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AC Electrolyser

Low cost Electrolysis if safety is not an issue
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I'm risking the fishbones, to get a real explanation of whats bad (or good) about this idea, and not just to be waved aside, with no explanation.

This idea is about a low cost Electrolysis machine, if safety is not an issue. Useful for sea or other remote manufacturing, or for low quantity Hydrogen creation, where safety is less of an issue.

Use AC with graphite or platinum electrodes. Hydrogen mixed with Oxygen will be produced by this low cost ($20 - $100) electrolysis box.

Should be clear so you can see the bubbles.

Lines showing 2/3 and complete values, can help show where the hydrogen (lighter so floats up) is.

Perhaps some kind of contraption can devide the oxygen from the hidrogen so they go into separate compartments. (This is halfbakery...)

pashute, Mar 29 2006

[link]






       Granite electrodes?
I imagine something like a collection of vertical cylinders, like the cylinder of a revolver, synced to the AC frequency.
coprocephalous, Mar 29 2006
  

       Heh - one of my childhood experiments. This is how I learned the difference between AC and DC.
Shz, Mar 30 2006
  

       Electrolysis with AC current really does not work well at all. You are much better off with a DC current even if you just rectify it from the AC. This is bad science.
jhomrighaus, Mar 30 2006
  

       //granite// Do you mean graphite? If you want the hydrogen and oxygen to be separated then it's probably simplest to rectify the AC. A full-wave bridge rectifier costs mere cents, or a few dollars for a high current version. However, if you don't mind mixed H2 and O2 then this would be cheap, as you say, because the device could be very simple. I recently electrolysed water in the inner part of a light globe using mains AC. Kind of fun, but pretty stupid and dangerous. Also, if you use mains voltage the process will not be efficient and the water will tend to boil. But if it's cheap and nasty you want, sure, do without a step-down transformer too. But it mightn't take long for the wasted electricity to cost more than the transformer.
spidermother, Mar 30 2006
  

       Erm... if I might point out that platinum is a) not low cost and b) a catalyst that can cause the spontaneous ignition of a stoichiometric mixture of hydrogen and oxygen at low temperature?   

       Also, due to Brownian motion, the hydrogen and oxygen produced will remain mixed rather than separating out.   

       What is the idea here? You seem to be suggesting electrolysing water to get hydrogen and oxygen, which is not new. What part of the idea makes it low cost?
david_scothern, Mar 30 2006
  

       Thank you all for the responses. (I do hate fishbones, but anyways...) So here goes:   

       * Yes I meant graphite. Correcting it.
* [Shz] What did you learn? I did not try it yet. First I'm checking what the power of Hydrogen is in small quantities, so that if it does burn, no harm will happen to me. In the meantime it seems for a small balloon (sandwich bag size) burning it is quite harmless, with very little energy in it. Will be happy if anybody can give me numbers. Anybody?
* [jhom] Why is it bad science? Did you try it? Do you have any numbers or explanations as to why this is not as good as DC? (When first invented, Edison was against AC: Said the electricity "would be going nowhere"...)
* [Spider] says its possible, but wastes electricity. I would like to understand why. Where is efficiency lost, (isnt AC to DC a bigger loss?) and why will the water 'tend to boil'? If its the high energy, or the electrodes being too close to each other, same problem would be with rectifier. * [David] says there's nothing new here.
If so why does everybody use DC. The innovation here is that I DONT care that the H/O are a mixture, as long as they are parted from the H2O mollecules, and also that I suppose it would be easy to continue separating the gases by mere weight (something I saw happen in a bottle where I used DC, mixing the H and O produced. The H bubbles go up in the water much faster, and it seems as if the Hydrogen bubbles shoot upwards thru a cloud of Oxygen.
* The amount of platinum needed here is very small, and if still expensive, I'll use graphite as mentioned above. Works pretty well, and only one is needed. The Hydrogen electrode can be copper, and from my experience nothing will happen to it,if the Oxygen electrode is not made of copper/aluminum/etc.
* I never heard of spontaneous ignition of Hydrogen and Oxygen. As far as I know, there is a need for a spark. There are other molecules and elements that DO combine with Hydrogen or Oxygen in an Exothermic reaction and even spontaneously ignite, in which case platinum may act as a catalyst. But these are not present in my contraption. Only a perfectly stoichiometric mixture of 2xH2 and O2 and H2O with trace amounts of minerals, not enough to cause a fire. At least not in the 1000 times I did it, with DC.
pashute, Mar 31 2006
  

       Ill take a crack at this.   

       disclaimer) I do not purport to be an expert on this topic but as a Degreed Chemist with an extensive bacground in analytical chemistry I am hopefully not totally misrepresenting the facts as I understand them. I also welcome any critisisms or corrections.   

       >>>>* [jhom] Why is it bad science? Did you try it? Do you have any numbers or explanations as to why this is not as good as DC? (When first invented, Edison was against AC: Said the electricity "would be going nowhere"...)<<<<   

       A brief Sideline on Edison here. The risks/ benefits of AC -vs- DC are not as significant as many might think. Its alot like the old VHS -vs- Beta war or Apple=vs-IBM. Beta was the better system but VHS saturated the market. In the case of DC it came down to ease of transmission and flexibility. that won the day. Modern advances have removed many of the shortcomings of DC power. IT should also be noted that DC powers all Automobile and most Electronic systems.   

       Though you would generate H2 and O2 using AC Current you have made assumptions about the nature of materials that are incorrect. First Using normal current for this purposes is a quick way to blow things up as the unrestricted flow of current will also generate EXTREME heat as well as overload of any Circuit it is connected to.   

       Second the efficiency of H and O formation in an AC cell is much less than in a DC cell as a suffcient electrolytic potential must build up before Electrolysis will Occur. With AC power this potential is built up and destroyed over and over so at a minimum the "time" available to electrolysis to occur is significantly less than in a constant DC Circuit, so less gas will be produced when compared to a similar voltage and current from a DC source.   

       Third with the flip flopping potentials both H and O will form at each electrode at effectivly the same time(from our prospective) This will have two effects, some recombination of O and H will occur and the resulting mixture of gas is HIGHLY explosive(as it very neatly fills 2 sides of the Fire Triangle, all you need is heat to get things going. combined with a closed vessel and youve got a neat little bomb)   

       I think you really need to do a little research on what you are talking about here as you are making VERY elementary observations on the nature of electricity, Physics and Chemistry.   

       >>>>* [Spider] says its possible, but wastes electricity. I would like to understand why. Where is efficiency lost, (isnt AC to DC a bigger loss?) and why will the water 'tend to boil'? If its the high energy, or the electrodes being too close to each other, same problem would be with rectifier. *<<<<<   

       See notes above also rectifier would be less efficient than say direct driving of a generator but the losses from rectification of the current are still less of a loss than the inherent inefficieny discussed above.   

       >>>>>[David] says there's nothing new here. If so why does everybody use DC. <<<<<<   

       Because DC is the simplest way to do it and has the additional benefit of being pretty darn efficient and Safe. It simply does a much better job.   

       >>>>>The innovation here is that I DONT care that the H/O are a mixture, as long as they are parted from the H2O mollecules, and also that I suppose it would be easy to continue separating the gases by mere weight (something I saw happen in a bottle where I used DC, mixing the H and O produced. The H bubbles go up in the water much faster, and it seems as if the Hydrogen bubbles shoot upwards thru a cloud of Oxygen.<<<<<   

       You have just massacred a half a dozen laws of physics with this set of assumptions. Gases do not behave in this way as a general rule, and in particular these two gases do not. They are both colorless gases that mix readily so you cannot seperate them using gravity, or magnetism or other physical processes(investigate Brownian Motion, behavior of Gases and stoiciomeric(sp) equations)This also means you cannot see them bubbling through one another either. I dont know what you think you saw going on but it was not H2 bubbling through a cloud of oxygen. It just doesnt work that way.   

       >>>>>>* The amount of platinum needed here is very small, and if still expensive,<<<<<<   

       Platinum is VERY, VERY, VERY expensive and in a Purified form as would be required here you would probably be paying Hundreds of dollars(say 400 to 600)Plus you would probably be losing some of it to Erosion through time. Graphite is better choice.   

       >>>>>> I'll use graphite as mentioned above. Works pretty well, and only one is needed. The Hydrogen electrode can be copper, and from my experience nothing will happen to it,if the Oxygen electrode is not made of copper/aluminum/etc.<<<<<   

       The materials used in AC circuits cannot generally be different from one another as they will be "switching places" many time a second so both the same is all that will really work.   

       >>>>>>>* I never heard of spontaneous ignition of Hydrogen and Oxygen. As far as I know, there is a need for a spark. There are other molecules and elements that DO combine with Hydrogen or Oxygen in an Exothermic reaction and even spontaneously ignite, in which case platinum may act as a catalyst. But these are not present in my contraption. Only a perfectly stoichiometric mixture of 2xH2 and O2 and H2O with trace amounts of minerals, not enough to cause a fire. At least not in the 1000 times I did it, with DC.<<<<<   

       Just becuase you got lucky when producing a few ml of watervapor , Hydrogen and Oxygen does not mean that what you did was safe or good practice. Hydrogen is an Excellent Fuel, Oxygen is THE perfect Oxidizer(wonder where this word came from, hmmm) and all you need as 1 teeny tiny little itty bitty spark and we will have to start calling you stumpy.   

       Please spend an hour on the internet researching this question and I think you will better understand.
jhomrighaus, Mar 31 2006
  

       //[Shz] What did you learn?//   

       I learned that I could oxidize just about any metal I used as an electrode almost instantly, and that the heavier the atomic weight of the metal, the slower it oxidized. I ended up using gold which worked for long enough to see some real results – those being rapid boiling of the water and a rather hefty explosion. The boiling made sense, given the heat, but why would pure oxygen and/or pure hydrogen explode?   

       Answer: They were not separated. AC works differently than DC. Oops. I was 8 years old and trying to build a car that ran on water. Silly concept.
Shz, Mar 31 2006
  

       Just a quick note on Boiling of Water. Many types of Lab equipment that use steam for distilation utilize very carefully calibrated AC Steam Generators. These systems use two SS electrodes that are about 1/4 inch apart and can generate steam in about a minute. These systems do not produce any significant amount of Hydrogen or Oxygen compared to the amount of Steam produced. Also over time the Electrodes are consumed and need to be replaced.
jhomrighaus, Mar 31 2006
  

       Fortunately, I didn’t get that far because I couldn’t make electrolysis work fast enough, which is why I was playing with wall current in the first place.   

       //borrowed// Choice word. They didn’t appreciate that much. Hence my next quest: making gold.
Shz, Mar 31 2006
  

       To clarify what I said earlier: Platinum is a catalyst (if you doubt this, it makes up part of the catalytic converter in a car; I think the rest is rhodium which costs less) which lowers the energy required to initiate a reaction between hydrogen and oxygen. It lowers it to such an extent that an explosion can occur at room temperature rather than at the high temperatures that a spark causes.
david_scothern, Mar 31 2006
  

       Platinum black (very finely divided platinum) acts as a catalyst, and will cause a mixture of a flammable gas and air to ignite. Some old gas stoves use a little coil of platinum wire coated in platinum black to ignite the flame. Ordinary platinum won't ignite a gas in this way.   

       [Pashute] I was referring to the high voltage of mains electricity (usually about 120V or 240V depending on country) as wasteful. Elecrolysis of water begins at about 1.4V, but because it is endothermic (takes in heat) the reaction will barely proceed at this voltage unless external heat is supplied. At about 1.7V this heat is supplied by the extra voltage, so the reaction will be faster and doesn't need external heat. If the voltage is higher than this, energy will be wasted as heat (a small increase in voltage is desirable to increase the rate though). So at 120V, only 1.4V/120V = .0117 of the energy will be used to make hydrogen and the remaining .988 will be wasted as heat, hence the boiling of the water.
spidermother, Apr 01 2006
  

       This idea has been talked about, i've seen better articles on this subject, and this entire subject is bad. Hydrogen is not something you can just create from water. It is a a complicated, time consuming, energy wasting process (unless it is done with solar power). It has also been done, and things like this have been made, so this is just copying what is there already. You might not have known this, but please just delete this article. And, as I've said before, no machine is 100% efficient. There will always be energy lost to friction, the air, whatever. You simply cannot get more energy out of a substance than it takes to manufacture the substance. Furthermore, i suggest everyone on this site go out and read about the laws of thermodynamics so us people that do know about them don't constantly have to tell others that some things just aren't possible.
craziness, Apr 01 2006
  

       Thanks for the remarks! I was proved wrong in almost all my assumptions, albeit non-trivial ones, including a fascinating anno from [Shz] who tried it at age 8. If you still think the idea and its refute are trivial please tell me, and I WILL delete this idea.   

       I was not suggesting getting energy for free. I was merely wondering about an easy way to get H and O using Mains electricity. My assumptions, not far-fetched, where:
(1) That voltage is in direct relation to power and rate of hydrolysis, [spider:1.7v at most]
(2) That the gases can be separated in some way while leaving the upper level of water, a bit before, or afterwards,
[I saw the bubbles in the water of course! not in the gas mixture, where they were definitely going faster. Still may be ways to separate H and O mixture, eg sending thru water again... ]
(3) That explosion of the mixture will occure only with a spark,
[jhom: still dangerous because the smallest spark makes large explosion... shz: experienced explosion from heat of Mains... david scoth:platinum can catalyze explosion in room temp. (see link)]
(4) That by using a large enough tank, I could prevent heat, [shz experience proves I'm wrong, david c explaines it] and (5) that I would need a very small amount of platinum (somehow in my last post forgot the two-sidedness of AC, but still claimed a trace amount would be needed to coat the copper). [Not important to discuss with all other assumptions negated]
pashute, Apr 02 2006
  

       And I still cant find anywhere what the amount of power for burning (or rather exploding) 1 litre of H/O mixture at 1 atm is.
pashute, Apr 02 2006
  

       //shz: experienced explosion from heat of Mains//   

       Actually, I attributed the boiling to heat. I can't say if there was also a spark or not, but it's possible given the less-than-ideal wiring job.
Shz, Apr 02 2006
  

       You can certainly do electrolysis and mix H2 and O2 gas. (the mixtrue is commonly called "Brown's gas")The next question is, what are you going to do with it? You can't compress it safely for storage.   

       It's not that hard to design an electrolyzer that automatically separates gases - all commercial ones do.   

       Now why AC... some have tried this to "shake" bubbles off the electrodes for higher efficiency, but the AC current destroys electrodes very quickly. Better to do proper cell design or higher pressure operation to reduce bubble size.   

       Finally, AC to DC power conversion losses can be on the order of 5% with large scale dedicated rectifiers.
strange606, Jul 14 2006
  

       Geesh, got responses from all types here huh.   

       1st off, electrolysis is of course useful for aiding in gasoline combustion. The key around most issues is to use it as you make it, and quickly.   

       2nd, several precious metals act as good catalytic electrodes without deterioration - how else could electrolysis manufacturers offer sealed solutions with 5 year warranties - aquatune.com   

       3rd, in recent years using pulses to drive the electrolysis has shown exponentially better results than DC or AC current. In fact there is a 4 conductor current called "Sully" with information available at sullydc.com. This is kind of like 3 phase AC current with a ground from what I understand. In the water however the voltage appears like DC current, since there is pressure acting on the water constantly.   

       4th, brown's gas is not the only hydrogen/oxygen that you can make with electrolysis - if you use ferrous (iron) material for the electrodes you are making brown's gas. Ferrous electrodes give you more parahydrogen and precious metal electrodes give you more orthohydrogen. There are other delineators for hydrogen too, but note on this link that the ortho to para hydrogen conversion material includes ferrous materials - http://www.cchem.com/opcat/ - I like the pretty pictures   

       5th, orthohydrogen is more volatile/unstable and likely to recombine or combust with oxygen to form water. If left together in storage for fractions of a second the components will begin recombining and release a static charge on the container (usually without exploding) This is how a fuel cell works using platinum and allowing the atoms to recombine to h20 -- no explosions -- orthohydrogen is better for combustion needs than parahydrogen or "brown's gas" (gagging on that term) because it generates a bigger boom - parahydrogen resembles an IMplosion   

       6th, people need to stop arguing about thermodynamics being the end of electrolysis because hydrogen and oxygen gasses when introduced into gasoline combustion are primarily aiding in vaporization and combustion of the gasoline - and you're not going to convince me that my vehicles aren't getting 60% better mpg than before I installed aquatune units on them. People that do so are very suspect in my eyes of working for an oil company.   

       Kudos on putting some ideas out there, but check out the products already on the market:) Here's my site with more background - tnhybrid.com
jdunagan, Jul 23 2006
  

       jdunagan   

       we generaly dont look to kindly to advertising pitches here on the half bakery. This is a discussion forum for halfbaked ideas. There are numerous other sites where advertising is welcome.
jhomrighaus, Jul 24 2006
  

       /...of working for an oil company./ Have a look round the site; it must look like an oil company's pages. I assure you, the world is not divided into those who believe in strange mileage extenders and those who work for oil companies.
david_scothern, Jul 24 2006
  
      
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