
By Paul Brown
An international team of scientists has developed a cheap way to provide fresh water to thirsty communities by making seawater drinkable without using electricity.
So long as the sun is shining, they say, their device will produce enough high-quality potable water to cover a family's needs, at a cost of around $100.
The scientists, from Massachusetts institute of Technology (MIT), U.S. and Shanghai Jiao Tong University, China, believe their brainwave offers a simple solution to thirsty islands and arid coastal areas which lack a reliable electricity supply but have access to seawater. It could even help to prevent some of the mass migrations expected with climate change.
The researchers report their work in the journal Energy and Environmental Science. Testing their prototype on a roof at the Massachusetts Institute of Technology, they produced more than 1.5 gallons of fresh drinking water every hour for every square meter of solar collecting area.
Their device is cube-shaped, with multiple layers of solar evaporators and condensers piled one on top of another, surmounted with a layer of transparent insulation. Essentially it is a multi-layer solar still, similar to those used for centuries to make strong liquor and used today in many applications.
Diagram illustrates the basic structure of the proposed desalination system. Sunlight passes through a transparent insulating layer at left, to heat up a black heat-absorbing material, which transfers the heat to a layer of wicking material (shown in blue), where it evaporates and then condenses on a surface (gray) and then drips off to be collected as fresh, potable water. Images courtesy of the researchers
A solar still uses flat panels to absorb heat which it then transfers to a layer of water, which begins to evaporate. The vapor condenses on the next panel and the water is collected, while the heat from the vapor condensation is passed to the layer above.
Whenever vapor condenses on a surface, it releases heat; in typical condenser systems, that heat is simply lost to the environment. But in this multi-layer version the released heat flows to the next evaporating layer, recycling the solar heat and boosting overall efficiency.
The efficiency comes from using each of the multiple stages to remove salt from the sea water, with the heat released by the previous stage harnessed instead of wasted. In this way, the team's demonstration device achieved an overall efficiency of 385 percent in converting the energy of sunlight into evaporation.
Evelyn Wang, a co-author, said: "When you condense water, you release energy as heat. If you have more than one stage, you can take advantage of that heat."
Cost Trade-Off
Although adding more layers increases the conversion efficiency of the system, each layer also adds cost and bulk. The team settled on a 10-stage system for their proof-of-concept device.
It delivered pure water that exceeded city drinking water standards, at a rate of 5.78 liters per square meter (about 1.52 gallons per 11 square feet) of solar collecting area. This is more than twice as much as the record amount previously produced by any such passive solar-powered desalination system, Professor Wang says.
And a big advantage of the system is that it has a self-flushing mechanism which will clean out the accumulation of salt each night and return it to the sea.
One possible way of using the system would be with floating panels on a body of saltwater. The panels could deliver constant fresh water through pipes to the shore so long as the sun was shining. Other systems could be designed to serve a single household, perhaps using a flat panel on a large shallow tank of seawater.
The team estimates that a system with a roughly one-square-meter solar collecting area could meet the daily drinking water needs of one person. In production, they think a system built to serve the needs of a family might be built for around $100.
Cheaper Replacements
The most expensive component of the prototype is the layer of transparent aerogel used as an insulator at the top of the stack, but the team suggests other less expensive insulators could be used instead. (The aerogel itself is made from very cheap silica but requires specialized drying equipment during its manufacture.)
"This new approach is very significant," says Professor Ravi Prasher of Lawrence Berkeley National Laboratory and the University of California at Berkeley, who was not involved in the research.
"One of the challenges in solar still-based desalination has been low efficiency due to the loss of significant energy in condensation.
"By efficiently harvesting the condensation energy, the overall solar to vapour efficiency is dramatically improved … This increased efficiency will have an overall impact on reducing the cost of produced water."
Reposted with permission from Climate News Network.
- Irish Teenager Wins Google Science Award for Removing ... ›
- Giant Floating Solar Farms Could Make Fuel and Help Solve the ... ›
- Solar-Powered Device Can Pull Water Out of Thin Air, Even in Deserts ›
By Kenny Stancil
Amid the ongoing climate emergency and the devastating coronavirus pandemic that has resulted in more than 500,000 deaths in the U.S. alone as well as an economic meltdown that has left millions of people unemployed, the Sunrise Movement on Thursday launched its "Good Jobs for All" campaign to demand that lawmakers pursue a robust recovery that guarantees a good job to anyone who wants one and puts the country on a path toward a Green New Deal.
<div id="c7fe3" class="rm-shortcode" data-rm-shortcode-id="5664692fdfd187db01eff5ac2787c564"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1367650177436311562" data-partner="rebelmouse"><div style="margin:1em 0">We’re coming together to fight for each other and guarantee #GoodJobsForAll Join us: https://t.co/MoJhmlzoaS https://t.co/IAPa8DeeLR</div> — Sunrise Movement 🌅 (@Sunrise Movement 🌅)<a href="https://twitter.com/sunrisemvmt/statuses/1367650177436311562">1614908186.0</a></blockquote></div>
- Climate Leader Alexandria Ocasio-Cortez Joins Hundreds of ... ›
- Sunrise Movement Rallies at Texas Capitol for Green New Deal ... ›
- 1,000+ Youth Activists Storm Capitol to Demand Green New Deal ... ›
EcoWatch Daily Newsletter
bpperry / Getty Images
By Tara Lohan
Each year the amount of plastic swirling in ocean gyres and surfing the tide toward coastal beaches seems to increase. So too does the amount of plastic particles being consumed by fish — including species that help feed billions of people around the world.
Blue shark at Cape Point, South Africa, 2016. Steve Woods / CC BY-NC-ND 2.0
Trending
Butterflies across the U.S. West are disappearing, and now researchers say the climate crisis is largely to blame.
- New Clues Help Monarch Butterfly Conservation Efforts - EcoWatch ›
- Monarch Butterflies Will Be Protected Under Historic Deal - EcoWatch ›
California faces another "critically dry year" according to state officials, and a destructive wildfire season looms on its horizon. But in a state that welcomes innovation, water efficacy approaches and drought management could replenish California, increasingly threatened by the climate's new extremes.
- Remarkable Drop in Colorado River Water Use Sign of Climate ... ›
- California Faces a Future of Extreme Weather - EcoWatch ›
Wisdom the mōlī, or Laysan albatross, is the oldest wild bird known to science at the age of at least 70. She is also, as of February 1, a new mother.