Tuesday, June 20, 2017

New Modular Off-Grid Desalination Uses Only Solar Energy

A federally funded research effort to revolutionize water treatment has yielded an off-grid technology that uses energy from sunlight alone to turn salt water into fresh drinking water. 

The desalination system, which uses a combination of membrane distillation technology and light-harvesting nanophotonics, is the first major innovation from the Center for Nanotechnology Enabled Water Treatment (NEWT), a multi-institutional engineering research center based at Rice University.

NEWT's "nanophotonics-enabled solar membrane distillation" technology, or NESMD, combines tried-and-true water treatment methods with cutting-edge nanotechnology that converts sunlight to heat. The technology is described online this week in the Proceedings of the National Academy of Sciences.

In conventional membrane distillation (top), hot saltwater is flowed across one side of a porous membrane and cold freshwater is flowed across the other. Water vapor is naturally drawn through the membrane from the hot to the cold side. In NEWT's "nanotechnology-enabled solar membrane distillation," or NESMD (bottom), a porous layer of sunlight-activated carbon black nanoparticles acts as the heating element for the process.
Credit: P. Dongare/Rice University

More than 18,000 desalination plants operate in 150 countries, but NEWT's desalination technology is unlike any other used today.

"Direct solar desalination could be a game changer for some of the estimated 1 billion people who lack access to clean drinking water," said Rice scientist and water treatment expert Qilin Li, a corresponding author on the study. "This off-grid technology is capable of providing sufficient clean water for family use in a compact footprint, and it can be scaled up to provide water for larger communities."



The oldest method for making freshwater from salt water is distillation. Salt water is boiled, and the steam is captured and run through a condensing coil. Distillation has been used for centuries, but it requires complex infrastructure and is energy inefficient due to the amount of heat required to boil water and produce steam. More than half the cost of operating a water distillation plant is for energy.

An emerging technology for desalination is membrane distillation, where hot salt water is flowed across one side of a porous membrane and cold freshwater is flowed across the other. Water vapor is naturally drawn through the membrane from the hot to the cold side, and because the seawater need not be boiled, the energy requirements are less than they would be for traditional distillation. However, the energy costs are still significant because heat is continuously lost from the hot side of the membrane to the cold.

"Unlike traditional membrane distillation, NESMD benefits from increasing efficiency with scale," said Rice's Naomi Halas, a corresponding author on the paper and the leader of NEWT's nanophotonics research efforts. "It requires minimal pumping energy for optimal distillate conversion, and there are a number of ways we can further optimize the technology to make it more productive and efficient."

NEWT's new technology builds upon research in Halas' lab to create engineered nanoparticles that harvest as much as 80 percent of sunlight to generate steam. By adding low-cost, commercially available nanoparticles to a porous membrane, NEWT has essentially turned the membrane itself into a one-sided heating element that alone heats the water to drive membrane distillation.

"The integration of photothermal heating capabilities within a water purification membrane for direct, solar-driven desalination opens new opportunities in water purification," said Yale University 's Menachem "Meny" Elimelech, a co-author of the new study and NEWT's lead researcher for membrane processes.

In the PNAS study, researchers offered proof-of-concept results based on tests with an NESMD chamber about the size of three postage stamps and just a few millimeters thick. The distillation membrane in the chamber contained a specially designed top layer of carbon black nanoparticles infused into a porous polymer. The light-capturing nanoparticles heated the entire surface of the membrane when exposed to sunlight. A thin half-millimeter-thick layer of salt water flowed atop the carbon-black layer, and a cool freshwater stream flowed below.

This scaled-up test bed of NEWT's direct solar desalination technology uses carbon black nanoparticles that convert as much as 80 percent of sunlight energy into heat. Results from an earlier prototype showed the technology could produce as much as six liters of freshwater per hour per square meter of solar membrane.

Credit: Jeff Fitlow/Rice University
Li, the leader of NEWT's advanced treatment test beds at Rice, said the water production rate increased greatly by concentrating the sunlight. "The intensity got up 17.5 kilowatts per meter squared when a lens was used to concentrate sunlight by 25 times, and the water production increased to about 6 liters per meter squared per hour."

Li said NEWT's research team has already made a much larger system that contains a panel that is about 70 centimeters by 25 centimeters. Ultimately, she said, NEWT hopes to produce a modular system where users could order as many panels as they needed based on their daily water demands.

"You could assemble these together, just as you would the panels in a solar farm," she said. "Depending on the water production rate you need, you could calculate how much membrane area you would need. For example, if you need 20 liters per hour, and the panels produce 6 liters per hour per square meter, you would order a little over 3 square meters of panels."

Established by the National Science Foundation in 2015, NEWT aims to develop compact, mobile, off-grid water-treatment systems that can provide clean water to millions of people who lack it and make U.S. energy production more sustainable and cost-effective. NEWT, which is expected to leverage more than $40 million in federal and industrial support over the next decade, is the first NSF Engineering Research Center (ERC) in Houston and only the third in Texas since NSF began the ERC program in 1985. NEWT focuses on applications for humanitarian emergency response, rural water systems and wastewater treatment and reuse at remote sites, including both onshore and offshore drilling platforms for oil and gas exploration.



Contacts and sources:
David Ruth
Rice University


Citation: Nanophotonics-enabled solar membrane distillation for off-grid water purification http://www.pnas.org/cgi/doi/10.1073/pnas.1701835114

3 comments:

  1. For those people who's relative are Alzheimer’s Disease sufferer and maybe reading this, I find it hard that people are still ignorant of herbal medicine when it comes to treating Alzheimer’s Disease.
    I have been through many phases over the last couple of years since my father's diagnosis, he was 53 years old and had Early Onset Alzheimer’s Disease and his diagnosis changed my life in many ways, I spend most of the time in denial and I keep thinking the tests were wrong. But deep down I knew they were correct. Though sharing his story is very difficult. He was always very successful in being able to accomplish anything he set his mind on doing. Alzheimer’s is a bitch of a disease. It began by robbing his recent memory, but it didn't stop there. It continues to steal, taking the most recent memories until it has pilfered all but the oldest memories, he experienced a decline in his ability to think, remember and make decisions. I feel a need to express my thoughts and feelings about how it affected his day to day living and how its deteriorated since despite the help of some wonderful medics and medicine.
    I remind myself how lucky to come across Charanjit rychtova's herbal medicine which is able to control this disease without any side effect, I felt a moment of relief hoping that he is free from this ailment, and nothing compares to the healing power of nature. Now I believe almost every health problem can be addressed in one natural way or another. The only thing I wanted was for him to feel better. I’m proud to say my Dad is Alzheimer’s free. You can also contact him for more info. at charantova@gmail.com

    ReplyDelete
  2. In my own case it was just over four years ago when my Mum began to sound different on the phone. She lived back East with my siblings and my husband and I were living on the West coast and in phone calls it became apparent that my Mum's voice no longer had the same tones of excitement and humor that she used to; and instead it was very flat. At the same time she began to tell us about a situation at work that just didn't seem possible; she was complaining that a group of fellow workers were conspiring to get her. Although Mum had much academic success as a teenager, her behavior had become increasingly odd during the past years. She quit seeing her friends and no longer seemed to care about her appearance or social pursuits. She began wearing the same clothes each day and seldom bathed. She lived with several family members but rarely spoke to any of us. Obviously this whole story seemed very unbelievable and we sensed something was wrong but had no clue as to what it could be. We recommended that my Mum quit her job and look for something else - as we began to wonder if she had a "mental breakdown" and would get better once out of the stressful job situation.
    In the case of Mum, she was having persecurtory delusions, auditory hallucinations and negative symptoms that had lasted for at least Three years. All of these symptoms fit with a diagnosis of Dementia. Her story reflects a common case, in which a high-functioning young adult goes through a major decline in day-to-day skills. Although family and friends may feel this is a loss of the person they knew, the illness can be treated and a good outcome is possible as it all got better when we started using a herbal medicine for her through Aparajita.
    My recommendation to people who are either wondering if they have Dementia or wondering if a friend or loved one has Dementia should contact aparajitatan@gmail.com. I think one of our key problems was that we didn't do this in the early days of my Mum's illness as we never thought of a natural alternative for her.

    ReplyDelete
  3. DOES HERBS WORK FOR DEMENTIA?

    This was the same question that prompted me to read further a testimony I saw on a blog. I would like to tell a story - hoping it will be useful to others - of my struggles and achievements with Dementia. I was diagnosed a little over 4 years ago, No doctors I met have any treatment or even suggestions apart western medications. I even sought advice on Youtube, to no avail. After using the conventional approach to medication treatment without improvement. I am glad something happens fast. There have been suicides due to people not being able to continue on living with the endless memory challenges. It is horrible. I learned about Dr. charanjit herbal medicine that works effectively for me without any negative effects. I have returned back to my normal life and I hope that the symptoms do not return again, It really helped me! If you have Dementia kindly contact Dr. Charanjit for help and necessary solution (charantova@gmail.com)

    ReplyDelete