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Old 02-11-2012, 01:59 PM   #131 (permalink)
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Originally Posted by IamIan View Post
It isn't quiet that bad ... especially from a 'energy I pay for' perspective.

From a Energy balance point of view to break even ... I think the current technological lower limit would be around ~138% efficient electrolysis ... and ~276% from what I've seen in things automotive size...
I think we may be defining "the device" differently. I am referring only to the electrolysis unit itself, which has an electrical input, and and output of H2 (and O2) that represents some fraction of the electrical input energy. (There are "real" H2/O2 combined gas electrolysis units used for jewelry welding: WAXCO-Oxyhiydro blowtorches . These produce 4 liters per minute with a .95 kw input. The H2 content is 66% of this.) Only the H2 has any fuel value. If you do the math, you find that even these professional units are not especially efficient, producing 1 liter per minute (the standard HHO promoter claim) from about 250 watts (not the 140 watts that is the standard HHO promoters claim.)

The requirement for 500% efficiency from the electrolyser device itself comes from the efficiency with which an engine and alternator produce electricity. The 20% I usually use for the sake of argument is actually high, because engines do not really operate at 25% efficiency, and alternators don't operate at over 75% efficiency. Realistically, engines in non-hybrid cars operate at more like 22%, and alternators are more like 65-70% -- we'll say 67%. So the efficiency from fuel to electricity is 15%. To just get to break even the electrolyser would have to operate at 666% efficiency.

The NASA study often referenced has nothing at all to do with HHO -- the injection amounts are far far higher, and the mixtures are far leaner, but most importantly the H2 comes from a tank.

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Old 02-11-2012, 02:13 PM   #132 (permalink)
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A Delco paper about 10 years old says typical alternator efficiency is 55%.
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Old 02-11-2012, 03:28 PM   #133 (permalink)
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Car alts aren't very efficient.
They have to spin so fast all the air drag kills efficiency.
At lower speeds running near full load for that speed they are most efficient.

H2 is a fuel just like propane or natural gas. But unlike propane, gasoline, diesel, alcohol or natural gas, hydrogen isn't a very good motor fuel.
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Old 02-11-2012, 04:59 PM   #134 (permalink)
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Originally Posted by IsaacMTSU View Post
...you could power a hydrogen car by hydrogen that you produce through electrolysis. Driving it while making it would be impossible and you would spend more on producing the fuel than would be practical.
^^ Everyone is arguing against me on this...?

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Was thermodynamics not part of your curriculum?
I know thermodynamics, that's why I said "driving it while making it would be impossible". You don't have to be so condescending, we're all on the same team here.
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Old 02-11-2012, 09:44 PM   #135 (permalink)
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Quote:
Originally Posted by Ken Fry View Post
I think we may be defining "the device" differently. I am referring only to the electrolysis unit itself, which has an electrical input, and and output of H2 (and O2) that represents some fraction of the electrical input energy.
We are thinking of similar things... just a hair different details... mainly along the limits of what current science would allow ... and the best current tech available... vs I think you were thinking of more average real world devices.

- - - - -
Bellow is the line of thinking I had for the 'ideal' case that doesn't violate science ... and how that relates to currently best case technology ... If you don't care to know the line of thinking I had in that context ... just skip the rest.
- - - - -

2(H2O) to 2H2+O2 is a reversible chemical reaction that can be driven by heat or electrical energy ... and like many other such reversible reactions there are conditions under which one direction is exothermic and there are conditions under which one direction is endothermic ... just like the reversible electrochemical reaction in many batteries ... like in batteries the endothermic reaction even when it does apply may not dominate the reaction if other reaction effects are larger... such as the heat generated from internal resistance.

If I recall correctly the maximum CoP ( Coefficient of Performance ) under ideal conditions of a 2(H2O) to 2H2+O2 to 2(H2O) as a crude heat pump is ~1.21 ... even if like other ideal case situations we will never actually see this level in the real world ... and it is still a far cry from the other modern Heat Pumps that in the real world can operate at up to ~5.8 CoP.

So under the most ideal conditions every 1 wh of electrical energy input results in 1.21 wh of energy for the ICE heat engine ... the other 0.21wh are exothermically absorbed from ambient heat sources that are 'free' to the operator ... although for these 'ideal' conditions we are momentarily ignoring things like the source of that ambient heat energy... which do come up in real world applications.

The most efficient combustion to electrical energy conversion I know of is just over 60% Efficient ... Co-Generation facilities can achieve higher % efficiency but the addition % of efficiency is not in the form of electrical energy it is in a useful application of the waste heat... but even Co-Generation Facilities as far as I know max out at about ~90% efficient.

So looking at the upper limit of max ideal case
60%*1.21= ~73% per cycle ... which means the electrolysis part would have to make up the difference or be ~138% efficient in order to break even ...even under ideal conditions... so like an ideal battery and and ideal engine he can't get to ideal but even ideal would need over 100% efficiency... which doesn't work... and the 60% efficient part AFAIK are currently city block sized facilities not automotive size.

While a lot of average ICE's average out much lower there are automotive sized systems that can produce ~30% of the fuel energy converted to electrical energy ... some even a bit more than this ... so at present 30%*1.21 Yields the Electrolysis part that would have to be ~275% efficient ... also still not going to happen.

Given the 1.21 heat pump effect ... that is where I got the maximum even under ideal conditions of the Chemical to Electrical back to Chemical cycle would have to be ~83% Efficient ... which won't happen with all those steps.

Although thinking about it now ... Sense H2O can be split with both Electrical and Heat Energy ... a Co-generation might actually be at least technically possible ... which could lower some of the ideal case conditions I figured the 1st time ... still not going to happen... Even if all 100% of a modern ~90% Efficient Co-Generation Facility could be used ... and it won't be due to the heat level differences ... This UBER ideal case would still need an over ~92% Efficient electrolysis ... at least it is under 100% ... but even with every ideal case I can think of , it still isn't enough... I don't know of any electrolyzer over 92% efficient.

Quote:
Originally Posted by Ken Fry View Post
The NASA study often referenced has nothing at all to do with HHO -- the injection amounts are far far higher, and the mixtures are far leaner, but most importantly the H2 comes from a tank.
While I agree with the differences ... I wouldn't go so far as saying 'has nothing at all' ... it helps to quantify one of the effects by itself ... that being Hydrogen Injections to improve ICE operating Efficiency via the LB benefits possible from Hydrogen's faster flame speed ... it isn't the whole system ... but it does help to put the LB benefits part in context ... unfortunately for HHO advocates those quantified benefits are too small and come at too high of a energy price.

The ~3.8% improvement they showed would only be a net benefit if you could somehow get the 1.5lbs/hr of hydrogen for less than that ~3.8%.

And Modern LB engines do better than ~3.8% without any of the HHO system losses.
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Old 02-12-2012, 10:59 AM   #136 (permalink)
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Originally Posted by IamIan View Post
2(H2O) to 2H2+O2 is a reversible chemical reaction that can be driven by heat or electrical energy .
Yer gonna have to show me a link (Not on an HHO website) that explains how this works. I have never heard it in my life, how do you heat water and turn it into its constituent parts? I know you get heat out when you combine them...so don't go pointing that out.

I work at nuclear power plants and used to operate the nuclear power plant on a submarine when I was in the Navy back in the 80's, it would be real interesting for me to know the conditions under which vast amounts of hydrogen can be created from water or steam by heating it.....I do imagine that it is heat that does it, cause getting hydrogen from ice would seem even a greater stretch.
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Old 02-12-2012, 05:39 PM   #137 (permalink)
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Yer gonna have to show me a link (Not on an HHO website) that explains how this works. I have never heard it in my life, how do you heat water and turn it into its constituent parts? I know you get heat out when you combine them...so don't go pointing that out.

I work at nuclear power plants and used to operate the nuclear power plant on a submarine when I was in the Navy back in the 80's, it would be real interesting for me to know the conditions under which vast amounts of hydrogen can be created from water or steam by heating it.....I do imagine that it is heat that does it, cause getting hydrogen from ice would seem even a greater stretch.
The use of Heat to split water into H2 and O2 is well known and old tech ... It is Thermal Decomposition or sometimes called thermolysis ... heat water hot enough and a greater and greater % of the gas begins to decompose from steam water into H2 + O2... initially with a small % of H2 being split and as the temperature continues to get higher and higher a great and greater % is split ... in order to harvest the split H2 you have to separate them from the O2 before cooling or it will just reform into H2O water again ... but they have different masses and densities so there are processes that can do that ... so it does exist ... and doesn't violate any science at all ... unfortunately some of the details make it less viable than HHO advocates would like ... to get significant % of H2 decomposition you need a lot of heat.

Hydrogen from ICE would 'just' take adding more heat energy to get it up to high enough temperature.

As for links ... a generic easy one is water splitting in Wikipedia ... which even goes a bit into the nuclear reactor side you mentioned.

But is is very old science ... I'm sure there are tons of other sources out there as well if you want to look for it.

The key thing to remember about using heat to split water ... is that is comes with it's own problems ... it is completely in proven science ... but as I tried to indicate previously ... even under ideal conditions , pushing science to the limit without breaking anything ... trying to get the yields out put needed for the HHO system to be viable is where the numbers get too high to be achievable.

Not 500% too high ... but too high none the less.

Here is a academic paper on a lower temperate version ... but you have to be a AAAS member or pay for it.

- - - - -

As for how it works ... the basics are basic chemistry ... Add enough heat and you have raised the energy state of the atoms high enough to break the chemical bonds holding them together... electrolysis does the same basic thing but with electrical energy instead of heat energy.

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Old 02-12-2012, 09:19 PM   #138 (permalink)
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OK, I looked into it and indeed H2O becomes disassociated at 1,800F, or about the melting point of Brass. I can see where it isn't a keen option for HHO generators in cars.
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Old 02-13-2012, 01:16 AM   #139 (permalink)
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Hi.. what's a BSFC chart ?
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Old 02-13-2012, 02:03 AM   #140 (permalink)
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Hho

Jeeez !! Ive just been reading the last 2 pages of HHO discusion. And since i don't have a degree in chemical engineering and what not, it was all a bit hard to understand. For simple guys like me, all we want is a dyno print out... not showing HP increases, but showing when you pull the HHO tube out, the HP drops... and in all the long years ive been reading HHO banter... still, not one dyno print out has appeared.... not one...and not one result from a Scan Gauge showing better fuel economy... the're the simplest test you could ever do and yet..... NOT ONE...
I'm getting soooooooo tired of reading about it... maybe the ecomodder web site should ban all writing about HHO.... the only thing ecomodders should be allowed to publish is a dyno print out or a Scan Gauge result.
It couldn't come soon enough...

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