Electric flight is coming, but the batteries aren’t ready

On 8/25/2018 1:45 PM, Larry Dighera wrote:
So, if the batteries are an issue, let's improve the electric motor's
power and efficiency while we're waiting for battery improvements

Sorry, but there really isn't much to be gained there. Motors already
can be well over 90% efficient, and they already are lighter and more
compact than an equivalent IC engine.

So that takes us right back to the battery!

Actually, thanks to technology from Tesla and others, existing battery
technology is probably already good enough for the training role (one
hour flight plus reserve), but bringing a new aircraft design to market
requires a huge investment and the market for training aircraft is
minuscule compared to the market for (say) automobiles. So it's really
going to be hard to make the business case for just the training market.

Plus don't forget the cost of the charging infrastructure that would be
needed for the training role! We would need high power recharging to
quickly "refuel" the plane for the next lesson. A plane sitting on the
ground isn't making the school any money. That charging infrastructure
will be neither cheap nor easy to do at a typical airport.

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Hello Vaughn,

Thank you for sharing your thoughts. You raise two very significant
points.

Agreed, electric motors are lighter and roughly 300% (3x) more
efficient than IC engines. And apparently there's a significant
improvement in electric motor efficiency and power density possible
with axial-flux design over the common radial-flux design. I would
think any improvement in electric motor operating characteristics
would be welcome in further enabling development of practicable
electric powered flight. But, as you implied, it's not going to be a
game changer.

With regard to charging infrastructure you mentioned, at the current
state in electrically powered aircraft development, the most practical
means of refueling is to have a second battery on recharge while one
is in use powering the aircraft in flight. Fast charge lithium
battery chemistry is currently being pursued by several corporate and
educational research departments. But, I doubt that it will ever be
possible to charge the battery in the brief time typically available
between flight lessons.

Using this information for an existing electric motor designed for
aviation use as a basis for rough calculations:

Message-ID:
Frank Anton, head of eAircraft for Siemens, said the SP70D motor
has been specifically designed for the needs of two-seat flight
trainers. “We know that safety, performance and cost of electric
propulsion in the flight training market will be game-changing,”
he said. The SP70D motor will operate with a 90kW peak (115 HP),
and a continuous rating of 70kW (90 HP), according to Siemens.

Gives us a ~292 Amp supply current at 240 VAC, or about six hours
charge time at 50 Amp charge rate for a 100HP/78kW motor. You're
right. Battery recharging infrastructure and time is a significant
concern that I hadn't considered. I chose 50 Amps, as that is roughly
equivalent to the power required for an electric range, and is in
common use. The cost of a 50 Amp charger should be somewhere around
that of a comparable arc-welder.

Thank you for bringing these issue to my attention.

Best regards,
Larry Dighera

PS: Below is an interesting new approach to electric aircraft
structure that may be somewhat applicable:

----------------------
https://newatlas.com/impossible-aero...1-drone/56283/
Battery-packed drone can fly for up to 2 hours per charge

DRONES

Paul Ridden

6 hours ago
2 PICTURES

Impossible Aerospace has already started selling its US-1 long range
drone to firefighters, police departments and search and rescue teams
ahead of more general availability in Q4 2018(Credit: Impossible
Aerospace)

VIEW GALLERY - 2 IMAGES

As well as taking aerial photography to the next level, small drones
can help tackle wildlife poaching, survey industrial sites, be used
for mapping, deliver packages or assist with policing an area. But
most battery-powered drones are limited by a relatively short battery
life. California's Impossible Aerospace says its upcoming US-1 drone
will fly for much, much longer per charge than competitors, and should
put electric drones on a par with gas-fueled systems.

"The US-1 is more than just a drone," said company CEO Spencer Gore.
"It's the first aircraft designed properly from the ground up to be
electric, using existing battery cells without compromise. It's not so
much an aircraft as it is a flying battery, leveraging an energy
source that doubles as its primary structure. This is how electric
aircraft must be built if they are to compete with conventional
designs and displace petroleum fuels in aviation."

And a flying battery it is, with 1.2 kWh of Li-ion cells spread
throughout its x-shaped body. That makes the 660 x 660 mm (26 x 26 in)
US-1 a bit of a weighty beast at 7.1 kg (15.7 lb) on its own, but it
is reported capable of carrying a payload of up to 1.3 kg (2.9 lb).

The US-1 drone can fly for up 120 minutes per charge without carrying
a payload, which...

With that payload, Impossible Aerospace says that users can expect a
flight time of up to 78 minutes between charges of around 2.5 hours.
An optional fast charger can be had to get the cells to 85 percent
capacity in 45 minutes though. And if not carrying any payload, up to
120 minutes in the air is possible.

The US-1 has a top speed of 19 meters per second (42 mph), is
IP43-protected against ingress and can operate in temperatures ranging
from 0° C to 50° C (32° F - 122° F). It comes in a hard case and 16
channel remote with a 128 x 64 backlit LCD panel displaying real-time
flight data.

Impossible Aerospace has already started selling its optical and
thermal sensor-packing drone to firefighters, police departments and
search and rescue teams across the US, but will make the system more
widely available beginning Q4 2018.

A basic version of the US-1 drone will cost US$7,500, while a model
designed for use with thermal imaging cameras will be priced at
$9,500. The hardshell case for the latter includes a 20-inch video
display and 12-inch control screen, a built-in battery and can receive
1080/60p footage from up to 1 km (0.62 mi) away at 1-2 ms latency. The
company can provide Flir thermal cameras at an additional cost.

You can get the briefest of brief looks at the US-1 in the video
below. https://youtu.be/cH89aFKTCfQ

Source: Impossible Aerospace: https://impossible.aero/
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On Thu, 6 Sep 2018 20:18:06 -0400, Vaughn Simon
wrote:

On 8/25/2018 1:45 PM, Larry Dighera wrote:
So, if the batteries are an issue, let's improve the electric motor's
power and efficiency while we're waiting for battery improvements

Sorry, but there really isn't much to be gained there. Motors already
can be well over 90% efficient, and they already are lighter and more
compact than an equivalent IC engine.

So that takes us right back to the battery!

Actually, thanks to technology from Tesla and others, existing battery
technology is probably already good enough for the training role (one
hour flight plus reserve), but bringing a new aircraft design to market
requires a huge investment and the market for training aircraft is
minuscule compared to the market for (say) automobiles. So it's really
going to be hard to make the business case for just the training market.

Plus don't forget the cost of the charging infrastructure that would be
needed for the training role! We would need high power recharging to
quickly "refuel" the plane for the next lesson. A plane sitting on the
ground isn't making the school any money. That charging infrastructure
will be neither cheap nor easy to do at a typical airport.

---
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