| Topic: |
Science > Physics |
| User: |
"Ian Parker" |
| Date: |
30 Oct 2006 05:34:47 AM |
| Object: |
Stern - Nonsense and dangerous nonsense |
Why do politicians and economists ignore technology as being key
factors. By 2050 we will be able to place mirrors at the Lagrange point
(L1) which will enable us to reduce the amount of solar energy falling
on Earth. This can be done either by a lightweight sunshield (55kg per
km^2) or by the use of a Von Neumann machine.
If we really want to do anything about global warming this is clearly
the route we should take. It is absolute nonsense to talk about 2050
without reference to the technologies which will be available then. So
1% of the world's economy will be devoted to reducing carbon emissions.
If one part in 10,000 of the world's economy were to be devoted to
research we could find a solution to both these problems.
I would be extremely surprised if by 2050 BOTH these technologies were
not available. Hence the folly of politicians and people like Stern.
This is even without an enhanced program of research. 44 years ago we
were just advancing into single discrete transistors. Is Stern
seriously telling us that there will be no Von Neumann machines, and
(presumably) no AI by 2050. He has taken complete leave of his senses.
We really ought to be thinking much more about how technology will look
in the future. Aircraft will be controlled completely by computers and
using liquid hydrogen. What we should be doing is developing innovative
technologies rather than telling people not to fly.
Carbon trading is nonsense and dangerous nonsense .If we accept that
poor governance is the main cause of poverty carbon trading is absolute
madness. North Korea produces very little CO2 and its nuclear weapons
program would get an enormous fillip from any carbon trading scheme.
Carbon trading will also encourage fundamentalism and have a
detrimental effect on the position of women in Moslem countries. You do
not need women if either :-
1) A sticky black substance comes out of the ground.
2) Mad economists like Stern donate you money.
If money were to be given to NGO such as Oxfam and Cafod this might be
different. Putting money in the hands of bad governments must be the
height of folly.
Stern is nonsense and is DANGEROUS nonsense to boot.
.
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| User: "Charlie Springer" |
|
| Title: Re: Stern - Nonsense and dangerous nonsense |
09 Nov 2006 08:34:50 AM |
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On Thu, 9 Nov 2006 01:30:37 -0800, Ben Newsam wrote
(in article <e6t5l211b2qjodia9paevt7hdag2hbtbal@4ax.com>):
This used to be a nice newsgroup with some smart contributors. Now it looks
like a home for smart asses. The .edu should have been a giveaway.
Which out of sci.physics, sci.space.policy, or rec.aviation.military
is the one with .edu? Sorry if that's a bit too smart for you.
rec.aviation.military
Someone keeps cross posting and I don't always notice. I usually limit to
rec.aviation.military.
Sorry if that's a bit too smart for you.
Think nothing of it. Really.
-- Charlie Springer
.
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| User: "Charlie Springer" |
|
| Title: Re: Stern - Nonsense and dangerous nonsense |
08 Nov 2006 08:48:00 AM |
|
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On Wed, 8 Nov 2006 00:25:36 -0800, wrote
(in article <4wg4h.8$b5.111@news.uchicago.edu>):
I explained to you clearly why the energy density of a capacitor must
remain far inferior to this of chemical fuels and, in fact, even
batteries. If you think that wikipedia is a more reliable source than
decent physics textbooks, that's your problem.
You "explained" in some sort of scio-bable that I, as a practiicing physicist
and teacher, didn't recognize as anything but a science version of babies
found in cabbage patches.
As for the Wikipedia URL, the reliability of that article is not in question
since it simply refers to available commercial products, as does the second
link.
The fact that people like you used to say a Farad HAD TO BE the size of a
lecture hall is wasted on you (surprise!). The 95+% efficiency of the new
caps might also give you a hint that your comparison to chemical bonding
energies might need a few other factors when applied to the real world.
Show us a calc. Compare a 50 Farad gel cap (2.5 volts) to its weight in your
favorite fuel. OK, use mass. How about .01 grams?
-- Charlie Springer
.
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| User: "" |
|
| Title: Re: Stern - Nonsense and dangerous nonsense |
08 Nov 2006 04:52:40 PM |
|
|
In article <61a924-o14.ln1@mail.specsol.com>, writes:
In sci.physics Charlie Springer <RAM@regnirps.com> wrote:
<snip>
Packaged for small applications, these gels have 10 Farads per cc and about
14 grams for 50 farads at 2.5 volts. The weight is all in the enclosure and
leads. The development curve is just at the beginning. They also hold charge
for weeks and can charge faster than you could fill a fuel tank. There are
many ways to get electricity, even in remote locations. Many more than 100LL
avgas.
Hmmm...
Gasoline is about 1.3X10^8 J/gal.
My Tiger holds 50 gallons, or about 6.5X10^9 J.
Assume a capacitor voltage of 100 V.
The energy in a capacitor = C*V^2/2.
Therefor, the capacitance required for the specified voltage and energy
is 1.3X10^6 F.
Since a discharged capacitor looks like a short, we will have to current
limit the charging process.
Lets use a standard AC outlet which is capable of the 100 V and limited
to 15 A.
A capacitor charges at I = C dv/dt.
At a 15 A charge rate, the capacitor will charge at 1.1X10^-9 V/S.
Therefor it will take 8.6X10^10 S to charge the capacitor to the
same energy level as the gas tanks in my Tiger.
It takes about 900 seconds to fill the tanks on my Tiger, most of
that time being fideling with the hose.
Feel free to double check the arithmatic, I did it quickly as I'm going
to go fly.
It is worse than this, supercaps are low voltage devices, like
2.2-2.5 V. So, you need way more capacitance.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
.
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| User: "" |
|
| Title: Re: Stern - Nonsense and dangerous nonsense |
08 Nov 2006 05:44:17 PM |
|
|
In article <kp5a24-7ph.ln1@mail.specsol.com>, writes:
In sci.physics wrote:
In article <61a924-o14.ln1@mail.specsol.com>, writes:
In sci.physics Charlie Springer <RAM@regnirps.com> wrote:
<snip>
Packaged for small applications, these gels have 10 Farads per cc and about
14 grams for 50 farads at 2.5 volts. The weight is all in the enclosure and
leads. The development curve is just at the beginning. They also hold charge
for weeks and can charge faster than you could fill a fuel tank. There are
many ways to get electricity, even in remote locations. Many more than 100LL
avgas.
Hmmm...
Gasoline is about 1.3X10^8 J/gal.
My Tiger holds 50 gallons, or about 6.5X10^9 J.
Assume a capacitor voltage of 100 V.
The energy in a capacitor = C*V^2/2.
Therefor, the capacitance required for the specified voltage and energy
is 1.3X10^6 F.
Since a discharged capacitor looks like a short, we will have to current
limit the charging process.
Lets use a standard AC outlet which is capable of the 100 V and limited
to 15 A.
A capacitor charges at I = C dv/dt.
At a 15 A charge rate, the capacitor will charge at 1.1X10^-9 V/S.
Therefor it will take 8.6X10^10 S to charge the capacitor to the
same energy level as the gas tanks in my Tiger.
It takes about 900 seconds to fill the tanks on my Tiger, most of
that time being fideling with the hose.
Feel free to double check the arithmatic, I did it quickly as I'm going
to go fly.
It is worse than this, supercaps are low voltage devices, like
2.2-2.5 V. So, you need way more capacitance.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
Yeah, I know, which makes "supercaps" pretty useless for powering
motors.
If you use too low a voltage you are expending all your energy heating
the wires to and in the motor.
If you use too high a voltage, you have control and arcing issues.
About 100 V is where you would want to run if "miraclecaps" are ever
invented.
There is still the problem of the 1 Gigamp current source you would
need to charge in a reasonable time, not to mention who's going to
be able to lift the connector you will need.
Yes, this will be interesting:-) In the meantime, anyway, their
energy density is really not up to far. The high-end quoted numbers
are circa 10 Wh/kg. That's 4 orders of magnitude below chemical
fuels.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
.
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| User: "Ian Parker" |
|
| Title: Re: Stern - Nonsense and dangerous nonsense |
10 Nov 2006 10:25:37 AM |
|
|
wrote:
There is still the problem of the 1 Gigamp current source you would
need to charge in a reasonable time, not to mention who's going to
be able to lift the connector you will need.
Yes, this will be interesting:-) In the meantime, anyway, their
energy density is really not up to far. The high-end quoted numbers
are circa 10 Wh/kg. That's 4 orders of magnitude below chemical
fuels.
There is one further idea the gyroscope. I am including it not so much
as a serious contender but because people have talked about elevators
and going to GEO.
If a drum is rotating its enery is v^2/2 per kg. The tensile strength
needed to contain the pressure will be v^2*density. This is known as
specific tensile strength. The specific strength of carbon fiber is
2GPa/density. This gives a velocity of 1.4 km/s and an energy density
of 10^3kw/s/kg. Nanotubes have been tested at 63GPa a specific strength
of about 20. This would (in theory) be capablle of useful flights at
10^4. You could stay aloft with 10% of your mass for about 2hr
@720km/h. Theoretical strengths of about 150 are postulated. Of course
there must always be a safely factor. GEO wouold represent about
10km/s. A drum rotating at at 10km/s would need a specific tensile
strength of 100. Now an elevator would be tapered. If we postulated e^4
ratio of sizes this gives a specific tensile strength of 12.5. (the
inverted bar requires 1/2 the tensile strength of the drum.
The strength required is dependent only on velocity and is independent
of soze. I am posting this to give you some idea of orders of
magnitude. You could rotate the tip of the model of the elevator so
that it was going at 7km/s (just below orbital velocity. The strength
requirements are the same.
-Ian Parker
.
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| User: "" |
|
| Title: Re: Stern - Nonsense and dangerous nonsense |
10 Nov 2006 05:13:09 PM |
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In article <1163175937.378041.191340@k70g2000cwa.googlegroups.com>, "Ian Parker" <ianparker2@gmail.com> writes:
mmeron@cars3.uchicago.edu wrote:
There is still the problem of the 1 Gigamp current source you would
need to charge in a reasonable time, not to mention who's going to
be able to lift the connector you will need.
Yes, this will be interesting:-) In the meantime, anyway, their
energy density is really not up to far. The high-end quoted numbers
are circa 10 Wh/kg. That's 4 orders of magnitude below chemical
fuels.
There is one further idea the gyroscope. I am including it not so much
as a serious contender but because people have talked about elevators
and going to GEO.
If a drum is rotating its enery is v^2/2 per kg. The tensile strength
needed to contain the pressure will be v^2*density. This is known as
specific tensile strength. The specific strength of carbon fiber is
2GPa/density. This gives a velocity of 1.4 km/s and an energy density
of 10^3kw/s/kg. Nanotubes have been tested at 63GPa a specific strength
of about 20. This would (in theory) be capablle of useful flights at
10^4. You could stay aloft with 10% of your mass for about 2hr
@720km/h. Theoretical strengths of about 150 are postulated. Of course
there must always be a safely factor. GEO wouold represent about
10km/s. A drum rotating at at 10km/s would need a specific tensile
strength of 100. Now an elevator would be tapered. If we postulated e^4
ratio of sizes this gives a specific tensile strength of 12.5. (the
inverted bar requires 1/2 the tensile strength of the drum.
The strength required is dependent only on velocity and is independent
of soze. I am posting this to give you some idea of orders of
magnitude. You could rotate the tip of the model of the elevator so
that it was going at 7km/s (just below orbital velocity. The strength
requirements are the same.
Well, you know, people know for a long, long time, that the yield
strength of single crystal metal whiskers (for various metals) can
exceed the yield strength of bulk metal by as much as two orders of
magnitude. And, this didn't translate ito "therefore we can make bulk
metals with this strength". Thus, it doesn't necessarily follow that
the yield strength of bulk materials made of nanotubes will be
anywhere near this of individual nanotubes. Bulk materials contain
imperfections and in this case the chain is as strong as the weakest
link.
So, if and when we'll have materials of sufficient strength, then
there'll be something to talk about. Before, not really.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
.
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| User: "Ian Parker" |
|
| Title: Re: Stern - Nonsense and dangerous nonsense |
11 Nov 2006 04:36:37 AM |
|
|
wrote:
In article <1163175937.378041.191340@k70g2000cwa.googlegroups.com>, "Ian Parker" <ianparker2@gmail.com> writes:
wrote:
There is still the problem of the 1 Gigamp current source you would
need to charge in a reasonable time, not to mention who's going to
be able to lift the connector you will need.
Yes, this will be interesting:-) In the meantime, anyway, their
energy density is really not up to far. The high-end quoted numbers
are circa 10 Wh/kg. That's 4 orders of magnitude below chemical
fuels.
There is one further idea the gyroscope. I am including it not so much
as a serious contender but because people have talked about elevators
and going to GEO.
If a drum is rotating its enery is v^2/2 per kg. The tensile strength
needed to contain the pressure will be v^2*density. This is known as
specific tensile strength. The specific strength of carbon fiber is
2GPa/density. This gives a velocity of 1.4 km/s and an energy density
of 10^3kw/s/kg. Nanotubes have been tested at 63GPa a specific strength
of about 20. This would (in theory) be capablle of useful flights at
10^4. You could stay aloft with 10% of your mass for about 2hr
@720km/h. Theoretical strengths of about 150 are postulated. Of course
there must always be a safely factor. GEO wouold represent about
10km/s. A drum rotating at at 10km/s would need a specific tensile
strength of 100. Now an elevator would be tapered. If we postulated e^4
ratio of sizes this gives a specific tensile strength of 12.5. (the
inverted bar requires 1/2 the tensile strength of the drum.
The strength required is dependent only on velocity and is independent
of soze. I am posting this to give you some idea of orders of
magnitude. You could rotate the tip of the model of the elevator so
that it was going at 7km/s (just below orbital velocity. The strength
requirements are the same.
Well, you know, people know for a long, long time, that the yield
strength of single crystal metal whiskers (for various metals) can
exceed the yield strength of bulk metal by as much as two orders of
magnitude. And, this didn't translate ito "therefore we can make bulk
metals with this strength". Thus, it doesn't necessarily follow that
the yield strength of bulk materials made of nanotubes will be
anywhere near this of individual nanotubes. Bulk materials contain
imperfections and in this case the chain is as strong as the weakest
link.
So, if and when we'll have materials of sufficient strength, then
there'll be something to talk about. Before, not really.
This is true. Are you from sci.space.policy or rec.aviation.military?
As I said I m writing more to let people get a flavor or orders of
magnitude rather than as a serious proposition. There are people out
there who talk about elevators. They convenienly forget that if you
could build an elevator you could lift a light aircraft (empty) onto
your back, and building an SSTO would be trivial. Thus if we could
build an elevator we probably would not want to! A fleet of SSTOs would
be a far better bet.
On the general question of (serious) materials science, it is moving in
the direction of composite materials. You make aircraft parts out of
plastic reinforced with carbon fiber and the best material (probably)
for super/hypersonics would be ceramic with carbon fiber.
- Ian Parker
.
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| User: "David M. Palmer" |
|
| Title: Re: Stern - Nonsense and dangerous nonsense |
11 Nov 2006 10:15:35 AM |
|
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In article <1163241397.072572.82590@f16g2000cwb.googlegroups.com>, Ian
Parker <ianparker2@gmail.com> wrote:
This is true. Are you from sci.space.policy or rec.aviation.military?
As I said I m writing more to let people get a flavor or orders of
magnitude rather than as a serious proposition. There are people out
there who talk about elevators. They convenienly forget that if you
could build an elevator you could lift a light aircraft (empty) onto
your back, and building an SSTO would be trivial. Thus if we could
build an elevator we probably would not want to! A fleet of SSTOs would
be a far better bet.
You can already lift a light aircraft onto your back. Of course, at
that point it is defined as an ultralight.
Building an SSTO is trivial compared to building a space elevator.
Even LockMart thought they could build one. (Or rather, they were able
to convince NASA that they could build one, which for LockMart is
easier and, for the people who probably could build SSTOs, harder.)
--
David M. Palmer (formerly @clark.net, @ematic.com)
.
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| User: "" |
|
| Title: Re: Stern - Nonsense and dangerous nonsense |
11 Nov 2006 11:24:32 AM |
|
|
In article <1163241397.072572.82590@f16g2000cwb.googlegroups.com>, "Ian Parker" <ianparker2@gmail.com> writes:
mmeron@cars3.uchicago.edu wrote:
In article <1163175937.378041.191340@k70g2000cwa.googlegroups.com>, "Ian Parker" <ianparker2@gmail.com> writes:
mmeron@cars3.uchicago.edu wrote:
There is still the problem of the 1 Gigamp current source you would
need to charge in a reasonable time, not to mention who's going to
be able to lift the connector you will need.
Yes, this will be interesting:-) In the meantime, anyway, their
energy density is really not up to far. The high-end quoted numbers
are circa 10 Wh/kg. That's 4 orders of magnitude below chemical
fuels.
There is one further idea the gyroscope. I am including it not so much
as a serious contender but because people have talked about elevators
and going to GEO.
If a drum is rotating its enery is v^2/2 per kg. The tensile strength
needed to contain the pressure will be v^2*density. This is known as
specific tensile strength. The specific strength of carbon fiber is
2GPa/density. This gives a velocity of 1.4 km/s and an energy density
of 10^3kw/s/kg. Nanotubes have been tested at 63GPa a specific strength
of about 20. This would (in theory) be capablle of useful flights at
10^4. You could stay aloft with 10% of your mass for about 2hr
@720km/h. Theoretical strengths of about 150 are postulated. Of course
there must always be a safely factor. GEO wouold represent about
10km/s. A drum rotating at at 10km/s would need a specific tensile
strength of 100. Now an elevator would be tapered. If we postulated e^4
ratio of sizes this gives a specific tensile strength of 12.5. (the
inverted bar requires 1/2 the tensile strength of the drum.
The strength required is dependent only on velocity and is independent
of soze. I am posting this to give you some idea of orders of
magnitude. You could rotate the tip of the model of the elevator so
that it was going at 7km/s (just below orbital velocity. The strength
requirements are the same.
Well, you know, people know for a long, long time, that the yield
strength of single crystal metal whiskers (for various metals) can
exceed the yield strength of bulk metal by as much as two orders of
magnitude. And, this didn't translate ito "therefore we can make bulk
metals with this strength". Thus, it doesn't necessarily follow that
the yield strength of bulk materials made of nanotubes will be
anywhere near this of individual nanotubes. Bulk materials contain
imperfections and in this case the chain is as strong as the weakest
link.
So, if and when we'll have materials of sufficient strength, then
there'll be something to talk about. Before, not really.
This is true. Are you from sci.space.policy or rec.aviation.military?
Neither, I'm from sci.physics (aka "the nuthouse":-))
As I said I m writing more to let people get a flavor or orders of
magnitude rather than as a serious proposition. There are people out
there who talk about elevators. They convenienly forget that if you
could build an elevator you could lift a light aircraft (empty) onto
your back, and building an SSTO would be trivial. Thus if we could
build an elevator we probably would not want to! A fleet of SSTOs would
be a far better bet.
That's a very good point, yes.
On the general question of (serious) materials science, it is moving in
the direction of composite materials. You make aircraft parts out of
plastic reinforced with carbon fiber and the best material (probably)
for super/hypersonics would be ceramic with carbon fiber.
Yep, the "reinforced concrete" solution, over again.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
.
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| User: "" |
|
| Title: Re: Stern - Nonsense and dangerous nonsense |
08 Nov 2006 05:35:02 PM |
|
|
In sci.physics wrote:
In article <61a924-o14.ln1@mail.specsol.com>, writes:
In sci.physics Charlie Springer <RAM@regnirps.com> wrote:
<snip>
Packaged for small applications, these gels have 10 Farads per cc and about
14 grams for 50 farads at 2.5 volts. The weight is all in the enclosure and
leads. The development curve is just at the beginning. They also hold charge
for weeks and can charge faster than you could fill a fuel tank. There are
many ways to get electricity, even in remote locations. Many more than 100LL
avgas.
Hmmm...
Gasoline is about 1.3X10^8 J/gal.
My Tiger holds 50 gallons, or about 6.5X10^9 J.
Assume a capacitor voltage of 100 V.
The energy in a capacitor = C*V^2/2.
Therefor, the capacitance required for the specified voltage and energy
is 1.3X10^6 F.
Since a discharged capacitor looks like a short, we will have to current
limit the charging process.
Lets use a standard AC outlet which is capable of the 100 V and limited
to 15 A.
A capacitor charges at I = C dv/dt.
At a 15 A charge rate, the capacitor will charge at 1.1X10^-9 V/S.
Therefor it will take 8.6X10^10 S to charge the capacitor to the
same energy level as the gas tanks in my Tiger.
It takes about 900 seconds to fill the tanks on my Tiger, most of
that time being fideling with the hose.
Feel free to double check the arithmatic, I did it quickly as I'm going
to go fly.
It is worse than this, supercaps are low voltage devices, like
2.2-2.5 V. So, you need way more capacitance.
Mati Meron | "When you argue with a fool,
meron@cars.uchicago.edu | chances are he is doing just the same"
Yeah, I know, which makes "supercaps" pretty useless for powering
motors.
If you use too low a voltage you are expending all your energy heating
the wires to and in the motor.
If you use too high a voltage, you have control and arcing issues.
About 100 V is where you would want to run if "miraclecaps" are ever
invented.
There is still the problem of the 1 Gigamp current source you would
need to charge in a reasonable time, not to mention who's going to
be able to lift the connector you will need.
--
Jim Pennino
Remove .spam.sux to reply.
.
|
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| User: "Charlie Springer" |
|
| Title: Re: Stern - Nonsense and dangerous nonsense |
08 Nov 2006 09:44:03 PM |
|
|
On Wed, 8 Nov 2006 15:35:02 -0800, wrote
(in article <kp5a24-7ph.ln1@mail.specsol.com>):
Yeah, I know, which makes "supercaps" pretty useless for powering
motors.
If you use too low a voltage you are expending all your energy heating
the wires to and in the motor.
If you use too high a voltage, you have control and arcing issues.
About 100 V is where you would want to run if "miraclecaps" are ever
invented.
There is still the problem of the 1 Gigamp current source you would
need to charge in a reasonable time, not to mention who's going to
be able to lift the connector you will need.
400 volts and higher (much higher sometimes) is preferred for the thrusters
on underwater vehicles. I interviewed several times at MBARI but was
uncomfortable with designing systems running thousands of volts DC at high
current for use on steel decks wet with sea water. There is some weight and
efficiency advantage but I have not studied it. It is counter-intuitive since
only current determines the magnetic field.
-- Charlie Springer
.
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|
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| User: "" |
|
| Title: Re: Stern - Nonsense and dangerous nonsense |
08 Nov 2006 11:35:03 PM |
|
|
In sci.physics Charlie Springer <RAM@regnirps.com> wrote:
On Wed, 8 Nov 2006 15:35:02 -0800, wrote
(in article <kp5a24-7ph.ln1@mail.specsol.com>):
Yeah, I know, which makes "supercaps" pretty useless for powering
motors.
If you use too low a voltage you are expending all your energy heating
the wires to and in the motor.
If you use too high a voltage, you have control and arcing issues.
About 100 V is where you would want to run if "miraclecaps" are ever
invented.
There is still the problem of the 1 Gigamp current source you would
need to charge in a reasonable time, not to mention who's going to
be able to lift the connector you will need.
400 volts and higher (much higher sometimes) is preferred for the thrusters
on underwater vehicles. I interviewed several times at MBARI but was
uncomfortable with designing systems running thousands of volts DC at high
current for use on steel decks wet with sea water. There is some weight and
efficiency advantage but I have not studied it. It is counter-intuitive since
only current determines the magnetic field.
Hardly.
Since I=V/R, the higher the voltage, the easier it is to get a higher
current with real world materials.
--
Jim Pennino
Remove .spam.sux to reply.
.
|
|
|
| User: "Ian Parker" |
|
| Title: Re: Stern - Nonsense and dangerous nonsense |
10 Nov 2006 06:14:47 AM |
|
|
wrote:
In sci.physics Charlie Springer <RAM@regnirps.com> wrote:
On Wed, 8 Nov 2006 15:35:02 -0800, wrote
(in article <kp5a24-7ph.ln1@mail.specsol.com>):
Yeah, I know, which makes "supercaps" pretty useless for powering
motors.
If you use too low a voltage you are expending all your energy heating
the wires to and in the motor.
If you use too high a voltage, you have control and arcing issues.
About 100 V is where you would want to run if "miraclecaps" are ever
invented.
There is still the problem of the 1 Gigamp current source you would
need to charge in a reasonable time, not to mention who's going to
be able to lift the connector you will need.
400 volts and higher (much higher sometimes) is preferred for the thrusters
on underwater vehicles. I interviewed several times at MBARI but was
uncomfortable with designing systems running thousands of volts DC at high
current for use on steel decks wet with sea water. There is some weight and
efficiency advantage but I have not studied it. It is counter-intuitive since
only current determines the magnetic field.
Hardly.
Since I=V/R, the higher the voltage, the easier it is to get a higher
current with real world materials.
No one has looked at fuel cells. They are at the moment about 1 order
of magnitude away from aviation. Capacitors or springs are 2 or more
orders away. At present the best fuel cells are about 7kg/kw. Aviation
requires just one OOM better, Let us assume a blended wing (L/D 20:1)
moving at 720km/h (200m/s). It needs too lift itself 10m/s and must
therefore provode thrust at 100w/kg (9.81 = 10 for rough and ready
calculations). Some energy will be lost in friction, we do not have an
infinite mass of air etc. Thus we arrive at about 130w/kg. This means
that (present technolgy) the whole mass of the aircraft is its fuel
cell. An order of magnitude gives workable figures.
How do we get out OOM. For aircraft we need high temperature cells, we
need a ceramic electolyte created by nanotechnology. That will produce
1kw/kg or better. I cannot see any other solution.
- Ian Parker
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| User: "" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
10 Nov 2006 10:05:03 AM |
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In sci.physics Ian Parker <ianparker2@gmail.com> wrote:
wrote:
In sci.physics Charlie Springer <RAM@regnirps.com> wrote:
On Wed, 8 Nov 2006 15:35:02 -0800, wrote
(in article <kp5a24-7ph.ln1@mail.specsol.com>):
Yeah, I know, which makes "supercaps" pretty useless for powering
motors.
If you use too low a voltage you are expending all your energy heating
the wires to and in the motor.
If you use too high a voltage, you have control and arcing issues.
About 100 V is where you would want to run if "miraclecaps" are ever
invented.
There is still the problem of the 1 Gigamp current source you would
need to charge in a reasonable time, not to mention who's going to
be able to lift the connector you will need.
400 volts and higher (much higher sometimes) is preferred for the thrusters
on underwater vehicles. I interviewed several times at MBARI but was
uncomfortable with designing systems running thousands of volts DC at high
current for use on steel decks wet with sea water. There is some weight and
efficiency advantage but I have not studied it. It is counter-intuitive since
only current determines the magnetic field.
Hardly.
Since I=V/R, the higher the voltage, the easier it is to get a higher
current with real world materials.
No one has looked at fuel cells.
Nonsense, there's lots of people looking at fuel cells.
They are at the moment about 1 order
of magnitude away from aviation.
More like 2 ignoring cost.
Capacitors or springs are 2 or more
orders away.
Capacitors are more like 4 orders of magnitude. The concept of a spring
powered, man carrying aircraft is ludicrous.
At present the best fuel cells are about 7kg/kw. Aviation
requires just one OOM better, Let us assume a blended wing (L/D 20:1)
moving at 720km/h (200m/s). It needs too lift itself 10m/s and must
therefore provode thrust at 100w/kg (9.81 = 10 for rough and ready
calculations). Some energy will be lost in friction, we do not have an
infinite mass of air etc. Thus we arrive at about 130w/kg. This means
that (present technolgy) the whole mass of the aircraft is its fuel
cell. An order of magnitude gives workable figures.
You pulled those numbers out of your *****, didn't you?
How do we get out OOM. For aircraft we need high temperature cells, we
need a ceramic electolyte created by nanotechnology. That will produce
1kw/kg or better. I cannot see any other solution.
Jet-A, FADC diesels.
--
Jim Pennino
Remove .spam.sux to reply.
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| User: "John C. Polasek" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
10 Nov 2006 08:15:54 AM |
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On 10 Nov 2006 04:14:47 -0800, "Ian Parker" <ianparker2@gmail.com>
wrote:
wrote:
In sci.physics Charlie Springer <RAM@regnirps.com> wrote:
On Wed, 8 Nov 2006 15:35:02 -0800, wrote
(in article <kp5a24-7ph.ln1@mail.specsol.com>):
Yeah, I know, which makes "supercaps" pretty useless for powering
motors.
If you use too low a voltage you are expending all your energy heating
the wires to and in the motor.
If you use too high a voltage, you have control and arcing issues.
About 100 V is where you would want to run if "miraclecaps" are ever
invented.
There is still the problem of the 1 Gigamp current source you would
need to charge in a reasonable time, not to mention who's going to
be able to lift the connector you will need.
400 volts and higher (much higher sometimes) is preferred for the thrusters
on underwater vehicles. I interviewed several times at MBARI but was
uncomfortable with designing systems running thousands of volts DC at high
current for use on steel decks wet with sea water. There is some weight and
efficiency advantage but I have not studied it. It is counter-intuitive since
only current determines the magnetic field.
Hardly.
Since I=V/R, the higher the voltage, the easier it is to get a higher
current with real world materials.
No one has looked at fuel cells. They are at the moment about 1 order
of magnitude away from aviation. Capacitors or springs are 2 or more
orders away. At present the best fuel cells are about 7kg/kw. Aviation
requires just one OOM better, Let us assume a blended wing (L/D 20:1)
moving at 720km/h (200m/s). It needs too lift itself 10m/s and must
therefore provode thrust at 100w/kg (9.81 = 10 for rough and ready
calculations). Some energy will be lost in friction, we do not have an
infinite mass of air etc. Thus we arrive at about 130w/kg. This means
that (present technolgy) the whole mass of the aircraft is its fuel
cell. An order of magnitude gives workable figures.
How do we get out OOM. For aircraft we need high temperature cells, we
need a ceramic electolyte created by nanotechnology. That will produce
1kw/kg or better. I cannot see any other solution.
- Ian Parker
Let whoever is promoting capacitors make up a capacitor flashlight
that should operate for at least 5 minutes with decent light. It would
be convincing proof of concept.
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| User: "Robert" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
10 Nov 2006 12:39:01 PM |
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"John C. Polasek" <jpolasek@cfl.rr.com> wrote in message
news:ha29l2l5lkgplaq0ct62m55lkl0ene7uug@4ax.com...
On 10 Nov 2006 04:14:47 -0800, "Ian Parker" <ianparker2@gmail.com>
wrote:
[trim]
Let whoever is promoting capacitors make up a capacitor flashlight
that should operate for at least 5 minutes with decent light. It would
be convincing proof of concept.
They are at Wal-Mart for $12.
All the current generation of 'emergency' crank flashlights work this way.
The ones that look like a phazor with a hand crank on the back.
The key for flashlights is using low power LED's. They beat the hell out of
my old crank flashlight that has a an incandescent bulb. Both on brightness
and runtime between cranks (mine requires almost continuous pumping), I was
too cheap to buy one of the ones with the wind-up spring, just to keep in
back of the seat of my pickup and only use when the battery in my maglite
didn't work. So I have one with a flywheel.
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| User: "" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
10 Nov 2006 10:15:02 AM |
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In sci.physics John C. Polasek <jpolasek@cfl.rr.com> wrote:
<snip>
Let whoever is promoting capacitors make up a capacitor flashlight
that should operate for at least 5 minutes with decent light. It would
be convincing proof of concept.
That's hardly a challenge.
The current crop of "supercapacitors" are good for about 2.5 V, more
than enough voltage to run bright LEDs. Moreover, the relatively tiny
total energy required to charge and run a flashlight for even an hour is
trivial to get from an ordinary household 15 A outlet.
This is no more a proof of concept test of making a capacitor powered
aircraft than a paper airplane is a proof of concept for a paper airliner.
--
Jim Pennino
Remove .spam.sux to reply.
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| User: "John C. Polasek" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
10 Nov 2006 01:24:59 PM |
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On Fri, 10 Nov 2006 16:15:02 GMT, wrote:
In sci.physics John C. Polasek <jpolasek@cfl.rr.com> wrote:
<snip>
Let whoever is promoting capacitors make up a capacitor flashlight
that should operate for at least 5 minutes with decent light. It would
be convincing proof of concept.
That's hardly a challenge.
The current crop of "supercapacitors" are good for about 2.5 V, more
than enough voltage to run bright LEDs.
You don't know what you're talking about. It's not about voltage at
all.
Moreover, the relatively tiny
total energy required to charge and run a flashlight for even an hour is
trivial to get from an ordinary household 15 A outlet.
Yes, I've even seen 'em run a toaster off 115.
Yes it's easy to charge a nicad so it will run a flashlight for an
hour. A capacitor is an entirely different thing. Let me tell you
about it.
A capacitor depends on its dielectric and every dielectric has a time
constant, could be seconds, might be a minute or two. It makes no
difference what the capacity is, the leakdown time is the
unchangeable.
The capacity is proportional to area over gap. The leakage rate is
proportional to area over gap. The ratio is farads x resistivity = T
seconds.
I don't think you will ever find a miracle dielectric with a 1 hour
time constant (leaks down to 37% in one hour).
This is no more a proof of concept test of making a capacitor powered
aircraft than a paper airplane is a proof of concept for a paper airliner.
Yes, it would be a proof of concept. Make such a flashlight and tell
me about it. And don't cheat with 20 mAmpere LED's. I need a
flashlight bulb that draws 300 mA.
John Polasek
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| User: "" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
10 Nov 2006 02:55:20 PM |
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In sci.physics John C. Polasek <jpolasek@cfl.rr.com> wrote:
On Fri, 10 Nov 2006 16:15:02 GMT, wrote:
In sci.physics John C. Polasek <jpolasek@cfl.rr.com> wrote:
<snip>
Let whoever is promoting capacitors make up a capacitor flashlight
that should operate for at least 5 minutes with decent light. It would
be convincing proof of concept.
That's hardly a challenge.
The current crop of "supercapacitors" are good for about 2.5 V, more
than enough voltage to run bright LEDs.
You don't know what you're talking about. It's not about voltage at
all.
Voltage is a peripheral issue, but relevant if you are going to run
a vehicle.
2.5 V would be a highly impractical motor voltage for a vehicle, but
entirely practical for a flashlight.
Moreover, the relatively tiny
total energy required to charge and run a flashlight for even an hour is
trivial to get from an ordinary household 15 A outlet.
Yes, I've even seen 'em run a toaster off 115.
Did you burn yourself in this endevour?
Yes it's easy to charge a nicad so it will run a flashlight for an
hour.
Who said anything about nicads? Are you hearing voices?
A capacitor is an entirely different thing.
No *****?
Let me tell you
about it.
I can hardly wait.
A capacitor depends on its dielectric and every dielectric has a time
constant, could be seconds, might be a minute or two. It makes no
difference what the capacity is, the leakdown time is the
unchangeable.
Capacitors don't have time constants, RC circuits have time contants.
Real capacitors do have leakage resistance that depends on the
dielectric material used and it's thickness. For high voltage capacitors
the insulation resistance becomes a bigger factor than the leakage
resistance.
The capacity is proportional to area over gap. The leakage rate is
proportional to area over gap. The ratio is farads x resistivity = T
seconds.
Well, not quite, but close enough.
I don't think you will ever find a miracle dielectric with a 1 hour
time constant (leaks down to 37% in one hour).
Trivially shown to be false by looking at capacitor manufacturers
catalogs.
Have you ever heard of a vacuum capacitor?
This is no more a proof of concept test of making a capacitor powered
aircraft than a paper airplane is a proof of concept for a paper airliner.
Yes, it would be a proof of concept.
Which, the flashlight or the paper airplane?
Make such a flashlight and tell
me about it. And don't cheat with 20 mAmpere LED's. I need a
flashlight bulb that draws 300 mA.
You do know you can buy such things, don't you?
John Polasek
--
Jim Pennino
Remove .spam.sux to reply.
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| User: "David M. Palmer" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
10 Nov 2006 02:38:50 PM |
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Modern capacitors really are something that's better than what our
grandparents had. Not nearly good enough for passenger aircraft yet,
but better than you expect.
In article <ctj9l2p11c4mc4qgbvl7i1ln74qeuq8blm@4ax.com>, John C.
Polasek <jpolasek@cfl.rr.com> wrote:
On Fri, 10 Nov 2006 16:15:02 GMT, wrote:
In sci.physics John C. Polasek <jpolasek@cfl.rr.com> wrote:
<snip>
Let whoever is promoting capacitors make up a capacitor flashlight
that should operate for at least 5 minutes with decent light. It would
be convincing proof of concept.
That's hardly a challenge.
The current crop of "supercapacitors" are good for about 2.5 V, more
than enough voltage to run bright LEDs.
You don't know what you're talking about. It's not about voltage at
all.
E = 1/2 C V^2
Take a typical off-the shelf ultracap like Maxwell's BCAP0350 E250
which puts 350 F at 2.5 V into a D-cell sized package. That's about a
kilojoule. Comparable to an alkaline AAA.
http://www.maxwell.com/pdf/uc/datasheets/BC_Cell_Energy_1009473_rev2.pdf
A capacitor depends on its dielectric and every dielectric has a time
constant, could be seconds, might be a minute or two. It makes no
difference what the capacity is, the leakdown time is the
unchangeable.
The capacity is proportional to area over gap. The leakage rate is
proportional to area over gap. The ratio is farads x resistivity = T
seconds.
I don't think you will ever find a miracle dielectric with a 1 hour
time constant (leaks down to 37% in one hour).
The leakage current of that capacitor is speced at 1 mA. So over 100
hours, it will leak 360 coulombs and so drop from 2.5 V to 1.5 V
(assuming that it doesn't do any better than its spec and maintains the
1 mA leakage at the lower voltage).
If you want a longer time constant, the 140 F 2.5V capacitor in the
same package has only 0.1 mA of leakage current. That's a time
constant of 40 days (Cue joke about Ark-lights)
This is no more a proof of concept test of making a capacitor powered
aircraft than a paper airplane is a proof of concept for a paper airliner.
Yes, it would be a proof of concept. Make such a flashlight and tell
me about it. And don't cheat with 20 mAmpere LED's. I need a
flashlight bulb that draws 300 mA.
Because the harsh light of a luxeon is so unflattering, you need the
warmth of tungsten to bring out your complexion.
350 F/300 mA -> about 20 minutes of light to go from 2.5 V to 1.5 V.
Of course you'd use a boost regulator so you'd uniformly suck joules
not amps to keep constant brightness. A 1 W flashlight like the
Surefire L1 (second on this list of bright flashlights
http://www.uwgb.edu/nevermab/led.htm
) would last for more like 15 minutes on full brightness.
--
David M. Palmer (formerly @clark.net, @ematic.com)
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| User: "John C. Polasek" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
11 Nov 2006 09:38:13 AM |
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On Fri, 10 Nov 2006 13:38:50 -0700, "David M. Palmer"
<dmpalmer@email.com> wrote:
Modern capacitors really are something that's better than what our
grandparents had. Not nearly good enough for passenger aircraft yet,
but better than you expect.
In article <ctj9l2p11c4mc4qgbvl7i1ln74qeuq8blm@4ax.com>, John C.
Polasek <jpolasek@cfl.rr.com> wrote:
On Fri, 10 Nov 2006 16:15:02 GMT, wrote:
In sci.physics John C. Polasek <jpolasek@cfl.rr.com> wrote:
<snip>
Let whoever is promoting capacitors make up a capacitor flashlight
that should operate for at least 5 minutes with decent light. It would
be convincing proof of concept.
That's hardly a challenge.
The current crop of "supercapacitors" are good for about 2.5 V, more
than enough voltage to run bright LEDs.
You don't know what you're talking about. It's not about voltage at
all.
E = 1/2 C V^2
Take a typical off-the shelf ultracap like Maxwell's BCAP0350 E250
which puts 350 F at 2.5 V into a D-cell sized package. That's about a
kilojoule. Comparable to an alkaline AAA.
http://www.maxwell.com/pdf/uc/datasheets/BC_Cell_Energy_1009473_rev2.pdf
A capacitor depends on its dielectric and every dielectric has a time
constant, could be seconds, might be a minute or two. It makes no
difference what the capacity is, the leakdown time is the
unchangeable.
The capacity is proportional to area over gap. The leakage rate is
proportional to area over gap. The ratio is farads x resistivity = T
seconds.
I don't think you will ever find a miracle dielectric with a 1 hour
time constant (leaks down to 37% in one hour).
The leakage current of that capacitor is speced at 1 mA. So over 100
hours, it will leak 360 coulombs and so drop from 2.5 V to 1.5 V
(assuming that it doesn't do any better than its spec and maintains the
1 mA leakage at the lower voltage).
If you want a longer time constant, the 140 F 2.5V capacitor in the
same package has only 0.1 mA of leakage current. That's a time
constant of 40 days (Cue joke about Ark-lights)
This is no more a proof of concept test of making a capacitor powered
aircraft than a paper airplane is a proof of concept for a paper airliner.
Yes, it would be a proof of concept. Make such a flashlight and tell
me about it. And don't cheat with 20 mAmpere LED's. I need a
flashlight bulb that draws 300 mA.
Because the harsh light of a luxeon is so unflattering, you need the
warmth of tungsten to bring out your complexion.
350 F/300 mA -> about 20 minutes of light to go from 2.5 V to 1.5 V.
Of course you'd use a boost regulator so you'd uniformly suck joules
not amps to keep constant brightness. A 1 W flashlight like the
Surefire L1 (second on this list of bright flashlights
http://www.uwgb.edu/nevermab/led.htm
) would last for more like 15 minutes on full brightness.
Well, you're right. These ultracaps are a new one on me. I googled
Ultracap technology and it's extremely interesting.
The activated carbon has an effective area of 2000 m^2/ gm, which if
it were water would mean a film 0.5 x 10^-9m or 1/2000th of a micron,
or equal to 5 angstroms(where 5000 angstroms is a representative
wavelength of visible light m/l).
I think you could make a strong case that it's a battery really, with
a lot of arcane chemistry, and with the disadvantage of output voltage
declining with use. .
In any case it looks like you would need a chopper to feed 2.5V to a
1.5V bulb which is preferably tungsten that has an appreciable thermal
lag, not an LED which presumably does not and might blow out if you
tried that (ordinary LED at .7V threshold is best fed through a
resistor or constant current device).
It sounds as if it could be terribly dangerous if you accidentally
shorted the terminals.
John Polasek
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| User: "Charlie Springer" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
10 Nov 2006 05:06:04 PM |
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On Fri, 10 Nov 2006 11:24:59 -0800, John C. Polasek wrote
(in article <ctj9l2p11c4mc4qgbvl7i1ln74qeuq8blm@4ax.com>):
Yes, it would be a proof of concept. Make such a flashlight and tell
me about it. And don't cheat with 20 mAmpere LED's. I need a
flashlight bulb that draws 300 mA.
John Polasek
I already have one. It has had several names since it hit the market like
"Forever Light". You shake it and a magnet passes through a solenoid. It
charges a cap: a 10 or 50 Farad cap about an inch in diameter and an inch and
a half long. It uses one large white LED (UV LED with phosphors like a
flourescent light). It holds charge for a a day or two. Two minutes of
shaking gives about 20 minutes of light. The latest caps will hold for weeks.
Case closed.
-- Charlie Springer
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| User: "Charlie Springer" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
09 Nov 2006 12:13:38 AM |
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On Wed, 8 Nov 2006 21:35:03 -0800, wrote
(in article <86ra24-j5g.ln1@mail.specsol.com>):
400 volts and higher (much higher sometimes) is preferred for the thrusters
on underwater vehicles. I interviewed several times at MBARI but was
uncomfortable with designing systems running thousands of volts DC at high
current for use on steel decks wet with sea water. There is some weight and
efficiency advantage but I have not studied it. It is counter-intuitive
since
only current determines the magnetic field.
Hardly.
Since I=V/R, the higher the voltage, the easier it is to get a higher
current with real world materials.
Which is why you get high power high voltage motors (also, with a 6,000 foot
tether you need to get the power to the other end). So, why did you (or
someone a while back) pick 100 volts as the sweet spot? I have seen 4,000
volt DC motors in the hundreds of horse power for special applications
lately. They are rather slim and light.
-- Charlie Springer
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| User: "" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
09 Nov 2006 10:45:04 AM |
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In sci.physics Charlie Springer <RAM@regnirps.com> wrote:
On Wed, 8 Nov 2006 21:35:03 -0800, wrote
(in article <86ra24-j5g.ln1@mail.specsol.com>):
400 volts and higher (much higher sometimes) is preferred for the thrusters
on underwater vehicles. I interviewed several times at MBARI but was
uncomfortable with designing systems running thousands of volts DC at high
current for use on steel decks wet with sea water. There is some weight and
efficiency advantage but I have not studied it. It is counter-intuitive
since
only current determines the magnetic field.
Hardly.
Since I=V/R, the higher the voltage, the easier it is to get a higher
current with real world materials.
Which is why you get high power high voltage motors (also, with a 6,000 foot
tether you need to get the power to the other end). So, why did you (or
someone a while back) pick 100 volts as the sweet spot? I have seen 4,000
volt DC motors in the hundreds of horse power for special applications
lately. They are rather slim and light.
-- Charlie Springer
Picking 100 V is what is called picking a reasonable example with
easy to follow numbers.
You like 4000 V better, fine, but now the capacitor take 40 times
longer to charge for the same capacitance and charging current.
--
Jim Pennino
Remove .spam.sux to reply.
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| User: "" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
08 Nov 2006 09:35:02 AM |
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In sci.physics Charlie Springer <RAM@regnirps.com> wrote:
<snip>
Packaged for small applications, these gels have 10 Farads per cc and about
14 grams for 50 farads at 2.5 volts. The weight is all in the enclosure and
leads. The development curve is just at the beginning. They also hold charge
for weeks and can charge faster than you could fill a fuel tank. There are
many ways to get electricity, even in remote locations. Many more than 100LL
avgas.
Hmmm...
Gasoline is about 1.3X10^8 J/gal.
My Tiger holds 50 gallons, or about 6.5X10^9 J.
Assume a capacitor voltage of 100 V.
The energy in a capacitor = C*V^2/2.
Therefor, the capacitance required for the specified voltage and energy
is 1.3X10^6 F.
Since a discharged capacitor looks like a short, we will have to current
limit the charging process.
Lets use a standard AC outlet which is capable of the 100 V and limited
to 15 A.
A capacitor charges at I = C dv/dt.
At a 15 A charge rate, the capacitor will charge at 1.1X10^-9 V/S.
Therefor it will take 8.6X10^10 S to charge the capacitor to the
same energy level as the gas tanks in my Tiger.
It takes about 900 seconds to fill the tanks on my Tiger, most of
that time being fideling with the hose.
Feel free to double check the arithmatic, I did it quickly as I'm going
to go fly.
--
Jim Pennino
Remove .spam.sux to reply.
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| User: "Charlie Springer" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
08 Nov 2006 09:36:48 PM |
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On Wed, 8 Nov 2006 07:35:02 -0800, wrote
(in article <61a924-o14.ln1@mail.specsol.com>):
Packaged for small applications, these gels have 10 Farads per cc and about
14 grams for 50 farads at 2.5 volts. The weight is all in the enclosure and
leads. The development curve is just at the beginning. They also hold
charge
for weeks and can charge faster than you could fill a fuel tank. There are
many ways to get electricity, even in remote locations. Many more than
100LL
avgas.
Hmmm...
Gasoline is about 1.3X10^8 J/gal.
My Tiger holds 50 gallons, or about 6.5X10^9 J.
Assume a capacitor voltage of 100 V.
The energy in a capacitor = C*V^2/2.
Therefor, the capacitance required for the specified voltage and energy
is 1.3X10^6 F.
About 13 cubic meters in today's tech. You could put a lot in the fuse and
wings since it is nearly weightless. But I'll say more like 5 cubic meters
given that most of your fuel energy is going to turn into heat. The
equivalent cap would be more like 325,000 Farads.
Since a discharged capacitor looks like a short, we will have to current
limit the charging process.
Lets use a standard AC outlet which is capable of the 100 V and limited
to 15 A.
Let's not. I bet you have a 20 amp in your kitchen. How about 220V/200 amps
= 44 kWatts = 44,000 joulse/sec. Or about 10 hours. However, if you use
these things the way they are already being used; to store up energy for
motors and solenoids in a relatively low current system, then your charging
station would itself have enough supercaps to service planes. No one says you
have to charge the whole thing through one wire or directly from the utility
system.
A capacitor charges at I = C dv/dt.
At a 15 A charge rate, the capacitor will charge at 1.1X10^-9 V/S.
Therefor it will take 8.6X10^10 S to charge the capacitor to the
same energy level as the gas tanks in my Tiger.
It takes about 900 seconds to fill the tanks on my Tiger, most of
that time being fideling with the hose.
Feel free to double check the arithmatic, I did it quickly as I'm going
to go fly.
-- Charlie Springer
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| User: "" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
08 Nov 2006 11:35:02 PM |
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In sci.physics Charlie Springer <RAM@regnirps.com> wrote:
On Wed, 8 Nov 2006 07:35:02 -0800, wrote
(in article <61a924-o14.ln1@mail.specsol.com>):
Packaged for small applications, these gels have 10 Farads per cc and about
14 grams for 50 farads at 2.5 volts. The weight is all in the enclosure and
leads. The development curve is just at the beginning. They also hold
charge
for weeks and can charge faster than you could fill a fuel tank. There are
many ways to get electricity, even in remote locations. Many more than
100LL
avgas.
Hmmm...
Gasoline is about 1.3X10^8 J/gal.
My Tiger holds 50 gallons, or about 6.5X10^9 J.
Assume a capacitor voltage of 100 V.
The energy in a capacitor = C*V^2/2.
Therefor, the capacitance required for the specified voltage and energy
is 1.3X10^6 F.
About 13 cubic meters in today's tech. You could put a lot in the fuse and
wings since it is nearly weightless. But I'll say more like 5 cubic meters
given that most of your fuel energy is going to turn into heat. The
equivalent cap would be more like 325,000 Farads.
The energy efficiency of electric motors to internal combustion is more
like 3:1 than 4:1 for modern motors, but that hardly matters.
Since a discharged capacitor looks like a short, we will have to current
limit the charging process.
Lets use a standard AC outlet which is capable of the 100 V and limited
to 15 A.
Let's not. I bet you have a 20 amp in your kitchen. How about 220V/200 amps
= 44 kWatts = 44,000 joulse/sec. Or about 10 hours. However, if you use
these things the way they are already being used; to store up energy for
motors and solenoids in a relatively low current system, then your charging
station would itself have enough supercaps to service planes. No one says you
have to charge the whole thing through one wire or directly from the utility
system.
Sorry, wrong answer.
The charge rate for a current source is independant of the voltage, though
the voltage does have to be high enough to deliver the required current.
Once again, a capacitor charges at I = C*dv/dt.
So, if you have a 200 A source, and a 325,000 F capacitor, it would take
about 45 hours to charge to 100 V.
Lowering the voltage would make things worse since the energy in a
capacitor is directly proportional to the capacitance and the square
of the voltage.
If you cut the voltage in half, you have to have 4 times the capacitance
for the same energy, and for the same charging current, it takes twice
as long to charge.
A capacitor charges at I = C dv/dt.
At a 15 A charge rate, the capacitor will charge at 1.1X10^-9 V/S.
Therefor it will take 8.6X10^10 S to charge the capacitor to the
same energy level as the gas tanks in my Tiger.
It takes about 900 seconds to fill the tanks on my Tiger, most of
that time being fideling with the hose.
Feel free to double check the arithmatic, I did it quickly as I'm going
to go fly.
-- Charlie Springer
--
Jim Pennino
Remove .spam.sux to reply.
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| User: "Charlie Springer" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
09 Nov 2006 12:08:56 AM |
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On Wed, 8 Nov 2006 21:35:02 -0800, wrote
(in article <spqa24-j5g.ln1@mail.specsol.com>):
station would itself have enough supercaps to service planes. No one says
you
have to charge the whole thing through one wire or directly from the
utility
system.
Sorry, wrong answer.
Just don't get it eh? Charging in parallel is too complicated?
I = C dv/dt. Are you solving this for t? Are you nuts? This isn't freshman
lab. Can't I use a constant current source?
-- Charlie Springer
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| User: "" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
09 Nov 2006 12:15:02 PM |
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In sci.physics Charlie Springer <RAM@regnirps.com> wrote:
On Wed, 8 Nov 2006 21:35:02 -0800, wrote
(in article <spqa24-j5g.ln1@mail.specsol.com>):
station would itself have enough supercaps to service planes. No one says
you
have to charge the whole thing through one wire or directly from the
utility
system.
Sorry, wrong answer.
Just don't get it eh? Charging in parallel is too complicated?
I = C dv/dt. Are you solving this for t? Are you nuts? This isn't freshman
lab. Can't I use a constant current source?
-- Charlie Springer
I already posted looking at this using constant current as well as
capacitors in parallel and series.
Now let's look at real world sources.
If the electrical service to the charging facility is 200 V at 200 A,
(round, easy numbers) that does not mean the current is limited to
200 A by some foldback mechanism, it means that if you exceed 200 A,
a current limiting device (usually a breaker or fuse) will open and
shut you off.
Now when you first apply the 200 V to the discharged capacitor, the
current trys to go to infinity and the breaker blows.
So, you have to limit the startup current.
200 V / 200 A = 1 Ohm.
So if the total resistance between the voltage source and the capacitor
is 1 Ohm, you can safely apply the voltage and you have a simple RC
circuit.
The relationship between the voltage on a capacitor (Vc) and the
applied voltage (Va) at any time t in seconds for a RC circuit is
Vc = Va * (1 - e^(-t/(R*C)))
Solving for t, we get t = -R*C*ln (1 - (Vc/Va)
Plugging in R=1 Ohm, C=300,000 F, Va=200V, Vc=100V we get the time
to get to 100 V as 2.1X10^5 seconds, versus the 1.5X10^5 seconds for
a contant current source.
As startup, the resistance has to dissipate 200 V X 200 A, or 40 KW.
At the end of the charge period, the resistance still has to dissipate
100V X 200 A, or 20 KW.
I'll leave it as a excersise to calculate the total energy that has
to be thrown away to get the capacitor charged.
--
Jim Pennino
Remove .spam.sux to reply.
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| User: "" |
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| Title: Re: Stern - Nonsense and dangerous nonsense |
09 Nov 2006 10:45:03 AM |
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In sci.physics Charlie Springer <RAM@regnirps.com> wrote:
On Wed, 8 Nov 2006 21:35:02 -0800, wrote
(in article <spqa24-j5g.ln1@mail.specsol.com>):
station would itself have enough supercaps to service planes. No one says
you
have to charge the whole thing through one wire or directly from the
utility
system.
Sorry, wrong answer.
Just don't get it eh? Charging in parallel is too complicated?
I = C dv/dt. Are you solving this for t? Are you nuts? This isn't freshman
lab. Can't I use a constant current source?
-- Charlie Springer
The relationship between voltage, current, and capacitance for a charging
capacitor is I=C*dv/dt. This is basic physics.
The relationship says that the voltage change per second is I/C. This
is basic algebra.
If you apply a constant current to a capacitor, the voltage rises in
a linear fashion at dv/dt.
All real world sources are current limited.
So, for example if you charge a 300,000 F capacitor with a source limited
to 200 A, the voltage on the capacitor rises at 200/300,000, or
6.6X10^-4 volts per second.
Assuming your current source can maintain the full 200 A all the way
to full charge and you want to charge to 100 V, the time it takes is
100 V / 6.6X10^-4 V/S, or 1.5X10^5 seconds.
If your current source lacks the voltage capability to maintain 200 A
until full charge, it takes longer.
The total capacitance of capacitors in parallel is the sum of the
individual capacitances. For a total capacitance of C, all your
capacitors would have to already be in parallel.
However, for a total capacitance C, if you were to build it from two
identical capacitors of C/2 and charge them in series, the total
capacitance of the series network becomes C/4 since the total capacitance
in a series network is 1/Ct = SUM (1-n) 1/Ci.
The individual capacitors still need to be charged to 100 V and the
total voltage of the network becomes the sum of the individual voltages.
The net effect is that now the 200 A current source will charge the
network in 4/2, or 2 times faster.
But, now the voltage requirements for the current source have also
doubled.
There is no free lunch.
Of course, none of this considers the energy efficiency of such an
arrangement.
Let's look at the original problem at the point where the capacitor
has charged to 10 V.
At that point in time you have 10 V times 200 A, or 2 KW going into
the capacitor.
If your source is capable of 200 V, that means somewhere you are
disipating (200 V - 10 V) X 200 A, or 38 KW .
If you let R be the sum of all the resistances involved, you
can minimize these loses by building a source that maintains the
relationship of Vo = Vc + (R X I) where I is the charging current,
Vc is the instantaneous capacitor voltage, and Vo is the instantaneous
source voltage.
I leave it to you as a design problem to come up with such a source.
--
Jim Pennino
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