Re: High-frequency electrolyzers

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?


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

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?

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.


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!

100% efficiency due to volume changes because they were not at STP
conditions. They explained why some people sometimes make such claims
and were careful to show how such bogus results are sometimes arrived
at.

I thought so too until I saw the rest of the site.

I didn't see the rest of the site. So, I don't know specifically what
you're talking about. I just saw the paper and thought, that looks a
heck of a lot like what I've done, and a quick scan shows they did
their maths right - with some adjustments for the figures you
mentioned it gives a pretty clear idea to a newbie what's involved.
It even went into variation of current and voltage and why that's
important on alkaline type fuel cells - so, that was relevant to the
original question of this thread.
..
The only apparent
way for the article to get on the site is by the authours contribution
which without at least some sort of disclaimer presents a somewaht tacit
endorsement of its representation.

Now you're grasping at straws. If they made a mistake in calculating
something it would be far easier just to say what the mistake was.
Assuming you are being fair about not being sure they're right.

The disclaimer seems more of a nudge,
nudge, wink, wink effort given the context.

Oh for heavens sake, I don't get that at all. If anything they were
arguing with the enthusaists in their own camp explaining (likely YET
AGAIN) why things look like they're greater than 100% when they're
really NOT! So, I see it just the opposite way. Some practical
engineering types who have befriended some enthusiasts and are trying
to nudge them toward sanity. That was one of the things I liked best
about the paper. (See I actually looked at the paper, and didn't take
the time as you did, to look at the site it came from - funny you had
time to do that, but didn't have time to figure out specifically what
was wrong in their maths)

I may be doing the author a
disservice

??? Yes, especially if you've misread their pleas that you can't go
over 100% efficiency as hints that you might. Sheez.

but you should know better.

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

It's also not commercially
available which would seem to be a minimum requirement to meet your
claims(1).

??? Since when was it impossible for a company to manufacture
stainless steel products ??? And what does this have to do with
efficiency claims ???

I didn't mean to imply it had anything to do with efficiency. It does
have a great deal to say about the ready availability of such units
though.

Yes. Most fuel cells and electrolyzers are limited production items
at best. Producing 1,000,000 or 10,000,000 units will dramatically
affect cost. Also, setting up a production plant to do millions of
units per month would drive costs down to material costs alone - which
means getting rid of Pt! lol.

Robert

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