Re: High-frequency electrolyzers

In article <1181545591.201413.56700@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Williamknowsbest says...
On Jun 9, 5:59 pm, Robert Adsett <s...@xxxxxxxxxxxxxxxxxxxxx> wrote:
In article <1181376476.771491.24...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
says...

On Jun 8, 11:11 pm, Robert Adsett <s...@xxxxxxxxxxxxxxxxxxxxx> wrote:
In article <1181306147.880719.176...@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
says...

On Jun 7, 8:20 pm, Robert Adsett <s...@xxxxxxxxxxxxxxxxxxxxx> wrote:
In article <1181259760.318128.268...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
says...

But my variable load electrolyzers are 85% efficient in the
electrolysis step. Proton Exchange Membranes (PEM) can be even more
efficient (single step) but not by much - but the costs are
tremendously high. The advantage of PEM is that you can go either way
with fair efficiency - 80% electricity to hydrogen to electricity -
under ideal condtions -but these fall off rapidly in less ideal
conditions..

Where do you get a > 80% efficient PEM cell?

http://waterfuelcell.org/WFCprojects/Tero/series_cell_v1.2.pdf

Well it's not PEM,

That's true its just plain old stainless steel

More to the point it's an alkaline cell. In my experience with fuel
cells the alkaline units I saw were substantially more efficient than
the PEM units. Although to be fair they were not as far along the
commercialization route.

Yes.

My understanding is
that for very sound fundamental reasons PEM is far more efficient than
plain old stainless steel. If you can show plain old stainless is
more efficient than PEM I'd like to see it.

You just did. You've yet to show a PEM unit that comes close to your
claim.

Well, there are Alkaline Units, Polymer PEM, and Solid Oxide Ceramic
Exchange Membrane - it seems pretty straightforward to go look up the
best available in each of these classes wouldn't you say?

Hey, you are the one who claimed the existance of > 80% PEM cells. All
I was asking for was an example, I've not seen one. I've seen fuzzy
references to 60% for a bare stack, but that becomes considerably less
when balance of plant etc... is taken into account. However, I've not
seen a pointer even to that.

The best actual PEM cell I've actually seen was considerably less than
50%, although getting efficiency figures out of manufacturers data
sheets can be quite an excercise. I'm not actively searching for a cell
at the moment so I'm not inclined to do the excercise for many
manufacturers out there, even the few you can get data sheets from. If,
however, there was an 80% cell I would be interested in it.



it's not > 80% efficient

Yes it is. Its over 80% efficient electrolyzer and it talks about why

They claim 80%, you need quite a bit above that to meet your round trip
claim.

Yes you do - you need 90% each way to get to 81% round trip

Maybe even higher than that, I thing mentioned in my wanderings is that
convetionally Fuel cells use the lower heating value when calculating
efficiency and electrolyzers use the higher heating value. If that
holds ther's an additional nearly 15% to account for leading to a need
for on the order of 97% efficiency for each.


the shape of the power is important - it quite specifically talks
about actually building stuff and explains things in gory detail -
specifically answering the original poster's questions and supporting
nearly everything I said in response to it.

(and I don't trust the
figures they do give).

Why is that exactly? They go into detail relating the volume of gas
at STP to precise measurement of power they give. They lay everything
out in a lot of detail. What details did they get wrong?

They haven't done any measurements of how much hydrogen they actually
have. As opposed to say water vapour. I'd expect a fair amount of the
latter given the description. The also don't measure voltage drop to
see where it's occuring. They have made no attempt to determine leakage
current.

These are good points. Any idea how much these are likely to change
their efficiency estimates? PLUS or minus 2% perhaps?

At a guess 50% wouldn't surprise me.


Finally I believe they've used the wrong figures for
determining efficiency from voltage drop even if they did have proper
figures to start with.

Please explain that. What did they get wrong specifically? Its all
there, if they made a mistake you should be able to tell me
specificially what the mistake is. I'm the one that scanned it and I
admit they may have made one I didn't see. But if you saw a specific
mistake, then it should be easy for you to say what it was shouldn't
it? But you didn't say. So, I'm asking you.

Specifically I'm concerned about their use of 1.48V for their
electrolyzing efficiency in the calculations. I think they are
including voltages other than those contributing to electrolysis and
getting artificially high efficiency figures as a result.

Giving a link to a site promoting > 100%
efficient electrolysis is a VERY bad start.

First off, I didn't say anything about the site, I referenced the
paper which was quite detailed. Please show me where anyone said
anything about >100% efficiency. They didn't. They spoke of APPARENT

http://waterfuelcell.org/Peoples%20Projects.html

This isn't the paper I cited is it? haha.. NO!

It's the site you cited. Any post on a perpetual motion site will be
heavily discounted. Period.


but you should know better.

About what precisely? These vauge dismissive comments with no
referent.

That references are judged partially on the company they keep. I
wouldn't expect references to papers on flight that lead to a UFO site
to be taken highly seriously either.

Robert

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