How to Draw a 5,000 Cubic Meter Vacuum

Imagine (if you can) a small tumulus of rocks. The rocks on the surface will be heated during the day but those which are under the first layer will not get so much radiated energy and thus will not be as hot as the 1st layer. Their temperature oscillations will be less. In the space between rocks air (hot and thus with a higher possible water content since at higher temperatures the absolute humidity grows even at same relative humidity) will enter during the day. Over night the tumulus will lose heat and because the thermal heat of rocks is not so high the temperature will decrease giving conditions for water condensation. If the tumulus is around a tree the condensed water will flow to the roots and supply the needs of the tree to grow. This I read about 20 years ago was found as explanation why in different parts of the middle east trees were planted centuries ago. The principle was tested and it worked as for more as 2000 years (or more).

For Kysine especially an explanation: I may have not described the whole in all details from the start but be sure I did not understand only when I wrote about. In fact I over appreciated your facility to understand. Sorry you have my deepest apologize. In the future I promise to give all details from the start in order to supply ALL explanations and avoid a misunderstanding. However I really appreciate your progress in the vocabulary you use it is most promising.

Please consider my comment as BB says "no offence" only an open discussion between gentlemen.

Dear BB. I very well know what you have to support at the beginning of your participation and you know that you have my whole appreciation and respect. I know that a comment or question comming from you has no offence of any kind and please be sure I shall ever answer your question the best I can.

Hi nick name,

I appreciate your thoughtful and kind mention. No need to apologise, OK? We are having a discussion thats all. All be it a very interesting one, right?

Take care and enjoy the rest of the holiday if it is indeed a 'holiday' where you live, OK? No offence!............. Sorry but I had to so it. I think that phrase can sometimes cool tempers down a little when one starts to get 'tunnel vision' through concentration too much.

Actually, that is usually me, getting the tunnel vision!

Take care and good luck.............. It looks as if this thread may be getting closer to an understanding to the difficulties in trying to recover water by adiabatic processes? Sounds nearer than earlier at least.

Actually, the problem is 3600 times worse than I thought in post 52!! My arithmetic goof: to convert from 2500 m3/s to I should have MULTIPLIED (not divided) by 60. So now we need an air (vacuum) pump for 5,328,000 cfm. (At least the compression ratio is low....)

I don't have a psychro chart in front of me, but if this is applied in a place with 10% RH, the moisture content per pound of air is rather low. One stroke of piston = how many thimblefuls of water?

Oh well, not every hopeful idea is ready for prime time.

Guys we are missing the point. Did you know that Singapore has no naturally occurring fresh water sources. They create all their water through reverse osmosis/desalination and pump it across the island. I have had conversations with high level government officials they are very concerned about water issues for this reason. Someone needs to maintain and pay for that infrastructure. I agree that putting this device in the middle of the Sahara is not a clever idea. But putting this system 20 miles inland in India, where it is still hot and humid, will make a lot of sense. Especially to the people who need to decide do they build a desalination plant and pumping stations and run pipes underground, or do they build a system like mine and place it next to the point of need. I am not trying to say that this technology will replace all water creation technologies. I believe that the world needs a portfolio of technologies that are well suited for the diverse needs of the global community.

I find it easier to see the forest when I step back from the trees.

Pretty rhetoric is perhaps only 10% of the point. The remaining 90+% is engineering practicality, which is not being addressed by all participants in this forum. Let's put it this way: cockamamie engineering schemes ARE NOT GREEN.

It takes about 1000 Btu/lb to evaporate water, as in a distillation plant. I understand reverse osmosis takes less, but I am not very familiar with it. I will try to do a quickie calc on this adiabatic process within the next day or so.

Or maybe right now: it turns out I do have a psychrometric chart here at home after all. In whatever case, the 5000 m³ (176,567 ft³) ≈ 13,419 lb of air (@0.076 lb/ft³).

Case 1: 85°F; 90%RH; 0.024 lb H₂O/lb dry air x 13,419 ≈ 322 lb H₂0. This is intriguing, but much of the fog will remain suspended in the air; how would this be harvested? Even if it all precipitates on the walls and floor, what sort of collapsible or circular-arc squeegee is in mind to collect the water? ... More to follow.

Hi AE,

Are you able to give an idea of what kind of machine you would use to recover this water?

I have seen various sites which give various water content per M³. But assuming this for the moment, that the temp' in 20 ℃ and an RH of 50%, = 8.65 grams per M³.

How much water vapor are you basing your calcs on? And air you thinking ~ of the Equatorial areas to supply with these machines? Any idea of the cost of a machine and or system to recover 5000 m³ X 8.65 grams?

Sorry that is clumsy but my brain is not working very well.

Good luck

BabyBear,

Sorry for the delay in my reply. I have no excuse other than spending time with my family during the holidays. I use Stuve graphs to plot most of my temp, pressure, relative humidity info on, but don't know how to attach such graphics to this kind of posting. But these graphs clearly outline the thermodynamic process of my device. To answer your question - here are some numbers that you can use: 70F, 1000 millibars, 100% RH will hold roughly 15 grams of water per Kg of air. The most affordable water is the initial water that can be condensed. As the adiabatic decompression is increased and the temp drops in the hopes of condensing more water you hit diminishing returns.

As I mentioned earlier my designs have focused on a much more modest sized device of roughly 1 cubic meter. I was asking this illustrious crowd how they would go about designing a LARGE scale device. I frankly don't know how to do that and thus the original question. I will bet that there is one simple approach, but many Rube Goldberg approaches that are like white rabbits begging me to follow them. Alas the simple approach seems to be vexing everyone on this thread. I hear a lot of declarations that this is a fools errand, but few optimistic positive suggestions.

I will put forward another suggestion that seems obvious to me. Rather than approaching this from a start stop point of view (piston cylinder, baffle), I think that the answer lies in a continuous flow approach. Create a massive flow of air that sucks the air through a specially designed body that expands the air adiabatically and cyclonically separates the condensed water prior to recompression. I understand that pulling half an atmosphere vacuum in a large space will be difficult but so was putting a man on the moon.

Thanks for all the great comments. I hope you had a great holiday.

AE, if you want to use a 'compressor', in effect, to draw a vacuum, then why not compress the air, cool it (condensation will occur) then expand it through a cyclonic water separator. So long as it cools in expansion below the dew point, what fog there is remaining will then be caught.

A typical industrial air plant dries air in this manner. You need not go the the high HP end of compression (i.e. 120 psi/800 kPa) so the energy numbers may be 'not too bad'.

It is a lot easier to get a relative pressure above 1 atm than a relative pressure below.

The 'expanding gas' doesn't know the difference. (well not in this context)

Hi AE

How about these guys.

http://www.aquaer.com/

They seem to have done their home work. With this there will always be room for improvement and coming up with some thing will take a huge effort on the hardware side.

What I am thinking of would not be appropriate to publish here and I will need some extra time to verify my approach. Big bubbles it is for now, Ky.

Ky,

Thank you for the website. I have looked at a number of the "water from air" companies that use condensation technology. Some work better than others, but all are very legitimate technologies. I think that you and I will agree there is NO silver bullet solution to our water problem, but a portfolio of technologies is the best approach.

My niche is focused on consumers that value water & time highly, so they want to generate water in a short period of time. I have an ACTIVE system that allows a person to adjust the systems operating characteristics to suit the local ambient conditions. I consider condensation and desiccant systems to be PASSIVE systems that operate at a "steady state" without the ability to be sped up or slowed down. Another key selling point is that my system does NOT use VOC's or any chemicals, and is therefor environmentally benign and has a lower cost of maintenance. In addition to water my system (as well as the condensation systems) produces hot air which can be used for space heating. But unlike either the condensation or desiccant systems my system also produces COLD air at NO additional cost. So my value proposition is water, hot air and cold air. I acknowledge that my system will probably take marginally more energy to run than a condensation based system, but when you take into account the speed of water production and the addition of hot and cold air I create a unique value proposition.

Hi AE, maybe get some of these _{^{(I've left the links in, as both should be interesting)}}

(i.e. no mechanicals or process chemicals, lubricants and so on)

I agree that some sort of continuous process seems more promising. Maybe drawing ambient air through an orifice, expanding it to double volume (half pressure) in a suitable chamber that exhausts through a screw compressor (operating as a vacuum pump). How much of the moisture would migrate to the chamber walls, where it could be wiped off and collected; versus how much would remain as fog that would need to be otherwise separated to keep it from exiting through the compressor? Some good ideas might turn up along these lines.

Hi europium,

Hope your holidays are going well!

I think you may have gotten slightly confused, even though your 'art work' is pretty good.

To those 'in the know', he says winking his eye!............... The Purple 'Animal' version would most likely be more efficient and work is half the time! LOL! But, if you have only the yellow 'standard' version, well, I guess sometimes you just have to make do?

Take care and easy on the 'grog'!

"I think you may have gotten slightly confused, ..."

No need to speculate.

"...even though your 'art work' is pretty good."

Gosh, BB! Thanks!

I planned initially to sketch a vac made by Lucas Electric, as it's their only product that doesn't suck. (As for my sentiments along these lines, I owned an M.G. once. Guess who made the electrical system? The Prince of Darkness).

Which reminds me:

Q: Why do the British drink warm beer?

A: Lucas makes refrigerators, too.

I've been sick as a run-over dog this holiday season, but I'm doing better now, thanks to the miracle of antibiotics (don't worry, this post has been thoroughly autoclaved prior to shipment).

Hope you and yours are having a fab time there in Blighty Land. Don't get snowed-in, my good friend, and watch those other drivers come New Years. We want you to stick around awhile, non?!

Hi europium,

A huge thank you for a funny and often wise,//////////// I had to say that but have yet to 'follow' your wisdom!

No, thanks for a real funny post my friend.

This is going to sound real odd but, I hope it is you only that is sick. No I did not mean it like that. Its just that with just the three of you including the most beautiful girl, it leaves few others to take care of each other you know? Makes you wonder where that nasty infection came from with you living in the middle of no-where so as to speak? Sorry for letting all your secrets out. At least I did not give the map reference................ its.......... No can't do that!

What was it and do you have any idea where you got it? Not that you may want to know the details of which there might be too much, but I have been ill from the other end for a couple of days which is why I was unable to reply to you or anyone else yesterday. Think I am OK know. Just to brighten everyone one on here............. I had to 'rescue' a friend who tried to commit suicide the night of the 29th December. Her third time in as many months.. Fortunately unsuccessful! It may have been the shock, (when I thought her mind was kinda working as it should right now?) which may have made me ill for a couple of days? Nowhere near as bad as you or her though. 'Stress' sometimes shows itself in some weird ways?

I don't drive so the danger in the icy and very snowy conditions over the last two weeks was more of someone skidding off and hitting me than visa versa! I actually did get snowed in for over a week. Down to eating my candles by the time I could get out!................ That was after the butter and lard, very nice........ erm, not! Was going to eat 'second hand potato skins' but thought better of it. I rinsed the maggots and fried them. Taste like "Whichetty grubs" apparently?

The 'MG' was a car I always wanted to own but never did and now I cannot drive I am never likely to own one of course.

I am alone other than when I have my superman outfit on for rescuing others, but do not tell everyone OK? It is a really nice colour blue though,...... h-hem, Just our secret OK? So I usually just have me to 'worry' about me. As long as I have potato peelings and lard (see earlier in the post for those whom have not been paying attention) I am OK! Mmmm, scrumptious! NOT!

Take care and I hope you are fully better soon and that your loved one do not come down with the same thing.

(Continuing from #85)

Oil mists can be separated from process streams by means of coalescing elements, typlcally a pleated configuration of fine wire mesh. The oil droplets impinge on the mesh. Neighboring droplets merge (coalesce) with each other, and the aggregated larger drops drain down the mesh by gravity to be collected and recycled. If this scheme works with water droplets, it might answer the collection problem.

Energy estimates of this versus refrigerated condensation are now needed.

I hereby preempt the name "OasisGuy" for this device, if it comes to fruition....

I suspected this stood a fighting chance (after all, water droplets coalesce into ploppy big drops even in air, and a substrate ought to help). These FogQuest folks aren't very far away from here. Get Christo to do another "Running Fence" where the Horse Heaven Hills break over into the Yakima River Valley, and it would be industrial scale at the right times of year.

The hidden art form of Christo and Jeanne-Claude was the patient and prolonged negotiation to get various permissions. And all self-financed by the sale of preliminary drawings, models, collages, etc.

Even if this adiabatic expansion idea is physically feasible, I'm wondering about the energy input. We'll (eventually) see how the comparison with refrigeration works out. The FogQuest scheme is very small-scale, but by being passive it could be economical and well suited to individual homes, farms, and small villages.

On the other end of megaprojects, there is another CR4 thread on whether or not to use VFDs in one honkin' big pump station. What ever happened to such projects as towing the Ross Ice Shelf to Abu Dhabi or wherever? Oh yeah, the money....

Fogquest's FAQ considers:

"How much water is in fog? There is typically from 0.05 to 0.5 grams of liquid water in a cubic meter of fog."

Assuming these numbers are correct and assuming the chamber were filled with dense fog, at 100% collection efficiency we'd gather around 5000 m³ * 0.5g/m³ = 2.5 liters H₂O per cycle.

Not promising.

Hi europium,

Unless your ideas are going onto something else, forget the 'chamber' entirely and have miles of fencing to collect the moisture? With details as per my post where there is a pipe with a slit under the fence to collect the water and prevent evaporation? And the fence could be hidden by bushes or be made a feature?

Perhaps all fences could be made like this with the bottom third in find wire or whatever is appropriate, and even in Countries where there in no water shortage these could save water and relieve the general water companies need to collect so much? I see this working on Farms and distant villages especially.

As Tornado and you kind of point out by listing the link, it also has no moving parts. Being passive it may only br necessary to replace it every 20 years or so?

Take care

One problem with fog fences that Fogquest points out is that these things can (and usually do) collect more than water. Specifically, bird-shit and bugs.

Grandma called it "roughage."

Hi europium,

Anyplace that gathers water including a roof, will have the bird and bug and other rubish like leaves. But line the collecting pipe with charcoal and the water can be drunk directly it exits the pipe into a resivuoires or underground water hole which leads to a well and or a pump and tap?

Take care

BB advises, "Unless your ideas are going onto something else, forget the 'chamber' entirely..."

Yer preachin' to the choir, my friend! You know how hard it is for me stay true to the topic. I mentioned that chamber biz cuz it kinda seemed relevaHey look! A squirrel!

Hi europium,

Sorry, did not mean to 'preach'! I just was not sure if that post was going onto another to explain something. Despite optimism about the amount of water to be recovered I still think a fence is by far the best method to collect water from the air. That is if that is what has to be done?

It obviously would be easier to collect water from a river or lake but collecting too much can lead to a situation where, as lake Baikal shows, it just has more being removed than is entering?

Take care and happy new year.

Aren't there always consequences when you start collecting & storing water?

Throwing up miles of fencing will have effects on the local fauna, not to mention intrusion by opportunistic flora. I think I remember reading about fog fencing being used well off the ground in Peru. Back to putting Cristo to work...

The OP is long gone, having succeeded in his quest of getting us all wound up & feeling like he's whipped it, got the break through, that will revolutionize the field

"Aren't there always consequences when you start collecting & storing water?"

GA from me.

Hi Garthh,

Hope you had a nice holiday and good new year?

Thank you for your reply post.

I was thinking of putting fencing only where there is fencing or field walls etc. It should not make to much difference to the fauna in this case?

As you say the OP seems like they have sailed away, perhaps not really caring because they did not get the confirmation or answer they wanted?

Well, it may not be on topic but the last 50 posts have been off topic also so I fell I am a nice cosy 'club'! What we are talking of right now can and is used in many ares. I had not heard of it until europium listed the link. The is ifs and buts with all recovery system and this is no different. But even if is provides say half or less for the animals to drink, or, where it is for people for them to use after proper filtration.

In lots of areas of Africa and the far east they seem to have to drink water we, in the West, would not think of as "drinking water", so even the charcoal filtration in the pipe that the water is collected in may be enough to get pretty drinkable water from? IE. It is better than nothing? That was and is my philosophy when discussing this. Some make call it hard, but if an area has water but it is dirty, or it has water but it is not reliable, then perhaps a system of underground, .................. or ground-level collection would suffice?

Perhaps the same fence used to keep a few heads of cattle in can also collect some drinking water?

The Fog-Fencing I have seen is on the listed site only. I have not searched for it, which I am about to do after answering several posts. But yes, that is way off the ground. Not sure why but it may be to stop solar radiation from evaporating the bottom part of the net?...........

I have not had time to read much on the site other than what was on the first page, but I have downloaded the Magazine to read later.

Take care...............

"Sorry, did not mean to 'preach'!"

You weren't.

"Yer preachin' to the choir" is a common idiom (here in the S. US, anyway) meaning "I completely agree!" and, as such, is not to be taken as literally meaning that you're preaching/lecturing/etc. at me/someone.

I should've been more clear. Sorry, Pastor Bear.

Hi europium,

Sorry for any confusion. I am new to this English, having used it for only 50 odd years!

I am pleased you understood my cryptic reference!

You may go now from pastor beat. Before you go, 'pass da' biscuits please!'

Well yet another crooked joke falls flat even before I have sent it. I keep trying though! Some say I am 'very trying'!

Take care and I really appreciate your post and explanation. I was not aware of the meaning as you said.

Bloody stupid green horns eh? LOL! I have yet to learn to speak American, or to be specific, 'Texan Americanese', which could perhaps be called 'Red-Neck' speak? Spoken by a fellow whom has a far broader knowledge of words than myself.

Hi europium,

GA to you Sir!

Take care

[scratches head] Hmm...did that GA go to me or to ...

Hi europium,

I gave the deciding point for the GA to go to you. As you found the fogfence. Which I think is more effective.

Take care

Hi Tornado,

I pretty much agree with just about all you say.

Something like the "Fog-catchers" could be part if not all of any fence and it can drip into a slit into a mostly buried pipe which runs to reservoirs?

This need not be an eye-soar as it could be covered with bushes so it is not actually visible?

Take care

"This need not be an eye-soar as it could be covered with bushes..."

In this scenario the bushes would do the 'collection', then, and the fence would get the dregs. These fences need to be out in the open to maximize exposure to the elements.

Insofar as their being eye-sores, you could always pre-print 'em with images of scantily-clad Venusian nymphs or whatever appeals to the prurient interests of the local culture (you'd be amazed).

Kyzine? Please advise?

Hi europium,

Depends on your definition of 'open space'?

But the idea was that the bushes and the fence would collect water?

You have just gone too far now and I will never talk to you again..................... Till the next time.

Take care

"In this scenario the bushes would do the 'collection',"

GA for same reason as "always consequences" GA to Garthh

Hi europium,

Well researched Sir! And very close to what was originally mentioned. And no 'moving' apparatus' whatsoever! Perhaps the 'invention' has already been invented and is use eh?

Take it easy.

Hi Tornado,

"Pleated fine wire mesh", presumably to give more 'surface area'?

Take care.

Picking one somewhat arbitrary data point for illustration, let's assume 90°F air at 20% RH, which gives 0.006 pounds of moisture per pound of air. The air is about 0.078 pounds per cubic foot, so the moisture is about 0.00047 pcf. We expand 5000 m³ of air (≈ 176,600 ft³) x .00047 ≈ 83 pounds (10 gallons) of water. Not all of this will be recoverable, so let's guess 8 gallons per stroke. Hmm, this might prove to be respectable, even though earlier calcs put the HP pretty high.

How often can this one-stroke cycle be repeated? What happens if the air around this is stagnant, in which case it will dry out and yield less? More to ponder....

Hi Tornado. as you are curious, this is one way of 'balancing' out some of the atmospheric forces. Watt steam engine

This is a way of collection of condensate; stirling engine

Not literally - ok - just mechanical illustration of gauze 'wiper' piston.

But it is going to be a slow cycle - say in the range of Newcomen's atmosphere engine.

In the link it speaks of 12 cycles/min. but swept volume will affect that a fair bit.

You are getting close but not close enough. This

http://video_demos.colostate.edu/mechanisms/double_slider-crank.wmv

is not the solution but is quiet interesting as a starting point. Why have only one if you could have many?

Good luck to all in twentyten, Ky.

Cute ky, puts you one up in "starting point" stakes - and My best to U in 2010

Hi ky,

I am not able to 'read' anything from your link. I just get gobbledygook. My Mac system my have something to do with it?

Take care and happy new year

Hi Kyzine,

Nice illustrations!

Even if this engine works and collected tiny amounts, it is working al the time, so would collect in theory substantial water.

Though I no of no place that needs water where fog lingers for 24/7. It, like the nodding donkeys may well be more efficient in recovering water.

The water vapor and rain are more or less constant amounts in the air as I understand it. Do you or anyone reading this think it would be better to recover water from the air than from 'standing' water like lakes? Lake Baikal is a case in point where so much water was taken/diverted that there is something like only have left. Taking water from the air would effect weather to a tiny degree, but at lest no lakes or rivers would dry up?

Take care

Hi Tornado,

Not arguing just querying........................

After getting used to a metric system I find it hard work translating from the pounds to Kilos. I know its not, but when it has to be done with every equation it is!

Can you provide a site for reference please? As the 10 Gallons sound optimistic to the extreme. I worked it out in a previous post, and I am not saying it was correct, but a lot of other post said the same or similar amount of water in 5000 M³, and that was 1.5 L which is very roughly 2 pints. Quite a disparity?

Take care

Let me try again and see if I made a mistake (which happens more than I like)...

My psychro chart is from the Carrier Handbook of Air Conditioning System Design; that's the source for my starting point of 90dF 20%RH 0.006 lb water per lb air. The density I used (0.078 lb/ft³) was just a quick grab from memory, and is a bit off. The point in question shows air volume just less than 14 ft³/lb; the reciprocal is 0.0714 lb/ft³. This works to 0.006 x 0.0714 ≈ 0.00043 lb water per ft³ of air.

One m³ ≈ 35.31 ft³; 5000 m³ ≈ 176,600 ft³; finally, 176,000 x 0.00043 ≈ 75.9 lb of water, roughly 9 gallons. That surprised me, too, but if there is a mistake in this I haven't found it yet. It does puzzle me why this seems so out of line with the fog figures.

(My first air density figure is for colder air; that's why it stuck in my mind.)

I'm guessing now that in foggy air, much of the moisture is still molecular, not yet coagulated into mist. If so, it may not be readily collectible; i.e., a coalescing element captures the mist, but the rest just goes on through.

The fog figures relate to some (unstated, I think) ambient T, likely ~ 30's F. 90F x 20% would make a big difference in moisture mass held.

Hi Kyzine,

You are right this would make a huge difference! Even .01g per M³ would make a big difference. I cannot recall how I worked out my figures though I probably have the page saved. I will look when I find time.

Take care.

Hi Tornado,

I really appreciate your reply post, thank you.

I really cannot understand why the Math you did does seem so wrong? Maybe it is the source book which is wrong or at least not applicable to a fog fence system?

I thank you for double checking though!

There is an awful lot of posts to go through and I am not going to search for it but, I did figure out that the amount of liquid that is contained in 5000 M³ is ~ 1.5L. And I also worked it out at 90°F (~32 °C).

I agree that most of the water is a vapor or turning into a vapor and would coalesce on the right type of fine fence.............. Saving it for use would be almost a bigger achievement?

I will go back through my posts that were on topic to see if I posted the address of the site I got my figures from, unless you have noticed it?

Take care and good luck.

I'm still looking to see if I've missed something in my calcs. If so, I (nor anyone else) has found it yet. Maybe I've missed it, but I but I don't yet see the calcs for the 1.5 liter number.

If an adiabatic expansion process has any chance at all, I think the arrangement of an orifice expanding into a chamber, and pumped out through a coalescer by a screw compressor, is the best bet. (I have my doubts, but I'm trying to give AE the best possible chance.) (Where the hell did he/she disappear to, anyway?)

There are some alternative processes to consider: Compression/refrigeration, for which some sources have already been given. Desiccant wheel, not yet mentioned.

I want to run some energy numbers on these. For the first, I don't know how well an air stream inpinges on a cooling coil--does the coil condense all or most of the moisture, or does some get by? I am untutored on desiccant wheels. I don't know how soon I can get around to these ideas.

Hi Tornado,

Looks like you will be busy trying to figure the details of this out for a while, and then it will become obvious where or if there was an error on your part.

I seem to recall it was not the easiest thing to research and in the end I found some charts and worked it out via those.

Good luck!