Satellite Banner
Technology
Networks
Scientific Communities
 
Become a Member | Sign in
Home>News>This Article
  News
Return

The Power of Salt

Published: Wednesday, August 20, 2014
Last Updated: Wednesday, August 20, 2014
Bookmark and Share
MIT study investigates power generation from the meeting of river water and seawater.

Where the river meets the sea, there is the potential to harness a significant amount of renewable energy, according to a team of mechanical engineers at MIT.

The researchers evaluated an emerging method of power generation called pressure retarded osmosis (PRO), in which two streams of different salinity are mixed to produce energy. In principle, a PRO system would take in river water and seawater on either side of a semi-permeable membrane. Through osmosis, water from the less-salty stream would cross the membrane to a pre-pressurized saltier side, creating a flow that can be sent through a turbine to recover power.

The MIT team has now developed a model to evaluate the performance and optimal dimensions of large PRO systems. In general, the researchers found that the larger a system’s membrane, the more power can be produced — but only up to a point. Interestingly, 95 percent of a system’s maximum power output can be generated using only half or less of the maximum membrane area.

Leonardo Banchik, a graduate student in MIT’s Department of Mechanical Engineering, says reducing the size of the membrane needed to generate power would, in turn, lower much of the upfront cost of building a PRO plant.

“People have been trying to figure out whether these systems would be viable at the intersection between the river and the sea,” Banchik says. “You can save money if you identify the membrane area beyond which there are rapidly diminishing returns.”

Banchik and his colleagues were also able to estimate the maximum amount of power produced, given the salt concentrations of two streams: The greater the ratio of salinities, the more power can be generated. For example, they found that a mix of brine, a byproduct of desalination, and treated wastewater can produce twice as much power as a combination of seawater and river water.

Based on his calculations, Banchik says that a PRO system could potentially power a coastal wastewater-treatment plant by taking in seawater and combining it with treated wastewater to produce renewable energy.

“Here in Boston Harbor, at the Deer Island Waste Water Treatment Plant, where wastewater meets the sea … PRO could theoretically supply all of the power required for treatment,” Banchik says.

He and John Lienhard, the Abdul Latif Jameel Professor of Water and Food at MIT, along with Mostafa Sharqawy of King Fahd University of Petroleum and Minerals in Saudi Arabia, report their results in the Journal of Membrane Science.

Finding equilibrium in nature

The team based its model on a simplified PRO system in which a large semi-permeable membrane divides a long rectangular tank. One side of the tank takes in pressurized salty seawater, while the other side takes in river water or wastewater. Through osmosis, the membrane lets through water, but not salt. As a result, freshwater is drawn through the membrane to balance the saltier side.

“Nature wants to find an equilibrium between these two streams,” Banchik explains.
As the freshwater enters the saltier side, it becomes pressurized while increasing the flow rate of the stream on the salty side of the membrane. This pressurized mixture exits the tank, and a turbine recovers energy from this flow.  

Banchik says that while others have modeled the power potential of PRO systems, these models are mostly valid for laboratory-scale systems that incorporate “coupon-sized” membranes. Such models assume that the salinity and flow of incoming streams is constant along a membrane. Given such stable conditions, these models predict a linear relationship: the bigger the membrane, the more power generated.

But in flowing through a system as large as a power plant, Banchik says, the streams’ salinity and flux will naturally change. To account for this variability, he and his colleagues developed a model based on an analogy with heat exchangers.

“Just as the radiator in your car exchanges heat between the air and a coolant, this system exchanges mass, or water, across a membrane,” Banchik says. “There’s a method in literature used for sizing heat exchangers, and we borrowed from that idea.”

The researchers came up with a model with which they could analyze a wide range of values for membrane size, permeability, and flow rate. With this model, they observed a nonlinear relationship between power and membrane size for large systems. Instead, as the area of a membrane increases, the power generated increases to a point, after which it gradually levels off. While a system may be able to produce the maximum amount of power at a certain membrane size, it could also produce 95 percent of the power with a membrane half as large.

Still, if PRO systems were to supply power to Boston’s Deer Island treatment plant, the size of a plant’s membrane would be substantial — at least 2.5 million square meters, which Banchik notes is the membrane area of the largest operating reverse osmosis plant in the world.

“Even though this seems like a lot, clever people are figuring out how to pack a lot of membrane into a small volume,” Banchik says. “For example, some configurations are spiral-wound, with flat sheets rolled up like paper towels around a central tube. It’s still an active area of research to figure out what the modules would look like.”

“Say we’re in a place that could really use desalinated water, like California, which is going through a terrible drought,” Banchik adds. “They’re building a desalination plant that would sit right at the sea, which would take in seawater and give Californians water to drink. It would also produce a saltier brine, which you could mix with wastewater to produce power. More research needs to be done to see whether it can be economically viable, but the science is sound.”

This work was funded by the King Fahd University of Petroleum and Minerals through the Center for Clean Water and Clean Energy and by the National Science Foundation.




Further Information

Join For Free

Access to this exclusive content is for Technology Networks Premium members only.

Join Technology Networks Premium for free access to:

  • Exclusive articles
  • Presentations from international conferences
  • Over 4,000+ scientific posters on ePosters
  • More Than 5,300+ scientific videos on LabTube
  • 35 community eNewsletters


Sign In



Forgotten your details? Click Here
If you are not a member you can join here

*Please note: By logging into TechnologyNetworks.com you agree to accept the use of cookies. To find out more about the cookies we use and how to delete them, see our privacy policy.

Related Content

Radiation-Free Imaging in the Brain
Scientists create sensors that use proteins to detect particular targets through induced blood flow changes.
Monday, December 05, 2016
New Method for Analyzing Crystal Structure
Exotic materials called photonic crystals reveal their internal characteristics with new method.
Monday, November 28, 2016
Biomarker Guiding Cancer Therapy
Biologists link levels of Mena protein to breast cancer cells’ sensitivity to chemotherapy.
Tuesday, November 22, 2016
Capsule Achieves Long-Term Drug Delivery
Novel drug delivery method could aid in elimination of malaria and treatment of many other diseases.
Monday, November 21, 2016
Synthetic Cells Isolate Genetic Circuits
Encapsulating molecular components in artificial membranes offers more flexibility in designing circuits.
Tuesday, November 15, 2016
Turning Greenhouse Gas into Gasoline
New catalyst provides design principles for producing fuels from carbon dioxide emissions.
Tuesday, November 15, 2016
New Approach Against Salmonella
Researchers have developed a strategy to immunize against microbes that invade the gastrointestinal tract, including Salmonella.
Tuesday, November 08, 2016
Laser Particles Could Provide Sharper Tissue Images
New imaging technique stimulates particles to emit laser light, could create higher-resolution images.
Tuesday, November 08, 2016
Engineers Design New Weapon Against Bacteria
Researchers have successfully engineered antimicrobial peptides that can kill bacterial strains resistant to existing antibiotics.
Thursday, November 03, 2016
Predicting Cancer Cells’ Response to Chemotherapy
Researcher develop method for testing cell ability to perform different types of DNA repair, which can reveal tumors’ sensitivity to drugs.
Wednesday, November 02, 2016
Nanobionic Spinach Detects Dangerous Chemicals
Scientists have changed spinach plants into biosensors that can detect harful chemicals and wirelessly relay the information.
Tuesday, November 01, 2016
Fighting Cancer with the Power of Immunity
Researchers at MIT have used a combination of four different therapies to activate both of the immune system’s two branches, producing a coordinated attack that led to the complete disappearance of large, aggressive tumors in mice.
Friday, October 28, 2016
Fighting Cancer with Immune Response
New treatment elicits two-pronged immune response that destroys tumors in mice.
Tuesday, October 25, 2016
MRIs for Fetal Health
Algorithm could help analyze fetal scans to determine whether interventions are warranted.
Monday, October 24, 2016
Mapping Serotonin in the Living Brain
Imaging technique that creates a 3D video of serotonin transport could aid antidepressant development.
Monday, October 24, 2016
Scientific News
Big Genetics in BC: The American Society for Human Genetics 2016 Meeting
Themes at this year's meeting ranged from the verification, validation, and sharing of data, to the translation of laboratory findings into actionable clinical results.
Stem Cells in Drug Discovery
Potential Source of Unlimited Human Test Cells, but Roadblocks Remain.
Cancer Genetics: Key to Diagnosis, Therapy
When applied judiciously, cancer genetics directs caregivers to the right drug at the right time, while sparing patients of unnecessary or harmful treatments.
Transporting Microscopic Cargo Between Human Cells
Scientists have developed a virus-inspired delivery system for material transport between cells.
Tissue Damage Is Key for Cell Reprogramming
Researchers have shown tissue damage is important for cells to return to an embryonic state for cell reprogramming.
Metabolite Promotes Cancer Cell Transformation
Researchers have identified a metabolite that promotes cancer cell transformation and colorectal cancer spread.
Improving Drug Production with Computer Model
A model has been developed that can be used to improve and accelerate the production of biotherapeutics, cancer drugs, and vaccines.
Bird Flu Confirmed in the Netherlands
An outbreak of H5 avian influenza was confirmed in the Flevoland province of the Netherlands.
Pasteurised Bacterium Reduces Obesity and Diabetes
Researchers have discovered that an intestinal bacterium provides a lasting effect on the intestinal barrier.
Turning Off Asthma Attacks
Researchers discover a critical cellular “off” switch for the inflammatory immune response that causes asthma attacks.
Scroll Up
Scroll Down

SELECTBIO Market Reports
Go to LabTube
Go to eposters
 
Access to the latest scientific news
Exclusive articles
Upload and share your posters on ePosters
Latest presentations and webinars
View a library of 1,800+ scientific and medical posters
4,000+ scientific and medical posters
A library of 2,500+ scientific videos on LabTube
5,300+ scientific videos
Close
Premium CrownJOIN TECHNOLOGY NETWORKS PREMIUM FOR FREE!