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Floating Solar Device Boils Water Without Mirrors (arstechnica.com)
An anonymous reader quotes a report from Ars Technica: Researchers from MIT and the Masdar Institute of Science and Technology, led by George Ni, describe a prototype design that boils water under ambient sunlight. Central to their floating solar device is a "selective absorber" -- a material that both absorbs the solar portion of the electromagnetic spectrum well and emits little back as infrared heat energy. For this, the researchers turn to a blue-black commercial coating commonly used in solar photovoltaic panels. The rest of the puzzle involves further minimizing heat loss from that absorber, either through convection of the air above it or conduction of heat into the water below the floating prototype. The construction of the device is surprisingly simple. At the bottom, there is a thick, 10-centimeter-diameter puck of polystyrene foam. That insulates the heating action from the water and makes the whole thing float. A cotton wick occupies a hole drilled through the foam, which is splayed and pinned down by a square of thin fabric on the top side. This ensures that the collected solar heat is being focused into a minute volume of water. The selective absorber coats a disc of copper that sits on top of the fabric. Slots cut in the copper allow water vapor from the wick to pass through. And the crowning piece of this technological achievement? Bubble wrap. It insulates the top side of the absorber, with slots cut through the plastic to let the water vapor out. Tests in the lab and on the MIT roof showed that, under ambient sunlight, the absorber warmed up to 100 degrees Celsius in about five minutes and started making steam. That's a first. The study has been published in two separate Nature articles: "Steam by thermal concentration" and "Steam generation under one sun enabled by a floating structure with thermal concentration."
Can this be used in desalination plants? If so, it could provide fresh water - would make a big difference all around the world!
i would hate to be you too
"a material that both absorbs the solar portion of the electromagnetic spectrum well and emits little back as infrared heat energy"
The "solar portion of the electromagnetic spectrum" ? Is that trying to say "visible light" ?
And "...emits little back as infrared heat energy ..." ? (This part brought to you by the Department of Redundancy Department?)
Isn't the point of the device to emit more infrared?
Biggest problem would be contamination, wicks do not remove salt or sea contamination, they wick that too. So salt would be deposited on the paint layer stopping it working.
But suppose you have a clear hard layer ontop of the paint. Something that could be scraped clean easily. Then you could scrape the salt away.
Imagine a steam powered blade, turning around slowly (geared down), scraping off the salt and pushing it off the edge. I think even a small low tech mechanical approach could fix that problem.
A magnifying lens under sunlight can burn things, no mirrors required.
There has been enough technology to end world hunger and thirst for well over a century, but it is not being utilized to do so. It is not profitable and nobody who "matters" really cares about it.
Why is the number of suns relevant? I don't often visit places with two.
Confucius say, "Find worm in apple - bad. Find half a worm - worse."
There's a much easier way to get steam. Details are available here.
"To boil water using the Sun, we typically burn fossil fuels carrying several-hundred-million-year-old solar energy that was extracted from underground at great expense."
Who is "we"?
A reasonable first post, and four good responses in a row.
Solar hovercraft?
A desalinization tool like that could save a lot of lives.
Where can I get something like this to heat my pool water?
Rather hypocritical of you, seeing how you are spreading the gospel of darwinism you were indoctrinated into absent any understanding, and sprinkled with racism. His comment had nothing to do with souls or religion, his point was nobody gets to chose, and you wouldn't be barking that cr@p had you been born in the "wrong place", cuz you'd be jerky drying under the sun regardless of how "fit" you consider yourself to be.
using the sun to create steam that turns the generators
Sounds like something for the survival pack or go-bag to very quickly sterilize questionable water, that wouldn't run out.
And how much water is heated? 10 centimeters or ?
Sir, I'd like a thumbnail of tea please.
The things that make water not potable (chemicals, life forms, plain old suspended dirt) will no doubt kill this ivy-covered, idealized notion dead within a day.
Theoreticians never seem to work with, nor allow for, the real world of Friction and Filth (Oh! Great cover band name; I claim copyright).
So this thing produces 'steam'. Or more accurately it speeds up the evaporation of water above the base case of a pond sitting out in the sunlight. But how much more evaporation does it produce? And assuming we want to do something other than dry up puddles, what about the rest of the system? To utilize this steam for generation, you need to do a lot more than produce water vapor at 100 C.
I'd like to see some numbers that relate the energy captured per unit time to the insolation rate. The Arstechnica article didn't have any specifics and the Nature web site appears to be Slashdotted.
Have gnu, will travel.
Solar thermal collectors that can boil water have existed for decades. You don't need concentration for that, simply use a black absorber plate with pipes under a glass plate and put a vacuum between the absorber and the glass. Selective absorbers or glasses will improve the efficiency.
There are two problems with it: The generated steam will have a low temperature not much above boiling water. Most industrial applications need process steam of a much higher temperature (although there are some exceptions).
There are also problems with the two-phase flow of the steam-water mixture in the pipes, which is generally unstable and difficult to control. Technically it is much easier to concentrate sunlight, use an oil with a high boiling point as the carrier liquid and use it to generate the steam in a seperate unit.
I'm having some trouble understanding why using a commercial product, BluTec copper, in a manner in which it is intend to be used (heating water via unconcentrated sun) is news? When you build a colar water heater normally you are working to not have it boil the water. It's more efficient not to. In fact the article even says they get better efficiencies when they-- get this-- run it below 100c. Wow! alert the media and publish it in nature.
So what they did was create a thermally insullated restricted flow system so the water super heats which is completely expected and precisely what designers expect and thus try to avoid in commerical systems.
Blutec solar heated are made in massive quatitites.
So can some one explain why this is news? I'm being serious not sarcastic.
Some drink at the fountain of knowledge. Others just gargle.
Noted two years ago at another web site.
If you want CIA versions of this device go to Alex Jones's sites. He is CIA.
I'm having a hard time here deciding which of these I hate the most: niggers, wetbacks, towelheads, kikes, chinks, faggots, or Linux users. All of them are fucking awful and should be exterminated. My hate is strong and I'm damned proud of it. In fact, my hate is getting stronger as I talk to you people. There's nothing racist about my post, though. I'm definitely not racist, either. That word is a tool used by asshole Linux users to try to discredit anyone they disagree with. Linux users consider Microsoft to be racist. Damn, I hate Linux so much. We need to kill the kikes, send the niggers into the sun, and nuke the sand niggers over and over again. It's the only way to be safe from greed, nigger crime, and terrorism. And Hillary Clinton is the only person who can accomplish this. HILLARY 2016!
That's understandable. It's because of your low sense of self-worth. You are compelled to hate all but two others - your sister, your mother, the dog, and your father.
I'm having a hard time here deciding which of these I hate the most: niggers, wetbacks, towelheads, kikes, chinks, faggots, or Linux users. All of them are fucking awful and should be exterminated. My hate is strong and I'm damned proud of it. In fact, my hate is getting stronger as I talk to you people.
If you hate so many but can't decide who to hate most, the logical answer is to kill yourself. Problem solved.