High-frequency electrolyzers

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Williamknowsbest

Posted: Wed Jun 13, 2007 10:23 am

Guest

On Jun 11, 11:19 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:

Quote:

In article <1181545591.201413.56...@c77g2000hse.googlegroups.com>,
Williamknowsbest says...

On Jun 9, 5:59 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181376476.771491.24...@k79g2000hse.googlegroups.com>,
says...

On Jun 8, 11:11 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181306147.880719.176...@p77g2000hsh.googlegroups.com>,
says...

On Jun 7, 8:20 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181259760.318128.268...@w5g2000hsg.googlegroups.com>,
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.

Its not a claim dude. Fuel cells are NOT limited by the same
thermodynamic relations that a heat engine is.

I don't know what your problem is. You are a knowledgeable person.
Its common knowledge that under large loads and the higher
overvoltages to create them fuel cells have about 60% efficiency as
you say at their peak power density.

But under low loads with high quality oxygen and hydrogen inputs they
have greater than 90% efficiency! .

Plainly operating a fuel cell under the appropriate load to produce
high efficiencies increases efficiencies to over 90%. So, 90% or more
is possible under ideal conditions.

Now, one immediately comes up against the idea that hey, you can get
high thermal efficiencies but the capital efficiency sucks! You
drop the current density to 0.1 A/cm2 and the cost per watt increases
five times from when you run at 0.6 A//cm2!

So, you've got superlative efficiencies, but who can afford it?

Now I ask you, what if there were a membrane that was 1/2% the cost of
Nafinol available?

That would change things wouldn't it!

You'd get your cost per watt WAY down, and your optimal load would
tend to fbe less than peak power density and avor something in the 80%
range, and if energy use were cricital you could even crank it up to
90% in those cases.

So, efficiencies can be 90% - TODAY - if we wanted them to be by
dropping overvoltages to 1/6th their values at 60% efficiency which
cuts power density accordingly.
..
Reducing overvoltages by a factor of 6 cause fuel cell efficiencies to
increase from 60% range to 90% range on the power production side.
And efficiencies in electrolysis are 90% already.

Now reduce the cost of membranes by a factor of 200 - and you can make
them big enough to get energy density down to the point where you're
90% efficient each step and over 80% efficiency overall.

Quote:

All
I was asking for was an example, I've not seen one.

You've got to know that the 60% efficienct systems that you are citing
easily run at 90% efficiency in electrolyzer mode, and run 90%
efficient when power densities are cranked down to 15%-20% peak
densities right?

Quote:

I've seen fuzzy
references to 60% for a bare stack,

Its difficult to finjd papers that discuss what is common knowledge.
ANY stack that's reasonably efficient at peak load will be supremely
efficient at low loads. This is common knowledge.

Quote:

but that becomes considerably less
when balance of plant etc... is taken into account.

True - details count. And the most important detail for high fuel
cell efficiency is current density across the membrane and the
overvoltage needed to drive it.

Very low current densities mean very low overvoltages and very high
efficiencies. Again this is plainly common knowledge, so what is your
point?

Anyone who knows anything also knows that ANY of the fuel cells that
operate at peak power density - with efficiencies of 60% or so, also
operate at 90% efficiency at power densities that are 1/6th as great.

Quote:

However, I've not
seen a pointer even to that.

What sort of pointer are you looking for? This is common knowledge.
Increase overvoltage to increase current, and you increase power
density across the membrane - and reduce efficiency. Lower
overvoltage, the current drops, power density drops, and efficiencies
go to 90%. What trouble do you have with this?
..

Quote:

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.

50% at peak power density yes. But THOSE SAME FUEL CELLS may operate
at 90% efficiency at 1/5th this power level. This is common
knowledge. You've got to know it. So, why are you being obtuse about
it?

Quote:

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.

Any cell that operates at 60% efficiency at peak power density easily
achieves 90% efficiency in electrolysis mode and 90% efficiency in
fuel cell mode AT LOW POWER DENSITIES WITH THE ASSOCIATED LOW
OVERVOLTAGES.

Quote:

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.

Then there's Gibbs free energy and chemical energies. haha.. Lots of
details count. But generally speaking operating at low overvoltages
increase efficiency, so those efficiencies that you quote - are for
peak power density - they get the most power at the least cost and
least weight - are dramatically improved in the same cells at lower
power densities. To over 90% - which is my point.

Quote:

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.

Why guess when you can look at actual expeience? Fact is you're
being obtuse about my comments. Why? I don't know. You are clearly
smart enough to know that fuel cells can easily operate at 90% and
knowledgeable enough to know why it isn't reported in the literature,
and aware enough to know that the 60% efficiencies quoted in the
literature are under very specific load conditions. PEAK EFFICIENCIES
90% for these very same cells that you quote at efficiencies for at
PEAK POWER DENSITY.

Why are you trying to confuse everyone?

Quote:

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.

Where do you imagine these voltages are coming from and why wouldn't
it show up in their experimental apparatus?

Quote:

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.

I looked at the paper not the cite.

Quote:

Any post on a perpetual motion site will be
heavily discounted. Period.

The paper I cited DOES NOT claim perptual motion and DOES NOT claim
greater than 100% efficiency. It goes to great lengths to point out
efficiencies of 80% ore very high.

Quote:

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 merely looked at a paper that came up when I did a google search -
because you wanted a paper. This one I thought covered the basics.
Apparently rather than read the paper for its content, you went and
did something I didn't do. Examine the web site it was found on until
you found a reason to discount it - however lame.

One has to wonder what is motivating you in being so obtuse.

Quote:

I
wouldn't expect references to papers on flight that lead to a UFO site

haha.. Are you claiming this paper made claims about the paranomral
and UFOs? haha.. What a crock! What are you going to say next
about this paper? That it worships satan? lol. You're a trip Robert
you know that? haha..

Quote:

to be taken highly seriously either.

We're talking electrolyzers in this paper. Earlier you were talking
about PEM fuel cells and the full cycle efficiency.

So, lets not get confused.

Any person knowledgeable in the art would look AT THIS PAPER and see
that they cover the basics of electrolysis construction. And that is
all you need to show that very simple systems can be very efficient at
creating gases. As you say there are details in heating value
calculation that can affect teh result. There are well known to any
undergrad chemistry student, and need not concern us here, to build a
case against this paper on that basis is ludicrous.

Now, as to your need to see support of my PEM full cycle PEAK
EFFICIENCY numbers I guess I'd refer you back to the basics. You're a
knowledgeable person - you know that the efficiencies you bandy about
are measured at PEAK POWER DENSITY. And you also know that by backing
off the power density you can get efficiencies exceeding 90% at each
step - giving greater than 80% efficiency full cycle

So what's your beef really?

You have none - but you act like you do.

Get a grip - and accept the fact. Fuel cells can store and retrieve
energy with 80% efficiency if operated at power densities that reduce
overvoltages to a minimum.

Quote:

Robert

--
Posted via a free Usenet account fromhttp://www.teranews.com- Hide quoted text -

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Robert Adsett

Posted: Wed Jun 13, 2007 10:49 pm

Guest

In article <1181748228.240503.113020@q19g2000prn.googlegroups.com>,
Williamknowsbest says...

Quote:

On Jun 11, 11:19 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181545591.201413.56...@c77g2000hse.googlegroups.com>,
Williamknowsbest says...

On Jun 9, 5:59 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181376476.771491.24...@k79g2000hse.googlegroups.com>,
says...

On Jun 8, 11:11 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181306147.880719.176...@p77g2000hsh.googlegroups.com>,
says...

On Jun 7, 8:20 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181259760.318128.268...@w5g2000hsg.googlegroups.com>,
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.

Its not a claim dude.

Sure it is, you typed it in black and white just a few lines above.

Quote:

As I said I'd like some sort of reference as to where you would get such
a device. I've not seen any PEM cell with this claim. The PEM fuel
cells I looked at for use were a lot less efficient, the alkaline was
rather higher. It may be that the existance of such devices is common
knowledge but I've not seen them.

Quote:

No, even if I were to accept your comparison that still leaves the fuel
cell side and the question of how the efficiencies are calculated. I
had not realized until going through this that fuel cell and
electrolyzers were commonly calculated using different reference points.

Quote:

However, I've not
seen a pointer even to that.

What sort of pointer are you looking for?

Product literature, a paper, a textbook. Something that points to > 80%
fuel cell. My original request was actually for a fuel cell reference
as Graham suggested but it was not as clear as it could have been. And
since you started down the electrolysis cell route I figured we'd start
there.

Quote:

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.

50% at peak power density yes.

Quite a bit less than that actually.

Quote:

But THOSE SAME FUEL CELLS may operate
at 90% efficiency at 1/5th this power level. This is common
knowledge. You've got to know it.

Why? In fact I would expect the efficiency to drop again as the
external load decreased and balance of plant costs started being a
significant portion of the requirements.

Quote:

So, why are you being obtuse about
it?

All I asked for is an example. So far you haven't provided any.

Quote:

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.

Where do you imagine these voltages are coming from and why wouldn't
it show up in their experimental apparatus?

The 1.48V is their figure not mine. As near as I can tell they should
be using 1.23V.

I have not figured out where they get their extra 250mV but I wouldn't
be surprised if it came from their choice of electrode material. See
for example ftp://ftp.strath.ac.uk/Esru_public/documents/MSc_
2003/papagiannakis_i.pdf where 1.23V is used along with the note that
the voltage required is usually higher and notes some of the possible
loss sources. Now that is on PEM rather than alkaline so there may some
differences. I could spend some more time on it but I need some better
starting point then they've given for their determination. It could be
they have the right figure, it just doesn't track with me. Someone else
here probably knows. Since 1.23eV is what I remember as being the
energy required for splitting a water molecule 1.23V seems a better
number to use. I'll keep working on it.

Quote:

I don't actually. The references I've seen appear to be referring to
low load cases for efficiencies in PEM of as high as 60% since they
refer to it dropping under load. But as I said they are kind of fuzzy
so I wouldn't use them as a reference.

It's interesting really, I just found a reference. I've done a little
more searching and found this reference.

http://books.nap.edu/openbook.php?isbn=0309091632&page=222

referring to future(1) possible efficiency of 75%, Now that's using LHV
for hydrogen so the HHV equivalent would be around 88%. The LHV would
be a better value to use for round trip efficiencies though, They
mentiones actual achieved efficiencies of around 64% (LHV).

The same reference notes that efficiences drop (from a higher unnoted
value) to 75% at 1000A/Sq ft from what appears to be about 97% at zero
load. This doesn't include the neceassary overhead to actually run the
cell which they don't estimate separately. Note that that 97%
efficiency pretty well has to be at HHV so that gives an 82.5%
efficiency at LHV figure that would normally be used when measuring fuel
cell efficiency. In order to achive the round trip efficiency of 80%
that you mentioned the fuel cell would need an efficiency of 97%. Even
at that with the figure being a no load figure it's not of anything
other than academic interest as a limiting condition.

The same reference notes that alkaline cells are more efficient at
electrolysis than PEM cells, but notes that purification and handling is
more difficult.

Now if you can provide similar backing for fuel cell efficiency you will
have managed to back your claim, if not as broadly as your original
context made it appear(2).

Robert

(1) It's dated 2004 so it's a few years out of date but not hugely so.
(2) Your original post appeared to indicate this was a practical round
trip efficiency to consider. Subsequent posts re-enforced that this is
an ideal no-load case with none of the necessary support.

--
Posted via a free Usenet account from http://www.teranews.com

Bill Ward

Posted: Thu Jun 14, 2007 1:16 am

Guest

On Wed, 13 Jun 2007 23:49:20 -0400, Robert Adsett wrote:

<snip>

Quote:

I have not figured out where they get their extra 250mV but I wouldn't be
surprised if it came from their choice of electrode material. See for
example ftp://ftp.strath.ac.uk/Esru_public/documents/MSc_
2003/papagiannakis_i.pdf where 1.23V is used along with the note that the
voltage required is usually higher and notes some of the possible loss
sources. Now that is on PEM rather than alkaline so there may some
differences. I could spend some more time on it but I need some better
starting point then they've given for their determination. It could be
they have the right figure, it just doesn't track with me. Someone else
here probably knows. Since 1.23eV is what I remember as being the energy
required for splitting a water molecule 1.23V seems a better number to
use. I'll keep working on it.

The equilibrium reaction voltage (no current) is 1.23V. The electrolysis
direction is endothermic, requiring heat to proceed. The 1.48V value is
the point at which just enough heat is supplied by the current to
allow the reaction to proceed without cooling the environment. In
practice, more voltage is needed to increase the rate of reaction,
depending on the activation energy (catalysis) of the electrodes, the
current density, and the I2R losses in the cell itself.

This means, of course, that the fuel cell direction of the reaction
must be exothermic, so IIRC, only about 83% is available as electric
energy, with 17% lost as heat. Heated and pressurized cells can shift
that somewhat at the cost of more complexity. For simple cells, 83% is a
maximum efficiency, with I2R and overvoltage losses subtracted from that.

Bill Ward

Williamknowsbest

Posted: Thu Jun 14, 2007 6:55 am

Guest

On Jun 13, 11:49 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:

Quote:

In article <1181748228.240503.113...@q19g2000prn.googlegroups.com>,
Williamknowsbest says...

On Jun 11, 11:19 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181545591.201413.56...@c77g2000hse.googlegroups.com>,
Williamknowsbest says...

On Jun 9, 5:59 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181376476.771491.24...@k79g2000hse.googlegroups.com>,
says...

On Jun 8, 11:11 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181306147.880719.176...@p77g2000hsh.googlegroups.com>,
says...

On Jun 7, 8:20 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181259760.318128.268...@w5g2000hsg.googlegroups.com>,
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.

Its not a claim dude.

Sure it is, you typed it in black and white just a few lines above.

Cute. So, you have no real issue with what I say so you are reduced
to making shit up just because you LIKE to argue and lose? haha..

Quote:

Wait a minute. Are you saying you are unaware that nearly all fuel
cells that have 50% to 60% efficiency at peak power - you are unaware
that those very same fuel cells operate at 80% to 90% efficiency at
very low power? Are you saying this? Are you saying you need a
REFERENCE for this?

Wow.

Quote:

I've not seen any PEM cell with this claim.

Dude, you know don't you that fuel cells operate at a particular
current and voltage - and that this current and voltage are related.
You also know that there is a peak power density, you can't go
above., It is at THAT current and voltage you get 50% to 60%
efficiency. Now, reduce the voltage what happens? You reduce the
current. Power density goes down. But overvoltage is reduced too.
And with it, efficiency increases. What it increases to depends on
your catalysts and membrane. But most membranes that have 50% to 60%
efficiency at peak power density, rise to over 80% some to over 90% at
low power levels.

Quote:

The PEM fuel
cells I looked at for use were a lot less efficient, the alkaline was
rather higher.

Yes.

Quote:

It may be that the existance of such devices is common
knowledge but I've not seen them.

Obviously. That's why its hard to point to a discussion about it.
Let me see..

http://www.fuelcelltoday.com/FuelCellToday/FCTFiles/FCTArticleFiles/Article_516_FordFocusFCV.pdf

I don't know if the Ballard 902 fuel cell stackis PEM or solid oxide
or some other technology - but you see a clear reference to how the
fuel cell efficiency varies.

Clearly with lowered membrane costs, larger membrane areas are
possible for a given investment, and higher efficiencies are
possible.

Quote:

All
I was asking for was an example, I've not seen one.

You've got to know that the 60% efficienct systems that you are citing
easily run at 90% efficiency in electrolyzer mode, and run 90%
efficient when power densities are cranked down to 15%-20% peak
densities right?

No, even if I were to accept your comparison that still leaves the fuel
cell side and the question of how the efficiencies are calculated.

Quote:

had not realized until going through this that fuel cell and
electrolyzers were commonly calculated using different reference points.

Its part of what makes chemistry such a difficult subject to newbies!
haha.

Quote:

However, I've not
seen a pointer even to that.

What sort of pointer are you looking for?

Product literature, a paper, a textbook.

Well, there is a vague reference to it in the Ford literature above.
Its common knowledge, sort of the elusive obvious you know? People
don't generally talk about things that everyone takes for granted.

Quote:

Something that points to > 80%
fuel cell. My original request was actually for a fuel cell reference
as Graham suggested but it was not as clear as it could have been. And
since you started down the electrolysis cell route I figured we'd start
there.

Since you have said you were looking for a primer on the subject, here
is a good place to start;

http://en.wikipedia.org/wiki/Electrolysis#Electrolysis_of_water

Quote:

Depends on the details and which system you're talking about
obviously.

Quote:

??? How does the cost of the plant affect the efficiency fuel is
used in a fuel cell? haha.. You've lost it here Robert. Gone off
track I think.

Quote:

So, why are you being obtuse about
it?

All I asked for is an example. So far you haven't provided any.

Alright, now that I realized you truly don't know what I'm talking
about I gave you a couple of references. They're not papers per se
because papers are not written about stuff that's common knowledge you
know?

Quote:

Alright

Quote:

I have not figured out where they get their extra 250mV but I wouldn't
be surprised if it came from their choice of electrode material.

I see So, you think they're not using platinum electrodes - but some
other material?

Quote:

See
for exampleftp://ftp.strath.ac.uk/Esru_public/documents/MSc_
2003/papagiannakis_i.pdf where 1.23V is used along with the note that
the voltage required is usually higher and notes some of the possible
loss sources.

Alright.

Quote:

Now that is on PEM rather than alkaline so there may some
differences. I could spend some more time on it but I need some better
starting point then they've given for their determination.

Yes. I gave this paper as something that was easily accessible and
showed quite clearly the basics. You have brought up some good points
- details count.

Quote:

It could be
they have the right figure, it just doesn't track with me.

Certainly.

Quote:

Someone else
here probably knows.

That'd be refreshing.

Quote:

Since 1.23eV is what I remember as being the
energy required for splitting a water molecule 1.23V seems a better
number to use. I'll keep working on it.

As you wish.

Quote:

Now, as to your need to see support of my PEM full cycle PEAK
EFFICIENCY numbers I guess I'd refer you back to the basics. You're a
knowledgeable person - you know that the efficiencies you bandy about
are measured at PEAK POWER DENSITY.

I don't actually. The references I've seen appear to be referring to
low load cases for efficiencies in PEM of as high as 60% since they
refer to it dropping under load.

hmm..

Quote:

But as I said they are kind of fuzzy
so I wouldn't use them as a reference.

Right. That's my problem. It would be an arcane subject at some
graduate school somewhere - its not something that's talked about
generally since its a pretty straightforward result. But I agree,
that people should be made aware of how things operate.

Quote:

It's interesting really, I just found a reference. I've done a little
more searching and found this reference.

http://books.nap.edu/openbook.php?isbn=0309091632&page=222

referring to future(1) possible efficiency of 75%, Now that's using LHV
for hydrogen so the HHV equivalent would be around 88%. The LHV would
be a better value to use for round trip efficiencies though, They
mentiones actual achieved efficiencies of around 64% (LHV).

The problem here is that again details count. I've installed a
Ballard fuel cell and captued both the hydrogen AND oxygen at high
pressure and reuse it. I use the fuel cell to capture energy and get
that energy back at night when the sun isn't shiining. Here the HHV
makes sense since I'm capturing both O2 and H2 - and water - in a
closed system - using a fuel cell like a battery.

Quote:

The same reference notes that efficiences drop (from a higher unnoted
value) to 75% at 1000A/Sq ft from what appears to be about 97% at zero
load. This doesn't include the neceassary overhead to actually run the
cell which they don't estimate separately. Note that that 97%
efficiency pretty well has to be at HHV so that gives an 82.5%
efficiency at LHV figure that would normally be used when measuring fuel
cell efficiency. In order to achive the round trip efficiency of 80%
that you mentioned the fuel cell would need an efficiency of 97%.

No to have 81% round trip efficiency it would only need to have a one
way efficiency of 90% each way. 0.9 x 0.9 = 0.81

Quote:

Even
at that with the figure being a no load figure it's not of anything
other than academic interest as a limiting condition.

Between peak load and no load there are an infinite number of useful
loads. The real question is capital cost. And once you get the
basics right, you can focus your attention at reducing those.

Sure, my $50,000 Ballard fuel cell equipped with hydrogen and oxygen
storage (in an underground tube at high pressure) may store no more
than $5,000 worth of car batteries -haha - but its damned efficient
otherwise!! haha,, and once you get the basics right, your mind is
clear to focus on reducing THOSE COSTS - so that you achieve what
you've just achieved at a very high cost, but at a far far lower cost
with proper focus on technical improvements.

Quote:

The same reference notes that alkaline cells are more efficient at
electrolysis than PEM cells, but notes that purification and handling is
more difficult.

Solid KOH is a bitch to handle. Its also known as drain cleaner.

Quote:

Now if you can provide similar backing for fuel cell efficiency you will
have managed to back your claim, if not as broadly as your original
context made it appear(2).

As with anything there are caveats. But I stand by my claim. Full
cycle efficiencies are achievable - yes, you must capture the oxygen
as well as the hydrogen, yes, you must operate at low loads - but, you
can achieve 80% full cycle efficiency in energy storage. Now, as to
cost, and load, well,that's an issue of reducing the cost of membrane
area - and that's where I've focused my attention.

Quote:

Robert

(1) It's dated 2004 so it's a few years out of date but not hugely so.
(2) Your original post appeared to indicate this was a practical round
trip efficiency to consider. Subsequent posts re-enforced that this is
an ideal no-load case with none of the necessary support.

You are being overly critical of the low load case. Between 97% no
load and 60% peak load there is 90% some load - haha - and 0.9 x 0.9
is 0.81 - 81% - which is what I quoted.

Quote:

--
Posted via a free Usenet account fromhttp://www.teranews.com- Hide quoted text -

- Show quoted text -

Eeyore

Posted: Thu Jun 14, 2007 8:08 am

Guest

Williamknowsbest wrote:

Quote:

Apparently you require one to 'prove' that Varta can make a simple 2700mAh NiMH cell !

I suppose you think Varta are lying ?

Quote:

Wow.

WOW indeed.

Just buy a Varta 2700mAh NiMH and check it out. On sale now - the battery you claim *CAN'T BE MADE*
!

Graham

Eeyore

Posted: Thu Jun 14, 2007 12:05 pm

Guest

Williamknowsbest wrote:

Quote:

Eeyore wrote:
Williamknowsbest wrote:
Wait a minute. Are you saying you are unaware that nearly all fuel
cells that have 50% to 60% efficiency at peak power - you are unaware
that those very same fuel cells operate at 80% to 90% efficiency at
very low power? Are you saying this? Are you saying you need a
REFERENCE for this?

Apparently you require one to 'prove' that Varta can make a simple 2700mAh > NiMH cell !

I suppose you think Varta are lying ?

Wow.

WOW indeed.

Just buy a Varta 2700mAh NiMH and check it out. On sale now - the battery > you claim *CAN'T BE MADE*
!

Don't be a fool. I'm not doubting 2700 mAh AA NiMH batteries.

You were a few posts back.

Quote:

I'm doubting that such batteries have energy densities 3x higher than
accepted figures.

Early NiMH AAs had a capacity of ~ 1000mAh. Which one conforms to 'accepted figures' ?

Quote:

This whole issue arose from Graham's statement that the figures Honda
quoted in their EV website as being 1/3 the currently accepted figures
for NiMH batteries. Graham said that not me.

I never referenced Honda. You introduced them. I have no interest whatever in what they have to say on
the matter. Their work was clearly with older technology batteries.

Quote:

This came from the observation that Honda needs 800 pounds of
batteries and Graham said he can get the same performance out of 160
pounds of the same kind of batteries because a) his auto design is
better than the best Honda can do, and b) he uses more modern
batteries are 3x more energy dense per kg than Honda is able to come
up with.

In response to these bold claims I asked Graham for pointers to any
literature that supports his latter contention. To which he came up
with some figures about AA NiMH batteries- which I found unconvincing
- and still do.

The energy density figures are a fact.

Graham

Don Lancaster

Posted: Thu Jun 14, 2007 12:11 pm

Guest

Eeyore wrote:

Quote:

Williamknowsbest wrote:

Eeyore wrote:

Williamknowsbest wrote:

Wait a minute. Are you saying you are unaware that nearly all fuel
cells that have 50% to 60% efficiency at peak power - you are unaware
that those very same fuel cells operate at 80% to 90% efficiency at
very low power? Are you saying this? Are you saying you need a
REFERENCE for this?

Apparently you require one to 'prove' that Varta can make a simple 2700mAh > NiMH cell !

I suppose you think Varta are lying ?

Wow.

WOW indeed.

Just buy a Varta 2700mAh NiMH and check it out. On sale now - the battery > you claim *CAN'T BE MADE*

!

Don't be a fool. I'm not doubting 2700 mAh AA NiMH batteries.

You were a few posts back.

I'm doubting that such batteries have energy densities 3x higher than
accepted figures.

Early NiMH AAs had a capacity of ~ 1000mAh. Which one conforms to 'accepted figures' ?

This whole issue arose from Graham's statement that the figures Honda
quoted in their EV website as being 1/3 the currently accepted figures
for NiMH batteries. Graham said that not me.

I never referenced Honda. You introduced them. I have no interest whatever in what they have to say on
the matter. Their work was clearly with older technology batteries.

This came from the observation that Honda needs 800 pounds of
batteries and Graham said he can get the same performance out of 160
pounds of the same kind of batteries because a) his auto design is
better than the best Honda can do, and b) he uses more modern
batteries are 3x more energy dense per kg than Honda is able to come
up with.

In response to these bold claims I asked Graham for pointers to any
literature that supports his latter contention. To which he came up
with some figures about AA NiMH batteries- which I found unconvincing
- and still do.

The energy density figures are a fact.

Graham

There was a fundamental breakthrough in NiMh and NiCad a year or two

back in which they learned to control three outer shell electrons
instead of just two.

Which gave a theoretical 50% bump to the maximum energy density.

It was basically a question of learning how to stabilize.

--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss: http://www.tinaja.com/whtnu.xml email: don@tinaja.com

Please visit my GURU's LAIR web site at http://www.tinaja.com

Eeyore

Posted: Thu Jun 14, 2007 12:54 pm

Guest

Don Lancaster wrote:

Quote:

Eeyore wrote:
Williamknowsbest wrote:

In response to these bold claims I asked Graham for pointers to any
literature that supports his latter contention. To which he came up
with some figures about AA NiMH batteries- which I found unconvincing
- and still do.

The energy density figures are a fact.

Graham

There was a fundamental breakthrough in NiMh and NiCad a year or two
back in which they learned to control three outer shell electrons
instead of just two.

Which gave a theoretical 50% bump to the maximum energy density.

It was basically a question of learning how to stabilize.

That would explain the step increase in capacity.

Previous advances are I imagine just a result of improved manufacture / process refinement.

There are also now these NiMHs with low self-discharge too, good for about 80% capacity remaining after one
year 'on the shelf'.

Graham

Williamknowsbest

Posted: Fri Jun 15, 2007 2:24 am

Guest

On Jun 14, 1:05 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
wrote:

Quote:

No I doubted your assertion that 2700 mAh proved that Honda's figures
were off by a factor of three.

Quote:

I'm doubting that such batteries have energy densities 3x higher than
accepted figures.

Early NiMH AAs had a capacity of ~ 1000mAh. Which one conforms to 'accepted figures' ?

I tend to think Honda's experience with EVs is to be trusted more than
your gut instincts and poor math skills. haha.. I know that's a
shocker to you, and a blow to your inflated ego. But that's my
position, and you haven't said anything to change it. Though I'm
still talking to you.
..

Quote:

This whole issue arose from Graham's statement that the figures Honda
quoted in their EV website as being 1/3 the currently accepted figures
for NiMH batteries. Graham said that not me.

I never referenced Honda. You introduced them.

That's right. I pointed to the experience of Honda as a reasonable
expectation. You said you could go 100 miles or so with 160 pounds of
NiMH batteries and I said Honda can go about 100 miles with about 800
pounds of NiMH batteries - and doubted your figures. In response you
said you were better at building cars than Honda and their engineers
didn't know a damn thing about batteries and to prove it you did a
calculation with a AA battery you bought which proved their numbers
were 1/3 the value you got and they were all wet or using old data.

In response I asked you to show me any literature anywhere that touted
a 3 fold increase in the energy density of NiMH -

At that point you launched into a vituperous personal attack of me and
interestingly enough academics and peer reviewed literature. haha..

At that point I marked you off as a self-important nutjob.

But I'm still interested to see what you're going on about... lol

Quote:

I have no interest whatever in what they have to say on
the matter.

Oh no, I agree, your abilities and experience in building automobiles
far surpases theirs! HAHAHAHAHAHA!

Quote:

Their work was clearly with older technology batteries.

That's not clear at all. More likely you got your numbers wrong and
they're using the very same batteries - except they're really
engineers who know what they're doing and you're just a guy with a AA
battery and the package it came in doing your maths wrong.

Quote:

Please point to anything anywhere that says that NiMH is 3x more
energy dense today than it was a few years ago, and prove that Honda
doesn't know what they're doing.

Quote:

Graham- Hide quoted text -

- Show quoted text -

Williamknowsbest

Posted: Fri Jun 15, 2007 2:24 am

Guest

On Jun 14, 1:11 pm, Don Lancaster <d...@tinaja.com> wrote:

Quote:

Eeyore wrote:

Williamknowsbest wrote:

Eeyore wrote:

Williamknowsbest wrote:

Wait a minute. Are you saying you are unaware that nearly all fuel
cells that have 50% to 60% efficiency at peak power - you are unaware
that those very same fuel cells operate at 80% to 90% efficiency at
very low power? Are you saying this? Are you saying you need a
REFERENCE for this?

Apparently you require one to 'prove' that Varta can make a simple 2700mAh > NiMH cell !

I suppose you think Varta are lying ?

Wow.

WOW indeed.

Just buy a Varta 2700mAh NiMH and check it out. On sale now - the battery > you claim *CAN'T BE MADE*

!

Don't be a fool. I'm not doubting 2700 mAh AA NiMH batteries.

You were a few posts back.

I'm doubting that such batteries have energy densities 3x higher than
accepted figures.

Early NiMH AAs had a capacity of ~ 1000mAh. Which one conforms to 'accepted figures' ?

This whole issue arose from Graham's statement that the figures Honda
quoted in their EV website as being 1/3 the currently accepted figures
for NiMH batteries. Graham said that not me.

I never referenced Honda. You introduced them. I have no interest whatever in what they have to say on
the matter. Their work was clearly with older technology batteries.

This came from the observation that Honda needs 800 pounds of
batteries and Graham said he can get the same performance out of 160
pounds of the same kind of batteries because a) his auto design is
better than the best Honda can do, and b) he uses more modern
batteries are 3x more energy dense per kg than Honda is able to come
up with.

In response to these bold claims I asked Graham for pointers to any
literature that supports his latter contention. To which he came up
with some figures about AA NiMH batteries- which I found unconvincing
- and still do.

The energy density figures are a fact.

Graham

There was a fundamental breakthrough in NiMh and NiCad a year or two
back in which they learned to control three outer shell electrons
instead of just two.

Which gave a theoretical 50% bump to the maximum energy density.

It was basically a question of learning how to stabilize.

--
Many thanks,

Don Lancaster voice phone: (928)428-4073
Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552
rss:http://www.tinaja.com/whtnu.xml email: d...@tinaja.com

Please visit my GURU's LAIR web site athttp://www.tinaja.com- Hide quoted text -

- Show quoted text -

Well, that's a 50% improvement - I'll grant you. But its not a 3x
improvement is it.

Williamknowsbest

Posted: Fri Jun 15, 2007 2:35 am

Guest

On Jun 14, 1:54 pm, Eeyore <rabbitsfriendsandrelati...@hotmail.com>
wrote:

Quote:

Don Lancaster wrote:
Eeyore wrote:
Williamknowsbest wrote:

In response to these bold claims I asked Graham for pointers to any
literature that supports his latter contention. To which he came up
with some figures about AA NiMH batteries- which I found unconvincing
- and still do.

The energy density figures are a fact.

Graham

There was a fundamental breakthrough in NiMh and NiCad a year or two
back in which they learned to control three outer shell electrons
instead of just two.

Which gave a theoretical 50% bump to the maximum energy density.

It was basically a question of learning how to stabilize.

That would explain the step increase in capacity.

Previous advances are I imagine just a result of improved manufacture / process refinement.

There are also now these NiMHs with low self-discharge too, good for about 80% capacity remaining after one
year 'on the shelf'.

Graham- Hide quoted text -

- Show quoted text -

At the beginning of the industrial revolution improvements were
largely wrougnt through economies of scale favoring the development of
large capital intensive companies. Into this melieu came Noyce and
Moore with their IC technology. The central feature of this
technology is that the size of circuits were very large when compared
to the size of atoms. And in the limit, the size of atoms was where
the technology would end up. So, there arose a period of continuing
exponential advance in IC capacity - the Moore Curve - doubling value
every 3 years or so. And this has continued from the 1960s to today
and is projected to continue through 2030 - where we'll reach the
ultimate limit, unless we find there are more things we can do at the
sub-atom level. So, this has created a situation where CHANGE, not
economies of scale dominate. And in an era of massive change,
economies of scale become diseconomies of scale - and the ability to
come up with the next new idea and be ahead of the curve - pays far
more dividends than economies of scale. In fact in an era of change,
investment in huge capital infrastructures and standing armeis of
people - becomes a DISECONOMY of scale. And so, flexibility and the
presumption of continuing progress has become the NEW paradigm, the
new conventional wisdom of management, which reviles the older
paradigms that assumed lack of change and focused on economies of
scale.

The problem with all of this is that details count. Moores
development works in consumer electronics because the size of circuits
are millions of times bigger than atoms. And are getting smaller all
the time. So, improvements seem to be only a matter of time and
effort.

Which is true for electronics while we're on the Moore curve - in this
epoch.

Its not true generally.

And its not true that you can just do research and arbitrarily pump up
the number of electron volts in a reaction by being clever. Nature
doesn't work that way. But you talk that way. Which tells me you are
clueless.

Don must really hate my guts to support such a clueless notion. Its a
weakness of his perhaps. That he wants to see me wrong so much, he'll
eagerly be wrong himself to say dismissive things about me.

But the fact is, an extra electron particpating in the reaction -
might increase energy density by 50% - I'd still want to see the
literature to see if that's true. That's still not a 3x increase -
and it still doesn't make Grahams bogus numbers about his imagined EV
right.

Eeyore

Posted: Fri Jun 15, 2007 4:32 am

Guest

Williamknowsbest wrote:

Quote:

Eeyore wrote:

Early NiMH AAs had a capacity of ~ 1000mAh. Which one conforms to > 'accepted figures' ?

I tend to think Honda's experience with EVs is to be trusted more than
your gut instincts and poor math skills. haha.

Answer the damn question will you ?

Graham

Eeyore

Posted: Fri Jun 15, 2007 4:33 am

Guest

Williamknowsbest wrote:

Quote:

At the beginning of the industrial revolution improvements were
largely wrougnt through economies of scale favoring the development of
large capital intensive companies.

YAWN.

What does this have to do with improving battery technology ?

Graham

Robert Adsett

Posted: Fri Jun 15, 2007 5:00 pm

Guest

In article <pan.2007.06.14.06.16.35.486578@REMOVETHISix.netcom.com>,
Bill Ward says...

Quote:

On Wed, 13 Jun 2007 23:49:20 -0400, Robert Adsett wrote:

snip

I have not figured out where they get their extra 250mV but I wouldn't be
surprised if it came from their choice of electrode material. See for
example ftp://ftp.strath.ac.uk/Esru_public/documents/MSc_
2003/papagiannakis_i.pdf where 1.23V is used along with the note that the
voltage required is usually higher and notes some of the possible loss
sources. Now that is on PEM rather than alkaline so there may some
differences. I could spend some more time on it but I need some better
starting point then they've given for their determination. It could be
they have the right figure, it just doesn't track with me. Someone else
here probably knows. Since 1.23eV is what I remember as being the energy
required for splitting a water molecule 1.23V seems a better number to
use. I'll keep working on it.

The equilibrium reaction voltage (no current) is 1.23V. The electrolysis
direction is endothermic, requiring heat to proceed. The 1.48V value is
the point at which just enough heat is supplied by the current to
allow the reaction to proceed without cooling the environment. In
practice, more voltage is needed to increase the rate of reaction,
depending on the activation energy (catalysis) of the electrodes, the
current density, and the I2R losses in the cell itself.

This means, of course, that the fuel cell direction of the reaction
must be exothermic, so IIRC, only about 83% is available as electric
energy, with 17% lost as heat. Heated and pressurized cells can shift
that somewhat at the cost of more complexity. For simple cells, 83% is a
maximum efficiency, with I2R and overvoltage losses subtracted from that.

Ah, now that makes sense.

Thanks Bill

Robert

--
Posted via a free Usenet account from http://www.teranews.com

Robert Adsett

Posted: Fri Jun 15, 2007 5:57 pm

Guest

In article <1181822139.003897.8430@n15g2000prd.googlegroups.com>,
Williamknowsbest says...

Quote:

On Jun 13, 11:49 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181748228.240503.113...@q19g2000prn.googlegroups.com>,
Williamknowsbest says...

On Jun 11, 11:19 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181545591.201413.56...@c77g2000hse.googlegroups.com>,
Williamknowsbest says...

On Jun 9, 5:59 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181376476.771491.24...@k79g2000hse.googlegroups.com>,
says...

On Jun 8, 11:11 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181306147.880719.176...@p77g2000hsh.googlegroups.com>,
says...

On Jun 7, 8:20 pm, Robert Adsett <s...@aeolusdevelopment.com> wrote:
In article <1181259760.318128.268...@w5g2000hsg.googlegroups.com>,
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.

Its not a claim dude.

Sure it is, you typed it in black and white just a few lines above.

Cute. So, you have no real issue with what I say so you are reduced
to making shit up just because you LIKE to argue and lose? haha..

Now that just doesn't parse.

Quote:

I don't know what your problem is. You are a knowledgeable person.
Its common knowledge that under large loads and the higher
overvoltages to create them fuel cells have about 60% efficiency as
you say at their peak power density.

But under low loads with high quality oxygen and hydrogen inputs they
have greater than 90% efficiency! .

As I said I'd like some sort of reference as to where you would get such
a device.

Wait a minute. Are you saying you are unaware that nearly all fuel
cells that have 50% to 60% efficiency at peak power - you are unaware
that those very same fuel cells operate at 80% to 90% efficiency at
very low power? Are you saying this? Are you saying you need a
REFERENCE for this?

Yes, why do you think I asked?

Quote:

The PEM fuel
cells I looked at for use were a lot less efficient, the alkaline was
rather higher.

Yes.

It may be that the existance of such devices is common
knowledge but I've not seen them.

Obviously. That's why its hard to point to a discussion about it.
Let me see..

http://www.fuelcelltoday.com/FuelCellToday/FCTFiles/FCTArticleFiles/Article_516_FordFocusFCV.pdf

I don't know if the Ballard 902 fuel cell stackis PEM or solid oxide
or some other technology - but you see a clear reference to how the
fuel cell efficiency varies.

Ballard will be almost certainly PEM. AFAIK they haven't done anything
with other types. Good to have a reference.

Quote:

Well, there is an over-voltage right? You have a voltage at which the
cell operates. Increase that voltage and efficiencies drop. Higher
voltages lead to higher currents and so, you have a situation where
you must choose between fuel efficiency and capital efficiency.

had not realized until going through this that fuel cell and
electrolyzers were commonly calculated using different reference points.

Its part of what makes chemistry such a difficult subject to newbies!
haha.

That's less chemistry than simple calculation using the same
definitions. Since they tend to use different definitions the resulting
combined efficiency is not a simple matter of combining the individual
efficiencies.

Quote:

But THOSE SAME FUEL CELLS may operate
at 90% efficiency at 1/5th this power level. This is common
knowledge. You've got to know it.

Why? In fact I would expect the efficiency to drop again as the
external load decreased and balance of plant costs started being a
significant portion of the requirements.

??? How does the cost of the plant affect the efficiency fuel is
used in a fuel cell? haha.. You've lost it here Robert. Gone off
track I think.

I was referring to energy cost, not currency.

Quote:

Only if both efficiencies refer to the HHV of hydrogen. I don't think
I've ever seen a fuel cell efficiency refer to the HHV and from what I
can tell the usual practice is to use the LHV. That being the case you
are missing a factor of approx 0.85 (giving about 0.69). I doubt Ballard
would differ from usual practice in this respect, if for no other reason
than it would lower their efficiency numbers(1)

But you've answered my original question.

Thanks
Robert

(1) Along that same vein I believe I've seen ICE efficiency figures that
quoted efficiency as a percentage of the maximum Carnot cycle
efficiency. Not useful if you are comparing different techniques and
certainly overstates efficiency. And let's not forget battery energy
denisties reported w/o needed support like cases. insulation and in some
cases, pumps.

--
Posted via a free Usenet account from http://www.teranews.com

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