TMC is an independent, primarily volunteer organization that relies on ad revenue to cover its operating costs. Please consider whitelisting TMC on your ad blocker or making a Paypal contribution here: paypal.me/SupportTMC

Electric planes

Discussion in 'Electric Vehicles' started by doug, Jun 29, 2008.

  1. doug

    doug Administrator / Head Moderator

    Joined:
    Nov 28, 2006
    Messages:
    15,913
    Location:
    Stanford, California
    #1 doug, Jun 29, 2008
    Last edited: Jan 5, 2009
    Personal, green airplanes set to take off - Page1 -Â* MSN Tech & Gadgets - Green News and Features
    [​IMG]
    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?

    [​IMG]
     
  2. graham

    graham Active Member

    Joined:
    Dec 2, 2007
    Messages:
    1,572
    Location:
    Aptos, California
    #2 graham, Jan 3, 2009
    Last edited by a moderator: Jan 5, 2009
    I hope he starts on this after they ship the Model S...
     
  3. TEG

    TEG TMC Moderator

    Joined:
    Aug 20, 2006
    Messages:
    17,249
    Location:
    Silicon Valley
    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)?
     
  4. dpeilow

    dpeilow Moderator

    Joined:
    May 23, 2008
    Messages:
    8,572
    Location:
    Winchester, UK
    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?!?
     
  5. Tdave

    Tdave Member

    Joined:
    May 16, 2008
    Messages:
    721
    Location:
    Columbia, MD
    Anyone want to extrapolate this to flight speed?

    [​IMG]
     
  6. dpeilow

    dpeilow Moderator

    Joined:
    May 23, 2008
    Messages:
    8,572
    Location:
    Winchester, UK
    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?
     
  7. Tdave

    Tdave Member

    Joined:
    May 16, 2008
    Messages:
    721
    Location:
    Columbia, MD
    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.
     
  8. doug

    doug Administrator / Head Moderator

    Joined:
    Nov 28, 2006
    Messages:
    15,913
    Location:
    Stanford, California
    #8 doug, Jan 5, 2009
    Last edited: Jan 5, 2009
    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.


    .
     
  9. dpeilow

    dpeilow Moderator

    Joined:
    May 23, 2008
    Messages:
    8,572
    Location:
    Winchester, UK
    #9 dpeilow, Jan 5, 2009
    Last edited: Jan 5, 2009
    $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.
     
  10. GSP

    GSP Member

    Joined:
    Dec 28, 2007
    Messages:
    1,995
    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 :rolleyes:) 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
     
  11. Tdave

    Tdave Member

    Joined:
    May 16, 2008
    Messages:
    721
    Location:
    Columbia, MD
    Perhaps bringing this thread down to earth and off on a new heading...

    I have heard about adding electric propulsion for taxiing, firing up the jet engines just before takeoff and shutting them down immediately after touchdown. That seems to make a lot of sense.

    Is there enough time at the gate to recharge the batteries if only used for that purpose?
     
  12. doug

    doug Administrator / Head Moderator

    Joined:
    Nov 28, 2006
    Messages:
    15,913
    Location:
    Stanford, California
    #12 doug, Jan 7, 2009
    Last edited: Nov 7, 2009
    I think you mean the F35. One of the most awesome planes I've ever had a chance to see in person.

    If that's all it's going to do, you might be better off just using some kind of EV to tow the plane to and from the runway. (Might have to take more precautions to avoid ground collisions, though.)
     
  13. dpeilow

    dpeilow Moderator

    Joined:
    May 23, 2008
    Messages:
    8,572
    Location:
    Winchester, UK

    You are right, but the Dash 8 does have a much faster cruise speed than a DC-3 so it needs the extra power. I was looking at that plane as an example of the masses that could be saved if one around that size was made electric, just to see if this idea would fly (ahem). I suppose that the advantage of an electric design would be that you could have 2MW motors for take off if needed and still throttle back to a lower speed only using the power talked about above.

    As for the usefulness, well around the UK and Ireland there are plenty of turboprops flying routes well under 150 miles and I'm sure that is the case with other island nations too. So if this can significantly lower running costs, there could be a market there. It's worth a closer look I think.


    I believe that the original PML Flightlink pancake motors were developed for aircraft landing gear. Was this the intended purpose?

    Well, having a high power charger in that environment is more likely to be approved than on the street, and if the fuel saved in taxing more than offsets the mass, then this could be an application for the AltairNano battery (hey, if EEstor come through, that would be excellent for this discussion).


    The friend at Rolls Royce that I mentioned in the Lotus EV thread is working on the lift fan for that. But he said that the vertical take-off done by the prototype was basically a stunt that only that plane could do - the production F-35B spec will be short take-off/vertical landing.

    But I agree, it is awesome.


    Not sure if it is with EVs, but Richard Branson proposed doing this.
     
  14. TEG

    TEG TMC Moderator

    Joined:
    Aug 20, 2006
    Messages:
    17,249
    Location:
    Silicon Valley
  15. dpeilow

    dpeilow Moderator

    Joined:
    May 23, 2008
    Messages:
    8,572
    Location:
    Winchester, UK
    That's the same - but I remember reading it on PML's site that they were proposing that 30 years ago. (BTW it was trying to find that again that I saw the bad news.)
     
  16. GSP

    GSP Member

    Joined:
    Dec 28, 2007
    Messages:
    1,995
    Ah.... Island hopping. I hadn't thought of that. My midwest US mentality just assumed that I could drive 150 mi and be at my destination faster and cheaper than flying, and have my car, luggage, etc! Doesn't work to well once you get to land's end (a concept that I've read about, but rarely experienced).:rolleyes:

    I don't understand the 2 MW motor comment though. If the motors were any more powerful than needed for takeoff, wouldn't that add a *lot* of unnecessary weight?

    GSP
     
  17. dpeilow

    dpeilow Moderator

    Joined:
    May 23, 2008
    Messages:
    8,572
    Location:
    Winchester, UK
    Well, I know that in some other applications, double the output for a short time is possible. It was only in answer to whether that much power was needed for the Dash 8-sized airframe. There must be a runway length / engine power trade-off and this is where we have to go off and do some proper engineering :smile:

    By the way, I've recently read that for sustained output, just over 1kW/kg is a good number for a state-of-the-art motor. How does that compare with Tesla's?
     
  18. TEG

    TEG TMC Moderator

    Joined:
    Aug 20, 2006
    Messages:
    17,249
    Location:
    Silicon Valley
    Tesla eMotor:
    ~185kW, ~35kg. ~5kW/kg. Not bad. And that isn't even the sport motor.
     
  19. dpeilow

    dpeilow Moderator

    Joined:
    May 23, 2008
    Messages:
    8,572
    Location:
    Winchester, UK
    Hmm... I thought circa 200kg seemed a tad on the heavy side.

    Well, I guess that calls into question the claims of the other source, although they would have to run flat out at very high power levels for hours at a time (and it is a well respected electrical engineering company).

    More investigation required...
     
  20. TEG

    TEG TMC Moderator

    Joined:
    Aug 20, 2006
    Messages:
    17,249
    Location:
    Silicon Valley
    Maybe ~35kg is a bit on the low side.

    I see a fair amount of variation in reported motor weight...

    Tesla Roadster
    Green Car Congress: Tesla to Use Interim Transmission to Get Production Roadster Out the Door
    Medieval's Blog!: The Tesla Roadster
    apr 07 business | The Global Intelligencer
    Tesla Motors - think
    Thermal Systems: Tesla Motors
    Tesla Motors - under the skin (Motor section)
    The Tesla Roadster - the perfect Elise? (by The Racing Geek)
    So, depending on where you look the motor weighs between 70 and 125lbs (32-56kg). Perhaps the old/lower number was without cooling fan shroud? I don't know why the weight would have gone up over time.
     

Share This Page