui, an associate professor of materials science and engineering, who led the research team, said anywhere freshwater enters the sea, such as river mouths or estuaries, could be a potential site for a power plant using such a battery. The limiting factor, he said, would be the amount of freshwater available. “We actually have an infinite amount of ocean water; unfortunately we don’t have an infinite amount of freshwater,” he said. The positive electrode of the battery is made from nanorods of manganese dioxide, which increases the surface area available for interaction with the sodium ions by roughly 100 times compared with other materials. Cui’s team achieved 74 percent efficiency in converting the potential energy of the battery into electrical current in lab experiments. A power plant operating with 50 cubic meters of freshwater per second, and using this technology, could provide electricity for about 100,000 households. The group knows that river mouths and estuaries are environmentally sensitive areas. As Cui says, “You would want to pick a site some distance away, miles away, from any critical habitat. We don’t need to disturb the whole system, we just need to route some of the river water through our system before it reaches the ocean. We are just borrowing and returning it.” The discharge water would be a mixture of fresh and seawater, and would be released into an area where the two waters were already mixing, at the natural temperature. Cui said it was possible that even treated sewage water could work for his battery. “I think we need to study using sewage water,” he said. “If we can use sewage water, this will sell really well.” The article can be viewed online at the link below.
http://news.stanford.edu/news/2011/march/saline-rechargeable-battery-032811.html