doug

Personal, green airplanes set to take off - Page1 -Â* MSN Tech & Gadgets - Green News and Features

Edit: Holy link-rot, Batman! MSN and Yahoo are really suck wrt link longevity. Here's a similar article from around the same time:
Greentech Media | Will Electric Planes Take Off?

graham

I hope he starts on this after they ship the Model S...

TEG

Hasn't it been said many times that electric planes would be impractical due to the low energy density of stored electricity (compared to liquid fuels)?

dpeilow

Indeed. While a short range (i.e. under 1 hour range) prop plane might be possible - think Dash 8 with 30 passengers replaced with batteries and slower - an electric supersonic jet?!?

Tdave

Anyone want to extrapolate this to flight speed?

dpeilow

Well, a refurbed DC-3 has 2x 1000bhp (745kW) engines and a cruise speed of around 150mph.

So how many Tesla batteries would you need to run that for an hour?

Tdave

Well, the current battery runs at 185kW for about 15 minutes, right? So to run at 745kW for an hour would require 16 of them, or 16,000 pounds worth of battery costing over $300k.

doug

Commercial supersonic flight barely worked with jet fuel due to the energy costs (i.e. the power required for sustained supersonic flight). Short of Mr. Fusion, electric supersonic flight is an engineering challenge to say the least. Still would be really cool, though.


.

dpeilow

$300k isn't outrageous in the scheme of things for a plane.


I was thinking 2x 745 = 1490kW


Take the Dash 8 as an example, reducing passengers to ~50:

Fuel = 3.5 tonnes
30 pax and luggage = 3 tonnes
Mass dif. between gas turbine and electric motors = 0.5 tonnes (?)

So there could be 7 tonnes to play with.


1490kWh / 7000kg = 212Wh/kg - in the upper end of the ballpark for Li-ion.


Or looking at it another way: 7 tonnes roughly equals 14 current Tesla packs

14 x 59kWh = 826
60 x 826/1490 = 33 minutes run time


Or with 3600mAh cells

14 x 91kWh = 1274
60 x 1274/1490 = 51 minutes run time


These numbers assume no losses or DoD considerations, *but* assume the motors run at 100%, which of course after the take-off climb they probably wouldn't.

GSP

Very interesting, but 50-60 min run time is pretty limited.

However, wasn't the 2 x 745 kW for the DC-3 engines? According to Wikipedia (ultra reliable, I'm sure) the Dash 8 has 2 x 1800 shp turboprops. So 2686 kW would be required instead of 1490 kW, reducing the run time from 60 min to only 33 min.

Perhaps a new airframe, designed more like a glider, cruising at about 80 mph, could be feasible for a BEV private aircraft. I can't see how the economics could work for commercial passenger aircraft (slow, expensive, and reduced payload).

The electric launch gliders, like the two-seat Pipistrel in Doug's link above and the one-seat Antares 20E, seem to have lots of advantages over their ICE competitors. But only for the lucky ones that can afford it (like the Telsa Roadster ) Lots of good info at the Antares 20E web site:

Lange Aviation - Home

Elon must be smoking some pretty good stuff with his comments about electric supersonic vertical launch aircraft. As Doug pointed out, this plenty hard to do even with the energy density of jet fuel. I think only the most recent Harrier has achieved both vertical launch and supersonic flight in the same aircraft.

His ultracap comments are a little worrisome as well.

GSP