Desalination - Social Anxiety Forum
 
Thread Tools
post #1 of 5 (permalink) Old 01-06-2020, 09:35 AM Thread Starter
Yoink
 
sabbath9's Avatar
 
Join Date: Dec 2014
Posts: 2,662
Lightbulb

Desalination


There must be a cheap way to desalinate sea water enough to use for fire fighting.



Wildfires in California, Australia and other places could be extinguished from ample supply of water in the Pacific Ocean.


Use solar panels to power the process.


Store water wherever humans or animals might need it.


The stored water could be used regularly to combat droughts.


If the oceans are going to rise then we can use the excess water to water our lawns, forests, agriculture, etc.


Spraying the desalinated water in the air could even cool down the area.


https://www.atlasobscura.com/article...lination-plant


Quote:
Fish Flock to the Super-Salty Wastewater of the Sydney Desalination Plant

Sydney’s technological solution for drought is having unexpected effects on marine life.

by Sabrina Imbler January 2, 2020



In 2019, Australia ushered in the new year by shooting off fireworks and restarting the Sydney Desalination Plant. The plant began sucking in seawater, purifying it through a process called reverse osmosis, and producing a flood of clean drinking water for residents of the drought-stricken city. What was left—a blend of wastewater with twice the salinity of the sea—was pumped back into the ocean.


Brendan Kelaher, a marine biologist at Southern Cross University, suspected this extra-salty discharge might drive away fish populating the area. But, surprisingly, many fish flocked to it, creating a mini metropolis in a reef just outside of Sydney, according to a study Kelaher published December 18 in Environmental Science & Technology.


2019 was Australia’s hottest, driest year on record, and New South Wales, whose state capital is Sydney, has faced a crippling drought since 2017, according to The New York Times. In 2010, the city built its desalination plant, one of the largest in the world and capable of meeting a sixth of Sydney’s annual freshwater needs. The plant turns on whenever water levels in the city’s dams sink below 60 percent, indicating a need for an extra source of freshwater, according to the Australian Broadcasting Corporation. Today the plant provides approximately 66 million gallons of drinking water a day, according to the study.

And I always thought this would be
the land of milk and honey
Oh but I came to find out that it's
all hate and money
And there's a canopy of greed holding me down.
sabbath9 is offline  
Sponsored Links
Advertisement
 
post #2 of 5 (permalink) Old 02-12-2020, 09:05 AM Thread Starter
Yoink
 
sabbath9's Avatar
 
Join Date: Dec 2014
Posts: 2,662
http://news.mit.edu/2020/passive-sol...alination-0207



Simple, solar-powered water desalination

System achieves new level of efficiency in harnessing sunlight to make fresh potable water from seawater.


David L. Chandler | MIT News Office
February 6, 2020




Quote:
A completely passive solar-powered desalination system developed by researchers at MIT and in China could provide more than 1.5 gallons of fresh drinking water per hour for every square meter of solar collecting area. Such systems could potentially serve off-grid arid coastal areas to provide an efficient, low-cost water source.


The system uses multiple layers of flat solar evaporators and condensers, lined up in a vertical array and topped with transparent aerogel insulation. It is described in a paper appearing today in the journal Energy and Environmental Science, authored by MIT doctoral students Lenan Zhang and Lin Zhao, postdoc Zhenyuan Xu, professor of mechanical engineering and department head Evelyn Wang, and eight others at MIT and at Shanghai Jiao Tong University in China.


The key to the system’s efficiency lies in the way it uses each of the multiple stages to desalinate the water. At each stage, heat released by the previous stage is harnessed instead of wasted. In this way, the team’s demonstration device can achieve an overall efficiency of 385 percent in converting the energy of sunlight into the energy of water evaporation.


The device is essentially a multilayer solar still, with a set of evaporating and condensing components like those used to distill liquor. It uses flat panels to absorb heat and then transfer that heat to a layer of water so that it begins to evaporate. The vapor then condenses on the next panel. That water gets collected, while the heat from the vapor condensation gets passed to the next layer.


Whenever vapor condenses on a surface, it releases heat; in typical condenser systems, that heat is simply lost to the environment. But in this multilayer evaporator the released heat flows to the next evaporating layer, recycling the solar heat and boosting the overall efficiency.


“When you condense water, you release energy as heat,” Wang says. “If you have more than one stage, you can take advantage of that heat.”


Adding more layers increases the conversion efficiency for producing potable water, but each layer also adds cost and bulk to the system. The team settled on a 10-stage system for their proof-of-concept device, which was tested on an MIT building rooftop. The system 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 two times as much as the record amount previously produced by any such passive solar-powered desalination system, Wang says.


Theoretically, with more desalination stages and further optimization, such systems could reach overall efficiency levels as high as 700 or 800 percent, Zhang says.


Unlike some desalination systems, there is no accumulation of salt or concentrated brines to be disposed of. In a free-floating configuration, any salt that accumulates during the day would simply be carried back out at night through the wicking material and back into the seawater, according to the researchers.


Their demonstration unit was built mostly from inexpensive, readily available materials such as a commercial black solar absorber and paper towels for a capillary wick to carry the water into contact with the solar absorber. In most other attempts to make passive solar desalination systems, the solar absorber material and the wicking material have been a single component, which requires specialized and expensive materials, Wang says. “We’ve been able to decouple these two.”


The most expensive component of the prototype is a 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 as an alternative. (The aerogel itself is made from dirt-cheap silica but requires specialized drying equipment for its manufacture.)


Wang emphasizes that the team’s key contribution is a framework for understanding how to optimize such multistage passive systems, which they call thermally localized multistage desalination. The formulas they developed could likely be applied to a variety of materials and device architectures, allowing for further optimization of systems based on different scales of operation or local conditions and materials.


One possible configuration would be floating panels on a body of saltwater such as an impoundment pond. These could constantly and passively deliver fresh water through pipes to the shore, as long as the sun shines each day. Other systems could be designed to serve a single household, perhaps using a flat panel on a large shallow tank of seawater that is pumped or carried in. The team estimates that a system with a roughly 1-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.


The researchers plan further experiments to continue to optimize the choice of materials and configurations, and to test the durability of the system under realistic conditions. They also will work on translating the design of their lab-scale device into a something that would be suitable for use by consumers. The hope is that it could ultimately play a role in alleviating water scarcity in parts of the developing world where reliable electricity is scarce but seawater and sunlight are abundant.


“This new approach is very significant,” says Ravi Prasher, an associate lab director at
Lawrence Berkeley National Laboratory and adjunct professor of mechanical engineering at the University of California at Berkeley, who was not involved in this work. “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 vapor efficiency is dramatically improved. … This increased efficiency will have an overall impact on reducing the cost of produced water.”


The research team included Bangjun Li, Chenxi Wang and Ruzhu Wang at the Shanghai Jiao Tong University, and Bikram Bhatia, Kyle Wilke, Youngsup Song, Omar Labban, and John Lienhard, who is the Abdul Latif Jameel Professor of Water at MIT. The research was supported by the National Natural Science Foundation of China, the Singapore-MIT Alliance for Research and Technology, and the MIT Tata Center for Technology and Design.



And I always thought this would be
the land of milk and honey
Oh but I came to find out that it's
all hate and money
And there's a canopy of greed holding me down.
sabbath9 is offline  
post #3 of 5 (permalink) Old 02-12-2020, 03:08 PM
The Wanderer
 
Musicfan's Avatar
 
Join Date: Mar 2017
Gender: Male
Posts: 1,430
They could dig deep and use the earth's heat for distilling sea water. The distillation steam could also power turbines for electricity.

[Everyone disliked that.]
Musicfan is offline  
 
post #4 of 5 (permalink) Old 02-13-2020, 06:28 AM Thread Starter
Yoink
 
sabbath9's Avatar
 
Join Date: Dec 2014
Posts: 2,662
Quote:
Originally Posted by Musicfan View Post
They could dig deep and use the earth's heat for distilling sea water. The distillation steam could also power turbines for electricity.

Good Idea! The Pacific Ocean is surrounded by The Ring of Fire, volcanoes and geologic fault lines that bring magma and lava close to the surface. Hawaii, Iceland, Italy also have plenty of geothermal energy available.



And I always thought this would be
the land of milk and honey
Oh but I came to find out that it's
all hate and money
And there's a canopy of greed holding me down.
sabbath9 is offline  
post #5 of 5 (permalink) Old 02-13-2020, 01:20 PM
🧱
 
Paul's Avatar
 
Join Date: Sep 2005
Location: California Republic
Language: None
Age: 39
Posts: 6,284
Nonexistence of water is not a big issue for 99% of fire fighting. It's having sufficient water pressure in the exact location where the fire develops that's nearly impossible. Forests are big, you can't put hydrants in them. Other fire suppressants dropped from planes tend to work better than dropping water from a plane, though some of both is best.

Most of California's fires happen nowhere near the coast, and in areas with plenty of fresh water (because deserts can't grow fire fuel). You can see the fire scars going right up to the edges of the lakes. Sometimes a plane will take water from the lake to use to fight the fire, but that's just one tactic, and it's not essential: https://en.wikipedia.org/wiki/Aerial_firefighting

And it's not that desalinization is all that expensive for what it does -- it's that it's impossible to compete with the price of just using fresh water that's already sitting there waiting. And the unfathomable amounts of water we want to use for things.

SA Game | Sacramento SA Meetup

"Many people need desperately to receive this message: 'I feel and think much as you do, care about many of the things you care about, although most people do not care about them. You are not alone.'" ― Kurt Vonnegut
Paul is offline  
Reply

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 
For the best viewing experience please update your browser to Google Chrome