CAFE Electric Aircraft Symposium Set For May 1

Larry Dighera wrote in
:

I hadn't considered the explosive environment created by venting liquid
hydrogen. How is that dealt with by suppliers, laboratories and users
today?

Perhaps the venting H2 could be captured and run through the fuel-cell
and the resulting electric power stored in batteries for future use to
preclude the explosive atmosphere forming.

Just more equipment that can fail and adds weight and cost. I'm
sure the airlines would like that. Or, would you like that on
your car?



I'm wondering if the heat produced by a fuel-cell could be used to
change the liquid H2 into the gaseous phase, and if the resulting
cooling of the fuel-cell will contribute to its efficiency.

Why would you want to heat liquid H2? The reason tanks vent is
because it's boiling off. It's very difficult to insulate a tank
to LH2 temperatures, so some of it boils off. If you don't vent
it... KABOOOM!

Remember Challenger? That's what happens when the tank breaches.

Speaking of rockets, ever notice how they are constantly venting
while on the pad? They close the valves just before lift-off. If
the launch is delayed the valves are reopened to prevent too much
pressure from building. After launch it's not a problem because
the fuel is being consumed fast enough.

Personally, I find the whole argument on hydrogen as a replacement
for gasoline a joke. It's basic physics. So unless the laws of
physics go out the window.... Well, there are those who think
science and basic physics are a conspiracy to keep the truth from
being revealed... But I'm not assuming anyone here is in that camp.
Yet.

Brian
--
http://www.earthwaves.org/forum/index.php - Earth Sciences discussion
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Sed quis custodiet ipsos Custodes?

On Fri, 8 May 2015 01:39:59 +0000 (UTC), Skywise
wrote:

Larry Dighera wrote in
:

I hadn't considered the explosive environment created by venting liquid
hydrogen. How is that dealt with by suppliers, laboratories and users
today?

Perhaps the venting H2 could be captured and run through the fuel-cell
and the resulting electric power stored in batteries for future use to
preclude the explosive atmosphere forming.

Just more equipment that can fail and adds weight and cost. I'm
sure the airlines would like that. Or, would you like that on
your car?


I wasn't considering electric airliners yet; I was thinking more along the
lines of GA-sized aircraft. I'm still curious how venting H2 is kept from
producing an explosive atmosphere in laboratories and at the gas plants where
it is produced. Surely the technology exists...


I'm wondering if the heat produced by a fuel-cell could be used to
change the liquid H2 into the gaseous phase, and if the resulting
cooling of the fuel-cell will contribute to its efficiency.

Why would you want to heat liquid H2?

I was thinking it might be necessary to heat the LH2 so that it could keep up
with the fuel demand of the fuel-cell producing the power to produce the motive
thrust.

The reason tanks vent is because it's boiling off. It's very difficult to
insulate a tank to LH2 temperatures, so some of it boils off.

It would be interesting to know just how difficult it is to insulate a LH2
vessel, so that the boil-off rate is reasonably slow.

If you don't vent it... KABOOOM!

Yeah. I recall the resounding POP that occurs when a burning splint is
inserted into the inverted test tube containing the evolved H2 from
electrolysis. It's a definite issue, as is the explosive atmosphere created by
venting gasoline vapors. But, obviously methods have been successfully
developed to deal with it.


Remember Challenger? That's what happens when the tank breaches.


My recollection was that the seals on the Solid Rocket Boosters on the sides of
the big central O2-H2 tank had failed, and the hot SRB gases had breached the
big tank. I wasn't aware of an H2 venting issue.

Speaking of rockets, ever notice how they are constantly venting
while on the pad? They close the valves just before lift-off. If
the launch is delayed the valves are reopened to prevent too much
pressure from building. After launch it's not a problem because
the fuel is being consumed fast enough.


Agreed.

Ever notice the main rocket nozzles suddenly ice-up shortly after ignition? I
believe that's a result of the cold liquid combustion gases being routed
through tubing coiled around the rocket motors to keep them from melting and
assist in atomizing the gases, so that they will react more readily. Just a
guess.

Personally, I find the whole argument on hydrogen as a replacement
for gasoline a joke.

The limited research I conducted years ago seemed to suggest that there wasn't
much else that approached the energy density of gasoline/kerosene. So, while
perhaps not ideal, hydrogen is a somewhat viable alternative to petroleum, that
has the potential to provide efficiencies several times better than the ~30%
efficiency obtained with internal combustion power plants. If you consider
that only one third the fuel will be required to achieve the current
performance, the numbers begin to make more sense.

With 70% of the energy blowing out the exhaust as heat, internal combustion
engine efficiency is comparable to an incandescent lamp that consumes ~90% of
its energy usage to produce heat, and only ~10% to produce light. LEDs, on the
other hand, can be 90% more efficient than tungsten filament lamps, and they
last many times longer too.

It's basic physics. So unless the laws of physics go out the window....

I understand what you are saying, and I agree; the solution isn't obvious, but
it may be possible. Apparently a lot of large commercial entities seem to
think so...

Well, there are those who think science and basic physics are a conspiracy to
keep the truth from being revealed... But I'm not assuming anyone here is in
that camp. Yet.

Brian


Hey. Let's leave T. Cruz and Santorum out of this discussion. :-)


--
Irrational acts are ultimately founded on irrational beliefs.
-- Larry Dighera

Larry Dighera wrote in
news
I wasn't considering electric airliners yet; I was thinking more along
the lines of GA-sized aircraft. I'm still curious how venting H2 is
kept from producing an explosive atmosphere in laboratories and at the
gas plants where it is produced. Surely the technology exists...

It's burned off to prevent just such a situation.


Why would you want to heat liquid H2?

I was thinking it might be necessary to heat the LH2 so that it could
keep up with the fuel demand of the fuel-cell producing the power to
produce the motive thrust.

Stop refridgerating it? LH2 is -423F/-253C. It doesn't take much
to heat it up. That's why the tanks vent.



The reason tanks vent is because it's boiling off. It's very difficult
to insulate a tank to LH2 temperatures, so some of it boils off.

It would be interesting to know just how difficult it is to insulate a
LH2 vessel, so that the boil-off rate is reasonably slow.

I'm sure you could eliminated venting altogether with s sufficiently
strong tank and MAINTAINED crygenic cooling.



Remember Challenger? That's what happens when the tank breaches.


My recollection was that the seals on the Solid Rocket Boosters on the
sides of the big central O2-H2 tank had failed, and the hot SRB gases
had breached the big tank. I wasn't aware of an H2 venting issue.

My point was the size of the KABOOOM.

Perhaps a better example.... Hindenburg.





Ever notice the main rocket nozzles suddenly ice-up shortly after
ignition? I believe that's a result of the cold liquid combustion gases
being routed through tubing coiled around the rocket motors to keep them
from melting and assist in atomizing the gases, so that they will react
more readily. Just a guess.

You're correct.

http://www.nasa.gov/mission_pages/co...edia/cece.html

https://www.youtube.com/watch?v=5QJNnTRRLOo

Although not all rocket engines do this.



With 70% of the energy blowing out the exhaust as heat, internal
combustion engine efficiency is comparable to an incandescent lamp that
consumes ~90% of its energy usage to produce heat, and only ~10% to
produce light. LEDs, on the other hand, can be 90% more efficient than
tungsten filament lamps, and they last many times longer too.

Good analogy. But that is an example not of more efficient energy
production, but more efficient energy consumption. Although both
are needed in the grand scheme of things, IMO.

What's to say we can't find a more efficient way to consume fossil
fuels? Although it tends to sound conspiracy theory like, I think
there is some merit to the notion that more fuel efficiency in
cars is being held back for monetary reasons. It is a fact that
vehicles have been designed that get far higher MPG than you
typically find on the road. Why aren't they being sold?

For example, I just found the following on a VW diesel hybrid
capable of nearly 300 MPG.

http://hereandnow.wbur.org/2014/09/1...uel-efficiency

http://www.wired.com/2013/05/volkswagen-xl1-driven/

This leads to another point I learned myself while driving. People
race from red light to red light. Not don't get me wrong. I like
to drive fast just like anyone else. But what I learned to do is
to not make it a drag race. I still go ten over on the streets,
cruise 80-85mph on the freeway (I'm in LA). I just don't stomp
on the gas pedal to get there.

I did a comparison on this change in driving style. I increased
my MPG by at least 10% just by changing the way I accelerate.
Funny thing is, I often find myself pulling up to the same cars
at the light... those racing off the line.




It's basic physics. So unless the laws of physics go out the window....

I understand what you are saying, and I agree; the solution isn't
obvious, but it may be possible. Apparently a lot of large commercial
entities seem to think so...

I guess I'm arguing against the public perception. There's a lot
of bad info out there. I don't profess to be any kind of expert
myself, but I know what I know, otherwise I shut up. So many
people think it's a simple thing to just convert all our cars
to some other form of energy and overnight we can change the
world. Well, we can't. We've had a hundred years to develop IC
engines. It may take another hundred years to replace them. What
happens in the lab does not always translate to real-world
practical application.

Can an alternative be found? I'm sure of it.



Well, there are those who think science and basic physics are a
conspiracy to keep the truth from being revealed... But I'm not
assuming anyone here is in that camp. Yet.

Hey. Let's leave T. Cruz and Santorum out of this discussion. :-)

Hey, the other side of the aisle isn't much smarter. Two sides
of the same coin if you ask me.

hehehe... well, there's a web forum that I visit regularly that
is chock full of nutters. Needless to say my actual participation
has been decreasing over time as I realize the futility of even
existing in such an environment.

The New Dark Ages are upon us.

Brian
--
http://www.earthwaves.org/forum/index.php - Earth Sciences discussion
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Sed quis custodiet ipsos Custodes?

On Fri, 8 May 2015 21:28:24 +0000 (UTC), Skywise
wrote:

Larry Dighera wrote in
news


I was thinking it might be necessary to heat the LH2 so that it could
keep up with the fuel demand of the fuel-cell producing the power to
produce the motive thrust.

Stop refridgerating it? LH2 is -423F/-253C.


That brings up an interesting opportunity for an electric power plant:
superconductivity. This liquid hydrogen fuel concept is beginning to become
more interesting... http://en.wikipedia.org/wiki/Superconductivity

Larry Dighera wrote in
:

On Fri, 8 May 2015 21:28:24 +0000 (UTC), Skywise
wrote:

Larry Dighera wrote in
news


I was thinking it might be necessary to heat the LH2 so that it could
keep up with the fuel demand of the fuel-cell producing the power to
produce the motive thrust.

Stop refridgerating it? LH2 is -423F/-253C.


That brings up an interesting opportunity for an electric power plant:
superconductivity. This liquid hydrogen fuel concept is beginning to
become more interesting...
http://en.wikipedia.org/wiki/Superconductivity

I really think you are completely missing the problem.

It takes energy to do these things. It is not a source of
energy.

It takes energy to make the hydrogen because it doesn't exist
in it's free state naturally on Earth. Currently, most hydrogen
is produced from natural gas, with CO2 as a byproduct.

It takes energy to compress it, or liquify it.

It takes energy to refridgerate it to such low temperatures.
and to keep it there.

Where is all that energy going to come from?

And you will never ever EVER get out of LH2 the amount of energy
that went into producing it.

It's a simple numbers game. Balance the books. You're in the red.

On the other hand, if you do find an alternate SOURCE of energy,
one that is so cheap and plentiful and does minimal or no harm
to the environment, then maybe you can look at things like LH2 as
a medium to store and use energy (after solving the CO2 problem),
and all the losses in it's production won't matter because the
actual SOURCE of energy is so cheap and plentiful you don't mind
wasting a bit of it.

Nuclear is the only source of producing mass quantities of energy
that I know of, but it has it's own inherent risks and challenges,
most of which I think are solvable except for the public relations
side of it. But, it does not emit CO2 which is the major argument
regarding fossil fuels.

Fusion reactors have been a decade away for the past 5 decades.

There aren't enough rivers to dam, and it harms ecosystems.

Wind is intermittent and too little. And kills birds.

Solar is viable, but only works during the day. It can be scaled
to compensate along with appropriate electricity storage mechanisms
to offset night and cloudy days. Perhaps Tesla's house battery is
a step in this direction? However, solar cells are still too
expensive to force people to switch. Folks can't see CO2. They
can't feel .2 degrees Celcius. But they CAN see the numbers on
their credit card bills.

Which brings up another point. The energy problem is as much a
human psychology problem as it is a technical problem. To put it
bluntly, the vast majority of people don't give a F.

Brian
--
http://www.earthwaves.org/forum/index.php - Earth Sciences discussion
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Sed quis custodiet ipsos Custodes?

On Mon, 11 May 2015 20:57:57 +0000 (UTC), Skywise
wrote:

Larry Dighera wrote in
:

On Fri, 8 May 2015 21:28:24 +0000 (UTC), Skywise
wrote:

Larry Dighera wrote in
news


I was thinking it might be necessary to heat the LH2 so that it could
keep up with the fuel demand of the fuel-cell producing the power to
produce the motive thrust.

Stop refridgerating it? LH2 is -423F/-253C.


That brings up an interesting opportunity for an electric power plant:
superconductivity. This liquid hydrogen fuel concept is beginning to
become more interesting...
http://en.wikipedia.org/wiki/Superconductivity

I really think you are completely missing the problem.

It takes energy to do these things. It is not a source of
energy.

It takes energy to make the hydrogen because it doesn't exist
in it's free state naturally on Earth. Currently, most hydrogen
is produced from natural gas, with CO2 as a byproduct.

It takes energy to compress it, or liquify it.

It takes energy to refridgerate it to such low temperatures.
and to keep it there.


Photovoltaic powered electrolysis of H2O would be my choice to produce
hydrogen. It might even power the compressor and condenser to liquefy it also.
Other than the energy used to make the solar cells, there is no energy cost and
no byproducts. Making this practical will take some ingenuity, but
theoretically, I'd suppose it is possible.


Where is all that energy going to come from?

And you will never ever EVER get out of LH2 the amount of energy
that went into producing it.


With free solar power, that isn't much of an issue.


It's a simple numbers game. Balance the books. You're in the red.

On the other hand, if you do find an alternate SOURCE of energy,
one that is so cheap and plentiful and does minimal or no harm
to the environment, then maybe you can look at things like LH2 as
a medium to store and use energy (after solving the CO2 problem),
and all the losses in it's production won't matter because the
actual SOURCE of energy is so cheap and plentiful you don't mind
wasting a bit of it.


Yep.


Nuclear is the only source of producing mass quantities of energy
that I know of,

If energy production is decentralized, mass quantities aren't required. Think
every home with rooftop photovoltaics.

Of course, that won't do for airline operations, but 250 megawatt solar
facilities are in operation in California and Nevada now:
http://investor.firstsolar.com/releasedetail.cfm?ReleaseID=793411, and even
the Air Force has a 14.2 megawatts installation:
http://www.cnet.com/news/air-force-base-in-nevada-goes-solar-with-14-megawatt-array/#!.


but it has it's own inherent risks and challenges,
most of which I think are solvable except for the public relations
side of it. But, it does not emit CO2 which is the major argument
regarding fossil fuels.


You believe the "inherent risks and challenges" are solvable, because they have
been woefully underestimated as have the costs.

The way I see the current state of nuclear is a lot like the oceans. When the
sea is calm, things are fine. But the sea has the potential for ENORMOUS
destruction, as born out recently in the Fukushima tsunami. Despite the sea
wall, the sea managed to cause massive destruction beyond what engineers had
estimated. And there's NOTHING to prevent an even larger tsunami from
occurring in the future.

The nuclear industry has voluntarily created a $12.6-billion insurance fund and
enacted legislation limiting their liability to that amount. The Fukushima
disaster is estimated at $500-billion. And after 29 years hundreds of square
miles of Chernobyl is still uninhabitable. Nuclear plants are continually
venting radio-active products into the environment during normal operation. And
in the event of a containment breach, the spread of radioactivity can be
alarming. Here's what happened as a result of the Chernobyl meltdown:

Chernobyl disaster effects
National and international spread of radioactive substances

Four hundred times more radioactive material was released from Chernobyl
than by the atomic bombing of Hiroshima. The disaster released 1/100 to
1/1000 of the total amount of radioactivity released by nuclear weapons
testing during the 1950s and 1960s.[88] Approximately 100,000 km² of land
was significantly contaminated with fallout, with the worst hit regions
being in Belarus, Ukraine and Russia.[89] Slighter levels of contamination
were detected over all of Europe except for the Iberian
Peninsula.[16][90][91]

The initial evidence that a major release of radioactive material was
affecting other countries came not from Soviet sources, but from Sweden. On
the morning of 28 April[92] workers at the Forsmark Nuclear Power Plant
(approximately 1,100 km (680 mi) from the Chernobyl site) were found to
have radioactive particles on their clothes.[93]

So, from my point of view, nuclear fission power is far too dangerous for
consideration as a "free" and "clean" power source. Just ask the residents who
have to pay to saw up, and haul away the entire San Onofre power plant. And
without a safe place to store the radioactive waste, it is just plane
irresponsible. And the potential for catastrophe has been under estimated by
several orders of magnitude, just like the potential of the sea.

But the military wants it, and the war profiteers are happy to oblige....


Fusion reactors have been a decade away for the past 5 decades.


How many years passed between the time Leonardo da Vinci conceived of the
helicopter and it's production?


There aren't enough rivers to dam, and it harms ecosystems.

Wind is intermittent and too little. And kills birds.


I recall living under the flight path of LAX in the '50s. You couldn't hold a
conversation at dinner time for the din of arriving B-707s. Today, I reside
very close to KSBA, and the airliners are significantly quieter than the GA
piston aircraft. Progress takes time...


Solar is viable, but only works during the day. It can be scaled
to compensate along with appropriate electricity storage mechanisms
to offset night and cloudy days. Perhaps Tesla's house battery is
a step in this direction? However, solar cells are still too
expensive to force people to switch.


Responsible people are switching voluntarily; no need to force them.

The price of solar panels is dropping all the time. Last I checked, it was
possible to purchase solar panels on eBay for ~$1/watt.


Folks can't see CO2. They
can't feel .2 degrees Celcius. But they CAN see the numbers on
their credit card bills.

Which brings up another point. The energy problem is as much a
human psychology problem as it is a technical problem.


The way I see it, it's more a matter of entrenched wealthy businessman
protecting their cash cows...


To put it bluntly, the vast majority of people don't give a F.

Brian

Fortunately, that is changing ...

So, the use of LH2 to generate electricity with a fuel-cell to drive an
electrical motor that employs superconductivity seem a worthwhile course to
investigate for powering future aircraft. Granted there are currently
obstacles to achieving a viable system, but I don't believe physics precludes
it; only the development of the technology stands in the way.

On 5/14/2015 1:49 PM, Larry Dighera wrote:
It takes energy to make the hydrogen because it doesn't exist
in it's free state naturally on Earth. Currently, most hydrogen
is produced from natural gas, with CO2 as a byproduct.

It takes energy to compress it, or liquify it.

It takes energy to refridgerate it to such low temperatures.
and to keep it there.

Photovoltaic powered electrolysis of H2O would be my choice to produce
hydrogen. It might even power the compressor and condenser to liquefy it also.
Other than the energy used to make the solar cells, there is no energy cost and
no byproducts. Making this practical will take some ingenuity, but
theoretically, I'd suppose it is possible.


Sorry, but there is no free energy, and there is no totally clean
energy, not even solar. At present, there isn't enough solar energy to
go around. There isn't likely to EVER be enough solar energy to go
around, that's also true of wind and hydro power.

More importantly, if we divert solar energy from the grid to make
hydrogen, then we must make up the difference from somewhere else, which
means burning more fuel. So there is no advantage to diverting "clean"
energy towards something like producing hydrogen, whilst we are burning
coal (or whatever) to make grid power. Energy is energy! Wasting
energy is always a dirty thing to do, even if it's solar. And the
hydrogen energy cycle is inherently wasteful.

On 5/8/2015 2:30 PM, Larry Dighera wrote:

Personally, I find the whole argument on hydrogen as a replacement
for gasoline a joke.
The limited research I conducted years ago seemed to suggest that there wasn't
much else that approached the energy density of gasoline/kerosene. So, while
perhaps not ideal, hydrogen is a somewhat viable alternative to petroleum, that
has the potential to provide efficiencies several times better than the ~30%
efficiency obtained with internal combustion power plants. If you consider
that only one third the fuel will be required to achieve the current
performance, the numbers begin to make more sense.

With 70% of the energy blowing out the exhaust as heat, internal combustion
engine efficiency is comparable to an incandescent lamp that consumes ~90% of
its energy usage to produce heat, and only ~10% to produce light. LEDs, on the
other hand, can be 90% more efficient than tungsten filament lamps, and they
last many times longer too.

Simply put, the problem with using hydrogen as a fuel is that we have no
natural source of it in unattached gaseous form. So we have to MAKE
hydrogen by reforming it from natural gas, or by some even more
energy-hungry method such as electrolysis of water.

So while hydrogen can be used as a fuel, it is not a SOURCE of energy
such as natural gas or gasoline is. Hydrogen is only a CARRIER of
energy (much like our electrical utilities are a carrier of energy, not
a source of energy). In the process of converting "something" to
hydrogen, you never have 100% efficiency, so on a whole-cycle macro
scale the efficiency picture of hydrogen can look pretty dismal.

Also, an article might extol the clean burning properties of hydrogen in
an engine or fuel cell, while failing the mention the pollution produced
by the manufacture of hydrogen.

Vaughn wrote:
On 5/8/2015 2:30 PM, Larry Dighera wrote:

Personally, I find the whole argument on hydrogen as a replacement
for gasoline a joke.
The limited research I conducted years ago seemed to suggest that there wasn't
much else that approached the energy density of gasoline/kerosene. So, while
perhaps not ideal, hydrogen is a somewhat viable alternative to petroleum, that
has the potential to provide efficiencies several times better than the ~30%
efficiency obtained with internal combustion power plants. If you consider
that only one third the fuel will be required to achieve the current
performance, the numbers begin to make more sense.

With 70% of the energy blowing out the exhaust as heat, internal combustion
engine efficiency is comparable to an incandescent lamp that consumes ~90% of
its energy usage to produce heat, and only ~10% to produce light. LEDs, on the
other hand, can be 90% more efficient than tungsten filament lamps, and they
last many times longer too.

Simply put, the problem with using hydrogen as a fuel is that we have no
natural source of it in unattached gaseous form. So we have to MAKE
hydrogen by reforming it from natural gas, or by some even more
energy-hungry method such as electrolysis of water.

So while hydrogen can be used as a fuel, it is not a SOURCE of energy
such as natural gas or gasoline is. Hydrogen is only a CARRIER of
energy (much like our electrical utilities are a carrier of energy, not
a source of energy). In the process of converting "something" to
hydrogen, you never have 100% efficiency, so on a whole-cycle macro
scale the efficiency picture of hydrogen can look pretty dismal.

Also, an article might extol the clean burning properties of hydrogen in
an engine or fuel cell, while failing the mention the pollution produced
by the manufacture of hydrogen.

If you burn hydrogen in an engine, you get lots of NOX byproducts, i.e.
smog, because air is mostly nitrogen and hydrogen has a very high
flame temperature.

Fuel cells do not have that problem as the temperatured involved are
much lower.



--
Jim Pennino

On 5/9/2015 4:32 PM, wrote:

If you burn hydrogen in an engine, you get lots of NOX byproducts, i.e.
smog, because air is mostly nitrogen and hydrogen has a very high
flame temperature.

Fuel cells do not have that problem as the temperatured involved are
much lower.



Yes, but my point was that you are still left with the problem of the
pollution and greenhouse gas generated by the production of your "clean"
hydrogen fuel.

Besides, for at least the last 30 years, mass consumer fuel cells have
been "just around the corner". Even if they suddenly became practical
and economical, we would still be left with the huge problems involved
in producing and distributing hydrogen.

You can wave your arms and talk about fuel cells all day, but the
problems with hydrogen won't go away. Hydrogen is not an energy source.
To make hydrogen, you make pollution.