Stanford researchers have developed a technology which will be able to harness energy from the places where saltwater and freshwater mingle using battery electrochemistry becoming the very first technology to do without using pressure or membranes, named as "blue energy". The research paper was published in American Chemical Society’s ACS Omega, and it describes the battery and suggests that it could be used to make coastal wastewater treatment plants energy-independent.
Blue energy is an immense and untapped source of renewable energy. Our battery is a major step toward practically capturing that energy without membranes, moving parts or energy input - Kristian Dubrawski, the Co-author of the article
Yi Cui, a professor of materials science and engineering, and Mauro Pasta, a postdoctoral scholar in materials science and engineering co-wrote the paper with Dubrawski and came up with the idea.
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 percent effectiveness in capturing the salinity gradient energy - Stanford News
If wastewater treatment plants are made energy independent, it would cut back on the electricity usages and consequently, emissions while at the same time become immune to blackouts.
Every cubic meter of freshwater that mixes with seawater produce about 65 kilowatt-hours of energy – enough to power the average American house for about 30 minutes. Globally, the theoretically recoverable energy from coastal wastewater treatment plants is about 18 gigawatts – enough to power more than 1,700 homes for a year - Stanford News
The news describes the process as follows:
First, sodium and chloride ions are released from the battery electrodes into the solution. A rapid exchange of wastewater effluent with seawater leads the electrode to reincorporate sodium and chloride ions and reverse the current flow. Blue Energy is recovered when both the freshwater and seawater is flushed.
The electrodes are made using Prussian Blue which costs less than $1 a kilogram, and polypyrrole which costs less than $3 a kilogram. “It is a scientifically elegant solution to a complex problem,” Dubrawski said. “It needs to be tested at scale, and it doesn’t address the challenge of tapping blue energy at the global scale - rivers running into the ocean - but it is a good starting point that could spur these advances.”