Electriflying

[Gatt]

A few years ago when people were discussing the possibility of
electric-powered flight, you'd get hacked on pretty hard for
suggesting such a thing would be practical or possible in our
lifetime. Obviously if you knew anything about physics or electrical
engineering, why, you'd know it was totally impossible.

So here you go.

http://www.wired.com/autopia/tag/electric-airplane/

"Flight times for two-seat electric aircraft in development already
exceed 90 minutes. That might not be enough for a long cross-country
flight, but it’s longer than the typical flight lesson lasts. And this
is what has caught the attention of flight schools.

The commercial side of electric airplanes may be less about going
places, and more about teaching student pilots how to fly. And the
first electric student pilot has already flown solo, learning the
basics entirely in a battery-powered airplane."

Even better will be a commuter aircraft so you could fly from, say,
Salem to Portland or Seattle to Port Townsend unencumbered by rush
hour traffic. My philosophy is, the faster and harder society advances
this technology the more likely we will be able to enjoy it in our
lifetime.

-c

[Bill Shatzer[_2_]]

Gatt wrote:

> A few years ago when people were discussing the possibility of
> electric-powered flight, you'd get hacked on pretty hard for
> suggesting such a thing would be practical or possible in our
> lifetime. Obviously if you knew anything about physics or electrical
> engineering, why, you'd know it was totally impossible.

"When a distinguished but elderly scientist states that something is
possible, he is almost certainly right. When he states that something is
impossible, he is very probably wrong."


- Arthur C. Clarke -

peace and justice,

[[email protected]]

In rec.aviation.owning Gatt > wrote:
> A few years ago when people were discussing the possibility of
> electric-powered flight, you'd get hacked on pretty hard for
> suggesting such a thing would be practical or possible in our
> lifetime. Obviously if you knew anything about physics or electrical
> engineering, why, you'd know it was totally impossible.
>
> So here you go.
>
> http://www.wired.com/autopia/tag/electric-airplane/
>
> "Flight times for two-seat electric aircraft in development already
> exceed 90 minutes. That might not be enough for a long cross-country
> flight, but it’s longer than the typical flight lesson lasts. And this
> is what has caught the attention of flight schools.

So is that 90 minutes plus the FAA mandated reserve time or 90 minutes
minus the the FAA mandated reserve time?

How long to recharge for the next student?


--
Jim Pennino

Remove .spam.sux to reply.

[george]

On Jun 23, 8:08*am, wrote:
> In rec.aviation.owning Gatt > wrote:
>
> > A few years ago when people were discussing the possibility of
> > electric-powered flight, you'd get hacked on pretty hard for
> > suggesting such a thing would be practical or possible in our
> > lifetime. Obviously if you knew anything about physics or electrical
> > engineering, why, you'd know it was totally impossible.
>
> > So here you go.
>
> >http://www.wired.com/autopia/tag/electric-airplane/
>
> > "Flight times for two-seat electric aircraft in development already
> > exceed 90 minutes. That might not be enough for a long cross-country
> > flight, but it’s longer than the typical flight lesson lasts. And this
> > is what has caught the attention of flight schools.
>
> So is that 90 minutes plus the FAA mandated reserve time or 90 minutes
> minus the the FAA mandated reserve time?
>
> How long to recharge for the next student?
>

They'd come under the heading of toys.
No crosscountry range, a useless rating and a constant changing of
battery packs.
However there IS a machine that is powered with photo voltaic cells on
the wing if you like air speeds of 40 knots 24/7 :)

[Lobby Dosser[_2_]]

"Bill Shatzer" > wrote in message
...
> Gatt wrote:
>
>> A few years ago when people were discussing the possibility of
>> electric-powered flight, you'd get hacked on pretty hard for
>> suggesting such a thing would be practical or possible in our
>> lifetime. Obviously if you knew anything about physics or electrical
>> engineering, why, you'd know it was totally impossible.
>
> "When a distinguished but elderly scientist states that something is
> possible, he is almost certainly right. When he states that something is
> impossible, he is very probably wrong."
>
>
> - Arthur C. Clarke -
>
> peace and justice,
>


And the Death by Global Warming bunch are Old Buggers.

--
"I'm the man who broke the bank at Monte Carlo ..."

[SMITH29]

On 6/22/2011 12:39 PM, Bill Shatzer wrote:
> Gatt wrote:
>
>> A few years ago when people were discussing the possibility of
>> electric-powered flight, you'd get hacked on pretty hard for
>> suggesting such a thing would be practical or possible in our
>> lifetime. Obviously if you knew anything about physics or electrical
>> engineering, why, you'd know it was totally impossible.
>
> "When a distinguished but elderly scientist states that something is
> possible, he is almost certainly right. When he states that something is
> impossible, he is very probably wrong."
>
>
> - Arthur C. Clarke -
>
> peace and justice,
>
xxxx
Clarke was one fine bull****ter.
An Art Bell on steroids.
A HoaXland with 1/2 a brain.

[Dylan Smith[_2_]]

On 2011-06-22, george > wrote:
> They'd come under the heading of toys.
> No crosscountry range, a useless rating and a constant changing of
> battery packs.

As things improve, electric aircraft may make for a great glider
towplane! Less noise for the neighbours to whine about, less concern
with cooking the engine on climbout and cooling the engine excessively
on descent, lower maintenance with far fewer moving parts.
Electric propulsion also would be good for a self-launching motorglider,
lower complexity, battery pack doesn't need to be all that big since
you only need power for perhaps 10 minutes (5 minutes to launch,
perhaps keep 5 minutes in hand just in case you need a second attempt
to find lift).

Of course, the Wright's first aircraft wasn't all that useful, but
with development it became useful. Battery and motor control technology
is improving. The electric aircraft will almost certainly remain a niche
aircraft for some time to come, but I wouldn't write it off forever.

[Alpha Propellerhead]

On Jun 22, 1:08*pm, wrote:

>
> So is that 90 minutes plus the FAA mandated reserve time or 90 minutes
> minus the the FAA mandated reserve time?
>
> How long to recharge for the next student?

Not sure, yet, but I'm sure the Wright Flyer wasn't an ideal trainer
either. My issue is with the Lithium Polymer batteries. When those
things burn--a bad charger will blow them up--they go incendiary like
fireworks. Some airplane builders around here say the next generation
is under development, but a lot more stable. That means batteries will
continue to become lighter and more stable, at the very least.

They're not going to replace the old Cessna 152 as a primary trainer
at flight schools anytime soon, but if I could buy a 152 with an
electric power plant for my own uses, I'd much rather fly that than
paying $6/gallon @ 5 gallons per hour just for the fuel.

Also, Diamond will be flying a hybrid at the Paris Airshow this year.

[Alpha Propellerhead]

On Jun 22, 1:49*pm, george > wrote:

>
> They'd come under the heading of toys.

So do the Kitfox and Talon LSAs that a couple of our students own,
but, my student's trailer-mobile toy airplane is cooler than any
Harley Davidson or muscle car ever made.

And, like I said: Five years ago people ridiculed the very
POSSIBILITY of electric flight, so ridiculing the practicality of it
is water off a duck's back at this point. 'Cause here's the deal:
Lots of people told the Wright Brothers that what they were doing
wasn't possible and in fact the French called them "fliers or liars"
until they went over there and proved it to them.

> No crosscountry range,

1 hour at 80 kts is cross country range for a commuter, especially in
regions like Seattle. I commuted 60 miles each way once between a
ten-hour work day, within five miles of airports at both directions.
Recharging batteries and enjoying a summer flight in my 2-seat
commuter, or idling on Interstate 5 all morning and afternoon... hmmm.

>a useless rating and a constant changing of battery packs.

And you're not burning $40/hr in fuel, oil and internal-combustion
maintenance. I just flew from St. George UT to Fairbanks in a 172,
and fuel costs at 7.5gph in the Yukon at $8/gallon--$60/hr in fuel and
oil alone--25 hours total time, is as prohibitive to the average
person as charging batteries might be.

You can fly an electric airplane with a private pilot's license. I'm
not sure what "useless rating" means. Is a motorcycle license
"useless"?

[Alpha Propellerhead]

On Jun 23, 8:35*am, SMITH29 > wrote:

> >> A few years ago when people were discussing the possibility of
> >> electric-powered flight, you'd get hacked on pretty hard for
> >> suggesting such a thing would be practical or possible in our
> >> lifetime. Obviously if you knew anything about physics or electrical
> >> engineering, why, you'd know it was totally impossible.


> Clarke was one fine bull****ter.

PSSST! Did you hear about the ELECTRIC AIRPLANES? The cynics all
said they were IMPOSSIBLE.

[John Smith]

Alpha Propellerhead wrote:
> and in fact the French called them "fliers or liars"

In fact, I'm almost certain that the French didn't call them English
names. I'm even almost certain that they didn't call them names at all,
as the secret of flying was revealed in Europe, and the French most
certainly were aware of it's possibility.

[SMITH29]

On 6/23/2011 10:44 AM, Alpha Propellerhead wrote:
> On Jun 23, 8:35 am, > wrote:
>
>>>> A few years ago when people were discussing the possibility of
>>>> electric-powered flight, you'd get hacked on pretty hard for
>>>> suggesting such a thing would be practical or possible in our
>>>> lifetime. Obviously if you knew anything about physics or electrical
>>>> engineering, why, you'd know it was totally impossible.
>
>
>> Clarke was one fine bull****ter.
>
> PSSST! Did you hear about the ELECTRIC AIRPLANES? The cynics all
> said they were IMPOSSIBLE.

xxxx
Gossamer Albatross goes one better.
http://www.diseno-art.com/encyclopedia/strange_vehicles/maccready_gossamer_albatross.html

Or:
http://www.youtube.com/watch?v=1NCOPLEJOl0

German battery plane:
http://www.youtube.com/watch?v=2RsWNiQuTP8

Nuclear powered aircraft:
http://www.century-of-flight.net/Aviation%20history/evolution%20of%20technology/nuke.htm

And the beat goes on.
Real science is far more interesting than fiction.

29

[[email protected]]

In rec.aviation.owning Alpha Propellerhead > wrote:
> On Jun 23, 8:35Â*am, SMITH29 > wrote:
>
>> >> A few years ago when people were discussing the possibility of
>> >> electric-powered flight, you'd get hacked on pretty hard for
>> >> suggesting such a thing would be practical or possible in our
>> >> lifetime. Obviously if you knew anything about physics or electrical
>> >> engineering, why, you'd know it was totally impossible.
>
>
>> Clarke was one fine bull****ter.
>
> PSSST! Did you hear about the ELECTRIC AIRPLANES? The cynics all
> said they were IMPOSSIBLE.

Utter nonsense.

What was said, and is still being said, and will be said absent some
astounding breakthrough in basic physics which enables batteries to be
about an order of magnitude better than they are, is that electric airplanes
are IMPRACTICAL.


--
Jim Pennino

Remove .spam.sux to reply.

[Vaughn]

> wrote in message
...
> So is that 90 minutes plus the FAA mandated reserve time or 90 minutes
> minus the the FAA mandated reserve time?

90 minutes is sort of a magic number. Gives you a 60-minute lesson with VFR
reserves.

>
> How long to recharge for the next student?

You have just identified the real issue!

Vaughn

[Vaughn]

"Alpha Propellerhead" > wrote in message
...
On Jun 22, 1:08 pm, wrote:

> My issue is with the Lithium Polymer batteries. When those
>things burn--a bad charger will blow them up--they go incendiary like
>fireworks.

Ever see what happens when avgas catches fire? They should outlaw that
stuff then invent airplanes that use a more stable fuel.

Vaughn

[[email protected]]

Alpha Propellerhead > wrote:
> On Jun 22, 1:08Â*pm, wrote:
>
>>
>> So is that 90 minutes plus the FAA mandated reserve time or 90 minutes
>> minus the the FAA mandated reserve time?
>>
>> How long to recharge for the next student?
>
> Not sure, yet, but I'm sure the Wright Flyer wasn't an ideal trainer
> either.

Apples and oranges.

The Wright Flyer wasn't build with mature technology.

Airplanes, electric motors, and batteries are all mature technologies.

> My issue is with the Lithium Polymer batteries. When those
> things burn--a bad charger will blow them up--they go incendiary like
> fireworks. Some airplane builders around here say the next generation
> is under development, but a lot more stable. That means batteries will
> continue to become lighter and more stable, at the very least.

Nope, basic chemistry and physics impose a limit on how much energy
density you can get out of a battery and we are already pushing the
limit.

> They're not going to replace the old Cessna 152 as a primary trainer
> at flight schools anytime soon, but if I could buy a 152 with an
> electric power plant for my own uses, I'd much rather fly that than
> paying $6/gallon @ 5 gallons per hour just for the fuel.

Batteries are both life and recharge cycles limited, so instead of paying
$6/gal @ 5gal/hr you pay something like something on the order of
$10,000 for a new, FAA certified, battery pack every 3 to 5 years.

> Also, Diamond will be flying a hybrid at the Paris Airshow this year.

The worst of all worlds for an airplane; airplanes aren't cars.


--
Jim Pennino

Remove .spam.sux to reply.

[[email protected]]

Vaughn > wrote:
>
> > wrote in message
> ...
>> So is that 90 minutes plus the FAA mandated reserve time or 90 minutes
>> minus the the FAA mandated reserve time?
>
> 90 minutes is sort of a magic number. Gives you a 60-minute lesson with VFR
> reserves.
>
>>
>> How long to recharge for the next student?
>
> You have just identified the real issue!

Nope, there is still the cost of a new, FAA certified battery pack every
3 to 5 years, which will likely be in the ballpark price of a used 150.


--
Jim Pennino

Remove .spam.sux to reply.

[Vaughn]

> wrote in message
...
> Vaughn > wrote:
>>> How long to recharge for the next student?
>>
>> You have just identified the real issue!
>
> Nope, there is still the cost of a new, FAA certified battery pack every
> 3 to 5 years, which will likely be in the ballpark price of a used 150.
>
The strange thing is, the price for the 150/152 engine, is also about the
same price as a used 150. In the flight training world, these things are
amortized and built into the training hourly rate. If the electric trainer
isn't cheaper, it won't sell except in nitch situations where its silence or
(perhaps) novelty are factors.

Vaughn

[[email protected]]

Vaughn > wrote:
>
> > wrote in message
> ...
>> Vaughn > wrote:
>>>> How long to recharge for the next student?
>>>
>>> You have just identified the real issue!
>>
>> Nope, there is still the cost of a new, FAA certified battery pack every
>> 3 to 5 years, which will likely be in the ballpark price of a used 150.
>>
> The strange thing is, the price for the 150/152 engine, is also about the
> same price as a used 150. In the flight training world, these things are
> amortized and built into the training hourly rate. If the electric trainer
> isn't cheaper, it won't sell except in nitch situations where its silence or
> (perhaps) novelty are factors.
>
> Vaughn

It isn't all that strange when you concider that a 1990 Toyota Corolla goes
for about $3k while a rebuilt to new specs engine for it costs about $2.5k.

Anyway, back to airplanes...

The only electric airplane that is even close to being practical is a self
launched glider.

And since we are already close to the fundemental limits of physics and
chemistry on batteries, that isn't going to change without a blinding
breakthrough in the science of portable electric storage.



--
Jim Pennino

Remove .spam.sux to reply.

[hierophant[_2_]]

On Fri, 24 Jun 2011 16:37:52 -0000, wrote:

> Vaughn > wrote:
>>
>> > wrote in message
>> ...
>>> Vaughn > wrote:
>>>>> How long to recharge for the next student?
>>>>
>>>> You have just identified the real issue!
>>>
>>> Nope, there is still the cost of a new, FAA certified battery pack every
>>> 3 to 5 years, which will likely be in the ballpark price of a used 150.
>>>
>> The strange thing is, the price for the 150/152 engine, is also about the
>> same price as a used 150. In the flight training world, these things are
>> amortized and built into the training hourly rate. If the electric trainer
>> isn't cheaper, it won't sell except in nitch situations where its silence or
>> (perhaps) novelty are factors.
>>
>> Vaughn
>
> It isn't all that strange when you concider that a 1990 Toyota Corolla goes
> for about $3k while a rebuilt to new specs engine for it costs about $2.5k.
>
> Anyway, back to airplanes...
>
> The only electric airplane that is even close to being practical is a self
> launched glider.
>
> And since we are already close to the fundemental limits of physics and
> chemistry on batteries, that isn't going to change without a blinding
> breakthrough in the science of portable electric storage.
>

Please get off this topic before "MarkIV" returns. heh

[george]

On Jun 25, 4:48*am, hierophant > wrote:
> On Fri, 24 Jun 2011 16:37:52 -0000, wrote:
> > Vaughn > wrote:
>
> >> > wrote in message
> ...
> >>> Vaughn > wrote:
> >>>>> How long to recharge for the next student?
>
> >>>> You have just identified the real issue!
>
> >>> Nope, there is still the cost of a new, FAA certified battery pack every
> >>> 3 to 5 years, which will likely be in the ballpark price of a used 150.

[hierophant[_2_]]

On Fri, 24 Jun 2011 13:18:08 -0700 (PDT), george wrote:

> On Jun 25, 4:48*am, hierophant > wrote:
>> On Fri, 24 Jun 2011 16:37:52 -0000, wrote:
>>> Vaughn > wrote:
>>
>>>> > wrote in message
...
>>>>> Vaughn > wrote:
>>>>>>> How long to recharge for the next student?
>>
>>>>>> You have just identified the real issue!
>>
>>>>> Nope, there is still the cost of a new, FAA certified battery pack every
>>>>> 3 to 5 years, which will likely be in the ballpark price of a used 150.
>>
>>>> The strange thing is, the price for the 150/152 engine, is also about the
>>>> same price as a used 150. *In the flight training world, these things are
>>>> amortized and built into the training hourly rate. *If the electric trainer
>>>> isn't cheaper, it won't sell except in nitch situations where its silence or
>>>> (perhaps) novelty are factors.
>>
>>>> Vaughn
>>
>>> It isn't all that strange when you concider that a 1990 Toyota Corolla goes
>>> for about $3k while a rebuilt to new specs engine for it costs about $2.5k.
>>
>>> Anyway, back to airplanes...
>>
>>> The only electric airplane that is even close to being practical is a self
>>> launched glider.
>>
>>> And since we are already close to the fundemental limits of physics and
>>> chemistry on batteries, that isn't going to change without a blinding
>>> breakthrough in the science of portable electric storage.
>>
>> Please get off this topic before "MarkIV" returns. heh
>
> I think he now calls himself Tom

Really? Well, there's a fella at Cox Communications that has a
standing arrest warrant for "Tom" if he ever as much as shows his
manic mania on Usenet again.

Seems "Tom" or Mark or whomever had a couple of friends who fingered
him in S.C. Peg leg and all. ;)

[Vaughn]

> wrote in message
...
> Vaughn > wrote:
>>
>> > wrote in message
>> ...
>>> Vaughn > wrote:
>>>>> How long to recharge for the next student?
>>>>
>>>> You have just identified the real issue!
>>>
>>> Nope, there is still the cost of a new, FAA certified battery pack every
>>> 3 to 5 years, which will likely be in the ballpark price of a used 150.
>>>
>> The strange thing is, the price for the 150/152 engine, is also about the
>> same price as a used 150. In the flight training world, these things are
>> amortized and built into the training hourly rate. If the electric
>> trainer
>> isn't cheaper, it won't sell except in nitch situations where its silence
>> or
>> (perhaps) novelty are factors.
>>
>> Vaughn
>
> It isn't all that strange when you concider that a 1990 Toyota Corolla
> goes
> for about $3k while a rebuilt to new specs engine for it costs about
> $2.5k.

You are the one who said "Nope, there is still the cost of a new, FAA
certified battery pack every
3 to 5 years, which will likely be in the ballpark price of a used 150." I
simply pointed out that is really no different from the flight training
150/152, which will also require expensive powerplant investment every few
years.

> Anyway, back to airplanes...

You are the one who got us away from airplanes...
>
> The only electric airplane that is even close to being practical is a self
> launched glider.

Unproven.

>
> And since we are already close to the fundemental limits of physics and
> chemistry on batteries,

Unproven


Vaughn

[Orval Fairbairn]

In article >,
"Vaughn" > wrote:

> > wrote in message
> ...
> > Vaughn > wrote:
> >>
> >> > wrote in message
> >> ...
> >>> Vaughn > wrote:
> >>>>> How long to recharge for the next student?
> >>>>
> >>>> You have just identified the real issue!
> >>>
> >>> Nope, there is still the cost of a new, FAA certified battery pack every
> >>> 3 to 5 years, which will likely be in the ballpark price of a used 150.
> >>>
> >> The strange thing is, the price for the 150/152 engine, is also about the
> >> same price as a used 150. In the flight training world, these things are
> >> amortized and built into the training hourly rate. If the electric
> >> trainer
> >> isn't cheaper, it won't sell except in nitch situations where its silence
> >> or
> >> (perhaps) novelty are factors.
> >>
> >> Vaughn
> >
> > It isn't all that strange when you concider that a 1990 Toyota Corolla
> > goes
> > for about $3k while a rebuilt to new specs engine for it costs about
> > $2.5k.
>
> You are the one who said "Nope, there is still the cost of a new, FAA
> certified battery pack every
> 3 to 5 years, which will likely be in the ballpark price of a used 150." I
> simply pointed out that is really no different from the flight training
> 150/152, which will also require expensive powerplant investment every few
> years.
>
> > Anyway, back to airplanes...
>
> You are the one who got us away from airplanes...
> >
> > The only electric airplane that is even close to being practical is a self
> > launched glider.
>
> Unproven.
>
> >
> > And since we are already close to the fundemental limits of physics and
> > chemistry on batteries,
>
> Unproven
>
>
> Vaughn

pretty good empirical evidence, though! If we weren't near the limits of
battery chemistry, we would have had an order of magnitude of change in
battery performance over the last century, since there have been major
needs for such performance: submarines, spacecraft, aircraft,
automobiles, laptop computers.

The last have made their major advances in the expansion of storage and
computing speed, while reducing their power requirements. The batteries
haven't advanced that far.

[[email protected]]

Vaughn > wrote:
>
> > wrote in message
> ...
>> Vaughn > wrote:
>>>
>>> > wrote in message
>>> ...
>>>> Vaughn > wrote:
>>>>>> How long to recharge for the next student?
>>>>>
>>>>> You have just identified the real issue!
>>>>
>>>> Nope, there is still the cost of a new, FAA certified battery pack every
>>>> 3 to 5 years, which will likely be in the ballpark price of a used 150.
>>>>
>>> The strange thing is, the price for the 150/152 engine, is also about the
>>> same price as a used 150. In the flight training world, these things are
>>> amortized and built into the training hourly rate. If the electric
>>> trainer
>>> isn't cheaper, it won't sell except in nitch situations where its silence
>>> or
>>> (perhaps) novelty are factors.
>>>
>>> Vaughn
>>
>> It isn't all that strange when you concider that a 1990 Toyota Corolla
>> goes
>> for about $3k while a rebuilt to new specs engine for it costs about
>> $2.5k.
>
> You are the one who said "Nope, there is still the cost of a new, FAA
> certified battery pack every
> 3 to 5 years, which will likely be in the ballpark price of a used 150." I
> simply pointed out that is really no different from the flight training
> 150/152, which will also require expensive powerplant investment every few
> years.

Umm, what I was pointing out is that a new power plant for an old vehicle
of any type is likely to be near the used price of the old vehicle.

>> Anyway, back to airplanes...
>
> You are the one who got us away from airplanes...
>>
>> The only electric airplane that is even close to being practical is a self
>> launched glider.
>
> Unproven.

Antares 20E, Alisport Silent 2 Targa, Pipsistrel Taurus.

Some have been around for decades.

>> And since we are already close to the fundemental limits of physics and
>> chemistry on batteries,
>
> Unproven

Basic physics and chemistry.

If you don't believe it, get a physics or chemistry degree and you will find
out why it is true.



--
Jim Pennino

Remove .spam.sux to reply.

[Vaughn]

> wrote in message
...
> If you don't believe it, get a physics or chemistry degree

Do you have yours? You are the one trying to make this case, not me.

Myself, I neither agree nor disagree, but am cautiously impressed with the
advances I have seen in the last few years.

Vaughn

[[email protected]]

Vaughn > wrote:
>
> > wrote in message
> ...
>> If you don't believe it, get a physics or chemistry degree
>
> Do you have yours? You are the one trying to make this case, not me.
>
> Myself, I neither agree nor disagree, but am cautiously impressed with the
> advances I have seen in the last few years.

It is easy enough to Google for.

Start here, a plain english overview of energy storage:

http://www.thebulletin.org/web-edition/columnists/kurt-zenz-house/the-limits-of-energy-storage-technology




--
Jim Pennino

Remove .spam.sux to reply.

[Orval Fairbairn]

In article >,
"Vaughn" > wrote:

> > wrote in message
> ...
> > If you don't believe it, get a physics or chemistry degree
>
> Do you have yours? You are the one trying to make this case, not me.
>
> Myself, I neither agree nor disagree, but am cautiously impressed with the
> advances I have seen in the last few years.
>
> Vaughn

Well, Vaughn, all you have to do is a simple back-of-the-envelope
calculation to see it.

First, calculate the fuel and air consumed in an internal combstion
engine:
1. fuel, at 6 lb/gal
2. air, at f/a ratio of 1:15.

This means that, for every pound of fuel, you consume 15 pounds of air.
You may use kilograms, if you please.

For a 20 gallon tank, you have 120 lb of fuel and use 1800 lb of air to
propel yourself through the air.

If you are using batteries, you now have to carry the equivalent of both
the fuel and the consumable air to do the same job, or almost a ton of
consumables. That is why battery technology is against a wall of
diminishing returns and is not a practical soultion to aircraft
propulsion.

[[email protected]]

Orval Fairbairn > wrote:
> In article >,
> "Vaughn" > wrote:
>
>> > wrote in message
>> ...
>> > If you don't believe it, get a physics or chemistry degree
>>
>> Do you have yours? You are the one trying to make this case, not me.
>>
>> Myself, I neither agree nor disagree, but am cautiously impressed with the
>> advances I have seen in the last few years.
>>
>> Vaughn
>
> Well, Vaughn, all you have to do is a simple back-of-the-envelope
> calculation to see it.
>
> First, calculate the fuel and air consumed in an internal combstion
> engine:
> 1. fuel, at 6 lb/gal
> 2. air, at f/a ratio of 1:15.
>
> This means that, for every pound of fuel, you consume 15 pounds of air.
> You may use kilograms, if you please.
>
> For a 20 gallon tank, you have 120 lb of fuel and use 1800 lb of air to
> propel yourself through the air.
>
> If you are using batteries, you now have to carry the equivalent of both
> the fuel and the consumable air to do the same job, or almost a ton of
> consumables. That is why battery technology is against a wall of
> diminishing returns and is not a practical soultion to aircraft
> propulsion.

100LL avgas has a specific energy of 44 MJ/kg not counting the air to
burn it.

The best theoretical battery has a specific energy of 2.54 MJ/kg.

So even ignoring the air, to get the same energy from a thoretical
battery that doesn't exist yet as 120 lb of 100LL, you would need a bit
over 2,000 lbs worth of battery.

If you factor in the fact that electric motors are about twice as efficient
in energy coversion as gasoline engines, you still need around 1000 lb
worth of battery.

That is why you hear people say batteries have to improve by an order of
magnitude, i.e. get 10 times better, before they will be generally practical
to power vehicles.

And phyiscs and chemistry says you can't do it.



--
Jim Pennino

Remove .spam.sux to reply.

[Dylan Smith[_2_]]

On 2011-06-25, Orval Fairbairn > wrote:
> pretty good empirical evidence, though! If we weren't near the limits of
> battery chemistry, we would have had an order of magnitude of change in
> battery performance over the last century, since there have been major
> needs for such performance: submarines, spacecraft, aircraft,
> automobiles, laptop computers.

Well, we have had an order of magnitude change. The first long life
rechargable battery (as in lasts many charge cycles), the lead acid
battery, has an energy density of 41 watt hours per kilogram.

The latest long life rechargable battery, the lithium polymer,
has an energy density of 128 watt hours per kilogram. That's pretty
close to an order of magnitude. (You could nit-pick and say the
lithium battery was invented a long time ago, but that lithium
battery was not rechargable and is a far cry from a modern Li-Poly).

Also the performance just within lithium polymer batteries has increased
enormously. Ten years ago, the maximum discharge rate of any kind
of rechargable lithium battery didn't exceed 1 to 2 C (1C = a current
equal to the amp hour capacity of the battery, so if you had a 10aH
Li-Ion with a maximum discharge of 1C, it would mean it could
give at most a current of 10 amps). I have a LiPoly battery here
that has a maximum discharge rate of 60C continuous, 120C peak.
It's the size of a cigar packet and can start a car engine. This just
wasn't possible even 10 years ago.

Additionally, UC San Diego is working on a battery that is expected
to give an energy density of around 1kWh per kilogram (an order of
magnitude better than current lithium rechargable batteries). It
remains to be seen what C rating it will have, which is enormously
important for anything that moves. Lithium cobalt oxide batteries
in the lab have a 500 watt hour/kg energy density. From past performance
it typically is about 10 years from being a "yeah it works in the lab"
to a commercial product.

[Dylan Smith[_2_]]

On 2011-06-25, Orval Fairbairn > wrote:
> Well, Vaughn, all you have to do is a simple back-of-the-envelope
> calculation to see it.
>
> First, calculate the fuel and air consumed in an internal combstion
> engine:
> 1. fuel, at 6 lb/gal
> 2. air, at f/a ratio of 1:15.
>
> This means that, for every pound of fuel, you consume 15 pounds of air.
> You may use kilograms, if you please.

Not correct, you don't consume the nitrogen which is around 80% of air.

> If you are using batteries, you now have to carry the equivalent of both
> the fuel and the consumable air to do the same job, or almost a ton of
> consumables.

But you're comparing apples and oranges! Batteries do NOT work on oxidation.
The thing that charges the battery may indeed work by oxidising the
fuel (but equally it may not, it may be a nuclear power plant, a wind
turbine, a solar panel or whatever). You cannot compare how a battery
works to how fuel is burned. They just aren't the same thing at all.

Additionally your calculation on the air consumed is quite significantly
wrong. Not just because you forgot about the nitrogen, but when calculating
how something burns you must consider how many moles of a substance
is reacting, i.e. its molecular mass.

Gasoline is a mix of quite a lot of chemicals, but mostly things like
C6H12 and these numbers will come out the same for any alkane.

To burn one mole of C6H12, we need 12 moles of O2
1 C6H12 x 12 O2 = 6 CO2 + 6 H2O

6 of the O2 molecules coming in make 6 carbon dioxide molecules,
the remaining 6 O2 molecules are used to make the 6 water molecules.

So we use 12 moles of O2 per one mole C6H12.

One mole of O2 is 32 grams.
One mole of C6H12 is 84.2 grams.

So for every 84.2g of fuel we need 320g of oxygen. This means the ratio
by mass of oxidiser to fuel is around 3.8 parts oxidiser to each part
of fuel -- NOT 15 parts oxidiser to each part fuel.

[Dylan Smith[_2_]]

On 2011-06-27, Dylan Smith > wrote:
> But you're comparing apples and oranges! Batteries do NOT work on oxidation.

Actually, I already stand (sit) corrected on that one looking a bit
closer at the chemistry. But that still doesn't mean a battery must
carry all of its reaction chemicals. Indeed, there is a type of lithium
rechargable battery that uses oxygen from the air (just as burning
avgas uses oxygen from the air). Still in research stages, and it
still remains to be seen what the maximum C rating of this kind
of battery would be.

[[email protected]]

Dylan Smith > wrote:
> On 2011-06-25, Orval Fairbairn > wrote:
>> pretty good empirical evidence, though! If we weren't near the limits of
>> battery chemistry, we would have had an order of magnitude of change in
>> battery performance over the last century, since there have been major
>> needs for such performance: submarines, spacecraft, aircraft,
>> automobiles, laptop computers.
>
> Well, we have had an order of magnitude change. The first long life
> rechargable battery (as in lasts many charge cycles), the lead acid
> battery, has an energy density of 41 watt hours per kilogram.
>
> The latest long life rechargable battery, the lithium polymer,
> has an energy density of 128 watt hours per kilogram. That's pretty
> close to an order of magnitude. (You could nit-pick and say the
> lithium battery was invented a long time ago, but that lithium
> battery was not rechargable and is a far cry from a modern Li-Poly).

That's close to an order of magnitude for those that feel 3.1 is close to
10.

> Also the performance just within lithium polymer batteries has increased
> enormously. Ten years ago, the maximum discharge rate of any kind
> of rechargable lithium battery didn't exceed 1 to 2 C (1C = a current
> equal to the amp hour capacity of the battery, so if you had a 10aH
> Li-Ion with a maximum discharge of 1C, it would mean it could
> give at most a current of 10 amps). I have a LiPoly battery here
> that has a maximum discharge rate of 60C continuous, 120C peak.
> It's the size of a cigar packet and can start a car engine. This just
> wasn't possible even 10 years ago.
>
> Additionally, UC San Diego is working on a battery that is expected
> to give an energy density of around 1kWh per kilogram (an order of
> magnitude better than current lithium rechargable batteries). It
> remains to be seen what C rating it will have, which is enormously
> important for anything that moves. Lithium cobalt oxide batteries
> in the lab have a 500 watt hour/kg energy density. From past performance
> it typically is about 10 years from being a "yeah it works in the lab"
> to a commercial product.


1kWh per kilogram is 3.6 MJ/kg.

100LL Avgas is 44 MJ/kg.

Batteries need to be able to produce better than 20 MJ/kg to be generally
usefull for transportation.


-
Jim Pennino

Remove .spam.sux to reply.

[Orval Fairbairn]

In article >, Dylan Smith >
wrote:

> On 2011-06-25, Orval Fairbairn > wrote:
> > Well, Vaughn, all you have to do is a simple back-of-the-envelope
> > calculation to see it.
> >
> > First, calculate the fuel and air consumed in an internal combstion
> > engine:
> > 1. fuel, at 6 lb/gal
> > 2. air, at f/a ratio of 1:15.
> >
> > This means that, for every pound of fuel, you consume 15 pounds of air.
> > You may use kilograms, if you please.
>
> Not correct, you don't consume the nitrogen which is around 80% of air.
>
> > If you are using batteries, you now have to carry the equivalent of both
> > the fuel and the consumable air to do the same job, or almost a ton of
> > consumables.
>
> But you're comparing apples and oranges! Batteries do NOT work on oxidation.
> The thing that charges the battery may indeed work by oxidising the
> fuel (but equally it may not, it may be a nuclear power plant, a wind
> turbine, a solar panel or whatever). You cannot compare how a battery
> works to how fuel is burned. They just aren't the same thing at all.

They still work on chemical reaction -- the point being that you have to
carry ALL of the chemicals with you, rather than getting the majority of
them from the air. In addition, your landing weight will be the same as
your takeoff weight, since nothing is dumped overboard as a result of
flying.


>
> Additionally your calculation on the air consumed is quite significantly
> wrong. Not just because you forgot about the nitrogen, but when calculating
> how something burns you must consider how many moles of a substance
> is reacting, i.e. its molecular mass.
>
> Gasoline is a mix of quite a lot of chemicals, but mostly things like
> C6H12 and these numbers will come out the same for any alkane.
>
> To burn one mole of C6H12, we need 12 moles of O2
> 1 C6H12 x 12 O2 = 6 CO2 + 6 H2O
>
> 6 of the O2 molecules coming in make 6 carbon dioxide molecules,
> the remaining 6 O2 molecules are used to make the 6 water molecules.
>
> So we use 12 moles of O2 per one mole C6H12.
>
> One mole of O2 is 32 grams.
> One mole of C6H12 is 84.2 grams.

Hextane? I don't think so! Don't you mean octane (C8H18)?
>
> So for every 84.2g of fuel we need 320g of oxygen. This means the ratio
> by mass of oxidiser to fuel is around 3.8 parts oxidiser to each part
> of fuel -- NOT 15 parts oxidiser to each part fuel.

I stand by my analogy in that, even though the nitrogen does not
participate in the chemical reaction, it still plays an important role
in the propulsion equation, by providing a working medium to receive
heat and expand to push pistons or to turn turbines.

Batteries still require at least an order of magnitude improvement to be
practical for transportation. And we still haven't talked about the
weight of the batteries themselves!

[vaughn[_3_]]

> wrote in message
...
>
> 100LL Avgas is 44 MJ/kg.

When burned in an IC airplane engine, most of those MJs are turned into waste
heat, not propulsion.

> Batteries need to be able to produce better than 20 MJ/kg to be generally
> usefull for transportation.

How many light planes are actually used for transportation?

Vaughn

[[email protected]]

vaughn > wrote:
>
> > wrote in message
> ...
>>
>> 100LL Avgas is 44 MJ/kg.
>
> When burned in an IC airplane engine, most of those MJs are turned into waste
> heat, not propulsion.

That is why I said batteries need to be able to produce better than 20 MJ/kg
to be generally usefull instead of better than 40 MJ/kg.

This takes into account the compartive real world energy efficiencies of
electric versus gasoline motors.

All of this neglects cost issues; even if batteries somehow get there,
they won't be economically practical if it turns out the cost of a battery
pack for something like a 172 costs a million bucks and has to be replaced
every 5 years.

>> Batteries need to be able to produce better than 20 MJ/kg to be generally
>> usefull for transportation.
>
> How many light planes are actually used for transportation?

All of them that fly unless they are remotely controlled.

The trip may be as short as 3 turns around the pattern to maintain currency,
but a person is still being moved.


--
Jim Pennino

Remove .spam.sux to reply.

[vaughn[_3_]]

> wrote in message
...
>> How many light planes are actually used for transportation?
>
> All of them that fly unless they are remotely controlled.
>
> The trip may be as short as 3 turns around the pattern to maintain currency,
> but a person is still being moved.
>
Sorry, but that's stretching a point beyond nonsense. You could also argue
that a pogo stick is a transportation device, but few would take you seriously.
"Three turns around the pattern" may actually be either recreation or training,
but hardly transportation. Most light planes are used for training and
recreation, not transportation. Regardless of the owner's intentions when they
buy them, few light planes are actually used for serious transportation.

This thread started with a post about a 2-place training aircraft with a 90-
minute endurance. Fact is, that plane (if it really exists) could handle many,
(possibly most) of the missions I see flown out of my local airport. If
available as a rental, it could handle about 70% of my own flights.

Vaughn

[[email protected]]

vaughn > wrote:
>
> > wrote in message
> ...
>>> How many light planes are actually used for transportation?
>>
>> All of them that fly unless they are remotely controlled.
>>
>> The trip may be as short as 3 turns around the pattern to maintain currency,
>> but a person is still being moved.
>>
> Sorry, but that's stretching a point beyond nonsense. You could also argue
> that a pogo stick is a transportation device, but few would take you seriously.
> "Three turns around the pattern" may actually be either recreation or training,
> but hardly transportation. Most light planes are used for training and
> recreation, not transportation. Regardless of the owner's intentions when they
> buy them, few light planes are actually used for serious transportation.
>
> This thread started with a post about a 2-place training aircraft with a 90-
> minute endurance. Fact is, that plane (if it really exists) could handle many,
> (possibly most) of the missions I see flown out of my local airport. If
> available as a rental, it could handle about 70% of my own flights.
>
> Vaughn

transportation, Noun

1. The action of transporting someone or something or the process of
being transported.

transport, Verb

1. To carry from one place to another; convey.


The word "transportation" implies nothing about either the purpose or the
distance of the movement. It just means movement.

If I fly 25 miles to get a hamburger, the airplane provided the
transportation.



--
Jim Pennino

Remove .spam.sux to reply.

[vaughn[_3_]]

> wrote in message
...
>
> transportation, Noun
>
> 1. The action of transporting someone or something or the process of
> being transported.
>
> transport, Verb
>
> 1. To carry from one place to another; convey.
>
>
> The word "transportation" implies nothing about either the purpose or the
> distance of the movement. It just means movement.
>
> If I fly 25 miles to get a hamburger, the airplane provided the
> transportation.
>


OK. This conversation has descended to idiocy.

See you next thread perhaps.

Vaughn

[[email protected]]

vaughn > wrote:
>
> > wrote in message
> ...
>>
>> transportation, Noun
>>
>> 1. The action of transporting someone or something or the process of
>> being transported.
>>
>> transport, Verb
>>
>> 1. To carry from one place to another; convey.
>>
>>
>> The word "transportation" implies nothing about either the purpose or the
>> distance of the movement. It just means movement.
>>
>> If I fly 25 miles to get a hamburger, the airplane provided the
>> transportation.
>>
>
>
> OK. This conversation has descended to idiocy.
>
> See you next thread perhaps.
>
> Vaughn

Sorry if my use of English words as defined by the dictionary offends
you somehow.



--
Jim Pennino

Remove .spam.sux to reply.

[Jim Logajan]

wrote:
> vaughn > wrote:
>>
>> > wrote in message
>> ...
>>>
>>> transportation, Noun
>>>
>>> 1. The action of transporting someone or something or the process of
>>> being transported.
>>>
>>> transport, Verb
>>>
>>> 1. To carry from one place to another; convey.
>>>
>>>
>>> The word "transportation" implies nothing about either the purpose
>>> or the distance of the movement. It just means movement.
>>>
>>> If I fly 25 miles to get a hamburger, the airplane provided the
>>> transportation.
>>>
>>
>>
>> OK. This conversation has descended to idiocy.
>>
>> See you next thread perhaps.
>>
>> Vaughn
>
> Sorry if my use of English words as defined by the dictionary offends
> you somehow.

I think perhaps he meant to say it had descended to pedantry, ergo idiotic.

[Orval Fairbairn]

In article >,
"vaughn" > wrote:

> > wrote in message
> ...
> >> How many light planes are actually used for transportation?
> >
> > All of them that fly unless they are remotely controlled.
> >
> > The trip may be as short as 3 turns around the pattern to maintain
> > currency,
> > but a person is still being moved.
> >
> Sorry, but that's stretching a point beyond nonsense. You could also argue
> that a pogo stick is a transportation device, but few would take you
> seriously.
> "Three turns around the pattern" may actually be either recreation or
> training,
> but hardly transportation. Most light planes are used for training and
> recreation, not transportation. Regardless of the owner's intentions when
> they
> buy them, few light planes are actually used for serious transportation.
>
> This thread started with a post about a 2-place training aircraft with a 90-
> minute endurance. Fact is, that plane (if it really exists) could handle
> many,
> (possibly most) of the missions I see flown out of my local airport. If
> available as a rental, it could handle about 70% of my own flights.
>
> Vaughn

That all depends on turnaround time. If it takes 8 to 12 hours to
recharge the batteries, the plane will be sitting idle for most of the
operating day -- not a good return on investment!

[[email protected]]

Orval Fairbairn > wrote:
> In article >,
> "vaughn" > wrote:
>
>> > wrote in message
>> ...
>> >> How many light planes are actually used for transportation?
>> >
>> > All of them that fly unless they are remotely controlled.
>> >
>> > The trip may be as short as 3 turns around the pattern to maintain
>> > currency,
>> > but a person is still being moved.
>> >
>> Sorry, but that's stretching a point beyond nonsense. You could also argue
>> that a pogo stick is a transportation device, but few would take you
>> seriously.
>> "Three turns around the pattern" may actually be either recreation or
>> training,
>> but hardly transportation. Most light planes are used for training and
>> recreation, not transportation. Regardless of the owner's intentions when
>> they
>> buy them, few light planes are actually used for serious transportation.
>>
>> This thread started with a post about a 2-place training aircraft with a 90-
>> minute endurance. Fact is, that plane (if it really exists) could handle
>> many,
>> (possibly most) of the missions I see flown out of my local airport. If
>> available as a rental, it could handle about 70% of my own flights.
>>
>> Vaughn
>
> That all depends on turnaround time. If it takes 8 to 12 hours to
> recharge the batteries, the plane will be sitting idle for most of the
> operating day -- not a good return on investment!

The current crop of electric cars "quick charge" times run from about
3 hours to 6 hours with 240V/48A service and 2 to 3 times that for
standard 110V service.

So allowing 1.5 hours to get the airplane in the air, do training, get
the airplane back on the ground, do the paperwork, hook up to the charging
station, then 4 hours of charge, you could get 2 flights per day in an
eleven hour day.

Cut the charge time in half to 2 hours and you can get 3 flights per day.


--
Jim Pennino

Remove .spam.sux to reply.

[vaughn[_3_]]

"Orval Fairbairn" > wrote in message
...
> That all depends on turnaround time. If it takes 8 to 12 hours to
> recharge the batteries, the plane will be sitting idle for most of the
> operating day -- not a good return on investment!

Yep. I actually agree 100%. We discussed that very point a few days ago.
That, along with the amortized hourly price of battery use are potential deal
killers, and are up to the manufacturers to solve if electric planes are ever to
make a dent in the training market.

Vaughn

[Curt[_3_]]

On Jun 22, 10:17*am, Gatt > wrote:
> A few years ago when people were discussing the possibility of
> electric-powered flight, you'd get hacked on pretty hard for
> suggesting such a thing would be practical or possible in our
> lifetime. Obviously if you knew anything about physics or electrical
> engineering, why, you'd know it was totally impossible.

Buddy of mine has a Tesla. It'll make Seattle on a charge, he says.
You couldn't have done that with an electric car even a few years ago.
It's amazing what they've been able to do, and it only gets better.

Curt

[Dylan Smith[_2_]]

On 2011-06-27, > wrote:
> 1kWh per kilogram is 3.6 MJ/kg.

But it is an order of magnitude (more or less) better than what we have
now, and would certainly be useful for electric ground transportation.

[Dylan Smith[_2_]]

On 2011-06-27, Orval Fairbairn > wrote:
> Hextane? I don't think so! Don't you mean octane (C8H18)?

It doesn't matter for this calculation, the numbers work nearly the same
for any alkane.

C8H18 + 25 O = 8 CO2 + 9 H2O

Molar weight of C8H18 = 114
Molar weight of O = 16

So for each 114g of C8H18 we need 400g oxygen. Or around 3.5 parts
oxidiser to each part fuel. Pretty much the same.

> I stand by my analogy in that, even though the nitrogen does not
> participate in the chemical reaction, it still plays an important role
> in the propulsion equation, by providing a working medium to receive
> heat and expand to push pistons or to turn turbines.

But it cannot be used to compare with chemicals required in batteries,
because batteries do not need this at all! If you want to compare
against the mass that must be included in a battery, how can you
include the nitrogen? It doesn't make sense, because batteries do
not need the equivalent of nitrogen carried along with them. Batteries
are not heat engines, they don't need a working medium to transfer heat
or turn turbines. So a comparison involving nitrogen is just not valid,
so I would reconsider standing by that particular analogy because it's
just incorrect.

[[email protected]]

Dylan Smith > wrote:
> On 2011-06-27, > wrote:
>> 1kWh per kilogram is 3.6 MJ/kg.
>
> But it is an order of magnitude (more or less) better than what we have
> now, and would certainly be useful for electric ground transportation.

That depends on what you mean by "what we have now".

The only chemistry seriously concidered for vehicle use these days is
lithium.

battery MJ/kg fraction of 3.6 MJ/kg

lithium sulphur 1.8 2
lithium ion .72 5
lithium manganse 1.01 3.6
lithium thionyl chloride 2.5 1.4
lithium ion nanowire 2.54 1.4

lead acid .14 25.7


So yeah, a 3.6 MJ/kg battery would be more than an order of magnitude
better than a lead acid battery, but nowhere near an order of magnitude
better than existing lithium technology as it is only 1.4 times better
than the best of the chemistries currently being developed.

--
Jim Pennino

Remove .spam.sux to reply.

[Jim Logajan]

wrote:
> 100LL Avgas is 44 MJ/kg.
>
> Batteries need to be able to produce better than 20 MJ/kg to be
> generally usefull for transportation.

The Avgas energy density is not comparable to battery energy density
because it doesn't factor in thermal to mechanical conversion. Current
automobile engines extract only about 20% of that 44 MJ/kg. Electric motors
are anywhere from 75% to 95% efficient in converting electrical power to
mechanical power.

So a battery with ~11 MJ/kg powering an 80% efficient electric motor has
the same usable energy density as Avgas powering an internal combustion
engine.

Setting the goal for battery energy density at 20 MJ/kg would simply be
wrong because it uses the wrong numbers.

[[email protected]]

Jim Logajan > wrote:
> wrote:
>> 100LL Avgas is 44 MJ/kg.
>>
>> Batteries need to be able to produce better than 20 MJ/kg to be
>> generally usefull for transportation.
>
> The Avgas energy density is not comparable to battery energy density
> because it doesn't factor in thermal to mechanical conversion. Current
> automobile engines extract only about 20% of that 44 MJ/kg. Electric motors
> are anywhere from 75% to 95% efficient in converting electrical power to
> mechanical power.
>
> So a battery with ~11 MJ/kg powering an 80% efficient electric motor has
> the same usable energy density as Avgas powering an internal combustion
> engine.
>
> Setting the goal for battery energy density at 20 MJ/kg would simply be
> wrong because it uses the wrong numbers.

There is a difference between the theoretical efficiency of a motor of
any type and the obtainable efficiency of a real world motor.

The 20 MJ/kg assumes that a real electric airplane motor would be about
twice as energy efficient as a real gasoline airplane motor.

We can quibble about exactly what that number is, but a factor of 2 seems
to me to be a realistic number.

And since airplane engines spend most of their time operating at a single
point in their power curve by design, while automobiles spend a lot of
time at different points in their power curve by necessity, the overall
real efficiency of an airplane engine is a bit better than an automobile
engine.


--
Jim Pennino

Remove .spam.sux to reply.

[James Robinson]

Jim Logajan > wrote:

> wrote:
>
>> 100LL Avgas is 44 MJ/kg.
>>
>> Batteries need to be able to produce better than 20 MJ/kg to be
>> generally usefull for transportation.
>
> The Avgas energy density is not comparable to battery energy density
> because it doesn't factor in thermal to mechanical conversion. Current
> automobile engines extract only about 20% of that 44 MJ/kg. Electric
> motors are anywhere from 75% to 95% efficient in converting electrical
> power to mechanical power.
>
> So a battery with ~11 MJ/kg powering an 80% efficient electric motor
> has the same usable energy density as Avgas powering an internal
> combustion engine.

A Lycoming is about 27% to 29% percent efficient at 70% power.

> Setting the goal for battery energy density at 20 MJ/kg would simply
> be wrong because it uses the wrong numbers.

There is also more to battery selection and technology than simply the
energy density of a fully-charged battery pack. Consider that a deep
discharge battery of current technology, such is used in a laptop
computer or a Prius, is rarely discharged below about 20% of capacity to
help extend its life. This is perhaps analagous to the unusable fuel in a
fuel tank of say 5%. That difference needs to be taken into account in
any comparison.

By the same token, to extend life, batteries are also rarely fully
charged, with maybe 10 to 15 percent of theoretical capacity unused.
That makes the usable capacity of a battery in the range of 65 to 70
percent of its theoretical capacity.

Further, there are other realities like the fact that all batteries lose
capacity when they are cold, as they age, and when (not if) cells in the
battery pack fail. That means a reserve calculation is a bit more
difficult, and would likely mean a traditional 5 or 10 percent reserve
would have to be increased to ensure there are no surprises.

Finally, you can also increase your payload with a conventional engine by
reducing the amount of fuel being carried, thereby sacrificing range.
That would not be possible with a battery, since more than likely you
would not be able to reduce cells to reduce weight. The packs would tend
to be a package deal to economize in overall design weight.

Therefore, any calculation using the theoretical energy density of a full
battery pack is wildly optimistic.

[Dylan Smith[_2_]]

On 2011-06-28, > wrote:
> There is a difference between the theoretical efficiency of a motor of
> any type and the obtainable efficiency of a real world motor.

The real-world efficiency of a modern brushless motor and its control
system is around 85%. It's only brushed motors which are merely twice
as efficient as an internal combustion engine. No one today uses
brushed motors for traction outside of golf-carts (and it wouldn't
surprise me if golf carts use brushless motors now).

[James Robinson]

Dylan Smith > wrote:

> > wrote:
>
>> There is a difference between the theoretical efficiency of a motor
>> of any type and the obtainable efficiency of a real world motor.
>
> The real-world efficiency of a modern brushless motor and its control
> system is around 85%. It's only brushed motors which are merely twice
> as efficient as an internal combustion engine. No one today uses
> brushed motors for traction outside of golf-carts (and it wouldn't
> surprise me if golf carts use brushless motors now).

Many railway locomotives still use brushed series-wound DC motors for
traction, and their efficiency exceeds 90 percent in the major part of
their operating range. Their operating efficiency is comparable to that of
AC motors through most of the typical speed range.

[vaughn[_3_]]

"Gatt" > wrote in message
...
>A few years ago when people were discussing the possibility of
>electric-powered flight, you'd get hacked on pretty hard for
>suggesting such a thing would be practical or possible in our
>lifetime. Obviously if you knew anything about physics or electrical
>engineering, why, you'd know it was totally impossible.

It's not totally irrelevant to this thread to note that a manned electric
airplane, the Solar Implulse, recently made a 12 hour, 59 minute international
flight. This also would have been said to be totally impossible not so many
years ago.

I make no claims that the Solar Impulse is a practical airplane. After all, its
average speed of advance was only some 27 knots. That said, gliders and hot air
balloons also generally fail the test of practicality, but there are plenty of
them around.

Vaughn

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In rec.aviation.owning vaughn > wrote:
>
> "Gatt" > wrote in message
> ...
>>A few years ago when people were discussing the possibility of
>>electric-powered flight, you'd get hacked on pretty hard for
>>suggesting such a thing would be practical or possible in our
>>lifetime. Obviously if you knew anything about physics or electrical
>>engineering, why, you'd know it was totally impossible.
>
> It's not totally irrelevant to this thread to note that a manned electric
> airplane, the Solar Implulse, recently made a 12 hour, 59 minute international
> flight. This also would have been said to be totally impossible not so many
> years ago.
>
> I make no claims that the Solar Impulse is a practical airplane. After all, its
> average speed of advance was only some 27 knots. That said, gliders and hot air
> balloons also generally fail the test of practicality, but there are plenty of
> them around.
>
> Vaughn

The word "practical" has implications of purpose and cost.

Recreation is a valid purpose.

If the purpose is to float through the air to sightsee as a recreation, a
balloon is practical for that purpose.

If a balloon costs too much, it becomes economically impractical.

Likewise, electric powered airplanes have already found a niche purpose
where they are practical for the specific purpose, economically practical,
and in production; self launched gliders.


--
Jim Pennino

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Dylan Smith > wrote:
> On 2011-06-28, > wrote:
>> There is a difference between the theoretical efficiency of a motor of
>> any type and the obtainable efficiency of a real world motor.
>
> The real-world efficiency of a modern brushless motor and its control
> system is around 85%. It's only brushed motors which are merely twice
> as efficient as an internal combustion engine. No one today uses
> brushed motors for traction outside of golf-carts (and it wouldn't
> surprise me if golf carts use brushless motors now).

As best as I can tell, the real world energy efficiency of modern airplane
engines is somewhere in the low 30% range.

We can quibble about the exact number all day long, but it is somewhere
a bit better than 2 and no greater than 3.

Even at 3, the required battery energy density would be 14.666 MJ/kg and
the best of the labratory batteries falls short by a factor of 5.8.



--
Jim Pennino

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