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PostPosted: Fri Jul 17, 2020 2:08 pm 
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We-e-e-l-l-ll. I´m sure Elon Musk will try to make some zlotnys on it!

Aluminum plate, while not cheap right now is plentiful. The laser tech is pretty straight forward. . .your local Lasix shop has the computer assisted Green Laser. Good optically clear glass is available. The political will in a relatively not corrupt eco-system, maybe not so much.

Orange and Google are providing internet and long range telecommunications with high altitude balloons in the Sub-Sahara. This appears to be an economically viable path. People want telecommunications and will pay for it somehow.

Procuring drinking water is burdensome and the economics right now are crippling. I think this might be a path forward. I can´t say if it will go forward on a small scale, each-one-teach-one model, or large infra-structure Aswan Dam/Three Gorges Dam model.

Bob

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PostPosted: Fri Jul 17, 2020 2:12 pm 
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Amazing. The 2.5 questions that occur to me:

Are the details of the micro/nanostructure important? Laser etching is slow on an industrial scale. You're not going to make a few a few thousand pieces a meter on a side a day cheaply. Regular old anodizing of aluminum is columnar growth with a high surface area. If the details are important, might it be made lithographically, which is a massively parallel process?

The 1.5 questions is, is this self-cleaning/would it stand up to salt water? The aluminum/aluminum oxide surface isn't very attractive to water, so I can't imagine that in dirty or salty water, it's only water molecules in contact with the surface. Oh, geez, now I'm not going to be able to think about anything else for a few days.

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PostPosted: Fri Jul 17, 2020 2:14 pm 
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an seanduine wrote:
Procuring drinking water is burdensome and the economics right now are crippling. I think this might be a path forward. I can´t say if it will go forward on a small scale, each-one-teach-one model, or large infra-structure Aswan Dam/Three Gorges Dam model.

Bit of both, I'm thinking.

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PostPosted: Fri Jul 17, 2020 2:34 pm 
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@Chas. The nano structure is crucial. However, the energy to produce these nano-capillaries is produced in femto-seconds long bursts. Nowhere like cutting metal, more like creating the pits in a recording CD. The whiz-kids with the pocket protecters will solve this wrinkle. :D

The salts are apparently easily rinsed away. They address this in the cited abstract.

Bob

edit to add: The wicking action is incredibly fast. The images show water wicking up 12mm in micro-seconds. :o This spead really is an order of magnitude (or more) faster than chemical interactions at ambient temperature. The salts are simple evaporative depositions with no apparent bonding to the aluminum substrate. Since the capillaries are open grooves they don´t have the clogging problems demonstrated by closed capillaries.

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PostPosted: Fri Jul 17, 2020 3:33 pm 
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an seanduine wrote:
It is good to be critical, but. . .
<snip> In many parts of the Sub-Sahara it takes between 2 to 4 man hours per day to procure potable water for a family of 4. This is a tremendous drain on productivity. Maintenance of a system scaled to provide the same amount of water would take between 15 minutes to one half hour per day.
No critical, challenging. How are you going to 'sell' that to the folks who have the responsibility for water development? What are the numbers, is it sustainable withing the local economy?

One target for access to water supply I am aware of is 15 litres/person/day within 30 minutes of the home. That would be a woman making three one-hour return trips with a 20 litre plastic can. Assuming the initial outlay for a 60/l/ day still, maintenance tools, training etc comes from a micro-finance setup (gifts are not sustainable) what are the long term outgoings for the family and is there an opportunity to use the time saved doing something that generates the cash to pay? What are the costs of other options for water supply? Do other options allow reduced initial outlay by using local skilled and unskilled labour?

I think technical fixes need to be assessed very carefully. What do the development agents on the ground think?


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PostPosted: Fri Jul 17, 2020 9:18 pm 
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@david_h I´m not selling a particular product, merely pointing up what I feel is a quantum leap in the technology of Solar Distillation of potable water. Water sourcing in the Sub-Sahara is very much a ´boots on the ground´ proposition. Each community has its own challenges. In communities with adequate waterfall, Sand Dams are a centuries old technology that works. . .but because after their construction, community involvement falls off, and self-interested parties take over the maintenance, which leads to ´gate-keeping´ of the water resource. This isn´t a technological problem, but a social and political problem. Additionally, often the proliferation of Sand Dams leads to conflicts between up-stream and down-stream communities by lessening an already diminished resource. Again, not a technological problem, but a ´people´ problem. Same thing with rehabilitating old wells, the cost and preventing biological contamination make this problematic. Drilling new wells helps, but is also expensive (one source gives about $8,000 USD per new well) and since this contributes to generally lowering the water table, also leads to conflicts. . .more people problems.
What there is, however, is a lot of contaminated water. In addition, people are a source of both black and grey water. The economics of Solar Distillation are well established and possible. A large, single basin distillation plant was built in 1872 using wooden bays with blackened bottoms using logwood dye and alum. The total area of the plant was 4,700 square meters. On a typical summer day the plant produced 4.9 kg of distilled water per square meter of still surface, more than 23,000 liters of distilled water per day. The plant was successfully operated for forty years.
With modern stills, the efficiency of such a still is generally 60%. This technology seems to promise jumping this efficiency up to
95% or higher. This with little need to input feed stock energy, as is the case with membrane, osmotic plants. The added bonus is recycling contaminated water. I feel it could be a long while before competition for contaminated water sources will rear its ugly head.

Bob

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PostPosted: Sat Jul 18, 2020 2:00 am 
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Fascinating.

Thanks for the post and discussion.

I particularly like the bit where they calmly discuss the speed and rate at which 'water flows uphill'.

Any sufficiently advanced technology will be indistinguishable from magic. (Asimov, I think)

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PostPosted: Sat Jul 18, 2020 1:29 pm 
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@DrPhil. Yes, ´water flowing uphill´ is a fun effect of the micro-capillaries. :D

That´s the thing about ´disruptive´ and ´transformative´ technologies. At first sight they do appear to be magic.

Another fun effect is that just the process of making nano-capillaries creates a surface that is ´blacker than black´. :D

The wicking effect seems to me to mean that even in darkness, with the system ´idling´, you may still get significant evaporation at ambient temperatures.

Bob

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PostPosted: Sat Jul 18, 2020 2:09 pm 
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an seanduine wrote:
Another fun effect is that just the process of making nano-capillaries creates a surface that is ´blacker than black´.

That's something I've been itching to ask about: Is there a property specific to solid aluminum that is key in this phenomenon, or could ceramics also be used and achieve the same effect? And no plastics, thankyouverymuch - it's high time we started weaning ourselves.

chas wrote:
... would it stand up to salt water?

Not if it's got to be bare aluminum. Aluminum does corrode in contact with salt, and that's partly why I asked the question above; the other reason is that if the technology works the same way (capillarity, purification, blacker-than-black appearance) more or less regardless of substrate material, then we're really onto something.

But if it absolutely has to be aluminum, that's no reason to toss the baby out with the bathwater.

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PostPosted: Sat Jul 18, 2020 2:56 pm 
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The ´blacker than black´ effect, as a WAG, comes from the irregularity of the interior of the nano-capillary. So not the substrate.

The speed of the ´wicking´ is orders of magnitude, it seems to me, faster than the speed of ordinary chemical interaction times. Corrosion has to have time for covalent interaction. Those water molecules are going by very fast, and then seemingly projected out into the atmosphere so fast that they are careening out in clusters, not just single molecules. If I had a concern it would have to do with ´cavitation erosion´.´

All grist for the mill.

Bob

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PostPosted: Sat Jul 18, 2020 3:06 pm 
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an seanduine wrote:
Corrosion has to have time for covalent interaction. Those water molecules are going by very fast, and then seemingly projected out into the atmosphere so fast that they are careening out in clusters, not just single molecules.

My concern is with the salt left behind, sitting on the aluminum plate. Certainly that must over time take a toll.

an seanduine wrote:
If I had a concern it would have to do with ´cavitation erosion´.

Essentially a type of friction, right?

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PostPosted: Sat Jul 18, 2020 3:54 pm 
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Singh and others wrote:
Further investigations to realize large-scale SWSA sheets are essential for generating sufficient amounts of clean water for personal use and for commercial applications.
I think that's an important aspect tucked away near the end of the paper. I read it that they are thinking of commercial scale processing. Only the first two references are about water supply and the second concerns Los Angeles, which is a long way from sub-Saharan Africa.

It's hard to see how at the moment they could have any idea of cents per litre for a family sized still and how that would weigh against the other options in the world walking three hours for water. How long for a standalone still on a stall on a rural African market at a price that a small holder farmer could consider? Or a village/small town supply that the local economy could fund?


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PostPosted: Sat Jul 18, 2020 4:32 pm 
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david_h wrote:
Singh and others wrote:
Further investigations to realize large-scale SWSA sheets are essential for generating sufficient amounts of clean water for personal use and for commercial applications.
I think that's an important aspect tucked away near the end of the paper. I read it that they are thinking of commercial scale processing. Only the first two references are about water supply and the second concerns Los Angeles, which is a long way from sub-Saharan Africa.

It's hard to see how at the moment they could have any idea of cents per litre for a family sized still and how that would weigh against the other options in the world walking three hours for water. How long for a standalone still on a stall on a rural African market at a price that a small holder farmer could consider? Or a village/small town supply that the local economy could fund?

Here it seems we're losing sight of the difference between water quality and water availability. The technology an seanduine introduces us to doesn't actually produce water; it purifies what is already on hand. This is a vitally important development for those whose water supplies are contaminated, but I repeat my assertion that long-term ingestion of totally pure water is not a good idea either, so to ameliorate that, some measure will be needed to re-introduce the right balance of beneficial, or at least safe, minerals to drinking water. Still, an extra step is better than sticking with poisoned water. But OTOH if you're looking to produce water where there is little to be had, there's already a proven and happily low-tech method available that pulls potable water literally out of thin air (!), even in arid conditions: the Warka tower.

These are relatively low-cost and can be built by anyone, and there are a number of sizes and designs, but the principle is the same throughout. Here's one design:

Image

This one has the added attraction of a shady gathering spot for the community.

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PostPosted: Sat Jul 18, 2020 10:39 pm 
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I am rapidly becoming a Fanboy for Chunlei Guo.

Here is a recent article (July 14,2020), summarizing what we have been discussing, in a suitable form for laymen. https://www.azolifesciences.com/news/20 ... risis.aspx

The Bill and Melinda Gates Foundation (Anti-Malaria) and the US DOD are putting money behind this technology.

The ´Blacker-than-Black´effect can be accomplished with treatment of nearly any metal. Aluminum can be cheap, but Stainless Steel, tungsten, titanium are all possible and can be rendered corrosion resistant.

The use of femto-second USP (Ultra Short Pulse) lasers to treat these metals can render the surfaces so hydrophobic as to render them essentially un-wettable. In short, plates can be made to float. Or, they can be rendered so hydrophilic as to rapidly pump water through nanocapillary grooves uphill.

As of 2016 femto-second USP laser manufacturing processes to produce non-heating metal ablation surface treatments pioneered by Dr. Guo were being commercially employed at mghz pulse rates-this is a manufacturing reality.

The surfaces used to capture solar radiation and evaporate water operate at over 100% efficiency of a theoretically perfect model.

The covalent bonds between water molecules and any en-trained salts appear to be directly disrupted. The water is dispersed directly into the atmosphere. The salts are simply deposited. Corrosion is the direct expression of covalent interaction. The water is stripped away from the salts before any interaction can occur. Essentially no water for the salts to interact with metallic ions. Hence no corrosion. These deposits are just periodically rinsed away. Sounds like Sorcery :lol:

This is Disruptive/Transformative Technology and it is moving very fast.

Bob

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PostPosted: Sun Jul 19, 2020 3:54 am 
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Nanohedron wrote:
Here it seems we're losing sight of the difference between water quality and water availability
I know. But I didn't introduce 3-4 hours to collect water or sand dams and I deleted quite a long paragraph responding to comments about them. Then I re-read the article and took the view that anything other than small-scale commercial applications (or even that) was a long way down the line.

My long paragraph pointed out that it might not be so much 3 hours to collect water that is the big issue, but three hours to collect dirty water. With surface water biological quality is usually the issue so my question was "under what circumstances is a high-tech still a better option than a low-tech sand filter (especially when the sun isn't shining)". Or, is there another way of accessing ground water before animals get to it (e.g. hand dug well with Afridev pump). For chemical quality problems, sure, a still may be the only option.

I have been involved with a several WASH (Water Sanitation and Hygiene) projects, joining UK funds with local water development expertise. It leaves me with an open mind but questioning approach to hi-tech developed-world fixes until I have had the chance to check them out with the local experts. I can almost hear one of them saying of the Warka tower "How is it in the wind?". It also makes me aware of how selective fund raising material can be in how it presents a problem. Personally I would prefer to give a full and interesting explanation, but highlighting the negative opens some cheque books that would remain closed. I like the Warka Tower web site, it takes time to include the "unnecessary" background, like the yellow 20 litre cans being re-used cooking oil containers. (Though I am surprised about the ex-gasoline ones, I think containers normally get downgraded away from food use). That makes me think these are people who ask "Why?" as they research a project. Almost as an aside they mention women having to stand in line for their previous water collection (adds weight to the case for opening the cheque book). I have asked "why" about that several times and always got illuminating answers.

Don't get me wrong I am not against technical fixes. The white LED has had an amazing effect - even using disposable dry cells it seems to have tipped a flashlight into a way of stealing time from the long tropical night. About 10 years ago a UK charity was donating solar powered lights to families so that kids could study at night. At least to start with they were shipped from Europe. We looked into supplying some and found that they were being imported but there was no distribution network. On asking 'why' the answer was that they were not financially viable for rural use. The initial outlay was too great and people could buy kerosene for a lamp week by week (and if they had no money "we sit in the dark and chat"). Solar kit with mobile phone chargers became available but again the outlay was too great and a lad provided a charging service by lugging a car battery around. However, only a few years later there they were on a stall in the market. No-one had any more money but incremental development of solar cells and batteries, coupled with a massive worldwide market for both, had brought the price down enough for some people. I wonder if the local entrepreneur who owned the car battery that the lad carried round was involved.

Hence my comment about seeing a family size still in a rural market. Until it is there and at least a few people can afford it then I don't think it is sustainable in a local economy. Maybe involvement from the likes of the Bill and Melinda Gates foundation and the military will allow the economies of scale.


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