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Efficient Electrolysis?

Move the ions to the electrodes
  (+4, -7)
(+4, -7)
  [vote for,

In the future, they say, we will replace our coal-burning and oil-burning and natural-gas-burning powerplants with hydrogen-based power. In one sense, there isn't a lot of choice, because fossil fuels will eventually all be used up (not to mention that there are much better uses for those substances than burning them, such as making plastic from them). Meanwhile, hydrogen is renewable in the sense that we can extract it from plain water, and the most common ways of using it to make power also yield water. (Eventually we'll be making helium from hydrogen, and obtaining even more power, of course.)

There is a problem with this scenario, however, and it is known as "overall efficiency". Consider oil-based power, for example: In a large power plant we can burn fuel to generate heat, and convert about 50% of that heat into electricity. In smaller power plants, such as auto engines, we can only convert about 30% of that heat into the mechanical motion of the auto. The rest is wasted, and that's just the way it is. We manage to live with it (however uncomfortably).

Now consider hydrogen: we extract it from water using the electrochemical process known as "electrolysis", which is about 66% efficient. THEN, when we use the hydrogen, we can either burn it (extracting useful power at 30% to 50% efficiency, just like oil), or we can reverse-electrolyze it in gadgets known as "fuel cells", which happen to work at (no surprise) about 66% efficiency. Note that AT BEST, the OVERALL efficiency is (E%)(66%)(66%), where E is the Efficiency at which the Electricity was generated, that we used to Electrolyze the hydrogen from the water in the first place. Even if that was 100, the electrolysis and reverse-electrolysis processes are INefficient enough that the overall efficiency drops to about 44%. Worse, since we get most of our electricity from power plants that are only about 50% efficient (and which is likely to be true even if we had fusion power plants), the overall efficiency of a "hydrogen economy" would be only 22% or so, at best.

SOMETHING MUST BE DONE. The fossil fuels WILL eventually run out, and a hydrogen economy of some sort will probably arise simply because we find small power sources so convenient -- and using hydrogen is one of the best options. (Batteries, for example, are electrochemical gadgets that are in one sense indistinguishable from fuel cells -- both work at about 66% efficiency. But batteries weigh a lot more, since they CONTAIN both fuel and oxidizer -- while fuel cells take advantage of the atmosphere, to get their oxidizer.)

Which brings me to the current idea. Is there a way to increase the efficiency of the electrolysis process? If so, can it be used to also increase the efficiency of the reverse process, in fuel cells? I dunno. But somebody with the right measuring equipment might try this and see...(I am going to simplify the following description a bit, by ignoring such additives as sulfuric acid, which promote ion formation in the water).

During the electrolysis process, two electrodes are dipped into water, and electric fields encourage various ions in the water to move toward the electrodes. It is THAT MOTION, of ions through the water, to get at the electrodes, that wastes energy. What if we simply moved the water, ions included, toward the electrodes? Imagine a circular trough, with electrodes located at intervals around the trough. (I need not really mention that the more surface area the electrodes have exposed to the water, the better, because that fact is well known.) So, at Electrode #1, hydrogen-rich ions interact with it, and two things happen: Hydrogen gas bubbles form, and oxygen-rich ions are created (this last is partly the result of water interacting with the electrode). If the water is in motion around the trough, then the flow carries the oxygen-rich ions to Electrode #2, where they interact to produce oxygen gas bubbles, and more hydrogen-rich ions. Then the water carries those new ions to Electrode #3, and so on, until the full circle takes place.

It seems to me that the more we can prevent ions from fighting their way through surrounding water molecules, to get at the electrodes, the more efficient the electrolysis process will be. Now all we have to do is find out if that is true!

Vernon, Jul 31 2001

(?) Send over a truckload of this, please, PS http://www.halfbake...m/idea/Clue_20Spray
[neelandan, Mar 05 2002, last modified Oct 17 2004]

(??) ElectroCrapoLysis http://www.fortunec.../bp/16/buerger1.htm
Way greater efficiency than Vernon gets with stirring the soup [neelandan, Mar 06 2002, last modified Oct 17 2004]

Energy calculations http://hyperphysics...hermo/electrol.html
Physics of fuel and electrolysis cells [neelandan, Mar 07 2002, last modified Oct 17 2004]

(?) Efficient electrolysis by Stuart http://www.stuarten...ogen/techreview.asp
Nothing to do with hair, folks. [neelandan, Mar 07 2002, last modified Oct 17 2004]

(?) madcapx's link as a link http://www.aist.go....iscl/ECOSfinal.html
This is the place to put it, [Mad_CapX]. [neelandan, Jul 30 2002, last modified Oct 17 2004]

Plasma Electrolysis http://energy21.fre...ectrolyticflows.htm
Beware of popups! [bungston, Oct 06 2004, last modified Oct 17 2004]

(?) A fusion reactor design that's claimed to be READY http://video.google...1996321846673788606
This link has nothing to do with electrolysis, and is only posted because of a couple annotations. [Vernon, Jun 13 2007]

Some Fusion Notions Three_20Fusion_20Reactor_20Variations
Perhaps we can continue this non-electrolysis dixcussion there. [Vernon, Jun 18 2007]

(?) Electrolytic Fusion http://www.newenerg...s/2006/NET19.htm#ee
Latest Cold Fusion news (at least this involves electrolysis!) [Vernon, Jun 23 2007]


       Well, considering that we are looking for a significant increase in electrolysis efficiency (let's pretend from 66% to 75%), and considering the total amount of power actually involved in the electrolysis process, I would expect the energy associated with pumping the water would be easily "afforded" by the efficiency increase (so call the overall efficiency 74% instead of 75%). For example, that is.
Vernon, Jul 31 2001

       damn! i thought this was going to be about hair removal!   

       vernon, you should patent these ideas.
mihali, Jul 31 2001

       mihali, I WISH!   

       But I prefer to know whether or not an idea actually can work before taking it to the Patent Office. And since testing the ones I've posted takes more money, time, specialized equipment, or other stuff than I have available, they'll just be wasted if I don't post them, so that the facts can be discovered.
Vernon, Jul 31 2001

       You could use solar energy to move the water if you installed this as a series of screen-like electrodes in, say, the turbine outlet at a dam.
beauxeault, Jul 31 2001

       The idea of preventing the ions from fighting the surrounding water may be vailid. This implementation of the the idea wouldn't work though. Even though the water is moving and being carried to the electrodes, they we still be accelerated by the electrodes. The electrodes will still waste energy kinetically accelerating the ions.   

       Also, the negative acceleration of one of the ions will act as a drag for the water. So you'd have to keep pumping to the water to maintain it's speed.   

       Also, it's true that the ions move towards the electrodes but they usually don't actually *reach* the electrodes. They lose their kinetic energy to the surrounding water and eventually precipitate into bubbles.
zephyr_prime, Jan 12 2002

       As [PeterSealy] implied, we're trading the energy wasted by ions moving toward the electrodes for the energy wasted moving *all* the water toward the electrons.
phoenix, Jan 13 2002

       This may not work, I don't know, but what about combining electrolysis with a large hydro electric source. For example using the momentum of the falling water to push itself through the electrodes, like a boost to the hydroelectric efficiency?
renwald, Jan 13 2002

       Time to reply to some of the comments....   

       zephyr_prime, I am aware that ions in the water will always be doing SOME fighting-their-way through surrounding molecules, to get at the electrodes. Only if the electrodes were so finely wrought (molecular scale) and so extensive (think steel wool as a starting point) that every ion was practically already in contact with an electrode, would such fighting be prevented.   

       And while an ion might not actually have to physically contact an electrode, it does have to get close enough for at least one electron to transfer between electrode and ion. (A positively charged hydrogen ion will acquire an electron, and become a neutral hydrogen atom, while a negatively charged oxygen ion will give up two electrons, and become a neutral oxygen atom. Somewhere along the way the atoms will form actual molecules of gas, but that is beyond the current scope.)   

       phoenix, you are apparently unaware of the vast difference in quantities of energy needed to electrolyze water, versus the amount needed to merely pump it slowly. In a circular trough, very little energy would be needed to maintain the circulation of the water, after getting it moving. And some extra energy would be needed to push newly-added water, needed to replace that dissociated via electrolysis.   

       Why only pump it slowly? Well, even in a plain ordinary copper wire, electric charges do not move very fast -- only a few millimeters per second, believe it or not. (Think of a tube full of glass marbles; if you add a marble to one end, another will be quickly pushed out the far end -- the force travels at speed of sound in glass. A wire full of loose electrons behaves much the same; push some electrons at one end, and others immediately come out at the other end -- the force travels at nearly light-speed. In neither example do the individual marbles or electrons move very fast.) Ions fighting their way through other molecules probably go slower than that.
Vernon, Feb 01 2002

       <ot>If this was about hair removal, could we use a person's legs like Volta used a frog's leg to generate electricity to zap the offending hairs? Self-powered depiliation.</ot>
pottedstu, Feb 01 2002


       Which does not respond to my statement at all. Welcome back, by the way.
phoenix, Feb 01 2002

       I've had some fun connecting plates to a dc supply and putting them in salt/acid/alkali solutions in the good old days.   

       At no time did, however, the resistance of the stuff correlate with the movement of the electrodes. As they became choked with gas bubbles the current would decrease, and increase when they were brushed off.   

       The central idea to this, that moving the electrolyte against the electrodes has an effect on the voltage drop, seems to me to be wrong. I'd welcome the results of any experiments anybody has carried out though.   

       It is easy to postulate a thought experiment and make it appear to substantiate your wrong theories, viz: Perpetuum Mobiles.
neelandan, Feb 02 2002

       phoenix, the point I was referencing (obliquely, I admit) is that if about 33% of the energy sent to electrolysis apparatus is (currently) wasted, this is FAR MORE than the energy needed to pump water slowly around a circular trough. So, if the idea has merit, we should indeed save energy (spent by ions fighting their way through the water), in spite of spending a little on pumping.   

       neelandan, what sort of electrodes did you use, that required the bubbles to be "brushed off"? In electrolysis that I saw way back in high school, the bubbles floated up off the electrodes easily, no extra effort required. Perhaps the difference was the shape of the electrodes? I might understand that a flat plate immersed in the water -- which is what I saw -- having far less surface area than a "wooly" electrode, might allow bubbles to escape more easily (the wool might trap the bubbles!).   

       I do see that if the idea works, one interpretation is that the overall resistance of the water+electrolyte is lessened, and thus more current should flow.   

       I also see that there is a relativity of motion, between moving the water and moving the electrodes. I chose to describe moving the water because one need not worry about electrical connections (and gas-collection-tubing connections) to stationary electrodes. Nevertheless, in your experimenting, can you say you managed to move the electrodes in a manner consistent with the overall/original description? That is. if a positive electrode is located at Point A, and a negative electrode is located at Point B, then after a few seconds of electrolysis, the water surrounding Point A should be enhanced with positive ions, while the water surrounding Point B should be enhanced with negative ions. If the electrodes do not move, then those extra ions have to migrate through intervening water to get at the opposite electrodes. But if the electrodes simply swap position, then the ions only have to move a little ways back, to get at the electrodes that they are attracted to.   

       DID you move the electrodes such that they exactly swapped positions?
Vernon, Feb 04 2002

       Cars move a lot. Car batteries die.
thumbwax, Feb 04 2002

       Now you've put me up to it, dear vernon, I'll try to be back with numbers from The Real World soonish.   

       Will electrolysis of NaCl in aqua with Carbon electrodes do?
neelandan, Feb 04 2002

       I wouldn't recommend electrolysis of water with table salt in it. One of the gases released will be chlorine, not oxygen. (If you used sodium FLUORIDE instead of NaCl, then oxygen will probably be released.)   

       I am unsure about carbon electrodes. Can you get some gold foil? Small quantities are usually not very expensive.   

       I might suggest that instead of moving the electrodes physically (which will mix up the ions in the water, diluting any local enhancement), install a switch that lets you simply change the polarity of the electrodes. Recognizing that for the purposes of the experiment, no gas need be collected, it would be OK to let hydrogen be produced at one electrode for a time, and then, after the polarity is switched, to let oxygen be produced at that same electrode.
Vernon, Feb 04 2002

       "Designed by Vernon" is regarded with derision at the halfbakery. Now you've done it again.   

       From your reply to Abhi in "time vs energy" I gather that (a) you know physics (b) you can present it concisely. I can only conclude that this is an effort to pull the wool over the eyes of unsuspecting halfbakers.   

       You have described an experiment designed to demonstrate exactly what your idea has proposed.
neelandan, Feb 14 2002

       neelandan, your comment does not compute.   

       If someone suggests a hypothesis, and an experiment to either prove or disprove it, that is the proper way to go about things in Science. I do not KNOW what will happen -- efficiency wise -- if the device described here is constructed, and so this qualifies as a half-baked idea. I am free, however, to be as clear and consistent in my speculations about the idea as I can manage. Someday someone will try it (with enough bucks and spare time, it would be me), and then we will know the extent of its validity.
Vernon, Feb 14 2002

       Doesn't need lot of bucks, just lot of spare time. Let us be consistent in what we are trying to demonstrate:   

       Inducing relative movement between electrolyte and electrodes is what your idea is about.   

       Switching electrodes is entirely different. An electrode becomes covered in gas bubbles and acts as a pole of a fuel cell. Immediately after reversing, the cell will show low resistance and thus validate your version of the theory.   

       I see this as a section of edge connector (gold plated) with alternate contacts connected together, placed in some easy to obtain acid or alkali solution. V / I to be monitored with / without stirring.
neelandan, Feb 14 2002

       I wasn't aware that just because an electrode may be covered in gas bubbles, it automatically qualifies as a pole of a fuel cell. Not to mention that if the right electrode material is used, no gas bubbles will stay attached to the electrode.   

       The thing that I thought would cost a lotta bucks was the equipment needed to measure electrolysis efficiency. Your ordinary/cheap volt/ammeter isn't accurate enough.   

       One variant of the overall notion concerns the "wooly" electrodes described in a prior annotation. *IF*, by reducing distance between electrodes to such a small amount that ions merely move extremely short distances from one electrode to the other, we gain a large increase in efficiency, it might be worth letting the two gasses mix together as they rise to the surface of the water/electrolyte. (It will be difficult to prevent mixing!) There will be some energy expense to separate the mixed gas, but that just-mentioned efficiency-increase should be associated with sufficient energy savings to make separating the mixed gas worthwhile.   

       The edge-connector setup you describe is a step in that direction (lesser distance between electrodes equating to greater difficulty in keeping the two gasses separated, as they are produced).   

       While I am unsure of the exact interior construction of those devices known as "electrolytic capacitors", I am aware that they manage to have a lot of electrode-surface area, separated by an insulator. If that insulator could be replaced by a water/electrolyte solution, then we even more closely approach the "wooly" electrodes previously described.
Vernon, Feb 14 2002

       well then, don't. If he's got a problem with a bit of fluff on legs, he can sod off. It's only the stubbliness that is unattractive - have one last wax, and then it'll grow back with soft ends. Then, never shave again.
sappho, Mar 07 2002

       I have sinned . . .
In what way?
This morning as I looked in the mirror I was proud that I was so beautiful . . .
That's only a mistake, dear. That is no sin.

       Well, Vernon, have you sinned or are you just mistaken? In other words, are you deliberately trying to lead halfbakers into confusion, or are you confused yourself? It is very hard to judge.   

       Somebody has said something somewhere - no, not that. To sculpt an elephant, you take a large enough block of marble and then proceed to chip away everything which does not look like an elephant. Simple.   

       To understand one of your ideas, Vernon, I take the raw text as appearing on the halfbakery and chip away everything that is not understandable. Until I am left with - uh oh, lemme try again.   

       With this idea, I was in luck - "Moving the electrolyte increases efficiency of a electrolytic cell" was the idea in my mind after all the fluff had been blown away.   


       Confession of ignorance (mea culpa) should immediately be followed by the prescribed penance, in this case a perusal of the textbooks of electrochemistry.   

       I had read about a fuel cell demonstration (School Science Success Review) which had two electrodes (Pt foil) immersed in dilute acid, half covered in hydrogen at one end and oxygen at the other. It was said to develop a potential of about a volt at a few milliamperes.   

       I have seen the effect of sticking in two bits of constantan wire into lemon juice (citric acid) and connecting a battery. Bubbles from both wires. It would supply current briefly when disconnected and connected to a measuring instrument (VOM in microamp range), most probably due to the effect of the gases evolved. Constantan wire, because it was said to resist acid.   

       During electrolysis, gas bubbles grow from microscopic spheres, become larger as they absorb other bubbles, and eventually break away and lift to the surface. In all the electrolysis experiments I have observed, small bubbles do stick to the electrode. They detach from the electrode when their lift due to buoyancy overcomes the force of adhesion to the electrode.   

       So, Vernon, there is literature out there, and I have personally observed, that if you cover an electrode in gas bubbles it becomes a pole of a fuel cell. In fact the electrodes of fuel cells are just that - fancy, porous, catalytic contraptions devised to bring a gas, an electrolyte and an electrode into intimate contact.   

       ----***<! sorry guys, to go on and on so, but - in Vernonland, do as Vernon does, you know.>   

       What is the force resisting the passage of a current through water? Three components. At the -ve electrode, the contact potential of Hydrogen. At the +ve electrode, the contact potential of Oxygen. In between, the resistance of the electrolyte.   

       A fuel cell is an electrolytic cell operated in reverse, to take in hydrogen, oxygen and give out water and electricity. As soon as you pass current through the electrodes of an electrolytic cell they become covered in a monoatomic layer of hydrogen (at the cathode) or oxygen (at the anode). It is the reaction of these layers that gives rise to the contact potential, about 1.48 volts. If the applied voltage is higher more gases will be evolved. If the voltage applied is less the gas layer will be absorbed and the cell will force a current in the reverse direction. This is the mechanism behind 'polarisation,' and the reason why most of the bulk of a dry cell is black carbon mixed with manganese dioxide. Detailed energy calculations are in the links.   

       The following two paragraphs are extracted from the stuart link:   

       "Energy efficiency (low power consumption) depends upon reducing the voltage needed to pass the current between the electrodes. This is accomplished by reducing the resistances to current flow, through employing advanced design features such as electro-catalysts, high surface electrodes, close electrode spacing, more conductive internal current paths and using materials capable of accepting higher operating temperature."   

       "Electrolysis at 1.48 volts (corresponding to 3.5 kWh per normal cubic metre of hydrogen) would be 100% efficient in the conventional sense. Practical electrolysers today achieve efficiencies of over 90% on this basis, electricity to hydrogen; in an energy sense, electrolytic hydrogen can therefore be regarded as a storable form of electricity."   

       So, Vernon, others are already addressing the problem of increasing the efficiency of electrolysis. And they do not seem to have hit on the obvious method of helping the ions on their way with a push from a pump. Why not?   

       Here is why not. The mechanism of current conduction in electrolytes is by ionic transfer. Ions move. The current flow is equal to the charge on an ion, multiplied by number of ions moving, per unit time. In water, there are Hydrogen ions H+ and Hydroxyl ions OH-. In an electrolyte carrying current, H+ ions move to the -ve electrode and OH- ions move to the +ve electrode. At any time, equal numbers of - and + ions will be moving in opposite directions. THEY WILL BE MOVING IN OPPOSITE DIRECTIONS! So if you move the electrolyte in one direction it will assist one type of ion and hinder the other type. The effects will cancel each other out. Now, if you were to postulate a pump which will selectively accelerate one type of ion - sort of a Maxwell's Demon - WIBNI, WIB C001, ky00t & orl dat 5tiff.   


       You do have the infernal gall, the preposterous cheek, the abominable brass to come up and say that the test equipment available out there is not accurate enough. Is one percent enough for you? I shall not talk about the rituals necessary to get a repeatable and meaningful reading from a six digit Digital Voltmeter. Instead I shall examine the fallacious implication that an "ordinary/cheap volt/ammeter isn't accurate enough".   

       Oompa pa PAAH! Oompa pa paAH! PAAA AH!!
Lay - dees and Gennelmen! On the red corner we 'ave the V cell,
The one with the stirred electrolyte,
And, competing for the medal, in the blue corner, the N cell, without.
The contest shall now begin. DinG! Phwee ee ee pp!

       How do we judge? Measure the hydrogen output of each cell. And the energy intake of each. Divide one by the other to get the efficiency. The one with the higher figure wins. Or, if the difference is within the resolution of the measuring instruments, within the margins of estimated error, we may have to call it a draw.   

       Now wait a minute. I am not going to blow my money on unnecessary instrumentation. Let us look at the Physics.   

       Four little electrons;
Let us call them
Nat, Pat, Dat and Tat.
Nat stuck himself to an OH group
Making it a negatively charged
Hydroxyl ion. So did Pat.
As did Dat and Tat.
Finding themselves in the soup,
A strange attraction they did spy
Towards a metal plate, shining bright
Surely 'tis the metal royal, Aurum be!
Positive! positive!! cried they out
Bouncing and jostling as they went
Onwards in their Brownian way.
Into the gilded matrix they jumped
Leaving the OHs in the lurch
Though not for long; two OHs
Did react together to form
One nascent Oxygen
And one molecule of sweet water
From whence they had sprung
Originally, as you shall see.
Two O's did together join
To make one molecule of Oxygen.
But what of our friends, Nat
And Pat, Dat and Tat?
Forgive me friends, long story
Cut short; we find them
Jumping off another plate
Into that self same soup.
Nat he espied a wand'ring Proton
Jumped he in, and held fast
Making up one nascent hydrogen;
As did Pat, and Dat, and Tat.
Four nascent hydrogens
Did together join
Making up; I do not lie
Two molecules of Hydrogen.
In the soup, water, H2O
Was splitting up into OH ion
And Hydrogen ion, Proton,
By themselves, unprovok'd,
Spontaneously, as they say.

       If we pass the same current through two electrolytic cells the amount of gas evolved in each will be the same. Merely by connecting the two cells in series we are spared the inconvenience of capturing and measuring gaseous volumes since we are, at present, only interested in the relative efficiencies. Unless, of course, Vernon has some method by which an electron is able to neutralise more than one ion.   

       If both cells have the same current through them, and are at the same temperature, the more efficient would be absorbing less energy. It will have less voltage drop. Which component is less? Just suppose V cell has less barrier potential due to the moving electrolyte, ie, the sum of the contact potentials of Oxygen and Hydrogen is slightly less than 'normal'.   

       Then I run a normal fuel cell, which will absorb the gases coming from the V cell and put out current. The voltage developed by it will suffice to drive the V cell because its potential is less. <take hat off> We have Perpetuum Mobile!   

       <see jutta coming> <cram hat into mouth> <chomp> <chomp>   

       Sorry guys. Perpetual motion machines are <gulp> not allowed <gulp chomp> at the <gulp> halfbakery.   

       The assumption that the barrier voltage can be reduced leads to the conclusion that a perpetual motion machine is possible. Therefore the barrier potential may not, at the present state of the art, be reduced (or increased).   

       So, the more efficient electrolytic cell has to have less voltage drop across its electrolyte. To that end, we increase the area of the electrode plates, move them closer together, and find a formulation of electrolyte which will have the lowest volume resistivity. Will pumping the electrolyte change something?   

       Parallel plates - stuff in between - doesn't that sound familiar? Yes. It is the construction of a parallel plate capacitor, with resistive stuff in the place of the dielectric. A formal analysis of the parallel plate capacitor, with maxwell's equations for the speed of propagation of electric signals, has been done by Ivor Catt in Wireless World a few years back. Interested halfbakers may please look that up. Of particular relevance is the time constant of relaxation of the electric field in a partially conducting dielectric.   

       So, in the experiment which I am not going to conduct, the V cell and the N cell are connected in series and a (constant) current passed through. The voltage across each is measured. The more efficient cell will show a lesser voltage drop. What accuracy do we need?   

       I purchased the cheapest meter I could find. Made in Taiwan. 3½ digit LCD, multirange, powered by a PP3. On its 2 volt range the voltage of an electrolytic cell can be measured to a precision of four digits. That is 0.1%. The accuracy of that reading would not matter much, since we are comparing two nearly equal voltages.   

       Therefore, with the proper experimental setup, Vernon, nonavailability of big funds need not stand in the way of your doing experimental verification of your conjectures, at least in this case. Good Luck.
neelandan, Mar 07 2002

       Egad. An annotation longer than the original idea, the original VERNON idea...and it WASN'T by Vernon. My ghast has been flabbered.
StarChaser, Mar 07 2002

       neelandan, thank you! That was a nice post!   

       And now to attempt to respond... First, I am truly not trying to lead anybody either astray or into confusion. I really try to explain things clearly -- obviously not always very successfully. (More failures seem to occur here than elsewhere, I've noticed.)   

       Next, yes, the basic idea here is that moving the electrolyte MIGHT increase the efficiency of an electrolytic cell. See the big question mark in the title of this idea! However, there was a bit more to it than mere motion, because a specific design was described.   

       Concerning the gas bubbles and the fuel cell, it truly was my understanding that the gases were supposed to be DISSOLVED in an electrolyte, to get them to work as fuel-cell fuel. Thus my doubts about the bubbles. Also, I assumed larger bubbles than you just described. I am actually not horribly ignorant of electrochemistry, but apparently am somewhat out of date.   

       Nevertheless, I would like to take issue with your description of a fuel cell, because you describe starting it by initially running it backwards, as an electrolytic cell, to create bubbles. Why? If I recall right, one design for a fuel cell goes (very crudely) something like this:   

       A B C D E   

       where A is an electrolyte containing dissolved hydrogen, E is an electrolyte containing dissolved oxygen, B and D are porous electrodes, and C is a very narrow region where water is actually formed, and exits. So, if the dissolved gases are already against the electrodes, why are bubbles needed?   

       Perhaps they have something to do with that greater efficiency you have already mentioned (and a different overall design, too).   

       Anyway, my original idea was not so much about fuel cells as it was about electrolysis. I had a particular DESIGN in mind, to go along with the idea of moving the electrolyte -- and I did not know how well that design would translate to fuel cells. I merely hoped it could be translated....   

       Yes, I do know that ions can go both directions through the electrolyte. But here is where my design MAY make a difference, because I suggested using multiple electrodes, and not just two. Here is a sketch:   

       - E + E - E + E - E + E - E + E (loop back to start)   

       =======>> flow of electrolyte   

       where E represents electrolyte in-between (-)negative and (+) electrodes. Also remember I specified a circular trough, so that there is a continuous loop for the electrolyte to constantly flow in the same direction.   

       In one of my other annotations I mentioned that electric charges do not move very fast (a few millimeters per second for electrons in wire -- I expect ions in electrolyte to go slower). So, if the electrolyte is made to flow faster than that, we DO NOT get the situation of ions flowing both directions in-between each electrode in the loop!!!   

       In each - E + segment above, negative ions leave (-) and flow toward (+). AT that electrode, all the negative ions are ideally consumed (oxygen production), and a surplus of positive ions is formed. THEY, in each + E - segment above, leave (+) and flow toward (-), where they are ideally all consumed (hydrogen production), and a new surplus of negative ions is formed. Both kinds of ions go the SAME direction, around the loop.   

       About the multimeter, I hadn't paid a lot of attention lately to the digital models. I have an old old moving-needle job, which was my definition of an ordinary cheap model.   

       Next, NOWHERE did I imply any sort of possibility for Perpetual Motion. I DID happen to suggest the possibility of increasing electrolysis efficiency from 66% to 75%, but one has to go AT LEAST up to 100% before one can talk about Perpetual Motion. Thus I formally accuse you of introducing some FUD into this discussion.   

       But I am encouraged to attempt to perform the experiment sometime, and for that I thank you again.
Vernon, Mar 08 2002

Fzzzzzzzzzt....Bam Bam Bam Fzzzzzzzzt
neelandan, Mar 08 2002

       //Cars move a lot. Car batteries die.//
-thumbwax, Feb 04 2002
I'm still waiting
thumbwax, Mar 08 2002

       thumbwax, to some extent car batteries are designed to die, so that the manufacturers of car batteries can continue to sell lots of their product. But even if they did their best, lead-acid batteries cannot last indefinitely. The chemical reactions that consume and rebuild the electrodes, as one is discharged and recharged, do not perfectly restore the shapes of those electrodes. Each cycle yields slightly-more-distorted electrode-shapes, and after enough cycles, the cells fail.   

       Other than that, what WERE you talking about?
Vernon, Mar 10 2002

       This idea hinges on the conjecture that moving the electrolyte moves the charge carriers and thus increases efficiency. My rebuttal to this is that the current in electrolytes is carried by both positive and negative ions and so any movement which helps one will hinder the other and the effects will cancel each other out.   

       Let us attack the problem from another angle. Mercury is a liquid and in it current is carried by electrons alone. If the Vernon hypothesis is correct then moving a stream of mercury in a tube will affect its resistance to current flow, depending on the relative direction of electron flow and mercury flow.   


       ABC is a thin capillary tube along which a high velocity stream of mercury is maintained, in direction A to B to C (say). A, B & C are electrical contacts with the mercury. An electrical current is passed into B, and extracted from A and C. The circuit is arranged as a Wheatstone bridge and adjusted to balance.   

       Now if the current is reversed, the bridge should show unbalance.   

       In the A-B segment, the mercury and electrons will be moving together and so will have low voltage drop. In segment B-C, they will be moving in opposite directions and so the voltage drop will be high.   

       This will serve to demonstrate whether the relative movement of conductor (or electrolyte) and current carriers (electrons or ions) has any effect on the resistance offered to the passage of an electrical current.   

       As you have so wisely observed elsewhere, Vernon, I am prejudiced against your ideas, even to the extent of thinking of them as being utter bollocks, and to be venerated just a little bit under that of the excrement of the husband of the holy cow. And I must admit that that extreme prejudice makes me think that the outcome of this experiment will be negative - a sort of Michelson-Morley stuff, if you will.
neelandan, Apr 27 2002

       neelandan, your analysis of what happens to electrons in a tube full of moving mercury seems to me to be quite correct. However, that analysis DOES NOT APPLY to the moving electrolyte-and-ions in this Idea, and here is why:   



       The electolyte comes in at left carrying negative ions to Electrode A. All are REPLACED with positive ions there, which are carried toward Electrode B. Again all are replaced, and a stream of negative ions is carried toward Electrode C. And so on.   

       Your analysis deals with just one type of moving charge, not two!!!   

       Now, certainly you may want to think that this is also going to happen:   



       AGAINST the flow of electrolyte-fluid. However, ions only travel through still liquid at a few millimeters per second at most, so if the fluid goes faster than that, they don't have a chance. Please remember that as far as electrical attraction is concerned, an ion generated at B is pulled EQUALLY toward A or C -- but if pushed by fluid flow towards C, it simply can never move toward A. So the overall flow should ONLY be as in the first depiction.
Vernon, May 13 2002

       You agree with me on the mercury experiment.   

       Perform it, and come back with the results. It might be an eye opener: whether you are really mad or just a normal one in pursuit of madness.   

       In my mind, I see no distinction.
neelandan, May 14 2002

       VERNON; I disagree with the Half baked critics I think your multi electrode Idea will likely work! The positive and neg. ions don't have to swim upstream ; each will have a appropriate electode nearby down stream. Also, the moving electrolyte will knock off the gas bubbles improving electrode to electrolyte contact. I might offer the thought; If the electrodes were layed flat at the bottom of the trough then gravity/bouency works in your favor and lessens toubolence in the fluid . Also try different pump speeds and power imputs to Maximize H2 output. TED3
Ted3, Jun 22 2002

       omg !! ..... you can't stop there.....another month and you will have been arguing about this for a year !!!!!! some sort of birthday party for your idea is in order vernon.......you must have very low self confidence if you feel u have to argue a case for a year and not get off your ass and prove it !!!!....regards to you neelandan :)
andypandy, Jun 24 2002

       Ted3, thanks for the vote of confidence.   

       andypandy, we all have priorities. I think I first thought this idea up about 20 years ago, but have simply been doing too many other things to get around to it. Not to mention that for most of those years I didn't have the quantity of $ that I believed would be needed to test it. Only during this discussion did I learn that it might be affordable. But that fact alone doesn't remove all the other priorities ahead of it on my To Do list.
Vernon, Jun 24 2002

       Ideally you want to use less electrodes not more, also as the efficiency goes up the shear amount of bubbles and motion will keep the solution moving. I would make a simple BUT effective electrolysis device and modify the solution.   

       In the article below high hydrogen yields are possible, wonder is carbon fiber nets might help instead   

Mad_CapX, Jun 25 2002

       Mad_CapX, that was interesting, but I do have a few doubts about it. Note that one of the ingredients for their chemical hydrogen-releasing reaction is Calcium Oxide (which exits the reaction combined with Carbon Dioxide, in the form of Calcium Carbonate). Calcium Oxide is not normally found in Nature; it has to be manufactured from Calcium Carbonate (limestone or sea-shells, usually), and it gets manufactured by adding quite a bit of heat. Yes, it is widely available, because Calcium Oxide is a primary ingredient of cement and concrete -- but that does not necessarily mean that we have a great overall energy efficiency of these chemical processes. I note specifically that it is proposed that some carbon (from coal) be burned, to generate the heat to reform Calcium Oxide. On the whole, then, those researchers are proposing that we burn coal to generate hydrogen. This is not the way to escape the Global Warming Greenhouse Effect! Meanwhile, with respect to electrolysis, the electricity needed can come from many non-fossil-fuel sources (wind, solar, hydro, nuclear, tidal, geothermal, OTEC, etc.)
Vernon, Aug 20 2002

       An interesting and entertaining thread. My observations: 1.) 66% efficiency is nothing to sneeze at. It beats out just about everything else. 2.) After we have adopted a hydrogen- based energy economy, it will become an economic imperative to increase electrolysis efficiency. At that time the real money will appear to fund such research. Don't expect any interest outside of academic circles until then. 3.) Perhaps direct electrolysis of seawater could be attempted on an ocean-going raft or a decommisioned deep-sea oil drilling rig, using solar energy or wave energy to power the apparatus. You'll need some non-corrosive electrodes. Maybe the salinity of the water would improve ion transfer? 4.) An alternative location would be Nevada- lots of sunshine and clear skies for solar cells. Water sources a bit of a challenge, though. On the other hand, what water there is is likely to contain lots of electrolytes, like arsenic...
whlanteigne, Oct 05 2002

       It occurs to me that a different route to accomplishing the end of enriching the vicinity of electrodes with the correct ions would be via centrifugation. A very fast centrifuge should sort out the different molecular species present. After determining which zones the different ions inhabit, electrodes could then be placed in these zones.
bungston, Sep 28 2003


       It seems to me that the bubbles that form on the electrodes have some potential energy that isn’t really being harnessed.   

       Would it be possible to shape the electrodes in such a way, that as the bubbles rose to the surface of the water, they’d impart a portion of their energy of motion to their surroundings?   

       In other words: could the bubbles rising be used to stir the water into a nice little vortex?   

       This way, no extra energy is needed to stir.
TIB, Sep 29 2003

       While again pondering how to descrease the resistance of the electrolyte, it occured to me that a high density plasma would serve well. Ions move very freely in a plasma. My quick search did find some references to electrolysis in plasma (link), though I am not sure they are using it to split water.
bungston, Feb 11 2004

       [reensure], thanks for the info. The thing about the plants is, they don't really do electrolysis so much as photodissociation. That is, they catch photons and use their energy (with catalysts) to leverage water molecules apart. Sure, it is efficient, but it is not electrolysis....   

       [bungston], in the plasma state molecules are mostly busted apart by thermal decomposition. It takes a LOT of energy to get them in that state. I don't really see this as being a route to efficient electrolysis, sorry.
Vernon, Feb 12 2004

       I would think that fighting the eddies and friction from the side of the container would add up to MUCH more than the (completely elastic?) forces of the ions flowing through water, which is not very dense to the ions perspective...most likely very little interaction with the actual water molecules. It might increase the efficiency in one part, but, the system wouldn't be more efficient.
nomel, Jun 10 2004

       //saving some of the energy wasted by ions bulling their way through the water//   

       Better way to do that: Put the electrodes very close together. Then you almost totally remove that loss.
david_scothern, Jun 11 2004

       Thanks; I agree with part of what you say, and disagree with part of it. I have no objection to the closely spaces large-surface-area electrodes (other than hood design). But I also am thinking of the Law of Conservation of Momentum, such that once we put the water in our looping trough into motion, it will take very little energy to maintain that motion. And I am pretty sure that electrically charged ions pushing neutral water molecules aside, to get at the electrodes, is indeed the major cause of ordinary electrolysis inefficiency.
Vernon, Jun 13 2004

       Seems to me that the idea of how a reacting solution really works, as was presented to me in my education, is being totally ignored here.   

       Correct me if I'm wrong, but it seems Vernon's idea depend on the notion that a water molecule is a water molecule, now and forever, in any given system. It follows that this molecule might hinder any ion's progress towards an electrode should it get in the way.   

       Makes sense on the surface, except that this is not how a solution works, according to how I was taught. Rather, even a system at equilibrium is just that- at equilibrium with the reactions that continue throughout the system. Equilibrium does NOT, in any way, imply a "static" state, in fact it's the opposite.   

       What does this have to do with an electrolytic cell? Well, Vernon's poor ions that were minding their own business on the way to an electrode will have a hard time getting there personally. The beauty is, it doesn't really need to. It has just as good of a chance of "getting it's point across," so to speak, through chemical instead of physical means. This means it could just as easily recombine through a chance collision, indirectly freeing another ion somewhere else across the system, possibly in closer proximity to an electrode.   

       In fact, the idea of moving the water past the plates would be completely invalidated by this model of a chemical system, since the ions you hope to steer towards the electrodes won't necessarily exist as an ion by the time it gets to the plate.   

       So tell me, am I woefully ignorant in my understanding of electrochemistry, or what?
otmShank, Jun 19 2004

       [otmShank], no, you are not woefully ignorant of electrochemistry, and indeed water molecules interact with ions quite frequently, just as you describe. Nevertheless, consider two simple facts: (1) Such interactions are not the ONLY things that ions engage in, when immersed in water; and (2) simple electrolysis wastes about 1/3 of the electrical energy supplied. If not what I described (or some equivalent such as ions shoving other ions), then what do YOU say is the source of that waste?
Vernon, Jun 20 2004

       "Well, since with NO flowing water, ions move through water at merely millimeters per second (if that much), it follows that we can push water at that speed to bring the same number of ions per second to the electrodes. This is a pretty low speed, as far as eddy-worries are concerned."   

       Where do you get millimeters per second? If an ampere is flowing through, that would mean 6,241,510,000,000,000,000 electrons would have to enter and exit the electrode...per second. No math involved, I would assume they would have to move faster than that! How did you calculate this speed?   

       I just don't think that the power required to move the water and fight it's resistance against the walls of the container would increase efficiency to a non neglible point. Not including that power loss, I think it would be more efficient. But, again, including that loss...I doubt it.   


       How is this possible!? The bubbles are created at atoms at a time! I don't think you'll find anything with a surface that these won't stick to.   


       Wouldn't some convert back into water, reducing efficiency? Pumps and whatnot would be required to seperate the gasses, again decreasing efficiency.   

       You bring up a good point. The moving water might get charged when passing the electrodes, moving the electrons from electrode to electrode without doing any usefull work, decreasing efficiency.   

       I would think a lot of the loss would come from the heat generated. That an electrons not doing any usefull work, in this case, not seperating the water molecules. This brings up a question. Do you want great ion movement? What if the ions move from electrode to electrode without seperating any water molecules? Effectively shorting the electrons? I don't know enough physics about electrolysis to know.
nomel, Jul 02 2004

       As usual the naysayers are full of themselves and wrong. Yes, electrolysis efficiency can be improved. One way is to shape the electrodes as plates alternately charged and very close together, then the ions don't have far to go! There are patents going back 20 years. See: US Patent 4,457,816 and 4,340,580.   

       I wish people would lift a brain cell and research a subject before posting their uninformed opinions, which after all, aren't worth very much. (Yawn); Here's evidence:   




thrival, Jul 15 2004

       <thrival>, I think your on a different subject or didn't read the idea or something...   

       Wasn't he mentioning moving the water to increase the efficiency? I don't see anywhere where anyone was disputing that the efficiency couldn't be improved. I personaly was just argueing that moving the water probably wouldn't increase the SYSTEM efficiency...the net result...the only thing that matters when obtaining the final product...which was what his idea was about.   

       And...can you explain the relevance of those links. I skimmed through them and didn't see anything related to what we were talking about...just electrolysis....nothing to do with moving the water to increase efficiency. Can you paste the relevant data...or something?   

       So, what is your opinion of *HIS* idea.
nomel, Jul 23 2004

       nomel, electrons really do flow at millimeters per second through ordinary wire, and so I assumed the same is true for ions in water. Sheer quantities of atoms in a wire (each contributing at least one electron) is the reason.
Vernon, Aug 04 2004

       Ah, Vernon. Good to see you're still here... all was quiet on the Vernon front for a while, and I was getting worried. The bakery wouldn't be the same without you...
david_scothern, Aug 05 2004

       If you cross at 90º an electromagnetic gradient and a electric potential one, through an electrolyte solution, you will get the electrolyte in motion, by the interaction between the ions and the liquid. You can do it with permanent magnets and DC current on a saline solution. So the ions and the water interact; a lot, too. Vernon's idea has merit (even if it's a bit long winded for my taste). Also, removing the bubbles will increase efficiency. How much all this improves the process efficiency is open to discussion, but improving the electrolisys, it does. Croissant for Vernon.
finflazo, Aug 06 2004

       You seem to be right, vernon. Have a croissant.
Kam_J_Peter, Sep 21 2006

       //In smaller power plants, such as auto engines, we can only convert about 30% of that heat into the mechanical motion of the auto.//   

       Only about 6% (or something like that) is actually used to move the passenger.
apocalyps956, Sep 21 2006

       // Eventually we'll be making helium from hydrogen... //   

       Extremely doubtful.   

       You're right about the poor efficiency of converting electricity to hydrogen and back. Even achieving 66% efficiency is difficult - it's only achieved in large, expensive, low current density set-ups. You can afford the space and weight in a stationary system, but you can't afford it in a small vehicle.   

       It's not the distance between the electrodes that's the problem - there's not much energy loss in ion transport in solution. Most of the loss is at the electrode surface - and it's to do with current density. A certain amount of surface folding helps, but too much surface folding results in entrapment of the evolved gases, blocking access of the solution to the surface. (This is in marked contrast to battery electrodes, where - in normal operation - no gases are evolved.)   

       These issues have been very well explored by the designers of these systems.
Cosh i Pi, Jun 12 2007

       [Cosh i Pi], why do you say that // Eventually we'll be making helium from hydrogen... // is "extremely doubtful"? The statement was a reference to nuclear fusion power (as a source of electricity), and was not meant to imply a particualar method for doing it.
Vernon, Jun 12 2007

       [Vernon] I'm highly sceptical that we'll ever achieve practical, economic fusion power. I'm a former nuclear engineer, with no salary to protect! It's one of those technologies that's conveniently always just over the horizon - so everyone involved in the work can expect to be paid until retirement without ever having to produce any real results.   

       It's just conceivable that we might be able to achieve D-T fusion on a scale that pays in energy terms - but whether it could possibly be economical is quite another question. And it's not nice clean technology: D-T fusion involves a far higher neutron flux than fission, with consequent high levels of radioactive activation products. It also consumes more tritium than you can reasonably expect to produce in its blanket - which implies you need another source of tritium to keep the reaction going. The only other source is fission reactors - in fact, you're likely to need several fission reactors to supply the tritium for a single fusion reactor.   

       The D-D reaction doesn't require tritium, but is much harder to make work - the D-T reaction is so difficult that we might never get it going on any useful scale; what are our chances of getting the D-D reaction to do so? D-D still produces loads of neutrons, too.   

       Finally, there's He3-He3 - which doesn't produce any neutrons, but is much more difficult still - and which requires a source of He3, which is an extremely rare component of the Earth's atmosphere (very expensive to extract, and with a total energy value equivalent to only about 25 years' worth of current electricity consumption), and not present at all in underground helium sources.
Cosh i Pi, Jun 12 2007

       [Cosh i Pi], thanks. I'm aware that nuclear fusion power is a difficult goal, but there is a difference between difficult and impossible. I've tended to think that one of the major problems has been a reluctance to spend enough money on the research, due to Big Oil. Well, now the oil is getting ready to run out, so if Big Oil still wants to be in the energy business, it's time for it to invest in fusion research. I've encountered what seems a good place to start. Dr. Robert Bussard has a reactor design that he claims, "the physics is DONE", so only engineering remains. I'll add a link.
Vernon, Jun 13 2007

       [Vernon] Indeed there is a difference between difficult and impossible - but it's very hard to know which side of the line this particular goal falls. My own suspicion is that it's impossible to make a practical D-T fusion reactor – that is, one that produces more energy that it consumes in the reactor, by a large enough margin to pay for all the energy consumed in all the supporting infrastructure. I also suspect that it's impossible to produce as much tritium in the blanket of the fusion reactor as is consumed in the reactor, and that therefore substantial numbers of fission reactors will be required to produce the tritium. (It's worth noting that unless it is a very small proportion of the tritium that is produced in fission reactors, the fission reactors will generate more energy than the fusion reactor.)   

       If these goals are not actually impossible, then they are certainly extremely difficult – leading me to suspect that even if practical D-T reactors are possible, then practical D-D or He3-He3 reactors are likely to be impossible.   

       D-D and D-T reactors, even if possible, are not clean power – very far from it. He3-He3 reactors would be clean, but there's a very limited fuel supply for them – only enough for a couple of decades of power at most, and you'd have to pass the Earth's entire atmosphere through a separator system to extract even that much.   

       An incredible amount of money has already been spent on this goal - if a similar amount had been spent on solar voltaic or solar thermal systems, they'd almost certainly be widespread by now. They're far, far more likely to be economical – and unlike fusion, they're quite certainly technically feasible.   

       As to Robert Bussard's reactor: it's a Farnsworth Fusor, and they can indeed be built in a back shed, and they work just fine. I can't believe anyone thinks they can produce more power than they consume, however. They might be a way to produce a small neutron flux without needing radioactive materials - at a high cost in energy. It would be nice to see a transcript of Dr Bussard's talk, though - that video's not a lot of use to us deaflugses.
Cosh i Pi, Jun 14 2007

       Bussard's Fusor uses magnetic confinement instead of electrostatic confinement. Basically, his experiments have convinced him that a large-enough version would hold enough volume of interacting nuclei to result in net energy production. Also note that due to the way a Fusor works, D+D isn't a lot more difficult than D+T. A little longer fall to the center, a little higher collision energy, see?   

       I'm curious what you think about using hydrogen gas, pressurized, outside the shell of the reactor core, as a neutron stopper. The light mass of ordinary hydrogen nuclei should easily absorb a lot of momentum from a colliding neutron, every time such a collision happens. If the neutron is stopped and breaks down, the result is more hydrogen neutron-blocking gas. If the neutron is absorbed, you get deuterium, maybe even tritium.
Vernon, Jun 14 2007

       [Vernon] Okay, I'd not seen Bussard's proposal before. It's interesting - I wouldn't dismiss it out of hand, I think it would be worth pursuing. I wouldn't be optimistic about success, however.   

       My instinct is that you don't stand much chance of getting back more usable energy than you put in, but it's much harder to analyse than Farnsworth's Fusor. I think that even if people do some pretty careful analysis, it's probably still worth doing quite a lot of experiments to confirm (or refute, or refine) the analysis.   

       Of course you always get nett energy out, as soon as you get any reaction at all: the goal is to get more _electrical_ energy out than the amount of _electrical_ energy you put in. If you put in 100 MW (electrical) and get out 130 MW (thermal), you're making a huge loss: converting that thermal energy back to electrical you'll be lucky to get 65 MW (electrical) out. An ordinary heat pump (your refrigerator, for example) can convert 100 W (electrical) to 130 W (thermal).   

       A hydrogen blanket for stopping neutrons wouldn't be bad if all you wanted to do was stop them. In practice, water is better: the oxygen is more or less irrelevant to the nuclear physics, but it's a convenient way of holding a lot of hydrogen in a small space without needing high pressures.   

       But for a practical fusion reactor (of the conventional kind - this doesn't apply to Bussard's), you don't just want to stop the neutrons, you want to use as many of them as you can to produce tritium. The most efficient way to do that is to absorb them in a blanket containing a lot of lithium, which produces tritium when it's smashed by neutrons.
Cosh i Pi, Jun 15 2007

       I'm definitely coming to like [Cosh I Pi]. He's talking about nuclear fusion, in detail, and I'm understanding. Well done, sir!
david_scothern, Jun 16 2007

       [Cosh i Pi], I agree about the energy consumption/production thing, and that's of course one reason why they plan on using superconductors whenever possible, in a fusion reactor. Lots of magnetic field with no steady electric bill!   

       Regarding production of tritium, note that if you start up a "pipelined" production line, with a several-years lead time, then you can actually be using decayed tritium in the reactor (He-3, that is) and thus reduce one of the problems you mentioned earlier (excess neutron production). The half-life of tritium is only 12 years or so, if I recall right.
Vernon, Jun 17 2007

       [Vernon] Superconducting coils enable you to create stronger magnetic fields than you otherwise could, but they don't save all that much energy: what you save in electrical resistance heating you spend in keeping the coils cooled to superconducting temperatures. This is especially problematical in the immediate vicinity of a device generating massive quantities of heat!   

       You can indeed manufacture He3 by allowing tritium to decay away, but this isn't really a useful thing to do (unless you have some use for the He3 other than power generation). If we're running the D-T reaction, then we need the tritium as fuel. If we're running the D-D reaction, then a certain amount of tritium will be produced in side reactions, but it will be immediately consumed in D-T side reactions. We won't be particularly trying to manufacture tritium, because we're using deuterium as our main fuel.   

       In that scenario, we could manufacture tritium using some of the spare neutrons, and allow that to decay to He3. You might then run some neutron-free reactors on He3 - but they'd be entirely dependent on a much bigger and more powerful D-D reactor, which wouldn't be neutron-free at all.   

       That's assuming you can make an He3 reactor that works at useful power levels at all.   

       In a mixed neutron-free/non-neutron-free power system of that kind, He3 fuel has two advantages over D-T: firstly, the He3-He3 reaction produces no neutrons, so some of your reactors are "clean"; secondly, He3 can be stored for long periods without it decaying like tritium does.   

       It has two serious disadvantages: firstly, it's a much more demanding engineering problem to make a practical reactor (very likely actually impossible); secondly, you get a lot less energy from each original atom of tritium in He3-He3 reactions than in D-T reactions.
Cosh i Pi, Jun 17 2007

       [Cosh i Pi], I'm beginning to think you are stuck in a rut. Do remember that the high-temperature superconductors only need liquid nitrogen (cheap as milk), so the electrical demands of keeping it cold are nowhere as severe as trying to keep other superconductors cold.   

       Also, just because tokamaks may not be worth building, that doesn't mean other designs aren't worth doing. I've posted a couple of them at this site, and will add a link or two. Meanwhile, variants of the Fusor are looking better and better, because its Modus Operandi easily scales to higher-energy collisions, for things like He-3 reactions.
Vernon, Jun 18 2007

       [Vernon] As I said, I wouldn't rule out the possibility that Bussard's design would work satisfactorily - but I certainly wouldn't be confident of it yet, on the basis of what I've seen so far.   

       The plain electrostatic fusor (Farnsworth's) doesn't really stand a chance - it's quite easy to analyse, and it's pretty obvious. It works, but it'll never be a practical power source.   

       Bussard's is very difficult to analyse. It has obvious advantages over Farnsworth's, but equally it shares some of the problems of the various torus designs (of which Tokamak is but one).   

       Liquid nitrogen is of course much cheaper than liquid helium, but unless things have changed recently, none of the high temperature superconductors can withstand the high magnetic fields that we're trying to create - they might have applications in power transmission, where linear conductors only have their own magnetic field to contend with, but I've not heard of any that are useful for electromagnets. That could change, of course - I don't think the physics is well enough understood to know whether the problems are inherent in the superconductivity mechanism - or indeed it might already have changed without me noticing.   

       Even so, liquid nitrogen isn't free, and the cooling costs make the economics even of superconducting power transmission pretty marginal in most cases. In power transmission, you've got no restriction on how well you can insulate, and you don't have a massive heat source next door. In Bussard's design, the magnets would have to be pretty close to the reactor - not much room for insulation, and a massive heat source right there.   

       I don't think I'm in a rut, no - but I'm generally pretty sceptical of extreme engineering. Not that it's not fun thinking about these things - but it's also important to see the problems, potential or actual. If I were in charge of the budgets, I'd certainly fund some more research - but I'd regard it as a long shot, great if it works out but probably a wild goose chase.   

       (Just spotted something else further upthread: I've electrolysed common salt with carbon electrodes. Carbon electrodes are the electrodes of choice for DIY set-ups - cheaply obtained from spent cheap dry cells - and won't dissolve in anything you're likely to use or produce. Chlorine is indeed evolved when you electrolyse table salt - so do it in the open air, but don't worry about it, you don't need much salt and all the chlorine will soon be gone. Then you're left with dilute sodium hydroxide solution, and the gases produced are hydrogen and oxygen. I did this when I was about thirteen...)
Cosh i Pi, Jun 18 2007

       The rut I'm talking about is how you go on about D-T reactions. If a Fusor-type device, or other method (heh, have you seen the latest about electrolytic Cold Fusion?) lets us use D-D reactions, then we can blanket the reactor core with water to stop neutrons, and production of radwaste will be minimized.
Vernon, Jun 23 2007

       // then we can blanket the reactor core with water to stop neutrons, and production of radwaste will be minimized //   

       Indeed, that's generally assumed with devices like these. Unfortunately you can't put the water between the reaction, and the reaction chamber and the magnets (for a Bussard Fusor). No-one would let the neutrons get to the outside world in any significant quantity - but you can't stop them getting to the reactor components and structure, and it's those that you're concerned about, because they become radioactive.   

       They also deteriorate functionally - losing mechanical strength, electrical conductivity, insulation value, magnetic permeability and so on - because of two effects of neutrons: firstly, they transmutate some of the atoms of the materials into atoms of other elements, and secondly, the neutrons (and radioactive decays of activation products) displace atoms from their original locations in molecules or crystal lattices. This deterioration means that you need to replace parts of the system sooner than you'd need to with similar engineering components in non-neutron environments - which means handling radioactive materials, and disposing of radioactive materials.   

       // have you seen the latest about electrolytic Cold Fusion // No. I don't bother to read things like that any more at all.   

       Farnsworth's Fusor is sound science. Bussard's fusor msy be sound science - it's not totally beyond the bounds of credibility. Electrolytic cold fusion is pseudoscience. Out there with the ghouls and ghosties. Fusion in collapsing bubbles is out there too, before you mention that - sonoluminescence is perfectly real, but it doesn't involve any fusion.
Cosh i Pi, Jun 23 2007

       [Cosh i Pi], when you proclaim something to be pseudoscience without looking at the evidence (link provided above), then the pseudoscientist is actually yourself. The latest experiments come complete with plastic showing the effects of high-energy particle bombardment.   

       Such a stuck-in-a-rut attitude means that doubt can be cast on various other of your proclamations, too. For example, if the superconducting magnets are big and powerful enough, there CAN be space between them and a hot-fusion reactor vessel, for a water-jacket to absorb neutrons. It comes down to how much money you want to spend up-front on capital equipment, versus how much you want to spend down the road replacing radioactive/damaged capital equipment, see?   

       Personally, I'd like them to finish building the tunnel they started for the SuperConducting SuperCollider, and then put a nice big fusion torus in there....   

Vernon, Jun 24 2007

       [Vernon] I'm sorry, but just because someone produces what they claim is evidence of ghouls and ghosties doesn't mean that I'm going to waste my time looking at the claimed evidence. I've only got a finite amount of time on this Earth. I've looked at more than I need to of such "evidence" before - and to date it's all been as convincing as one would expect evidence of incredible events to be. One could spend one's entire life investigating the alleged evidence provided by quacks; some people do so. Most of us have better things to do with our time.   

       You might be right that you could put the superconducting magnets outside the water jacket if they were strong enough. Obviously they would then need to be much bigger and more expensive and use more power to keep them cool (although it's true that having them further from the reactor does help with that, too). It would all boil down to a compromise: no amount of water would stop all the neutrons, but there'd be some optimum thickness of jacket that would reduce the neutron flux to a level that was acceptable for the magnets, and then beyond that you'd have further shielding to protect personnel and equipment that didn't need to be close to the reactor. My suspicion is that the optimum compromise wouldn't have a very thick jacket between the magnets and the reactor.   

       But I think you're wrong anyway: Bussard's reactor requires a complicated, strongly curved field, not just a very powerful one. Increase the power and put the magnets further away, and you get a more powerful field with the pretty shape spread over a larger volume - but it doesn't have the same tight curvature near the centre as it would with smaller magnets closer in. It would presumably be right for a bigger reactor.   

       The space for a water jacket would certainly be limited by the magnetic requirements - but it's true that this restriction might not prevent you having a useful jacket.   

       I don't think the Superconducting Supercollider tunnel is the right shape of torus for a fusion reactor - certainly not for any of the current ideas, which all have relatively small ratios of major:minor diameter. It's ideal for colliding beam fusion, but that's even less efficient as a power producing system than Farnsworth's fusor.
Cosh i Pi, Jun 24 2007

       [Cosh i Pi], that latest evidence comes from the Naval Research Laboratories. Do you think they don't know what they are doing? One thing that has kept those and other researchers interested is the observed fact of excess heat from their electrolysis cells. Even if fusion isn't the cause, and even if producing that heat hasn't been reliable, it is still a thing that has existed, and there must be SOME explanation for it.   

       I know of one possible explanation. Perhaps you are aware that the Original Cold Fusion Discovery occurred in the 1950s in liquid-hydrogen bubble tanks, involving "muon catalysis"? If you don't know that, look it up!   

       Well, palladium can absorb a LOT of hydrogren, and one way it might do so is if the hydrogen atoms break apart and give up their electrons into the "conduction band" of the metal. Note that electrolysis can help this, because dissociation of heavy water releases ATOMS, not molecules. Normally the atoms join to make molecules, and then bubble out of the electrolysis cell, but when palladium electrodes are involved, in this case the atoms have a chance to migrate into the palladium before that happens. It is my understanding that if the electrolytic cell is pressurized, the amount of deuterium that the palladium can absorb goes up by a decent percentage.   

       I think I recall reading somewhere that the excess heat starts getting produced when the number of deuteriums in the palladium is about 80% of the number of palladium atoms. So one reason the experiment has been unreliable is because it was difficult to do that, before they started pressurizing the cells.   

       Perhaps the excess heat is the atoms forming molecules inside the palladium. And perhaps the atoms have given up their electrons to the conduction band, and so bare nuclei are floating about inside the crystal lattice. Non-orbiting electrons can approach those nuclei quite closely. They may even be able to shield two nuclei from each other, allowing them to get close enough to fuse, just like happens in muon catalysis.   

       Next, I see you somewhat agreed with what I wrote about how much up-front expense you want to do, to make big magnets that you can get a water jacket between them and a hot-fusion reactor core. I do think, however, that if you can imagine a quite-large Bussard Fusor sphere, with correctly shaped magnetic fields, then you also can imagine a water jacket just inside the sphere. The net effect is, how much do you want to reduce the volume of the sphere, by adding the jacket?   

       The SuperConducting SuperCollider tunnel has the advantage that a torus in there is so gently curved that all of the original problems associated with high curvature disappear. Designs from the 1950s could be made to work!
Vernon, Jun 24 2007

       // latest evidence comes from the Naval Research Laboratories. Do you think they don't know what they are doing? // That's entirely possible. Military research has a tendency to follow many implausible leads, and individuals in the military are as liable to be mistaken, or to be fraudsters in some cases and gullible in others, as anybody else.   

       Think of all the airmen who claim to have seen UFOs, and how seriously they seem to be taken by some senior folks.   

       // it is still a thing that has existed, and there must be SOME explanation for it // Since others have tried and failed to reproduce the effect, there must be rather a lot of doubt about whether it really did exist.   

       // The net effect is, how much do you want to reduce the volume of the sphere, by adding the jacket? // No, that's not it at all. The question is whether the thing (which isn't remotely like a sphere, unlike Farnsworth's - it's a spiky shape with cusps all over) is actually still the right shape if you steal some of its outer surface for a water jacket. It seems likely that as long as you don't steal too much of it, then in the case of a large reactor, you might be able to steal a little. Steal too much, and you won't be able to make a reaction at all, apart from the question of how much extra power you use cooling these much bigger magnets - are you going to end up using all the power from the reactor just maintaining the magnetic field?   

       And no, the Superconducting Supercollider tunnel is NOT the right shape of torus: it's true that tight toruses have their own problems, but long thin toruses have different problems - mostly that the potential power output would be minuscule compared with the power required to maintain the magnets.
Cosh i Pi, Jun 25 2007

       [Cosh i Pi], regarding reproducibility, yes, SOME others failed to reproduce the original results. But other others did occasionally reproduce the results. It's obvious that the controversy exists because of that --but even without fudging data, how many opinionated scientists tend to get results that they EXPECT?. I'm well aware of the Coulomb barrier, that ordinary chemistry can't break through, to cause nuclear fusion, and which led many scientists to have strong opinions about the original announcement by Pons and Fleischmann.   

       Nevertheless, the NRL people are claiming that their recent results are highly reproducible, and have published in a fairly prominent journal.
http://www.springerlink.com/ content/75p4572645025112/
(I split the address in two parts due to a limitation here.)

       Regarding UFOs, it's well known that most are explainable by ordinary phenomena. Some are not explained, though, and likely some of THOSE are military secrets (the left hand trying to report on what the right hand is doing). Here's a joke: "Q: Why is a flying saucer not a UFO?" "A: Because it has been identified!" Since we don't know it all, yet, there remains room in Physics for ways to go faster than light or backward in time. Quantum Mechanics may yet have something to say about the structure of space-time, and what can be done to it. I don't rule out the possibility of an occasional alien or future visitor, therefore. If you choose to rule out even the possibility of such, what is your rationale?   

       Regarding Bussard's Fusor, remember he was working with a limited budget, and so had to work with a fairly minimal number of fields that could confine the ions. Six, I think, leading to a somewhat cubical device. But more-than-six coils were shown in at least one image of that Google video (eight more for the corners of the cube, I think it was), and so I wouldn't be surprised at all if a large Bussard Fusor ended up with as many facets as a soccer ball. Nearly spherical, that.   

       Next, you are forgetting economy-of-scale. This applies to refrigeration, much as it applies to other things. Also, remember that a water jacket will be a heat-absorber as well as a neutron shield. If you think that a hot fusion reactor MUST have its supercooled magnet coils right where they can aborb maximum heat from the reaction, I recommend you think again! Because that's about the most energy-wasting design imaginable, when the goal is to absorb heat to produce power.   

       Finally, the SCSC tunnel is big enough, I think, to hold a 3-meter-diameter minor-radius torus. Maybe 4 meters. I would not call that too small to hold a decent amount of plasma. It is small only in comparison to the major radius of the tunnel, but I'm pretty sure that is actually irrelevant to producing fusion power, EXCEPT with respect to how the low curvature of that major radius beneficially enhances plasma confinement. I'm aware that the thin-torus problem is a volume-to-surface-area problem, but the answer to that is the answer to this question: "Does this SEGMENT of the overall torus produce enough fusion to pay for cooling the magnets for the segment (and extra for sale)?" Whatever minor radius works to answer that, can work no matter how big the major radius is. If the SCSC tunnel is too small for that, OK, then obviously it needs to be bigger, heh. I'm sure I have the basic idea correct, even if I got a detail wrong. Also, the current use of a large-minor-radius in Tokamak devices is at least partly to compensate for the curvature problem of the major radius. The sheer volume of magnetic field compensates for the way its intensity diminishes from the inner wall to the outer wall of the torus. This means that when the curvature problem is eliminated, a smaller minor radius should be workable. Perhaps the SCSC tunnel is big enough, after all!
Vernon, Jun 26 2007

       electrolysis can be run at 80-94% and has been demonstrated successfully so 66% mentioned above is wrong
costellogroup, Jul 21 2007

       not only that, but hydrogen burns in oxygen at temperatures above anything most turbines can handle. maximum efficiency can be well over the current 50% available from hydrocarbon driven turbogenerators
costellogroup, Jul 21 2007

       // Now all we have to do is find out if that is true!- Vernon, Jul 31 2001 //   

       Have we yet, Vernon? It's been six years ...
neelandan, Jul 23 2007

       [neelandan], no, I've been busy doing other things. But a very recent annotation indicates that maybe this Idea isn't needed, anyway. Half-baked, it remains!
Vernon, Jul 24 2007

       [Now all we have to do is find out if that is true!]   

       Marked for tagline?
normzone, Jul 24 2007


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