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Old 20-02-2010, 14:22   #136
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Originally Posted by daddle View Post
:-) not do fast there Einstein. Sometimes in science it makes a difference whether one divides or multiplies. On this planet we would divide 12 by 4 to get the watt-hours per liter. So 3Wh per liter looks more like what I said. Plus figure your diving bell will slow considerably, then stop, as it becomes half full of water. Also consider how slow you'll be sailing with 500m of cable and a big iron sphere in the sea - compared to a watermaker in a locker. :-)
Minor detail! Unless you're steering a Mars probe...
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Old 20-02-2010, 15:06   #137
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Thanks for the new knowledge!

Ref post 121 about the energy potentials of fresh and Salt water I must say thank you Daddle for that new knowledge.

Life is really all about enjoying and learning!

Rgds

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Old 20-02-2010, 18:03   #138
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Hmmm... Back to the beer question. You know, W.C. Fields said "Don't drink water, fish fornicate in it"

This has been an interesting thread. Hopefully I'll have something more relevant tomorrow.
Bill
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Old 21-02-2010, 08:24   #139
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[Edit - things are obviously busy in this thread. I've just noticed two pages of posts between where this reply wound up and the post I was replying to. Sorry for any confusion]

OK guys'n'gals it is very simple.

To do anything requires some energy. Nature has a very simple rule - you get nothing for free. To separate salt from water requires energy no matter how you organise it and it will require a MINIMUM amount that you cannot avoid.

So, you can separate the salt by distillation (heat the water) or by RO using pressure but in either case energy must be used to boil the liquid or to drive the compressor.

To use pressure at the bottom of the sea would require an pressure differential which means a rigid box. One part of this box would need a lower pressure than the outside for the RO to work and this lower density region will make the box bouyant - it will try and float upwards so it must be weighted down.

If you then add up the energy expended to lower the box (which is very heavy due to its ballast) and raise it up again and compare that to the enegry needed to boil an equal amount of liquid or run an RO compressor, you will find that the energy expended will be the same or (more likely) more than that used by the other methods.

Nature's sums always add up. When you look at your starting position and your ending position and then calculate the TOTAL energy required to get you from one state to the other, you will find that there is always an energy budget.

The trick is to find an energy source that can be tapped at no financial cost and use that energy to power the water maker - whicheer method you use. The problem is that there are very few forms of energy that have no associated financial costs.
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Old 21-02-2010, 09:36   #140
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I don't mind a bit of financial set-up cost if it means a dependable long term solution
As long as its better than what we have now.....but thats the nut to crack...RO set-ups have come a long way as far as efficiency goes.
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Old 21-02-2010, 17:12   #141
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I like your posts but you do not get me into the box!

I love these thoughts just as I said in a very early post when Anjou was brave enough to share her thoughts about why not make water out of H2 and O2.
It is this sort of an approach that we have to put our faith into when it comes to making the much needed progress to make te World a better place for more people.

Look at me , I have a nice genset making the RO watermaker spinn perfecty making 130 litres of potable Water an hour besides topping up the batteries.
I belive and hope in having a financial situation than can leave me without worries when it comes to price of diesel so why do I care?

Perhaps from the fact that I having spent quite some time in a leading Management position and I do understand that either you are on the leading edge of things or you pay the price for not understanding what is happening.
Putting it in an other way we are on the brink of exhausting the high energy paradigm and we need to find another solution.

I do belive that the awnsers are all there and that there is a lot to be learned from the most competitive place of all ---Nature--!

Mintys pilot says it is really all very simple!

I do not agree. Since he is a Britt and Pilot I can not resist telling you all that the Spitfire was not the best Aircraft the world has seen...

I do fully agree on that a perpetum mobile is not possible but on the other hand why look for it??
No matter how you look on things energy has never been a problem on earth and will probably never be so if we all learn to use it wisely. ( before the sun dies)

The nice thing with the cruising crowd is that we have to start thinking in terms of energy efficency and consevation.

When it comes to this post I´m so very happy in joining you on the task how do we solve our problems.
I really do not care about if I am a better or bigger guy than the previous poster but ask for progress.

I still see that Anjous post about lifting sacks is not commented at all but it has been said that lifting a " heavy sphere " is " more likely of setting the ganis from not running a RO watermaker!!
I really like her courage in starting the thread with the common knowledge observation that Water is made out of H2 and O2

I wonder from just an energy efficiency point of view how you think?

Me not beeing the master of these things do humbly ask you to do the maths .
My genset efficincy factor abour 0.4 times my watermaker factor about 0.7 is not that impressive.
If I have to use my windlass I do get an energy factor of something like 0.8

From the beer point of view that has been a part of the last postings I do have to say I love beer on a really hot day if it is cool enough but really prefer good wine and water to keep me satisfied!!

Perhaps in an other way I can be described as a happy guy if he is nice and clean an not has to give up nice wine with his dinner.

Looking fwd to your thoughts!

Rgds

Kristian
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Old 22-02-2010, 03:28   #142
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Mintys pilot says it is really all very simple!

I do not agree.
I was referring to nature's "laws", in particular the Conservation of Energy and the Second law of Thermodynamics. Taken together they state that you do not get something for nothing and there is no way round a minimum energy requirement. Although I did not make my living as a physicist, my training in that area makes me very skeptical of people who have found ways to circumvent these basics.

I do not object to RO, but I am thinking ahead to my own boat and wondering, speculating, about running it on as low an energy budget as possible. It seems obvious to me that if I can utilise sunlight as an energy source that would be considerably more cost-efficient than running a generator for RO.

With regard to Anjou's "bags" idea the problem I see there is that RO requires a large pressure difference and that precludes a bag simply because it lacks the strength and rigidity to provide a volume at low pressure for the osmosis to work.


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Since he is a Britt and Pilot I can not resist telling you all that the Spitfire was not the best Aircraft the world has seen...
Kristian - I am a glider pilot. I'm not interested in the ones with the engines in. In any case it was not the Spitfire that won the Battle of Britain (there simply were not enough of them) but the Hawker Hurricane. For some reason the Spitfire got all the publicity. The Hurricane was slower but could outturn both the Spitfire and the Messerschmit.
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Old 22-02-2010, 05:28   #143
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What surprised me: some wrote that the weight to be lifted up was huge because besides the bell/anchor/whatever there was also this load of fresh water. But fresh water is lighter than salt water so you would need to keep it down instead of have more lifting power!

so, what about a hose up to the surface for the product water? ;-) you really need to pump up a lighter fluid?

cheers,
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Old 22-02-2010, 09:55   #144
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Learning all the time!

Special thanks to Mintyspilot for giving me the new knowledge on how the battle of Britain was won!
I know everything about how it is to beat a bigger bird with a smaller more agile in close air combat.
But my point was really that the fantastic planes of them days were the last ones of that paradigme.

In my last post I said that I do not belive in a perpetum mobile- that was my way of saying the same thing as Mintys pilot the basic laws of nature are there. What I ment when I said I do not agree is that you have to constantly try to make things better and constantly try to understand universe a fraction better. We are very far from the perfect solutions and saying it is impossible due laws of nature simply is not my cup of tea.

I belive Anjou´s bags are a bit missunderstod. If I got it right I belive she was referring to a way of lifting rather than producing.
From my time diving I remember that going up was not a problem , you actually accelerate towards the surface due to the fact that your wetsuit expands when going up and in this way you get more and more positive flotation the higher you get.

This adopted to the lifting problem leads me to the conclusion that you just have to initiate a lift with for instance a lifting bag and if you in addition to the rigid parts needed for pressure differentials have flexible parts the lift is very easy.

Now to some things I do know nothing about and perhaps there is someone sitting on the info.

Does RO need a big pressure alone , big pressure + big pressure differential or just a big pressure differential?

I know that temperature plays a major part since the RO output decreases with lower temperature.

Why??


Might sound like a strange question but please see it ths way.
Water is fantastic and you all know that trees do not suck water up in their high branches.
The pressure differential is just not there, without doing the maths I belive my memory says the highest you can suck water is somewhere around 35feet.
(The term suck water is of course al wrong since you use the atmosphere to push the water up.)

Without the capilary action of water trees would have to have ? gensets ??

Next thing I do not know is there a limit to how high the capilary action will transport water?

I do really agree about that using the sun to get your fresh water would be really nice.

Or the waves!
Or the wind!
Or any combination of what we have available " for free" including our own labour..

Really looking forward to learning from you all!

Rgds

Kristian
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Old 22-02-2010, 10:16   #145
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Your right Kristian, but leave my bags out of it. They are always being misunderstood.

33 feet is the magic number for syphoning (also deepest you can dive on pure oxygen)
Capilliary action is what draws water up in plants, due to fluid loss at the leaves from transpiration. Giant Sequoia trees are huge, hundreds of feet high.
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Old 22-02-2010, 11:44   #146
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Without Anjou´s Bags

Missing your Bags already but OK I´ll leave them out of it.
Even more of a challenge getting the thing up and emtied but perhaps it would be possible with capilliary action ...

I´d better move on to the sunny side of this thread and think of boiling water for a while.

Hard for a Swede like me right now with 4 feet of snow outside and a temperature of -25 Celsius.
Not so strange that it takes the poor brain the better part of an hour to cath some things when it is so severly deep frozen!

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Old 23-02-2010, 02:47   #147
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Quote:
Originally Posted by Kristian View Post
Special thanks to Mintyspilot for giving me the new knowledge on how the battle of Britain was won!


Quote:
Originally Posted by Kristian View Post
But my point was really that the fantastic planes of them days were the last ones of that paradigme.
Indeed. Nowadays with "Killer robot planes"..... it's getting more like "The Terminator" everyday.

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What I ment when I said I do not agree is that you have to constantly try to make things better and constantly try to understand universe a fraction better. We are very far from the perfect solutions and saying it is impossible due laws of nature simply is not my cup of tea.
Agreed

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I belive Anjou´s bags are a bit missunderstod. If I got it right I belive she was referring to a way of lifting rather than producing.
That makes more sense to me. I must have misunderstood her suggestion.

Quote:
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Does RO need a big pressure alone , big pressure + big pressure differential or just a big pressure differential?

I know that temperature plays a major part since the RO output decreases with lower temperature.

Why??
The normal (not reverse) osmotic pressure across a membrane is quite considerable which is why it requires a lot of pressure to make the RO work. Osmosis has a lot in common with the laws of Ideal gases and SImple Kinetic Theory and in SKT temperature and pressure are related - increasing one increases the other. From that viewpoint increasing the temperature increases the pressure (Boyle's Law) and that assists the RO


Might sound like a strange question but please see it ths way.
Water is fantastic and you all know that trees do not suck water up in their high branches.
The pressure differential is just not there, without doing the maths I belive my memory says the highest you can suck water is somewhere around 35feet.
(The term suck water is of course al wrong since you use the atmosphere to push the water up.)

Without the capilary action of water trees would have to have ? gensets ??

Next thing I do not know is there a limit to how high the capilary action will transport water?

I do really agree about that using the sun to get your fresh water would be really nice.

Or the waves!
Or the wind!
Or any combination of what we have available " for free" including our own labour..

Really looking forward to learning from you all!

Rgds

Kristian[/QUOTE]
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Old 23-02-2010, 09:05   #148
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Please correct me!

I got a bit interested in capillary action and found this:
Capillary action - Wikipedia, the free encyclopedia

Please help me out with the maths in the formula.
If I try 10 Angström as the radius of the capillary

( if I understand it right it would mean a capilliary with about 10 water molecules side by side)

I get a lifting of the Water of 14000 meters.???

I must have made some misstake.

Ref the RO and temperature thanks again to Mintyspilot ,
I do however understand it the other way around , higher temp means lower pressure needed and vice versa.
If I understand you correctly you are reffering to the osmotic pressure that is to be overcomed to produce fresh water and then I understand it all.

I said in a previous post that I really needed to start thinking about the other possibility with boiling water even thoug it is a litte harder to think of a hot merciless sun these days in Sweden.

Has anyone thought of the possibilities with solar panels that do get hot and to use them for water boiling as well as electricity production?

Part of the panels electrical power can run a small vaccum pump to lower the pressure where the water is and that way you get it to boil earlier.

I belive it is possible even with a small inexpensive pump to get the pressure down enough to start boiling in the region of 85-90 celsius.

Rgds

Kristian
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Old 24-02-2010, 09:17   #149
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Sun and freshwater possible.

I did start a new thred on the subject of using sun energy to produse our freshwater.

A copy here below of the first post. I hope we can keep this thread alive on the subject of RO since I belive a lot more can be learned there.
I would not had had a chance of getting even close of these thoughts if it was not for this thread!! Fantastic!!


I might be too stupid to understand why the described thing below not should work.
I´m sure there is someone that can give it thumbs up or down.

Before reading the thing below it might be a good thing reading the thread started by Anjou : Water water everywhere around , the thread inspired me into a lot of thinking in if we can get our freshwatersupply in a new way.

Let´s start with the general idea. Water heated by the sun boiling of stem that is condensed back to pure water.

I started in looking at what lowpressure is possible to get using a very low cost pump such as a reversed tire pump for your bike or a tirepump 12V for your car or why not a danfoss compressor from the refrigerator not working any more..
I got the result that the lowpressure achivable will make water boil in the 50-60 degrees celcius range! A lot better than I first thought .
I belive this temperature is very easy to achive with sun energy!

Getting the lowpressure ( Vacuum) is easy but you shuld not really have to be pumping all day to keep the low pressure as the water boils away so this little problem needed solving.

I belive this is fairly easy on a Sailing boat with a 12 Meter + high mast.
What I´m thinking of is using a thin tube high up connected to a coarse tube ( some 15 cm diameter) down below with a watertight piston within that is free to move upwards but can not fall out in the bottom.
You would start by filling this tower with potable water some 9 meters high. Next you pump out untill reaching your low pressure of aprox - 26 inches mercury and this way you will be lifting the watercolumn that will keep the lowpressure in the system with its own weight.

How will it work ones the water starts to boil?
The vapour will go in a tube from the "sun boiler" to the top of the fine tube in the mast. As this happens the watercollumn will start to sink keeping the low pressure. Vapour is around 16000 times bigger when it comes to volume than water. This fact works both ways and it will contract just as much ones it is cooled back to water in the column.

The thing will have to be restarted ones you have produced enough fresh water and the movable piston hits the lower restriction.

At this point you tap of the produced water and start all over again.

To Easy to work??

Why

Regards

Kristian
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