CAFE Electric Aircraft Symposium Set For May 1

On Mon, 27 Apr 2015 08:25:02 +1200, george152 wrote:

On 27/04/2015 1:58 a.m., Larry Dighera wrote:

Glaring omission: SOLAR IMPULSE
http://us3.campaign-archive2.com/?u=553e7fdb79a7f1570622b070d&id=5e3b071d05&e=2b92d 60fc6
Round the world flight with the Sun as sole fuel source!



Thanks for that Larry.
At present I'm extracting the urine (taking the ****) out of some-one
who thinks the Solar Impulse is a breakthrough.
Pointed out that that last leg took them 17 hours.
Most of the Cessnas and Pipers I fly would do it with 4-6 SOB in 4 hours


You are correct, George. Eric Raymond was flying solely on solar power many
years before the Solar Impulse project began. That said, I know of no other
solar powered aircraft that has succeeded, indeed embarked upon, a
round-the-world flight fueled solely by sunlight as the Solar Impulse has.

Comparing today's electrically powered aircraft to Cessnas and Pipers is a bit
like comparing the Wright Flyer to them; electrically powered aircraft are
still in their infancy of development.

What I found interesting about the symposium was the big names on the roster of
speakers: Airbus, Northrop-Grumman, NASA, Carnegie Mellon University ... It
would seem that electrically powered aircraft are making steady advances in
performance and credibility as they are continuing to be developed and
technology improves.

Personally, I believe that one day the world will look back on the
petroleum-based era of motive power as the "Model T" era, and be thankful for
the development of far more efficient and cleaner electrical power. But then,
as being a "card carrying" IBEW member for over 50 years, and having benefit of
the schooling they provided for four years, I may be a bit biased. :-)

On 28/04/2015 4:23 a.m., Larry Dighera wrote:
On Mon, 27 Apr 2015 08:25:02 +1200, george152 wrote:

On 27/04/2015 1:58 a.m., Larry Dighera wrote:

Glaring omission: SOLAR IMPULSE
http://us3.campaign-archive2.com/?u=553e7fdb79a7f1570622b070d&id=5e3b071d05&e=2b92d 60fc6
Round the world flight with the Sun as sole fuel source!



Thanks for that Larry.
At present I'm extracting the urine (taking the ****) out of some-one
who thinks the Solar Impulse is a breakthrough.
Pointed out that that last leg took them 17 hours.
Most of the Cessnas and Pipers I fly would do it with 4-6 SOB in 4 hours


You are correct, George. Eric Raymond was flying solely on solar power many
years before the Solar Impulse project began. That said, I know of no other
solar powered aircraft that has succeeded, indeed embarked upon, a
round-the-world flight fueled solely by sunlight as the Solar Impulse has.

Comparing today's electrically powered aircraft to Cessnas and Pipers is a bit
like comparing the Wright Flyer to them; electrically powered aircraft are
still in their infancy of development.

What I found interesting about the symposium was the big names on the roster of
speakers: Airbus, Northrop-Grumman, NASA, Carnegie Mellon University ... It
would seem that electrically powered aircraft are making steady advances in
performance and credibility as they are continuing to be developed and
technology improves.

Personally, I believe that one day the world will look back on the
petroleum-based era of motive power as the "Model T" era, and be thankful for
the development of far more efficient and cleaner electrical power. But then,
as being a "card carrying" IBEW member for over 50 years, and having benefit of
the schooling they provided for four years, I may be a bit biased. :-)


There was an electric aircraft in the 30s.
Had an endurance of 2 hours.
I checked through some of the current machines.
Apart from the self launched sailplanes most are two seaters with a two
hour endurance.
Any cross country would be limited by the reserve requirement. Don't
know what it is in the US but here minimum is 15 minutes.
Not a great range and the recharge will really stuff your day

On Tue, 28 Apr 2015 08:40:43 +1200, george152 wrote:

On 28/04/2015 4:23 a.m., Larry Dighera wrote:
On Mon, 27 Apr 2015 08:25:02 +1200, george152 wrote:

On 27/04/2015 1:58 a.m., Larry Dighera wrote:

Glaring omission: SOLAR IMPULSE
http://us3.campaign-archive2.com/?u=553e7fdb79a7f1570622b070d&id=5e3b071d05&e=2b92d 60fc6
Round the world flight with the Sun as sole fuel source!



Thanks for that Larry.
At present I'm extracting the urine (taking the ****) out of some-one
who thinks the Solar Impulse is a breakthrough.
Pointed out that that last leg took them 17 hours.
Most of the Cessnas and Pipers I fly would do it with 4-6 SOB in 4 hours


You are correct, George. Eric Raymond was flying solely on solar power many
years before the Solar Impulse project began. That said, I know of no other
solar powered aircraft that has succeeded, indeed embarked upon, a
round-the-world flight fueled solely by sunlight as the Solar Impulse has.

Comparing today's electrically powered aircraft to Cessnas and Pipers is a bit
like comparing the Wright Flyer to them; electrically powered aircraft are
still in their infancy of development.

What I found interesting about the symposium was the big names on the roster of
speakers: Airbus, Northrop-Grumman, NASA, Carnegie Mellon University ... It
would seem that electrically powered aircraft are making steady advances in
performance and credibility as they are continuing to be developed and
technology improves.

Personally, I believe that one day the world will look back on the
petroleum-based era of motive power as the "Model T" era, and be thankful for
the development of far more efficient and cleaner electrical power. But then,
as being a "card carrying" IBEW member for over 50 years, and having benefit of
the schooling they provided for four years, I may be a bit biased. :-)


There was an electric aircraft in the 30s.
Had an endurance of 2 hours.

First I've heard of it. Are you able to provide any more information about it?


I checked through some of the current machines.
Apart from the self launched sailplanes most are two seaters with a two
hour endurance.
Any cross country would be limited by the reserve requirement. Don't
know what it is in the US but here minimum is 15 minutes.
Not a great range and the recharge will really stuff your day

Yeah. Current electric aeronautical technology is still a bit nascent. Given
the comparatively high energy density of petroleum-based aviation fuels, it's
going to be difficult to achieve comparable endurance with any electric
technology other than perhaps highly pressurized hydrogen feeding a remarkably
efficient fuel cell generator.

The way I see it currently, is that a lighter than air craft, that doesn't
relies on power to maintain altitude, and could possibly be covered in
photovoltaic "fabric" (such technology is still pretty new.) is a reasonable
starting place with a far better probability of success than winged aircraft.

The high efficiency of electric power is somewhat enabling in potentially
replacing internal combustion power plants be they piston or turbine.

Larry Dighera wrote in
:

Yeah. Current electric aeronautical technology is still a bit nascent.
Given the comparatively high energy density of petroleum-based aviation
fuels, it's going to be difficult to achieve comparable endurance with
any electric technology other than perhaps highly pressurized hydrogen
feeding a remarkably efficient fuel cell generator.

Liquid H: 2,600 WattHours/Liter 39,000 WattHours/Kilogram
Gasoline: 9,000 WattHours/Liter 13,500 WattHours/Kilogram

Gasoline has nearly 3.5 times more energy per volume.

Although liquid hydrogen has nearly 3 times more energy per
unit weight, that does not take into account the mass of the
containment vessel. A liquid hydrogen tank is going to more
than 3 times as massive as a gasoline tank or fuel bladder,
thus resulting in a net loss of energy per unit weight of the
fuel plus it's container.

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, 4 May 2015 02:10:28 +0000 (UTC), Skywise
wrote:

Larry Dighera wrote in
:

Yeah. Current electric aeronautical technology is still a bit nascent.
Given the comparatively high energy density of petroleum-based aviation
fuels, it's going to be difficult to achieve comparable endurance with
any electric technology other than perhaps highly pressurized hydrogen
feeding a remarkably efficient fuel cell generator.

Liquid H: 2,600 WattHours/Liter 39,000 WattHours/Kilogram
Gasoline: 9,000 WattHours/Liter 13,500 WattHours/Kilogram

Gasoline has nearly 3.5 times more energy per volume.

Although liquid hydrogen has nearly 3 times more energy per
unit weight, that does not take into account the mass of the
containment vessel. A liquid hydrogen tank is going to more
than 3 times as massive as a gasoline tank or fuel bladder,
thus resulting in a net loss of energy per unit weight of the
fuel plus it's container.

Brian


Thank you for that information. I hadn't seen it before.

I'll agree that a liquid H2 tank will likely be more massive than today's
gasoline tanks, but couldn't liquid H2 be stored in a Styrofoam containing
vessel?

Aren't the relative efficiencies of electrical propulsion vs internal
combustion powerplants being overlooked here?

On 5/3/2015 10:10 PM, Skywise wrote:
Although liquid hydrogen has nearly 3 times more energy per
unit weight, that does not take into account the mass of the
containment vessel. A liquid hydrogen tank is going to more
than 3 times as massive as a gasoline tank or fuel bladder,
thus resulting in a net loss of energy per unit weight of the
fuel plus it's container.

I'm not sure where you got that information from, but it's wrong.
Compressed hydrogen takes a heavy tank because of the pressure.

On the other hand, liquid hydrogen need not be under pressure, so it
does not need a massive tank. However, cryogenic fuels have their own
issues! What a cryogenic fuel tank needs that is different from other
liquid fuels is insulation. That insulation need not be heavy, but it
will take up valuable volume in your airframe. Also, cryogenic tanks
are always venting unless you have heavy, expensive power-hungry
refrigeration equipment aboard. So that means that your liquid
hydrogen-fueled airplane could be assumed to be sitting in a cloud of
flammable gaseous fuel whenever it is fueled and sitting on the ground.
No thanks!

Larry Dighera wrote in
:

I'll agree that a liquid H2 tank will likely be more massive than
today's gasoline tanks, but couldn't liquid H2 be stored in a Styrofoam
containing vessel?

The problem is either temperature or pressure, or both.

Liquid H2 is cryogenic. It doesn't exert pressure any more than
water does in a tank. But it has to be kept at -423F or -253C.

Styorofoam would just take up space.

If the idea is to avoid the crygenic temperatures, you then
need to fight the pressure. If I did my math right, and read
the phase diagram for hydrogen right, then liquid H2 at room
temperature has a pressure of about 2.5 million atmospheres.
There's no tank in the world that can hold that back.

Pressurized hydrogen at room temperature is just compressed
gaseous hydrogen. So a vehicle with that is like carrying around
a bunch of scuba tanks, which IIRC are only 3000-4000 psi or
about 200 to 270 atmospheres pressure, and look at how heavy
those are!!

I have heard about efforts to store hydrogen in metallic foams
but don't know the state of that work.

The problem is, the energy is in the hydrogen atoms. The more
atoms you have, the more energy you have. So if you want a lot
of energy, you have to cram a bunch of hydrogen atoms together
in a small space.

Now here's the killer. The properties of hydrocarbon molecules
is such that gasoline has a higher density of hydrogen atoms
than even liquid hydrogen!!! There's more hydrogen atoms per
unit volume. That's why gasoline has a 3x higher energy/density
value than liquid hydrogen. There are simply more hydrogen atoms
and therefore more energy.



Aren't the relative efficiencies of electrical propulsion vs internal
combustion powerplants being overlooked here?

My thought on electrical propulsion is, how is the electricity
produced in the first place? One rule of reality is that every
time you convert one form of energy to another, there are losses,
eventually ending up as heat. Basic Laws of Thermodynamics stuff.

Internal combustion (or turbine) engines burn the fuel and directly
convert it to mechanical work. That's bascially only one stage of
conversion to have any conversion losses.

Or, burn the fuel to drive a generator (loss 1), which generates
electricity (loss 2), which is then stored in a battery (loss 3),
which then is drawn from the battery (loss 4) to power an electic
motor (loss 5).

All those conversion losses add up. That's why gasoline is so hard
to beat. Doesn't matter if you like fossil fuels or hate it, it's
a simple fact that right now and in the forseable future, it's the
most efficient energy storage mechanism around.

The only alternative I see is to use elctricity from batteries
but generate the electricity by some other means than fossil fuels.
After all, isn't the whole point of this? to stop burning oil and
polluting the atmosphere? Burning the fossil fuels to generate
electricity to run cars and busses and planes only changes the
location of where it's burned. All these people driving their
electric cars feeling smug about themselves are not realizing that
the electricity is most likely coming from a coal fired generating
plant. And due to conversion losses, there's a good chance they
are actually increasing their "carbon footprint" than decreasing it.

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

Vaughn wrote in :

On 5/3/2015 10:10 PM, Skywise wrote:
Although liquid hydrogen has nearly 3 times more energy per
unit weight, that does not take into account the mass of the
containment vessel. A liquid hydrogen tank is going to more
than 3 times as massive as a gasoline tank or fuel bladder,
thus resulting in a net loss of energy per unit weight of the
fuel plus it's container.

I'm not sure where you got that information from, but it's wrong.

http://www.tinaja.com/glib/energfun.pdf

The numbers can be confirmed by other sources.

But I think you misread what I wrote.

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, 04 May 2015 08:33:26 -0400, Vaughn wrote:

On the other hand, liquid hydrogen need not be under pressure, so it
does not need a massive tank. However, cryogenic fuels have their own
issues! What a cryogenic fuel tank needs that is different from other
liquid fuels is insulation. That insulation need not be heavy, but it
will take up valuable volume in your airframe. Also, cryogenic tanks
are always venting unless you have heavy, expensive power-hungry
refrigeration equipment aboard. So that means that your liquid
hydrogen-fueled airplane could be assumed to be sitting in a cloud of
flammable gaseous fuel whenever it is fueled and sitting on the ground.
No thanks!

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.

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.

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?