Still Waiting for Thermodynamic Limits On Battery Energy Den

[Bret Cahill]

The thermodynamic limits of some batteries' energy densities seem to
be on par with liquid fuel.

Someone needs to at least proffer _some_ reasoning on why the reality
is so much lower.

After all, any turbo engineer at GE can quantify the losses to at
least the nearest 1% as to why they get less than half Carnot
efficiency from gas turbines.

Any wind turbine engineer at GE can explain why they are only getting
2/3rds the Betz limits.

Even some bio algae folk are making claims of 5,000 gallons / acre -
year limits.

Why OH why is battery research still staggering around in the dark
when it comes to the limits on battery energy density?


Bret Cahill

 

[Cwatters]

"Bret Cahill" <BretCahill@aol.com> wrote in message
news:f34fba04-c85f-47cd-9603-b4ada789cbc6@a19g2000pra.googlegroups.com...

The thermodynamic limits of some batteries' energy densities seem to
be on par with liquid fuel.

Someone needs to at least proffer _some_ reasoning on why the reality
is so much lower.

With a liquid fuel the reaction products can be used to transport the energy
away from where the reaction is taking place. It's not so easy to do that
with a battery. There is a limit to how small the electrodes can be made.
Perhaps that's the answer - a design where the reaction producs are the
electrodes.

 

The thermodynamic limits of some batteries' energy densities seem to
be on par with liquid fuel.

Someone needs to at least proffer _some_ reasoning on why the reality
is so much lower.

With a liquid fuel the reaction products can be used to transport the energy
away from where the reaction is taking place.

Heat going out the stack or exhaust pipe isn't an advantage with heat
engines.

That's why recuperation is so widely used in power plants.

It's not so easy to do that
with a battery. There is a limit to how small the electrodes can be made.

Why would the electrodes need to be small in the first place?

Perhaps that's the answer - a design where the reaction producs are the
electrodes.

Continuing with the analogue, are there any pulse or intermittent
discharge batteries?

Temperatures reach 6,000 F in a diesel but since it's only for a
fraction of a millisecond the cylinder doesn't melt and no exotic
materials are necessary.

That approach _lowers_ energy density -- a continuous burn gas turbine
has 1 - 2 orders of magnitude higher power/weight than reciprocating
engines -- by the % time the battery is "off" but it might be worth it
if it kept prices down or efficiency up.

It could even _increase_ the energy density if it enhanced other
factors enough.


Bret Cahill

 

[zzbunker@netscape.net]

On Oct 18, 1:04 pm, Bret Cahill <BretCah...@aol.com> wrote:

The thermodynamic limits of some batteries' energy densities seem to
be on par with liquid fuel.

Someone needs to at least proffer _some_ reasoning on why the reality
is so much lower.

After all, any turbo engineer at GE can quantify the losses to at
least the nearest 1% as to why they get less than half Carnot
efficiency from gas turbines.

Any wind turbine engineer at GE can explain why they are only getting
2/3rds the Betz limits.

Even some bio algae folk are making claims of 5,000 gallons / acre -
year limits.

Why OH why is battery research still staggering around in the dark
when it comes to the limits on battery energy density?

Because they don't make them from liquid, They make them
from pastes, so they can dispose of them. Which is why people with
energy-engineering brains, rather than idiot thermo notions, have
switched to
hybrids of PV Cells, Bio-Lume, Ozone, A.I..Digital, Plastic,
Fiber Optics, Optical Computers, Holograms, H2 Collectors, and
Lasers.
to get super batteries, to replace the science wanks with super
batteries.

Bret Cahill

 

[Yevgen Barsukov]

On Oct 18, 12:04 pm, Bret Cahill <BretCah...@aol.com> wrote:

The thermodynamic limits of some batteries' energy densities seem to
be on par with liquid fuel.

It is very easy to calculate energy density of "theoretically most
energetic" battery.
It will be Li (lightest most energetic reducing agent) + F2 (lightest
and most energetic
oxidizer). Formula is
Energy Density = dG (LiF) (25C, atmospheric pressure) / molar weight
(LiF)

But - what does it help you considering that such battery will never
be made
because of extreme safety concerns and inconvenient storage?

Someone needs to at least proffer _some_ reasoning on why the reality
is so much lower.

Because active materials used in reality are satisfying lots of
engineering criteria
that are not thermodynamical in its nature but are needed to make
device practical.
Just to mention a few:

1) electrochemical couple should be possible to store in safe manner
under practical
usage conditions (e.g. no high pressure, liquid nitrogen cooling etc)

2) materials surrounding electrochemical couple (electrodes,
electrolyte) should be
able to survive in the environment long enough for 300-500 cycles
(cycleability)

3) materials have to be electrically conductive (if not, a lot of
weight will be
taken by a porous catalytic electrodes)

Above excludes majority of really energetic active materials. With
these which are left,
another consideration comes to play:

4) supporting materials (electrodes, electrolyte, separators, casing,
binders, conductive additives etc) have weight and volume.

Once all of the above is considered, energy density of a battery is
coinciding very
well with theoretically calculated value. It is a basic arithmetic and
there is nothing
mysterious.

Regards,
Yevgen

After all, any turbo engineer at GE can quantify the losses to at
least the nearest 1% as to why they get less than half Carnot
efficiency from gas turbines.

Any wind turbine engineer at GE can explain why they are only getting
2/3rds the Betz limits.

Even some bio algae folk are making claims of 5,000 gallons / acre -
year limits.

Why OH why is battery research still staggering around in the dark
when it comes to the limits on battery energy density?

Bret Cahill

 

The thermodynamic limits of some batteries' energy densities seem to
be on par with liquid fuel.

It is very easy to calculate energy density of "theoretically most
energetic" battery.
It will be Li (lightest most energetic reducing agent) + F2 (lightest
and most energetic
oxidizer). Formula is
Energy Density = dG (LiF) (25C, atmospheric pressure) / molar weight
(LiF)

But - what does it help you considering that such battery will never
be made
because of extreme safety concerns and inconvenient storage?

Another concern is living post peak without a good battery.

Someone need to spreadsheet the cost benefit risk analysis.

A battery that occasionally creates a crater in the road may start to
look pretty attractive.

Someone needs to at least proffer _some_ reasoning on why the reality
is so much lower.

Because active materials used in reality are satisfying lots of
engineering criteria
that are not thermodynamical in its nature

Thanks for pointing that out. I was getting sick and tired of people
invoking thermodynamics when that isn't the issue.

but are needed to make
device practical.
Just to mention a few:

1) electrochemical couple should be possible to store in safe manner
under practical
usage conditions (e.g. no high pressure, liquid nitrogen cooling etc)

2) materials surrounding electrochemical couple (electrodes,
electrolyte) should be
able to survive in the environment long enough for 300-500 cycles
(cycleability)

3) materials have to be electrically conductive (if not, a lot of
weight will be
taken by a porous catalytic electrodes)

Above excludes majority of really energetic active materials. With
these which are left,
another consideration comes to play:

4) supporting materials (electrodes, electrolyte, separators, casing,
binders, conductive additives etc) have weight and volume.

Once all of the above is considered, energy density of a battery is
coinciding very
well with theoretically calculated value. It is a basic arithmetic and
there is nothing
mysterious.

OK, put high energy density on the back burner for awhile.

Instead go to lower energy density but lower cost / higher cycling and/
or higher round trip efficiency.

What are the limits there?


Bret Cahill

 

On Oct 18, 10:04 am, Bret Cahill <BretCah...@aol.com> wrote:

The thermodynamic limits of some batteries' energy densities seem to
be on par with liquid fuel.

You want high energy density? Go for antiprotons. Accept no
substitutes.

Should be a stable technology in, oh, 300 years or so.

Michael

 

The thermodynamic limits of some batteries' energy densities seem to
be on par with liquid fuel.

You want high energy density? �Go for antiprotons. �Accept no
substitutes.

Should be a stable technology in, oh, 300 years or so.

They'll be saying that . . . 300 years from now.


Bret Cahill

 

[Bill Snyder]

On Tue, 21 Oct 2008 16:27:56 -0700 (PDT), mrdarrett@gmail.com
wrote:

On Oct 20, 10:25 pm, BretCah...@peoplepc.com wrote:
The thermodynamic limits of some batteries' energy densities seem to
be on par with liquid fuel.

You want high energy density? Go for antiprotons. Accept no
substitutes.

Should be a stable technology in, oh, 300 years or so.

They'll be saying that . . . 300 years from now.

Bret Cahill


Ha ha ha!

The tough part is keeping the antiprotons from leaking out... oh, and
gamma radiation shielding...

Not a problem; we know from all those cold fusion experiments that
a fraction of an inch of electrolyte is all it takes to stop any
kind of radiation whatsoever. And it even works on cluons, too.

--
Bill Snyder [This space unintentionally left blank]

 

On Oct 20, 10:25 pm, BretCah...@peoplepc.com wrote:

The thermodynamic limits of some batteries' energy densities seem to
be on par with liquid fuel.

You want high energy density? Go for antiprotons. Accept no
substitutes.

Should be a stable technology in, oh, 300 years or so.

They'll be saying that . . . 300 years from now.

Bret Cahill

Ha ha ha!

The tough part is keeping the antiprotons from leaking out... oh, and
gamma radiation shielding...

Michael

 

[Rob Dekker]

<BretCahill@peoplepc.com> wrote in message news:f559ce41-5fd2-4210-b823-fdd687b53831@h2g2000hsg.googlegroups.com...

The thermodynamic limits of some batteries' energy densities seem to
be on par with liquid fuel.

It is very easy to calculate energy density of "theoretically most
energetic" battery.
It will be Li (lightest most energetic reducing agent) + F2 (lightest
and most energetic
oxidizer). Formula is
Energy Density = dG (LiF) (25C, atmospheric pressure) / molar weight
(LiF)

But - what does it help you considering that such battery will never
be made
because of extreme safety concerns and inconvenient storage?

Another concern is living post peak without a good battery.

Someone need to spreadsheet the cost benefit risk analysis.

A battery that occasionally creates a crater in the road may start to
look pretty attractive.

Yevgen's reply about 'safety' is more than the risk of an occasional crater.
It's also about stability and reliability for years of operation under harsh conditions, and under 100's or 1000's of cycles.
Not to mention the toxicity of the material that leaks out upon fracture (due to accidents for example), and costs of recycling.

And the 'inconvenient storage' issue is also very real :
The most energy-dense electro-chemical reaction is (as Yevgen notes) using Lithium Fluoride. In charged form, the Lithium Fluoride
splits in Lithium and Fluorine.
But Fluorine is a (toxic and corrosive) gas. How do you store that dense and safe, for the discharge cycle ? Can't use a latex
balloon for that...

Besides this, there are numerous practical problems :
For one, Lithium Fluoride is a salt, which does not conduct ions by itself. You need to 'dissolve' it in an electrolyte. The
electrolyte adds mass to the cell, thus reducing it's energy density. Alternatively, you could melt the salt to make it (ion)
conductive, but that means heating the battery to 848 °C (1121 K). That's not so practical either.

So the main issue is making practical and safe cells around these powerfull electro-chemical reactions.
And that is an art that electr chemical engineers are getting better and better in with experience.

So in my view, development of safe, low-cost, reliable, high-energy density batteries is an evolutionary process.
There will probably be some sort of Moore's law, albeit at a much lower rate than microelectronic circuit manufacturing.
I think you are likely to see a 10% annual improvement in energy density in battery developments.

Someone needs to at least proffer _some_ reasoning on why the reality
is so much lower.

Because active materials used in reality are satisfying lots of
engineering criteria
that are not thermodynamical in its nature

Thanks for pointing that out. I was getting sick and tired of people
invoking thermodynamics when that isn't the issue.

Still that's the title of your post.

but are needed to make
device practical.
Just to mention a few:

1) electrochemical couple should be possible to store in safe manner
under practical
usage conditions (e.g. no high pressure, liquid nitrogen cooling etc)

2) materials surrounding electrochemical couple (electrodes,
electrolyte) should be
able to survive in the environment long enough for 300-500 cycles
(cycleability)

3) materials have to be electrically conductive (if not, a lot of
weight will be
taken by a porous catalytic electrodes)

Above excludes majority of really energetic active materials. With
these which are left,
another consideration comes to play:

4) supporting materials (electrodes, electrolyte, separators, casing,
binders, conductive additives etc) have weight and volume.

Once all of the above is considered, energy density of a battery is
coinciding very
well with theoretically calculated value. It is a basic arithmetic and
there is nothing
mysterious.

OK, put high energy density on the back burner for awhile.

Instead go to lower energy density but lower cost / higher cycling and/
or higher round trip efficiency.

What are the limits there?

For low-energy density, the limits are probably the cost of the materials.

Bret Cahill

 

The thermodynamic limits of some batteries' energy densities seem to
be on par with liquid fuel.

It is very easy to calculate energy density of "theoretically most
energetic" battery.
It will be Li (lightest most energetic reducing agent) + F2 (lightest
and most energetic
oxidizer). Formula is
Energy Density = dG (LiF) (25C, atmospheric pressure) / molar weight
(LiF)

But - what does it help you considering that such battery will never
be made
because of extreme safety concerns and inconvenient storage?

Another concern is living post peak without a good battery.

Someone need to spreadsheet the cost benefit risk analysis.

A battery that occasionally creates a crater in the road may start to
look pretty attractive.

Yevgen's reply about 'safety' is more than the risk of an occasional crater.
It's also about stability and reliability for years of operation under harsh conditions, and under 100's or 1000's of cycles.
Not to mention the toxicity of the material that leaks out upon fracture (due to accidents for example), and costs of recycling.

And the 'inconvenient storage' issue is also very real :
The most energy-dense electro-chemical reaction is (as Yevgen notes) using Lithium Fluoride. In charged form, the Lithium Fluoride
splits in Lithium and Fluorine.
But Fluorine is a (toxic and corrosive) gas. How do you store that dense and safe, for the discharge cycle ? �Can't use a latex
balloon for that...

Besides this, there are numerous practical problems :
For one, Lithium Fluoride is a salt, which does not conduct ions by itself. You need to 'dissolve' it in an electrolyte. The
electrolyte adds mass to the cell, thus reducing it's energy density. Alternatively, you could melt the salt to make it (ion)
conductive, but that means heating the battery to 848 �C (1121 K).. That's not so practical either.

So the main issue is making practical and safe cells around these powerfull electro-chemical reactions.
And that is an art that electr chemical engineers are getting better and better in with experience.

So in my view, development of safe, low-cost, reliable, high-energy density batteries is an evolutionary process.
There will probably be some sort of Moore's law, albeit at a much lower rate than microelectronic circuit manufacturing.
I think you are likely to see a 10% annual improvement in energy density in battery developments.



Someone needs to at least proffer _some_ reasoning on why the reality
is so much lower.

Because active materials used in reality are satisfying lots of
engineering criteria
that are not thermodynamical in its nature

Thanks for pointing that out. �I was getting sick and tired of people
invoking thermodynamics when that isn't the issue.

Still that's the title of your post.

I was just rubbing Uncle Al's nose into his own poop.

but are needed to make
device practical.
Just to mention a few:

1) electrochemical couple should be possible to store in safe manner
under practical
usage conditions (e.g. no high pressure, liquid nitrogen cooling etc)

2) materials surrounding electrochemical couple (electrodes,
electrolyte) should be
able to survive in the environment long enough for 300-500 cycles
(cycleability)

3) materials have to be electrically conductive (if not, a lot of
weight will be
taken by a porous catalytic electrodes)

Above excludes majority of really energetic active materials. With
these which are left,
another consideration comes to play:

4) supporting materials (electrodes, electrolyte, separators, casing,
binders, conductive additives etc) have weight and volume.

Once all of the above is considered, energy density of a battery is
coinciding very
well with theoretically calculated value. It is a basic arithmetic and
there is nothing
mysterious.

OK, put high energy density on the back burner for awhile.

Instead go to lower energy density but lower cost / higher cycling and/
or higher round trip efficiency.

What are the limits there?

For low-energy density, the limits are probably the cost of the materials..

How did LPS (low purity silicon) get such a bad reputation?


Bret Cahill

 

[Cwatters]

<BretCahill@peoplepc.com> wrote in message
news:ba93fffb-0dc9-470b-879c-9c8464c78023@m74g2000hsh.googlegroups.com...

Why would the electrodes need to be small in the first place?

Because the ratio of electrode to active material effects the energy
density. The mass of the battery case and terminals are also a factor. The
energy density of a AAA cell is worse than an AA cell for this reason.