Electrically Powered Ultralight Aircraft

In rec.aviation.piloting Larry Dighera wrote:
On Tue, 07 Aug 2007 19:14:59 GMT, wrote in
:

If you go to http://xtronics.com/reference/energy_density.htm you find
the energy densities of a lot of things.


Propane (liquid) 13,900 Wh/kg
Diesel 13,762 Wh/kg
gasoline 12,200 Wh/kg
Ethanol 7,850 Wh/kg
Methanol 6,400 Wh/kg
Secondary Lithium - ion Polymer 130 - 1200 Wh/kg
Primary Zinc-Air 300 Wh/kg
Lead Acid Battery 25 Wh/kg

So batteries have to improve by a factor of 10 to match gasoline.

When you compare the efficiency of internal combustion Otto Cycle
engines (30% - 40%) against electric motors (80% - 95%), it appears
that a factor of five might be a more realistic comparison of their
relative merits. Then there is the issue of power plant weight...

Well, you have to look at total system weight.

A 100 HP electric motor is not going to be particularly light and
the power cables are going to weigh a whole lot more than fuel lines
for example.

When you look at the total installed system, assuming you have batteries
5 times better than you have now, I doubt the total weight difference
will be all that much.

Electric motors don't lose power in thin air either. With regard to
reliability, electric motors have only one moving part compared to
scores of moving parts for IC engines, their failure rate should be
substantially greater than IC engines.

AC motors have only one moving part but would require a beefy inverter
to generate (and induce more system loss) the AC.

DC motors have brushes but motor control is simpler.

If the DC motor was designed for easy inspection and replacement of
the brushes, then the failure rate should be much lower than a gas
engine.


--
Jim Pennino

Remove .spam.sux to reply.

Larry Dighera wrote:
On Tue, 07 Aug 2007 19:14:59 GMT, wrote in
:

If you go to http://xtronics.com/reference/energy_density.htm you
find the energy densities of a lot of things.


Propane (liquid) 13,900 Wh/kg
Diesel 13,762 Wh/kg
gasoline 12,200 Wh/kg
Ethanol 7,850 Wh/kg
Methanol 6,400 Wh/kg
Secondary Lithium - ion Polymer 130 - 1200 Wh/kg
Primary Zinc-Air 300 Wh/kg
Lead Acid Battery 25 Wh/kg

So batteries have to improve by a factor of 10 to match gasoline.

When you compare the efficiency of internal combustion Otto Cycle
engines (30% - 40%) against electric motors (80% - 95%), it appears
that a factor of five might be a more realistic comparison of their
relative merits. Then there is the issue of power plant weight...

Electric motors don't lose power in thin air either. With regard to
reliability, electric motors have only one moving part compared to
scores of moving parts for IC engines, their failure rate should be
substantially greater than IC engines.

Here is a 100hp electric motor. I don't know if it is typical for an
electric motor but damn the thing weighs over half a ton. I might make the
601XL a little nose heavy. But it's priced right up there with a Lyc of
equal power.

http://www.baldor.com/products/detai...neralPur pose

Catalog Number: D50100P
Description: STOCK MOTOR,368AT,100HP,1750/2000RPM,DPFG
Ship Weight: 1,118 lbs.
List Price: $21,195
Multiplier Symbol: N2

"Gig 601XL Builder" wrDOTgiaconaATsuddenlink.net wrote in message
...

Let's take my 601XL. 2 aluminum 12 gallon tanks each tank ways let's say
10 pounds add in 145 lbs of fuel and you have 165 pounds of transportable
energy that will produce ~100HP for about 4 hours.

My question to anyone is what is the lightest battery that is capable of
powering any motor that will produce the equivilent power for and equal
amount of time?

Well, depending on which end of the gearbox it's measured, 40+ pounds of
NiCAD batteries got between 1-4 HP at maybe 70% motor power for 20 minutes
max before the battery output began to taper off. For perspective, the
Etek motor used on the ultralight in the link is probably about twice as
powerful as the motors we were using, so maybe for a ballpark measurement I
could double the battery time for the same weight. Theoretically if you
managed and cooled your batteries correctly you could get ~30 minutes for
that 40 pounds of batteries, or maybe two hours if you quadrupled it for
your ~160 pounds. Max.

Too much weight for an ultralight, and no way it's gonna get near 100HP.
Again, that's just a ballpark estimate.

-c

Gattman wrote:

I agree. It's on the way. Wasn't too long ago that terms like "lithium
ion" and "nickle metal hydride" were unheard of to the common consumer.


It takes a lot of energy to manufacture those batteries ... and recycle
them when they are used up. You have to factor that into the equation.

These batteries have high energy per unit volume but they cost a lot
of money because it takes a lot of energy to produce them.