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deltaH
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Hydrogen from [bio]glycerine by electrolysis for fuel cells
This is another backyard open innovation project of mine, this time in sustainable energy.
As most you already know, one of the big challenges of working with/within a hydrogen economy and specifically running electric cars on hydrogen fuel
cells, is how to store and transport the hydrogen.
My idea is for the onboard electrolysis of glycerine as it can be derived from renewable sources, for example, as a low cost byproduct of the
biodiesel industry.
The straight forward reaction would be:
C3H8O3 + 3H2O + electricity => 3CO2 + 7H2
The hydrogen being generated at the cathode nice and pure.
BUT my idea takes this a step further... running the electrolysis like this would take a lot of energy because of the water on the left hand side of
the equation, it's dGf is too low.
You want a more energetic source of oxygen that is also reactive and ideally can also contribute some hydrogen. I propose hydrogen peroxide as an
excellent candidate since it is a 'green oxidant', so your new electrolysis becomes:
C3H8O3 + H2O2 + H2O + electricity => 3CO2 + 6H2
In fact you can create a new liquid fuel by preparing a solution of glycerine and the 'green oxidant' hydrogen peroxide. I think with the proper
understanding and precautions, this is safe enough. I call such a mixture 'syrup of hydrogen' for fun 
This equation would be the low temperature equivalent of what occurs with the high temperature steam reforming of hydrocarbons. In that case you would
add a little oxygen to make the thermodynamics of the reaction more favorable.
You can read more about this on the open innovation site:
http://ideashack.org/category/energy/biofuel-hydrogen/
[Edited on 2-10-2013 by deltaH]
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papaya
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Quote: Originally posted by deltaH  |
As most you already know, one of the big challenges of working with/within a hydrogen economy and specifically running electric cars on hydrogen fuel
cells, is how to store and transport the hydrogen.
[Edited on 2-10-2013 by deltaH] |
I've seen hydrogen tanks (looks like other gas tanks from appearance) myself which are used in undustry, so what is the problem?
Also why electrolyze glycerol instead of water?
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deltaH
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Hi Papaya
| Quote: | I've seen hydrogen tanks (looks like other gas tanks from appearance) myself which are used in undustry, so what is the problem?
Also why electrolyze glycerol instead of water? |
The problem as I explained here is that while hydrogen has a very high heat of combustion on a mass basis, it has a very poor heat of combustion on a volume basis... this is
just another way of saying that compared to hydrocarbons, for example, it's a poor fuel because you need larger tanks to get the same job done... MUCH
MUCH larger tanks.
In fact, even liquid hydrogen is an inferior fuel on a volume basis compared to hydrocarbons! (see above link) The only reason it's used in rockets
for example is because there being light is of paramount importance to specific impulse!
In fact, as fuels go, one is hard pressed to beat hydrocarbons on energy density arguments alone, BUT the problem is that they are [generally] fossil
fuel derived and thus generally not sustainable.
Also, hydrocarbons, as chemists know, are pretty inert at low temperature, so it's very hard to access their hydrogen content under mild conditions.
As for water electrolysis, this can't be used for on board hydrogen generation say in a car, because you have only the electricity being produced by
the fuel cell available and that reacts hydrogen with oxygen to make water so what you would be proposing is a perpetual motion type system (not that
I suggest this would be what you were thinking).
The difference with using a fuel instead of water is that now you can split off the hydrogen with much much less energy, so overall the system runs
fine using that hydrogen to make water.
Some fuels like anhydrous ammonia stored in a tank as a liquid can also be electrolysed to produce a lot of hydrogen, BUT they in turn need a lot of
electricity to do so, so it's not as good if you consider the entire system, however attractive on carbon arguments as your system would only be
forming nitrogen and water vapours out of the exhaust... no CO2.
Glycerine with H2O2 and H2O is a compromise between chemical reactivity (how easy it is in terms of chemical kinetics to get access to the hydrogen at
low temperature) and hydrogen generation capacity, while also being a sustainable fuel.
Hope that answers your questions?
[Edited on 2-10-2013 by deltaH]
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kmno4
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| Quote: Originally posted by deltaH |
As most you already know, one of the big challenges of working with/within a hydrogen economy and specifically running electric cars on hydrogen fuel
cells, is how to store and transport the hydrogen.
My idea is for the onboard electrolysis of glycerine as it can be derived from renewable sources, for example, as a low cost byproduct of the
biodiesel industry.
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This is the most stupid idea I have read/heard recently.
No comment.
Слава Україні !
Героям слава !
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deltaH
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Hi kmno4
| Quote: | This is the most stupid idea I have read/heard recently.
No comment. |
Care to share why?
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papaya
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Yes, thanks, but it worth to invest time in the development of new fuel cells that could use glycerol/whatever directly, as the cycle you proposed
uses only H2 -H2O energy and C is just lost to CO2 during electrolysis (if I understand correctly), must be it's inferior to internal combustion
engines fueled with the same glycerol (not an expert here).
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deltaH
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| Quote: | | Yes, thanks, but it worth to invest time in the development of new fuel cells that could use glycerol/whatever directly, as the cycle you proposed
uses only H2 -H2O energy and C is just lost to CO2 during electrolysis (if I understand correctly), must be it's inferior to internal combustion
engines fueled with the same glycerol (not an expert here). |
Direct fuel cells may indeed someday offer better solutions if we can get them to perform better (currently they don't work nearly as well as hydrogen
fuel cells).
On your second point, in theory a fuel cell should be able to operate at greater efficiency because of the lower temperature (if properly
designed/functioning) on thermodynamic arguments alone. But at lower temperature comes chemical kinetic problems, hence the need to switch over to
functionalised molecules. I am simply borrowing from nature here. Nature meets it's quick energy needs by using sugars. Sugars molecules are mostly a
polyol, so hence I use the simplest cheapest liquid equivalent... glycerine (and some hydrogen peroxide as additional oxygen and hydrogen source).
It's a trade off / balance between reactivity and energy capacity and I think this beats many other technologies currently being considered.
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Traveller
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If you have enough onboard electricity to produce hydrogen through electrolysis, wouldn't it be somewhat (Canadian understatement for A WHOLE FRIGGIN'
LOT!) more efficient to eliminate the electrolysis and apply the electrical current directly to the electrical motor that drives the wheels?
Or do you have some kind of brain wave like mounting a windmill atop the car to capture energy from the wind generated by driving down the road?
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Metacelsus
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Yes, just using an electric motor would be much more sensible.
Assuming there is already a strong wind, mounting a windmill on top of a car is not a crazy idea, but using it when there is no pre-existing wind is
(except maybe for regenerative braking?).
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DeadHead
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Even then an electric engine that would brake the car and run as a generator while applying brakes would be much more efficient than a windmill I
would think.
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Nicodem
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| Quote: Originally posted by deltaH | Hi kmno4
| Quote: | This is the most stupid idea I have read/heard recently.
No comment. |
Care to share why? |
I don't know, if the question was serious or not, but this must be one of the most entertaining posts on the forum. Nevertheless, facepalm threads
like this one make the life of a moderator difficult: To detritus or not to detritus, that is the question.
http://www.youtube.com/watch?feature=player_embedded&v=v...
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deltaH
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Hi Traveler,
| Quote: | If you have enough onboard electricity to produce hydrogen through electrolysis, wouldn't it be somewhat (Canadian understatement for A WHOLE FRIGGIN'
LOT!) more efficient to eliminate the electrolysis and apply the electrical current directly to the electrical motor that drives the wheels?
Or do you have some kind of brain wave like mounting a windmill atop the car to capture energy from the wind generated by driving down the road?
|
I think when one hears the word electrolysis, we automatically think super energy drain, because we are all used to water electrolysis and that is
about as energy intensive a process one may get. BUT that's because at the anode, during water electrolysis, you have to oxidise
water to free oxygen. NOW put something there that wants to be oxidised, like a good fuel... like glycerine in this
case, now THAT half reaction becomes considerably easier. Add a little peroxide there as well and you 'fix' the dG of reaction and can get it pretty
close to zero.
So now the energy requirement to run the electrolysis is only a fraction of what the fuel cells puts out from the hydrogen that is generated by this.
Draw a big black box over the entire system and what you have is a car taking in a liquid fuel (glycerine+peroxide) and air and putting out water
vapour and CO2. There's nothing fishy here, you have just broken an internal step into two because each one is easier to optimise and get working well
with existing tech.
The reason we do this as opposed to a direct fuel cell running on this fuel is because alcohol based fuel cells don't as yet work very well. So we
break the system into two internal halves that do work very well, a hydrogen fuel cell which works great and organic electrolysis on a reactive fuel
system which should also work pretty great to generate the hydrogen at minimal energy cost (compared to what the fuel cells can put out).
One might ask, why do electrolysis and not a direct reaction? After all, this is the low temperature equivalent of steam reforming?
In principle, yes, there might be a catalyst that will work nicely for this reaction, but I like electrolysis better because it's simpler, robust and
generates a pure hydrogen stream, i.e. I don't need to separate it out from a mixture of CO2 (or if in a reactor, likely small amounts of CO as well).
If I told you, build this at home, you are probably going to choose to do it by electrolysis rather than a complex reactor- separation beast no? I
certainly also think an electrolysis system will be cheaper and easier to control.
I hope that shed's some light on the matter.
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deltaH
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Hi again Nicodem,
| Quote: | | To detritus or not to detritus, that is the question. |
If you believe my idea is flawed, kindly prove it by logical argument on the forum.
[Edited on 2-10-2013 by deltaH]
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Traveller
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| Quote: Originally posted by Cheddite Cheese | Yes, just using an electric motor would be much more sensible.
Assuming there is already a strong wind, mounting a windmill on top of a car is not a crazy idea, but using it when there is no pre-existing wind is
(except maybe for regenerative braking?). |
Uh, I was joking?? Don't you think a windmill mounted atop a car would sacrifice ten times more energy in DRAG than it could ever produce in
electricity?
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Traveller
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| Quote: Originally posted by deltaH | Hi Traveler,
| Quote: | If you have enough onboard electricity to produce hydrogen through electrolysis, wouldn't it be somewhat (Canadian understatement for A WHOLE FRIGGIN'
LOT!) more efficient to eliminate the electrolysis and apply the electrical current directly to the electrical motor that drives the wheels?
Or do you have some kind of brain wave like mounting a windmill atop the car to capture energy from the wind generated by driving down the road?
|
I think when one hears the word electrolysis, we automatically think super energy drain, because we are all used to water electrolysis and that is
about as energy intensive a process one may get. BUT that's because at the anode, during water electrolysis, you have to oxidise
water to free oxygen. NOW put something there that wants to be oxidised, like a good fuel... like glycerine in this
case, now THAT half reaction becomes considerably easier. Add a little peroxide there as well and you 'fix' the dG of reaction and can get it pretty
close to zero.
So now the energy requirement to run the electrolysis is only a fraction of what the fuel cells puts out from the hydrogen that is generated by this.
Draw a big black box over the entire system and what you have is a car taking in a liquid fuel (glycerine+peroxide) and air and putting out water
vapour and CO2. There's nothing fishy here, you have just broken an internal step into two because each one is easier to optimise and get working well
with existing tech.
The reason we do this as opposed to a direct fuel cell running on this fuel is because alcohol based fuel cells don't as yet work very well. So we
break the system into two internal halves that do work very well, a hydrogen fuel cell which works great and organic electrolysis on a reactive fuel
system which should also work pretty great to generate the hydrogen at minimal energy cost (compared to what the fuel cells can put out).
One might ask, why do electrolysis and not a direct reaction? After all, this is the low temperature equivalent of steam reforming?
In principle, yes, there might be a catalyst that will work nicely for this reaction, but I like electrolysis better because it's simpler, robust and
generates a pure hydrogen stream, i.e. I don't need to separate it out from a mixture of CO2 (or if in a reactor, likely small amounts of CO as well).
If I told you, build this at home, you are probably going to choose to do it by electrolysis rather than a complex reactor- separation beast no? I
certainly also think an electrolysis system will be cheaper and easier to control.
I hope that shed's some light on the matter.
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If you think you have a way to break a liquid fuel down to recover hydrogen, for your fuel cell, that will take only a fraction of the energy to make
hydrogen out of the total energy available from that hydrogen, I suggest you get to the patent office post haste.
And then find a good place to hide. You will have solved the world's energy problems but, the big oil companies will have someone shoot you.
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deltaH
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| Quote: | If you think you have a way to break a liquid fuel down to recover hydrogen, for your fuel cell, that will take only a fraction of the energy to make
hydrogen out of the total energy available from that hydrogen, I suggest you get to the patent office post haste.
And then find a good place to hide. You will have solved the world's energy problems but, the big oil companies will have someone shoot you.
|
Guys, breaking fuel down to make hydrogen is done routinely in the chemical industry, this is called steam reforming. You can also
make hydrogen from coal and water, this is called gasification. There's no voodoo here.
The only difference is finding a way to act on more reactive fuels so that you can do this at lower temperatures as opposed to what is required to do
this with hydrocarbons or coal.
As for patenting, I have purposefully decided to release this tech into the public domain so it's free for all. My reasons for this are complex and I
don't really want to go into that.
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papaya
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OK, how you render glycerol conductive ?
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deltaH
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Okay maybe we're jumping the gun here, lets take a big step back and consider a simpler example to get the principle across.
Consider formic acid, from wikipedia's table of standard electrode potentials, one can pull the following half reactions:
CO2(g) + 2 H+ + 2 e- <=> HCOOH(aq) E(std.) = −0.11V
and
2 H+ + 2 e− <=> H2(g) E(std.) = 0V
So for the overall reaction:
HCOOH(aq) => CO2(g) + H2(g) the dE = +0.11V
This is pretty close to 0V.
Now if you electrolyse formic acid, you can make quiet a lot of hydrogen pretty easily because that dE is close to zero. In reality, you have quite a
overpotential if you don't use a suitable electrocatalytic anode (platinum black anode would probably work well but who has that lying around?
In reality, formic acid is not that great a fuel because you can only generate 4.4% hydrogen by mass and it's also freaking corrosive and smelly, so
you don't want to be tanking that.
Glycerine with a the added peroxide has about 8% the hydrogen generating potential by mass. This is excellent as such systems go. Why so much higher?
Because glycerine is more reduced than formic acid... you get more hydrogen capacity because of that, but you loose some reactivity (it's harder to
free those hydrogen with glycerine) hence the need for the peroxide.
BTW make hydrogen from formic acid IS one of the technologies being HEAVILY studied for make hydrogen to power fuel cells, but I don't like it as much
as mine, for one, because it's capacity is much lower and also because it's corrosive and extremely acrid!
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watson.fawkes
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He's got no obligation
to do that. Posting crappy information and expecting others to correct it is one of the oldest methods of trolling on the internet. It comes from an
expectation that others will educate you. For example: "I've got perpetual motion! Prove me wrong!"
I've already stopped responding to you for this reason. I've got no time for someone who, when steered in the right direction, doesn't go off and do
some work before asking another question.
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deltaH
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| Quote: | | OK, how you render glycerol conductive ? |
I take it you mean ion conductive? The medium I'm proposing to carry out the electrolysis in is fairly concentrated sulfuric acid, probably starting
around 70% or so (remainder being water). This solution would sit between the electrodes. One would then feed the glycerine/peroxide fuel slowly
(dropwise) to this solution, probably in a stirred pot before it.
You would need to control the rate of adding the fuel to the rate at which gas is being evolved, but I would think this can be done by monitoring the
solutions conductivity. When it goes down too much, slow down the feed of fuel.
Anyhow, a 70% H2SO4 solution comprises mostly of HSO4- and H3O+, thus it's darn ionically conductive.
When the fuel hits it, the glycerine would probably be converted to glyceryl sulfuric acid ester anions (migrating to the anode) and the peroxide
would quickly form persulfuric acid anions also being drawn to the anode. There both would participate in a series of oxidation steps, ultimately
yielding CO2. The H+ generated migrates to the cathode and is reduced to H2(g)
[Edited on 2-10-2013 by deltaH]
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blogfast25
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| Quote: Originally posted by deltaH | So now the energy requirement to run the electrolysis is only a fraction of what the fuel cells puts out from the hydrogen that is generated by this.
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That smacks decidedly of creation ex nihilo of energy. And thus impossible.
The information (if it proves to be worthy of that term) you're putting out here is decidedly bitty. You're going to have to do a lot better that this
to get any serious attention.
Have you even remotely tried to electrolyse glycerol based conductive solutions, to see what you get? Add any magic powder you fancy, then get back us
with your results.
[Edited on 2-10-2013 by blogfast25]
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elementcollector1
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| Quote: Originally posted by deltaH | | Quote: | | OK, how you render glycerol conductive ? |
I take it you mean ion conductive? The medium I'm proposing to carry out the electrolysis in is fairly concentrated sulfuric acid, probably starting
around 70% or so (remainder being water). This solution would sit between the electrodes. One would then feed the glycerine/peroxide fuel slowly
(dropwise) to this solution, probably in a stirred pot before it.
[Edited on 2-10-2013 by deltaH] |
I see a major problem here.
If you use a 70% solution of H2SO4 with the balance being water, it's very true that the solution will now be very conductive.
But now, the electrode potential will be much higher because - you guessed it! You are now electrolyzing sulfuric acid and water. So, any glycerine
added will be both an insignificant source of hydrogen and an insignificant reactant to this mixture at the concentrations you're proposing.
You might want to read this - it might clear some things up. http://pubs.acs.org/doi/abs/10.1021/ie9016418
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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bfesser
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| Quote: Originally posted by Nicodem | | Nevertheless, facepalm threads like this one make the life of a moderator difficult: To detritus or not to detritus, that is the question.
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Here, let me help you with that. [closed]
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Endimion17
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cut-off
damn it, bfesser, I wrote a cold, rational smackdown of that water fueled car and you close the thread right in front my nose. 
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bfesser
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Post it here and I'll split/merge it.
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