Nanotechnology Now

Our NanoNews Digest Sponsors
Heifer International



Home > Press > Stanford researchers use river water and salty ocean water to generate electricity

The mouth of the Amazon River, where the world’s largest drainage basin flows into the Atlantic Ocean. A location such as this, where fresh and sea water mix, is a good spot for generating electricity with Yi Cui’s new battery.
The mouth of the Amazon River, where the world’s largest drainage basin flows into the Atlantic Ocean. A location such as this, where fresh and sea water mix, is a good spot for generating electricity with Yi Cui’s new battery.

Abstract:
Stanford researchers have developed a rechargeable battery that uses freshwater and seawater to create electricity. Aided by nanotechnology, the battery employs the difference in salinity between fresh and saltwater to generate a current. A power station might be built wherever a river flows into the ocean.

Stanford researchers use river water and salty ocean water to generate electricity

Stanford, CA | Posted on March 28th, 2011

BY LOUIS BERGERON

Stanford researchers have developed a battery that takes advantage of the difference in salinity between freshwater and seawater to produce electricity.

Anywhere freshwater enters the sea, such as river mouths or estuaries, could be potential sites for a power plant using such a battery, said Yi Cui, associate professor of materials science and engineering, who led the research team.

The theoretical limiting factor, he said, is 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.

As an indicator of the battery's potential for producing power, Cui's team calculated that if all the world's rivers were put to use, their batteries could supply about 2 terawatts of electricity annually - that's roughly 13 percent of the world's current energy consumption.

The battery itself is simple, consisting of two electrodes - one positive, one negative - immersed in a liquid containing electrically charged particles, or ions. In water, the ions are sodium and chlorine, the components of ordinary table salt.

Initially, the battery is filled with freshwater and a small electric current is applied to charge it up. The freshwater is then drained and replaced with seawater. Because seawater is salty, containing 60 to 100 times more ions than freshwater, it increases the electrical potential, or voltage, between the two electrodes. That makes it possible to reap far more electricity than the amount used to charge the battery.

"The voltage really depends on the concentration of the sodium and chlorine ions you have," Cui said. "If you charge at low voltage in freshwater, then discharge at high voltage in sea water, that means you gain energy. You get more energy than you put in."

Once the discharge is complete, the seawater is drained and replaced with freshwater and the cycle can begin again. "The key thing here is that you need to exchange the electrolyte, the liquid in the battery," Cui said. He is lead author of a study published in the journal Nano Letters earlier this month.

In their lab experiments, Cui's team used seawater they collected from the Pacific Ocean off the California coast and freshwater from Donner Lake, high in the Sierra Nevada. They achieved 74 percent efficiency in converting the potential energy in the battery to electrical current, but Cui thinks with simple modifications, the battery could be 85 percent efficient.

To enhance efficiency, the positive electrode of the battery is made from nanorods of manganese dioxide. That increases the surface area available for interaction with the sodium ions by roughly 100 times compared with other materials. The nanorods make it possible for the sodium ions to move in and out of the electrode with ease, speeding up the process.

Other researchers have used the salinity contrast between freshwater and seawater to produce electricity, but those processes typically require ions to move through a membrane to generate current. Cui said those membranes tend to be fragile, which is a drawback. Those methods also typically make use of only one type of ion, while his battery uses both the sodium and chlorine ions to generate power.

Cui's team had the potential environmental impact of their battery in mind when they designed it. They chose manganese dioxide for the positive electrode in part because it is environmentally benign.

The group knows that river mouths and estuaries, while logical sites for their power plants, are environmentally sensitive areas.

"You would want to pick a site some distance away, miles away, from any critical habitat," Cui said. "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," he said.

The process itself should have little environmental impact. The discharge water would be a mixture of fresh and seawater, released into an area where the two waters are already mixing, at the natural temperature.

One of Cui's concerns is finding a good material for the negative electrode. He used silver for the experiments, but silver is too expensive to be practical.

His group did an estimate for various regions and countries and determined that South America, with the Amazon River draining a large part of the continent, has the most potential. Africa also has an abundance of rivers, as do Canada, the United States and India.

But river water doesn't necessarily have to be the source of the freshwater, Cui said.

"The water for this method does not have to be extremely clean," he said. Storm runoff and gray water could potentially be useable.

A power plant operating with 50 cubic meters of freshwater per second could produce up to 100 megawatts of power, according to the team's calculations. That would be enough to provide electricity for about 100,000 households.

Cui said it is possible that even treated sewage water might work.

"I think we need to study using sewage water," he said. "If we can use sewage water, this will sell really well."

Funding for this research came from King Abdullah University of Science and Technology (KAUST) and the U.S. Department of Energy.

####

For more information, please click here

Contacts:
Yi Cui
Associate Professor
Materials Science and Engineering
McCullough rm. 343
476 Lomita Mall
Stanford, CA 94305
Mail Code: 4045
Phone: 650.723.4613
Fax: 650.736.1984

Copyright © Stanford University

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

New class of protein misfolding simulated in high definition: Evidence for recently identified and long-lasting type of protein misfolding bolstered by atomic-scale simulations and new experiments August 8th, 2025

Sensors innovations for smart lithium-based batteries: advancements, opportunities, and potential challenges August 8th, 2025

Deciphering local microstrain-induced optimization of asymmetric Fe single atomic sites for efficient oxygen reduction August 8th, 2025

Lab to industry: InSe wafer-scale breakthrough for future electronics August 8th, 2025

Govt.-Legislation/Regulation/Funding/Policy

New imaging approach transforms study of bacterial biofilms August 8th, 2025

INRS and ELI deepen strategic partnership to train the next generation in laser science:PhD students will benefit from international mobility and privileged access to cutting-edge infrastructure June 6th, 2025

Electrifying results shed light on graphene foam as a potential material for lab grown cartilage June 6th, 2025

Institute for Nanoscience hosts annual proposal planning meeting May 16th, 2025

Discoveries

Deciphering local microstrain-induced optimization of asymmetric Fe single atomic sites for efficient oxygen reduction August 8th, 2025

ICFO researchers overcome long-standing bottleneck in single photon detection with twisted 2D materials August 8th, 2025

New molecular technology targets tumors and simultaneously silences two ‘undruggable’ cancer genes August 8th, 2025

Simple algorithm paired with standard imaging tool could predict failure in lithium metal batteries August 8th, 2025

Announcements

Sensors innovations for smart lithium-based batteries: advancements, opportunities, and potential challenges August 8th, 2025

Deciphering local microstrain-induced optimization of asymmetric Fe single atomic sites for efficient oxygen reduction August 8th, 2025

Japan launches fully domestically produced quantum computer: Expo visitors to experience quantum computing firsthand August 8th, 2025

ICFO researchers overcome long-standing bottleneck in single photon detection with twisted 2D materials August 8th, 2025

Energy

Sensors innovations for smart lithium-based batteries: advancements, opportunities, and potential challenges August 8th, 2025

Simple algorithm paired with standard imaging tool could predict failure in lithium metal batteries August 8th, 2025

Portable Raman analyzer detects hydrogen leaks from a distance: Device senses tiny concentration changes of hydrogen in ambient air, offering a dependable way to detect and locate leaks in pipelines and industrial systems April 25th, 2025

KAIST researchers introduce new and improved, next-generation perovskite solar cell​ November 8th, 2024

Battery Technology/Capacitors/Generators/Piezoelectrics/Thermoelectrics/Energy storage

Sensors innovations for smart lithium-based batteries: advancements, opportunities, and potential challenges August 8th, 2025

Deciphering local microstrain-induced optimization of asymmetric Fe single atomic sites for efficient oxygen reduction August 8th, 2025

Simple algorithm paired with standard imaging tool could predict failure in lithium metal batteries August 8th, 2025

Enhancing power factor of p- and n-type single-walled carbon nanotubes April 25th, 2025

NanoNews-Digest
The latest news from around the world, FREE




  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project