Can Aircraft Be Far Behind?

Recently, Larry Dighera posted:

On Wed, 10 Jan 2007 15:39:17 -0000, Dylan Smith

It would be totally and utterly impractical to charge these
batteries at this rate. I'll let you do the calculations for the
equivalent in electricity that filling a Cessna 150 with avgas in 4
minutes (the typical time to do it at a self serve pump) would be.

The issue of high charging current is true, of course.

After studying the information available on the Altair web site
http://www.altairnano.com/markets_amps.html, it has become apparent
that their battery technology trades energy density for low internal
resistance. So their product is probably not the best choice for
aircraft due to weight considerations.

According to their W/kg chart, their batteries trade a lower specific
energy (W hr/kg) for a considerably higher specific power, but I would
think that Altair's operating temperature range would be a more important
factor w/r/t aviation, as the other batteries' performance suffers badly
in low-temperature environments. I doubt that a typical Li-ion battery
would deliver the indicated specific energy in aviation temperatures, so
any weight benefit would be compromised.

Neil

On 10 Jan 2007 12:59:43 -0800, "JD" wrote in
.com:

Check out the batteries from A123 Systems:
http://www.a123systems.com/html/technology.html

Li Ion batteries made with iron at 1/5 the price, twice the power and
half the weight of conventional Li Ions.
They are already on the market and are starting to show up in
DeWalt's/Bosch 36V cordless tools.
They have a weight to Watt ratio less than 1 lb / 1500W ( .9 to be
exact).

http://www.a123systems.com/html/_cha.../techComp.html

Parameter A123 Ml LiIon
----------------------------------------------------------------
Power Density 3,000 W/Kg 1,350 W/Kg

Weight to discharge @ 1,500W 0.9 lbs 2.75 lbs

Life at 100% DoD 1,000 500

So what's the downside to this cell for aviation applications?

Scheeesch if their stock ever goes public, I'll be standing in long
line of buyers.

If this is true:

http://www.a123systems.com/html/tech/power.html
A123Systems M1 cells offer the highest commercially available
power density of any Li Ion chemistry: Our high power products are
able to pulse at discharge rates as high as 100C and deliver over
3000W/kg, over an order of magnitude better than conventional
Lithium-Ion cells and with their low impedance and thermally
conductive design, A123 cells can be continuously discharged to
100% depth of discharge at 35C rate, a marked improvement over all
other rechargeable battery alternatives.

I share your enthusiasm.

On Mon, 15 Jan 2007 14:31:16 GMT, "Neil Gould"
wrote in
:

Recently, Larry Dighera posted:

On Wed, 10 Jan 2007 15:39:17 -0000, Dylan Smith

It would be totally and utterly impractical to charge these
batteries at this rate. I'll let you do the calculations for the
equivalent in electricity that filling a Cessna 150 with avgas in 4
minutes (the typical time to do it at a self serve pump) would be.

The issue of high charging current is true, of course.

After studying the information available on the Altair web site
http://www.altairnano.com/markets_amps.html, it has become apparent
that their battery technology trades energy density for low internal
resistance. So their product is probably not the best choice for
aircraft due to weight considerations.

According to their W/kg chart, their batteries trade a lower specific
energy (W hr/kg) for a considerably higher specific power, but I would
think that Altair's operating temperature range would be a more important
factor w/r/t aviation, as the other batteries' performance suffers badly
in low-temperature environments. I doubt that a typical Li-ion battery
would deliver the indicated specific energy in aviation temperatures, so
any weight benefit would be compromised.

Battery temperature is important. However it's important to realize
that batteries with a higher internal resistance will generate more
heat under load than those with lower internal resistance, so I doubt
low temperature would be an issue with conventional LiIon batteries.
In fact, the Tesla car needs a liquid cooling system to remove battery
heat, and I would suspect that some sort of cooling system would be
required for aviation applications also.

If it is the weight of the batteries that preclude the use of electric
power for airplane use, using the Altair batteries, with half the
energy density of conventional LiIon cells, wouldn't make very good
sense. The A123Systems M1 cells, with their claimed "the highest
commercially available power density of any Li Ion chemistry" may be
an enabling technology for electrically powered airplanes:
http://www.a123systems.com/html/home.html

On Thu, 11 Jan 2007 01:10:23 GMT, David CL Francis
wrote in
:

On Tue, 9 Jan 2007 at 14:38:16 in message
, Larry Dighera
wrote:

http://www.teslamotors.com/

Interesting. I see Vauxhall in the UK have just launched a similar car.

Environmentally they do not produce much pollution on the road but, of
course, where they do create it is at the providing power station

I believe the efficiency of commercial electric generating power
stations and electrical motors is far superior to that of internal
combustion Otto Cycle engines ~38%.

(except for Nuclear of course).

The jury is still out on Nuclear. It is relatively clean during
normal operation, but one Chernobyl incident pollutes vast amounts
land (and air) for centuries. And then there's the waste disposal
issue....

I am prejudiced - I have just purchased a Toyota Prius! Nothing like as
sporty of course!

And considerably less expensive than the Tesla Motors car by a factor
of four or so.

Batteries will have to have a very great capacity for their weight to
make a normal aircraft successful.

That seems to be the reality. It is because battery energy must be
expended to support the aircraft as well as propel it, except for
lighter than air airships and balloons.

Larry Dighera wrote:

I would think that the LiIon cells could be made lighter if
specifically designed for aviation use. Currently they are steel
jacketed AA sized. Steel might be replaced with Titanium (atomic
number 22). Lithium (atomic number 3) is a light metal as is the
carbon (atomic number 6) anode.

The problem is not how the chemicals are contained, the problem is the
weight of the chemicals themselves. There could be some minor
improvement in the overall weight of the batteries, but not enough to
overtake the high energy density of liquid fuels.

You seem to have a firm grasp of the issue. Given:

http://en.wikipedia.org/wiki/Lithium_ion_battery
Lithium ion battery
Specific energy density: 150 to 200 W·h/kg (540 to 720 kJ/kg)
Volumetric energy density: 250 to 530 W·h/L (900 to 1900 J/cm3)
Specific power density: 300 to 1500 W/kg (@ 20 seconds [2] and 285
W·h/L)


http://en.wikipedia.org/wiki/Gasoline
Gasoline
Energy content
Fuel type Megajoules/L MJ/kg BTU/US gal
Premium Gasoline 32.84 43.50 131,200

Can you quantify the prospect of replacing Avgas with LiIon batteries?

The key comparison is the specific energy density, since that would tell
you how far you could fly, and with what load. If batteries are going to
be competitive, they would have to have a weigh about the same as the
liquid fuel to be competitive in aviation use. Otherwise, either useful
load would drop, the range would be limited, or the aircraft would be
completely impractical.

To end up with a similar weight, they would need similar energy
densities, multiplied by the efficiency of the prime mover.

From the table provided above, the energy density of gasoline is 45
MJ/kg, and lithium batteries are 0.72, at best. A gasoline engine is
perhaps 25% efficient in an aircraft, and an electric motor, with its
control, would be about 90% efficient.

Multiplying the two to get the required useable energy density gives:
For gasoline engines: 43.5 X 0.25 = 10.88 MJ/kg
For batteries: 0.72 X 0.9 = 0.65 MJ/kg

Therefore, you would need a battery pack that weighed about 15 times as
much as the gasoline fuel and tank to be able to perform the same amount
of work. That isn't even close.

Given the huge difference in weight, the prospect of using lithium ion
batteries to power conventional aircraft is almost nil. Battery
designers don't need a breakthrough, they would need a miracle to get the
energy density to a point where it would be competitive with liquid fuel.

Larry Dighera wrote:

If it is the weight of the batteries that preclude the use of electric
power for airplane use, using the Altair batteries, with half the
energy density of conventional LiIon cells, wouldn't make very good
sense. The A123Systems M1 cells, with their claimed "the highest
commercially available power density of any Li Ion chemistry" may be
an enabling technology for electrically powered airplanes:
http://www.a123systems.com/html/home.html

Power density isn't the issue. That only means they can dump the energy
contained in the battery faster than other types. Their batteries would be
useful where you need high power for short bursts of time, like hand-held
drills, or photo flash units. Power density says nothing about how much
energy is contained in the battery.

The important measure for aircraft application is energy density. The A123
batteries have about 1/2 the energy density of current LiIon batteries,
which means you would need a battery that weighed twice as much as other
types of LiIon batteries. This is moving the wrong way, if they are to be
practical in aircraft application.

Larry Dighera wrote:

On 10 Jan 2007 12:59:43 -0800, "JD" wrote:

Check out the batteries from A123 Systems:
http://www.a123systems.com/html/technology.html

Li Ion batteries made with iron at 1/5 the price, twice the power
and half the weight of conventional Li Ions. They are already on the
market and are starting to show up in DeWalt's/Bosch 36V cordless
tools. They have a weight to Watt ratio less than 1 lb / 1500W ( .9
to be exact).

http://www.a123systems.com/html/_cha.../techComp.html

Parameter A123 Ml LiIon
----------------------------------------------------------------
Power Density 3,000 W/Kg 1,350 W/Kg

Weight to discharge @ 1,500W 0.9 lbs 2.75 lbs

Life at 100% DoD 1,000 500

So what's the downside to this cell for aviation applications?

The downside is that their energy density is something like 110 W-Hr/kg,
which is lower than other types of LiIon batteries, with can be as high
as 350. That means to get the same endurance, you would need twice the
weight of A123 batteries. Weight is the major issue with aviation
applications, so these batteries are heading the wrong way.

Larry Dighera wrote:

Here's another link to information about GM's 'Volt prototype hybrid
automobile dated Jan. 7, 2007.


http://www.canada.com/topics/finance...48-a654-4000-8
b3c-aff0354600aa&k=45978&p=2
Lutz said the engineering development of the car itself is 18
months from being completed. The batteries are about 18 months
behind the rest of the car.

How many years would that put GM's product behind the Japanese? :-(

None.

All of the car manufacturers are waiting for battery technology to get to
the point where such cars can be practical. The auto manufacturers have
put electric cars on the market in the past, mainly because of
California's ZEV requirements, but they were quickly pulled when the
California regulations were retracted, since the vehicles were expensive
and the batteries had relatively short lives. Battery technology at the
time wasn't good enough to make the vehicles practical.

Battery technology has improved somewhat since then, with about double
the energy density, but they still have a long way to go before they can
compete with liquid fuels foe convenience and cost.

This is like the days when stereo equipment manufacturers were in an
ouput power race, or today's speed race with personal computer
manufacturers. Every time a new improved type of transistor came on the
market, or a new microprocessor, the builders of the final product would
quickly market the highest power stereo, or the fastest computer. They
were all pretty well at the same place in the market at the same time,
based on what was available.

The same can be said for hybrid vehicles, plug in hybrids, or all-
electric vehicles. The manufacturers need appropriate batteries to make
their products practical and cost-effective.

As far as practical aviation applications, using batteries for primary
power is nowhere near possible today, and given the huge gulf in weight
that has to be overcome, they will only be practical after a huge
technical breakthrough, making the energy density something like ten or
fifteen times what it is today. At the present rate of improvement,
assuming it can be sustained, that will take something like 50 years.

The original developer of LiIon batteries has stated that such
improvements will never happen. He feels that improvements of existing
batteries will be in safety, cost, and the ability to more quickly charge
or discharge them, but there will be little improvement in energy
density, which is what would be required for aviation application.