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Old 02-11-2012, 09:44 PM   #135 (permalink)
IamIan
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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.

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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.
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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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