River mouths have recently been reported to have the capacity to produce renewable electricity that could support over half a billion people. A river mouth is where a river drains into the ocean. At that point there is a process termed as pressure-retarded osmosis (PRO) that takes place.
According to the new analysis, the pressure-retarded osmosis process has great power generation potential. This study was conducted by Menachem Elimelech and Ngai Yin Yip who are affiliated to the Chemical and Environmental Engineering Department of the Yale University. The report is documented in the most recent edition of the Environmental Science & Technology journal.
The two researchers note that tapping only a tenth of the global PRO potential enough electricity would be generated to free the world from the need of using fossil fuel, and thus no carbon dioxide would be emitted. Furthermore, they noted that the process could sustainably support electricity generation. The Stanford researchers’ 2011 conclusion was that 13% of the world’s energy demand by that time could be met by this renewable energy source.
The PRO mechanism of exploiting renewable energy utilizes the potential difference in saltiness between the salty oceanic water and the river’s fresh water. The American Chemical Society explains PRO as a process where “freshwater flows naturally by osmosis through a special membrane to dilute seawater on the other side.” The generated pressure from that flow spins or turns a turbine generator which in turn produces electricity.
The first prototype pressure-retarded osmosis plant was established in 2009 in Norway. Following this project, researchers set out to calculate and get a better understanding of what the actual contribution of this technology to future energy demands under real-world conditions is.
In their study, Yip and Elimelech conclude that PRO generated electricity could sustain 520 million people and yet emit no carbon dioxide in the process. To generate the same amount of power, in comparison, coal-fired plants would end up producing greenhouse gases to the tune of over a billion metric tons per year!