Mar 30

The All Electric Boeing 787

 

By George Bower

Advancements made in the electrification of the automobile are just one area in transportation to see such inherent improvements being introduced. For something slightly off-topic, but arguably related at least somewhat to what GM is doing with cars, we’ll take a brief look at what Boeing is doing with a cutting-edge aircraft.


Naturally the propulsion is still jet powered for the (otherwise) “all electric” airplane.

There has been lots of press about the Boeing 787 but usually relative to its advanced lightweight composite design. Little known is that the 787 is the first commercial aircraft to use an “all electric” design instead of the old “bleed air” design.

To see how these old and new designs compare please consider the following schematics.

The old design relied heavily on bleed air (compressed air) as a source of power. What can be lighter than air was the old logic. The bleed air was either bleed off the main engines or supplied by an auxiliary power unit located in the tail cone of the aircraft. Bleed air was used to start the main engines via an air turbine starter (ATS). Its other primary function was to provide air conditioning for the passengers via an environmental control system (ECS). While the air itself is very light, the associated ducting and valves are not. The new all-electric design eliminates the ducting and valves resulting in a lighter, more reliable system.

Starting of the main engines is no longer accomplished with an air turbine starter but with variable speed starter generators.

As Boeing says:

“The generators are directly connected to the engine gearboxes and therefore operate at a variable frequency (360 to 800 hertz) proportional to the engine speed. This type of generator is the simplest and the most efficient generation method because it does not include the complex constant speed drive, which is the key component of an integrated drive generator (IDG). As a result, the generators are expected to be more reliable, require less maintenance, and have lower spare costs than the traditional IDGs.”

The all-electric version relies on a higher voltage “hybrid” system, as Boeing elaborates:

“The 787 uses an electrical system that is a hybrid voltage system consisting of the following voltage types: 235 volts alternating current (VAC), 115 VAC, 28 volts direct current (VDC), and ±270 VDC. The 115 VAC and 28 VDC voltage types are traditional, while the 235 VAC and the ±270 VDC voltage types are the consequence of the no-bleed electrical architecture that results in a greatly expanded electrical system generating twice as much electricity as previous Boeing airplane models. The system includes six generators — two per engine and two per APU — operating at 235 VAC for reduced generator feeder weight.

“The ±270 VDC system is supplied by four auto-transformer-rectifier units that convert 235 VAC power to ±270 VDC. The ±270 VDC system supports a handful of large-rated adjustable speed motors required for the no-bleed architecture. These include cabin pressurization compressor motors, ram air fan motors, the nitrogen-generation-system compressor used for fuel-tank inerting, and large hydraulic pump motors.”

So you see ground transportation isn’t the only place where all electric prevails. It works in airplanes too. Why?… because it is more efficient … just like the Chevy Volt.

Source: Boeing

This entry was posted on Friday, March 30th, 2012 at 5:55 am and is filed under General. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

COMMENTS: 69


  1. 1
    codyozz

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    Mar 30th, 2012 (6:02 am)

    Electricity and batteries rule our lives more and more each day. I wonder when my toilet will be all electric?? :-)


  2. 2
    Sean

     

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    Mar 30th, 2012 (6:21 am)

    What! But how can that be?

    My dad says it’s impossible to make a jet to become electrified.

    Well you know what I’m adding this article to my favorites and when he sees this electrified
    electric-hybrid Boeing 787 he’s going to have a shock of a life time and boy will I’ll be laughing at him when he’s in total disbelief that jets can be electrified after all!


  3. 3
    Roy_H

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    Mar 30th, 2012 (6:39 am)

    Sean,

    Of course I am sure your father means for main propulsion. Electric powered jet engines are possible, but the battery weight is still way to high to make it practical in this application. Much like the non-plug in Prius all of the energy comes from the kerosene fuel.


  4. 4
    Gsned57

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    Mar 30th, 2012 (7:11 am)

    The 787 structure is about 50 composite compared to the next most composite Boeing plane the 777 which is between 5% and 10%. It’s pretty amazing that the skin and most of the frames of an aircraft can be made of composite yet we still haven’t incorporated this technology in cars at a large scale. Composites generally are better than steel in everything but compression. Must have something to do with crash tests and safety but it still doesn’t seem insurmountable. GM lost the spare tire for a lighter air compressor and can of fixaflat for weight purposes. Loosing a third of your body/frame weight by going to composites has to make a business case. Maybe we’ll see it in Gen 2. More range and same number of batteries would be a good thing.


  5. 5
    Loboc

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    Mar 30th, 2012 (7:24 am)

    It’s a matter of time and breakthroughs. With the newer cad/cam systems and high speed super computers, battery density equivalent to gasoline is inevitable.

    http://www.gizmag.com/solar-impulse-longest-flight/21994/


  6. 6
    kdawg

     

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    Mar 30th, 2012 (8:25 am)

    Loboc: It’s a matter of time and breakthroughs. With the newer cad/cam systems and high speed super computers, battery density equivalent to gasoline is inevitable.
    http://www.gizmag.com/solar-impulse-longest-flight/21994/

    Just like the movie John Carter, flying on rays of light.
    Too bad its not a jet and they could get the speed up to 1000mph (mach 1.3). Then they would not need to travel at night and could get rid of some of the batteries.


  7. 7
    George S. Bower

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    Mar 30th, 2012 (8:51 am)

    There are some things that puzzle me about this system. First, Why have the generators producing at 235 volts AC and then convert to +-270 VDC for the motors (like the motors that run the ECS)??? 270 is so close to 235 why not make the 2 voltages the same??


  8. 8
    Loboc

     

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    Mar 30th, 2012 (9:43 am)

    George S. Bower:
    There are some things that puzzle me about this system. First, Why have the generators producing at 235 volts AC and then convert to +-270 VDC for the motors (like the motors that run the ECS)??? 270 is so close to 235 why not make the 2 voltages the same??

    It’s probably an off-the-shelf issue.

    Some ex-military (de-classified or dual-purpose) product is different from commercial pieces. The battery can only be certain end voltage depending on cell count and cell configuration. The combination of the two and cost considerations could lead to a voltage differential.

    It also could be an engineering problem (EEs?). There may be some kind of reflection voltage/frequency that requires a converter to prevent it.


  9. 9
    Jackson

     

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    Mar 30th, 2012 (10:48 am)

    There was a story (quite a few years ago, now), that to save money, airlines were reducing the amount of air through the ECS. In the old system, the compressor stage of a jet engine not only supplies power for the air conditioner, but also the air itself which pressurizes the cabin. The thinking is, the more air available inside the engine, the more efficient the combustion (saving a little fuel). This has resulted in air of very poor quality, in many cases; in terms of airborne (so to speak) bacteria, if not elevated CO2 or insufficient oxygen (though this was never proven).

    Food for thought:

    http://www.elliott.org/the-travel-critic/stale-air-up-there/

    Given the stories this week of the pilot and passenger who suddenly went nuts (on separate flights), I thought of this story again. I could see the airlines playing this little fuel-saver game to extremes, with ever-rising kerosene prices. Are the full health risks of this practice known? I doubt it. Could there be transient neurological effects of stale air? The pilot and fear-of-flight passenger would have been in states of higher stress than the average flyer, which would have exacerbated such a situation. Even if such incidents are rare, enough people fly every day for it to appear once in a while.

    With the new Boeng design, however, the whole issue has the potential to disappear completely.


  10. 10
    Jackson

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    Mar 30th, 2012 (11:26 am)

    Roy_H:
    Sean,

    Of course I am sure your father means for main propulsion. Electric powered jet engines are possible, but the battery weight is still way to high to make it practical in this application. Much like the non-plug in Prius all of the energy comes from the kerosene fuel.

    The only electric propulsion I can imagine would be some kind of beamed power. As the plane enters a ‘power cel,’ a new beam would track it (or better yet, a solar-powered satellite in geosynchronous orbit would supply power continuously from above for the whole flight). An airplane is a pretty small target, so shorter-wavelength energy would have to be used (most likely a laser). This is pretty far-fetched, and not likely to be announced next week, but it is within the realm of the possible. Consider the following, which is already being contemplated:

    http://en.wikipedia.org/wiki/Lightcraft


  11. 11
    George S. Bower

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    Mar 30th, 2012 (11:43 am)

    Jackson: There was a story (quite a few years ago, now), that to save money, airlines were reducing the amount of air through the ECS.In the old system, the compressor stage of a jet engine not only supplies power for the , but also the air itself which pressurizes the cabin.The thinking is, the more air available inside the engine, the more efficient

    With the new Boeng design, however, the whole issue has the potential to disappear completely.

    Yes Jackson,
    from the Boeing source:

    “The 787′s no-bleed systems architecture will allow the airplane’s engines to produce thrust more efficiently — all of the high-speed air produced by the engines goes to thrust. Pneumatic systems that divert high-speed air from the engines rob conventional airplanes of some thrust and increase the engine’s fuel consumption.

    Boeing believes that using electrical power is more efficient than engine-generated pneumatic power, and expects the new architecture to extract as much as 35 percent less power from the engines. “


  12. 12
    BLIND GUY

     

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    Mar 30th, 2012 (11:53 am)

    I never knew that some airliners use compressed air to run some systems. Having an abundance of electrical power available on this 787; does anyone know if the polarization of the skin of the aircraft or the polarization of the air surrounding the skin would result in less friction or drag? I thought I read somewhere that this technique helped reduce fuel consumption in farm plowing. I also wondered if dimples stamped into the panels [like on golf balls] or a Teflon type coating would help lessen drag on jets or EVs? Sorry; just thinking out loud.


  13. 13
    pjkPA

     

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    Mar 30th, 2012 (11:59 am)

    Sounds like Good technology… thanks for the info.

    Still trying to hold out for CUV Voltec….. not easy.


  14. 14
    Jackson

     

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    Mar 30th, 2012 (12:12 pm)

    BLIND GUY:
    I also wondered if dimples stamped into the panels [like on golf balls] or a Teflon type coating would help lessen drag on jets or EVs? Sorry; just thinking out loud.

    The Mythbusters put golf-ball-like dimples on a car during a program testing fuel-economy myths. It seemed to work:

    http://boards.straightdope.com/sdmb/showthread.php?t=536942

    http://www.neatorama.com/2009/10/23/can-you-improve-your-cars-gas-mileage-by-adding-golf-ball-dimples/

    “Discussion threads on several auto forums discussing the Mythbusters episode note that “shark skin” textures on military fighter aircraft (and on America’s Cup yachts) serve the same purpose, that dimpling on the undercarriage of some Lexus cars reduces noise (by reducing friction), and that textured paint is banned on professional race cars.

    “Mythbusters achieved the dimpled effect using modeling clay applied to the surface of a Ford Taurus. It’s not clear whether the same effect could be achieved with a ball-peen hammer.”

    abbll.jpg

    Also no word on whether or not car buyers would put up with the appearance. Perhaps a smaller, computer-designed texture would work as well, or better. Sounds like something the Volt team should look into. Good one, BLIND GUY!


  15. 15
    Loboc

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    Mar 30th, 2012 (12:37 pm)

    Jackson: The Mythbusters put golf-ball-like dimples on a car during a program testing fuel-economy myths.It seemed to work:

    http://boards.straightdope.com/sdmb/showthread.php?t=536942

    http://www.neatorama.com/2009/10/23/can-you-improve-your-cars-gas-mileage-by-adding-golf-ball-dimples/

    “Discussion threads on several auto forums discussing the Mythbusters episode note that “shark skin” textures on military fighter aircraft (and on America’s Cup yachts) serve the same purpose, that dimpling on the undercarriage of some Lexus cars reduces noise (by reducing friction), and that textured paint is banned on professional race cars.


    “Mythbusters achieved the dimpled effect using modeling clay applied to the surface of a Ford Taurus.It’s not clear whether the same effect could be achieved with a ball-peen hammer.”

    Also no word on whether or not car buyers would put up with the appearance.Perhaps a smaller, computer-designed texture would work as well, or better.Sounds like something the Volt team should look into.Good one, BLIND GUY!

    Leave your car outside in Texas long enough and eventually hail will redesign it for you. :(


  16. 16
    CorvetteGuy

     

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    Mar 30th, 2012 (12:38 pm)

    Ha! Ha! I glanced at today’s headline and the first thing that came to mind was a plane-load of passengers with “Range Anxiety” !!! :)

    I’m glad it was about something else.


  17. 17
    Bruce Embry

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    Mar 30th, 2012 (12:45 pm)

    George S. Bower:
    There are some things that puzzle me about this system. First, Why have the generators producing at 235 volts AC and then convert to +-270 VDC for the motors (like the motors that run the ECS)??? 270 is so close to 235 why not make the 2 voltages the same??

    Actrully if you do the math they are the same. AC Voltage(RMS) = DCV * 0.7071 + some loses


  18. 18
    Jackson

     

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    Mar 30th, 2012 (12:56 pm)

    Jackson:
    The Mythbusters put golf-ball-like dimples on a car during a program testing fuel-economy myths. It seemed to work …

    Perhaps a smaller, computer-designed texture would work as well, or better. Sounds like something the Volt team should look into.

    Loboc:
    Leave your car outside in Texas long enough and eventually hail will redesign it for you.

    Maybe they could stamp a small enough pattern onto some kind of flexible, rubbery sheet and bond it to the exterior panels. It could double as a hail-resistant impact-absorbing barrier.

    Also, I thought your comment was pretty funny [+1], just continuing the “thinking out loud” …


  19. 19
    Raymondjram

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    Mar 30th, 2012 (1:08 pm)

    Electric aircraft engines could be the next technological step. We already have small electrical blowers in laptops and even tablets that use a few milliwatts, but does its job to extract heat from the CPU and other components. You can enter any hobby or even Radio Shack store and buy a helicopter or a small hovering airship with tiny electrical motors generating lift, and powered by small rechargeable batteries. There are large compressors with the electric motor built inside the compressor rotor. Maybe General Electric does have some large megawatt electrical aircraft motors in experimental development.

    This is one idea where hydrogen fuel is the possible solution. The aircraft can have large fuel cells which convert that hydrogen fuel into electricity to power the electric engines and generate the thrust needed to fly the aircraft. NASA has record-breaking solar-powered aircraft with electric motors driving large propellers. So the same can be developed for passenger and cargo aircraft someday.

    We never dreamed about electrical appliances and portable computers at the beginning of the twentieth century. Now it is time to dream about electrical aircraft, ships, and other clean transportation means within our lifetimes in this century.

    Raymond


  20. 20
    Jackson

     

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    Mar 30th, 2012 (1:20 pm)

    Raymondjram: This is one idea where hydrogen fuel is the possible solution. The aircraft can have large fuel cells which convert that hydrogen fuel into electricity to power the electric engines and generate the thrust needed to fly the aircraft. NASA has record-breaking solar-powered aircraft with electric motors driving large propellers. So the same can be developed for passenger and cargo aircraft someday.

    NASA tests have also shown that Hydrogen makes a better fuel for turbine engines than petroleum. It’s also lighter, a plus for aircraft. If it’s more efficient, perhaps an H2-powered motor might use fuel-cell generated electricity at cruise, and light off some hydrogen for extra power on takeoff. This would reduce the size and weight of the motor (and fuel cells), while making an acceptable trade-off for high power which is needed for less time.

    The problem with Hydrogen is the necessary tank for cryonic storage (I simply do not believe that H2 could be used in a practical airliner any other way). A spherical tank works best, due to low surface area (to minimize boil-off). There aren’t many places to put such a tank in a conventional aircraft shape. Certainly not in the wings. Perhaps something like this would work better:

    516kw4.jpg

    A toroidal tank like the one shown might work, but a semi-spherical tank (or hemisphere-capped cylinder) in the center would be better, IMO.

    This shape would work better for beamed power too, by providing a large central area for a receiver. Your motors would require less power than the laser-heated engines I imagined: perhaps some kind of microwave system would be adequate. Only enough hydrogen for takeoff, and to make it safely to an airport when a power beam fails, need be carried in such an aircraft.


  21. 21
    Raymondjram

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    Mar 30th, 2012 (1:21 pm)

    CorvetteGuy:
    Ha! Ha! I glanced at today’s headline and the first thing that came to mind was a plane-load of passengers with “Range Anxiety” !!!

    I’m glad it was about something else.

    Read my previous post above. Boeing could someday produce an “EA” (electrical aircraft) based on electrical aircraft engines, using a motor to generate thrust, instead of burning fuels. Less noise, cleaner airways, and maybe cheaper fares!

    BTW, if an aircraft does run out of fuel or energy, it can glide quite a distance and land. So “range anxiety” could be an issue, but it also happens to ICE planes, too!

    Raymond


  22. 22
    George S. Bower

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    Mar 30th, 2012 (1:21 pm)

    Raymondjram,

    Raymond,
    As an EE I was wondering if you would know why Boeing selected such odd voltages for the system. Why on earth would they go with 235 VAC out of the generators and convert to 270 VDC to drive the DC motors. Is it because as Loboc says in # 8 ie an off the shelf issue or as Bruce says in #17–”Actually if you do the math they are the same. AC Voltage(RMS) = DCV * 0.7071 + some loses”


  23. 23
    Richard Lam

     

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    Mar 30th, 2012 (2:47 pm)

    codyozz,

    My toilets are already electric….but I blame my mother and the Japanese for that =P.


  24. 24
    Jackson

     

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    Mar 30th, 2012 (3:06 pm)

    George Bower:

    The All Electric Boeing 787

    The real problem isn’t the electric airplane . . .

    It’s the extension cord!!!!

    :-P

    . . . inevitable . . .


  25. 25
    HaroldC

     

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    Mar 30th, 2012 (3:52 pm)

    li wonder if you covered a super tanker with photo voltaic panels 25 feet wider all around the ship ,if it would generate enough power to move it…..or save fuel as a hybrid.see ,you got me thinking now….lol
    HaroldC


  26. 26
    Loboc

     

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    Mar 30th, 2012 (4:33 pm)

    Raymondjram: it can glide quite a distance and land

    A jet glide path is a 45-degree angle or worse. It’s more a trajectory.


  27. 27
    Loboc

     

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    Mar 30th, 2012 (4:35 pm)

    HaroldC:
    li wonder if you covered a super tanker with photo voltaic panels 25 feet wider all around the ship ,if it would generate enough power to move it…..or save fuel as a hybrid.see ,you got me thinking now….lol
    HaroldC

    Or, you could use vertical panels. We could call them “sails”…


  28. 28
    kdawg

     

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    Mar 30th, 2012 (4:45 pm)

    I would like to see an airplane that runs on zoo dung.


  29. 29
    Loboc

     

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    Mar 30th, 2012 (4:45 pm)

    CorvetteGuy:
    Ha! Ha! I glanced at today’s headline and the first thing that came to mind was a plane-load of passengers with “Range Anxiety” !!!

    I’m glad it was about something else.

    If you knew how much ‘reserve’ they actually have, you’d have range anxiety on every flight! The more fuel they carry, the higher the drag. They calculate it so close it’s scary.


  30. 30
    kdawg

     

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    Mar 30th, 2012 (4:48 pm)

    Jackson: The problem with Hydrogen is the necessary tank for cryonic storage (I simply do not believe that H2 could be used in a practical airliner any other way). A spherical tank works best, due to low surface area (to minimize boil-off). There aren’t many places to put such a tank in a conventional aircraft shape. Certainly not in the wings. Perhaps something like this would work better:

    This design didn’t work out too well

    hindenburg.jpg


  31. 31
    Jackson

     

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    Mar 30th, 2012 (5:10 pm)

    kdawg: This design didn’t work out too well

    The design I described is used for things like this:

    w20zy8.jpg

    The principal difference between a cryogenic hydrogen tank and the Hindenburg is that the tank carries gas in refrigerated liquid form, typically, in a rigid aluminum vessel. I doubt that enough hydrogen in gaseous form can fuel, or be practically carried, on a jetliner. True, launch vehicles using LH2 fuel have failed catastrophically, but so have kerosene-fueled jet aircraft.

    Jackson: the necessary tank for cryonic storage

    BTW, the correct word is “Cryogenic,” not “Cryonic.” Oops:

    http://en.wikipedia.org/wiki/Cryogenics


  32. 32
    Jim I

     

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    Mar 30th, 2012 (5:15 pm)

    Loboc:
    It’s a matter of time and breakthroughs. With the newer cad/cam systems and high speed super computers, battery density equivalent to gasoline is inevitable.

    http://www.gizmag.com/solar-impulse-longest-flight/21994/

    =================================

    Didn’t I just read somewhere that EEStor was going to announce a new power source for jet planes before the end of the summer?????

    Wow! That would be just in time to make good use of the new electric systems in the Boeing 787!!!!!!!!

    Sorry – I just couldn’t resist……………..

    C-5277


  33. 33
    Raymondjram

     

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    Mar 30th, 2012 (6:17 pm)

    George S. Bower:
    Raymondjram,

    Raymond,
    As an EE I was wondering if you would know why Boeing selected such odd voltages for the system. Why on earth would they go with 235 VAC out of the generators and convert to 270 VDC to drive the DC motors. Is it because as Loboc saysin # 8 ie an off the shelf issue or as Bruce says in #17–”Actually if you do the math they are the same. AC Voltage(RMS) = DCV * 0.7071 + some loses”

    I really don’t know why. The high voltage allows less current, so it saves weight. But someone may ask an aviation technician about this. I know about the electrical circuits in computers (from mainframes to microcontrollers) and some GM vehicles, but only theory in aviation.

    Raymond


  34. 34
    George S. Bower

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    Mar 30th, 2012 (6:24 pm)

    Jackson: The real problem isn’t the electric airplane . . .

    It’s the extension cord!!!!

    . . . inevitable . . .

    Actually, you can plug it in.

    From the Boeing source:
    “The system, as shown in figure 3, features two forward 115 VAC external power receptacles to service the airplane on the ground without the APU and two aft 115 VAC external power receptacles for maintenance activities that require running the large-rated adjustable speed motors.”

    Boeing thinks of every thing. They also invented: 2 engines are safer than 3 (or 4).


  35. 35
    Bob G

     

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    Mar 30th, 2012 (7:13 pm)

    Loboc: It’s probably an off-the-shelf issue.

    Some ex-military (de-classified or dual-purpose) product is different from commercial pieces. The battery can only be certain end voltage depending on cell count and cell configuration. The combination of the two and cost considerations could lead to a voltage differential.

    It also could be an engineering problem (EEs?). There may be some kind of reflection voltage/frequency that requires a converter to prevent it.

    Nope. That system was custom-designed for the 787. I was there.


  36. 36
    Bob G

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    Mar 30th, 2012 (7:22 pm)

    George S. Bower:
    Raymondjram,

    Raymond,
    As an EE I was wondering if you would know why Boeing selected such odd voltages for the system. Why on earth would they go with 235 VAC out of the generators and convert to 270 VDC to drive the DC motors. Is it because as Loboc saysin # 8 ie an off the shelf issue or as Bruce says in #17–”Actually if you do the math they are the same. AC Voltage(RMS) = DCV * 0.7071 + some loses”

    The double voltage at the generator saves weight (smaller feeders). The conversion is not to 270 VDC, but rather to +/-270 VDC (i.e., 540 VDC centered over ground). This higher voltage is necessary to drive the huge motors in the air conditioning packs within a reasonable size and weight.


  37. 37
    Jackson

     

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    Mar 30th, 2012 (7:41 pm)

    Loboc: It’s a matter of time and breakthroughs. [...] battery density equivalent to gasoline is inevitable.

    Don’t forget that aircraft lighten as they burn fuel (which is why it is measured as “pounds”). This in turn requires less and less energy to keep airborne, as an airliner travels. Overall range is therefore greater compared to a plane which weighs the same at the beginning and end of it’s journey. A battery density greater than jet fuel would be needed to equal it.


  38. 38
    George S. Bower

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    Mar 30th, 2012 (8:11 pm)

    Bob G: The double voltage at the generator saves weight (smaller feeders).The conversion is not to 270 VDC, but rather to +/-270 VDC (i.e., 540 VDC centered over ground).This higher voltage is necessary to drive the huge motors in the air conditioning packs within a reasonable size and weight.

    Thx for the input Bob G. If you were there you would know. Great program/ airplane. I’m an old APU guy from Honeywell.

    It killed me when we lost the contract but I still love the airplane.!!!


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    Mar 30th, 2012 (8:19 pm)

    Another similarity to the Volt is that motor controllers provide electrical power to the generators to drive them as motors that then provide the shaft horsepower necessary to start the 787 jet engines. Once the jet engines are running, the generators begin to draw shaft horsepower from the engines to then generate electrical power. As well as being more efficient, this is expected to be significantly more reliable than the traditional air starters and their mechanical disconnect hardware.

    PS: We call it “more electric,” because, as has been pointed out here, “all electric” has a whole different meaning.


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    Mar 30th, 2012 (8:25 pm)

    Bob G: Another similarity to the Volt is that motor controllers provide electrical power to the generators to drive them as motors that then provide the shaft horsepower necessary to start the 787 jet engines. Once the jet engines are running, the generators begin to draw shaft horsepower from the engines to then generate electrical power.

    How challenging was it to produce motor/generators which operate at such high shaft speeds? Didn’t that require developing high power electronics which are also capable of high switching speeds?


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    Mar 30th, 2012 (8:29 pm)

    George S. Bower: Thx for the input Bob G. If you were there you would know. Great program/ airplane. I’m an old APU guy from Honeywell.

    It killed me when we lost the contract but I still love the airplane.!!!

    I agree that it is a great airplane, and although it was/is a very demanding program, being involved with the development of all of the new tech was cool.

    Don’t hate me, but I am an electrical power guy with the company who also makes the APU. :)


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    Mar 30th, 2012 (8:35 pm)

    I remember reading years ago the GM or a GM company had developed magnetic material that would allow stronger and smaller electric motors. I wonder if this has anything to do with this abilty to do things electrically more efficiently than with bleed air?


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    Mar 30th, 2012 (8:40 pm)

    Eco_Turbo:
    I remember reading years ago the GM or a GM company had developed magnetic material that would allow stronger and smaller electric motors. I wonder if this has anything to do with this abilty to do things electrically more efficiently than with bleed air?

    I believe you are thinking of GM’s “Magnequench” technology. The story is not a happy one:

    http://www.bloomingtonalternative.com/node/7950

    I don’t know how these differ from other neodymium-iron-boron magnets which we find in consumer products.


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    Mar 30th, 2012 (8:47 pm)

    Bob G: I agree that it is a great airplane, and although it was/is a very demanding program, being involved with the development of all of the new tech was cool.

    I am an electrical power guy with the company who also makes the APU.

    Thx for contributing!!


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    Mar 30th, 2012 (9:07 pm)

    Jackson: How challenging was it to produce motor/generators which operate at such high shaft speeds? Didn’t that require developing high power electronics which are also capable of high switching speeds?

    Because of the challenging (and often unique to each program) requirements for weight, size, reliability, safety, etc., not much in aerospace can be truly “off-the-shelf.” It takes a lot of fuel to fly unnecessary weight around the world for 30 years, so there is tremendous scrutiny over every pound.

    I’m not sure how much I can say in a public forum, but we make generators that turn much faster than these. They need good lubrication, must be very well balanced, and you need to pay close attention to rotor construction (keeping in mind that the forces increase with the distance from the center).

    The controller switching frequency needs to be high enough to produce a waveform at the desired power frequency (which is a function of the speed of the generator and its number of poles – around 400 Hz in this case) and high enough so that the output filter can condition the output acceptably, but not so high that losses create problems (i.e., Each time the transistors turn on or off, they swing briefly through the linear region and consume power, so the higher the switching frequency, the higher the losses.). And then there is audio and electromagnetic noise to consider. It’s a balancing act. :)

    The good news is that modern microprocessors, power electronics, and rotating machines are capable of incredible power, efficiency, and reliability. As you can see in the Volt, that tiny little electric motor provides more power than that huge gasoline engine (also smoother, quieter, cleaner, and more efficient). Battery technology is really the limiting factor. If we had batteries with characteristics similar to dino fuels, then electric cars, trucks, and aircraft would be the norm.


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    Mar 30th, 2012 (9:20 pm)

    Thanks George for this interesting little piece.

    For a couple years I’ve been thinking about getting into General Aviation a tiny bit. I’ve been on a couple tourist flights and I really love it (although my stomach could use some practice). In particular I think I like gliding / soaring the best.

    Recently it occurred to me that great strides are being made in TRULY all-electric aircraft (unlike what you describe here, title notwithstanding :) ) like the ElectraFlyer, Elektra One, Pipistrel … But quickly I came across the news that gliders are starting to become available with self-launching electric motors. YES, PERFECT, THAT.

    It’s probably a few years off for me, but I think that’s where I’m heading. It would dovetail nicely with all this EV stuff I’m immersed in now. And I’d finally put my aerospace engineering degree to use for the first time in 20+ years!


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    Mar 30th, 2012 (9:21 pm)

    Eco_Turbo:
    I remember reading years ago the GM or a GM company had developed magnetic material that would allow stronger and smaller electric motors. I wonder if this has anything to do with this abilty to do things electrically more efficiently than with bleed air?

    Jet engine thermodynamics is over my head, but from what I understand, it is hard to efficiently recover the energy from bleed air (which is at high pressure and high temperature). A shaft (connected to a generator) drawing mechanical energy directly from the engine is more efficient. Certainly, a more efficient generator would help too, but I don’t think permanent magnets came into play here (i.e., 3-phase synchronous machines with field windings).


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    Mar 30th, 2012 (9:33 pm)

    George S. Bower: Actually, you can plug it in.

    From the Boeing source:
    “The system, as shown in figure 3, features two forward 115 VAC external power receptacles to service the airplane on the ground without the APU and two aft 115 VAC external power receptacles for maintenance activities that require running the large-rated adjustable speed motors.”

    Boeing thinks of every thing. They also invented: 2 engines are safer than 3 (or 4).

    It would have been nice to use 230 VAC external power (to match the generator voltage and have less conversions), but every airport in the world already has 115 VAC external power equipment.

    Just like GM made the Volt take advantage of existing infrastructure (i.e., standard outlets and standard fuels) to do something new, Boeing needed to make the 787 fit into the existing airport infrastructure.


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    Mar 30th, 2012 (9:33 pm)

    Loboc: A jet glide path is a 45-degree angle or worse. It’s more a trajectory.

    Just in case you were serious, this is totally and laughably wrong.

    https://www.google.com/search?q=jet+glide+slope

    Ratio = 15 –> 3.8 degrees

    Ratio = 20 –> 2.9 degrees

    For more, you might want to Google terms like ETOPS, 120 rule time, Gimli Glider …


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    Mar 30th, 2012 (9:42 pm)

    Bob G: Jet engine thermodynamics is over my head, but from what I understand, it is hard to efficiently recover the energy from bleed air

    I don’t have an off design model for the main engines. …but my guess is they don’t like a lot of bleed air. they like shaft loads better!!(as you said)


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    Mar 30th, 2012 (9:54 pm)

    Chris C.:

    For more, you might want to Google terms like ETOPS,

    Yes Chris we were into ETOPS on the 777 project (we did win that one) …..another Boeing incredibly smart idea.


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    Mar 30th, 2012 (10:29 pm)

    Bad day for nasaman to be scarce …


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    Mar 31st, 2012 (3:49 am)

    You know that zoo has that poo rickshaw why not one of these electric trams that can carry 30 people maximum when equipped with 9-12 trailers!

    Now tell me is this better than a rickshaw or what?

    http://www.taylor-dunn.com/vehicle-details-standard.aspx?id=15

    Or how about this one it may not have have the option of 30 max but what do you think of this one?
    http://www.taylor-dunn.com/vehicle-details-standard.aspx?id=14

    So what one do you think the zoo should choose.
    The one that can connects up to 9-12 tram trailers of 30 people max capacity or the one with the hood.

    You be the judge!


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    Mar 31st, 2012 (9:10 am)

    Jackson: Bad day for nasaman to be scarce …

    I’m flattered, Jackson, but reading the many posts I might have comments on, I felt there was little more I could contribute —Bob G’s comments are excellent and there’s not much left unsaid.

    I agree that modern aircraft (and spacecraft) electrical systems have largely abandoned the old 28V power standard in the interest of efficiency (and because of very high conversion efficiencies). Most here have noted that EV designers have NOT standardized on the number or the configuration of Li-Ion cells used in the car’s main propulsion battery, opting instead for highest overall efficiency. The same design philosophy apparently applies to modern commercial jetliners like the 787.

    A key reason for today’s very high efficiencies is that losses due to factors like switching transistor saturation resistance and switching speeds are now minimal, whereas as little as 10-15 years ago these losses were much higher. Consequently, AC-DC, DC-AC and DC-DC conversion losses, once significant, are no longer major concerns. For example, 235VAC can now be converted to 270VDC (and vice versa) with very small losses. Therefore, designers of high power distribution systems can now focus on minimizing other factors like wiring and contact resistance losses to a much greater degree than in the past, both in EVs & in aircraft.


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    Mar 31st, 2012 (12:16 pm)

    Comparison to the Volt seems a bit of a stretch to me. This is just driving bigger starter/generators from the engine instead of bleeding compressor air. Starter/generators themselves aren’t even new to aircraft design. The propulsion is basically unchanged. This just changing how the accessories are driven.


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    Mar 31st, 2012 (12:36 pm)

    Jackson,

    I know, i was just in a TGIF mood.


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    Mar 31st, 2012 (12:38 pm)

    Jeff – is this going to be Monday’s story?

    http://www.autoguide.com/auto-news/2012/03/bush-senior-defies-republican-stereotype-buys-chevy-volt.html

    Another gem by Huw. Almost too good to be true.


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    Mar 31st, 2012 (12:48 pm)

    Bob G: The good news is that modern microprocessors, power electronics, and rotating machines are capable of incredible power, efficiency, and reliability. As you can see in the Volt, that tiny little electric motor provides more power than that huge gasoline engine (also smoother, quieter, cleaner, and more efficient). Battery technology is really the limiting factor. If we had batteries with characteristics similar to dino fuels, then electric cars, trucks, and aircraft would be the norm.

    Exactly, why the military is funding fuel cell research. Just how much more efficiently could that electricity be generated directly from the chemistry in the JP8 vice a PTO shaft? ;-)

    Sorry George, couldn’t help myself…thought I’d throw that in for old times sake! I enjoyed your article, thanks for taking the time to research/write it.


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    Mar 31st, 2012 (1:39 pm)

    OT – for those of you who rarely read the forum pages at GM-Volt.com, you really should check out this thread: “You-might-be-a-Volt-owner-if…”

    http://gm-volt.com/forum/showthread.php?12704-You-might-be-a-Volt-owner-if

    It will make you smile. :-)


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    Mar 31st, 2012 (2:56 pm)

    MichaelH,

    “You have to check your rearview mirror for tailgaters before you let of the accelerator”

    I liked this one because they used the word accelerator instead of gas-pedal.


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    Mar 31st, 2012 (3:21 pm)

    kdawg,

    I like the one about knowing more than the people at the dealer. I’ve “trained” people at at three dealerships.

    And this one is me completely – “You ordered and paid for a car you had never seen in person.”


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    Mar 31st, 2012 (4:29 pm)

    kdawg,

    Logic ultimately prevails with the open minded, as I always thought GHWB was thoughtful as well.

    A previous CEO of EXXON once said that if gasoline demand was down by ten percent, the price of gas would plummet. While that was about 8 or so years ago, and, far more demand has come on line for gasoline from China and India, still, a core component of at least suppressing price volatility would be electrification.

    Also, if the oil subsidies are redirected to promote the sale of electrified vehicles as an incentive at point of sale for American citizens, not as a tax credit, then the question to ask would be “Would the difference in the crude oil cost of the oil companies be absorbed/be seen in less volatility, and, in fact, come out of the speculators’ margins?”

    The percentage ratio nowadays for that four billion in relationship to the approximate one trillion in US dollars going abroad would not seem to make a big difference nowadays at about four dollars a gallon. But adding some spark to the end-price point of sale as a direct credit would definitely make the demand balance swing quickly at this point if also the base price came down by four thousand dollars from what it is now.

    I think President Obama sees these aspects at the current cost of gas, and I think also those subsidies ought to be redirected for awhile toward direct credits at point of sale for American citizens, and to try this out at least for a while.


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    Mar 31st, 2012 (7:04 pm)

    Great to see this posted here. I have a personal attachment to the 787 I work for the airline that operates the heavily modified 747 aircraft that haul around the large components from Italy and Japan to the US. I spent a year and a half running our operation at Boeing Charleston putting the “plane in the plane” very unique gig. I used to love showing our pilots the electric “packs” when I would take them in the Mid body building to show them what they were flying. Reactions varied mostly depending on age, older guy’s were a little concerned since they have decades of experience with “bleed air” systems, younger guy’s not so much so.

    I have since moved onto a regional managers position in the South Pacific (Sydney) but miss my 787. Can’t wait to ride in one and tell the passenger next to me I knew it before it was born! Then show them pictures of what I did!


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    Mar 31st, 2012 (7:08 pm)

    Gsned57,

    It is simply cost at this point. I worked with the 787 so understand it pretty well.


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    Mar 31st, 2012 (8:11 pm)

    Sort of OT but interesting ..(or maddening)……l saw a gas station in Montreal today selling premium (which is suggested for the Volt) at $7.43/Cdngal …$6.17/USgal……chilling…..
    HaroldC


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    Mar 31st, 2012 (9:39 pm)

    Rooster: Exactly, why the military is funding fuel cell research.Just how much more efficiently could that electricity be generatedt?

    George, couldn’t help myself…thought I’d throw that in for old times sake!I enjoyed your article, thanks for taking the time to research/write it.

    Thx for the visit Rooster. !!


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    Mar 31st, 2012 (9:47 pm)

    Chris Negele:
    Great to see this posted here. I have a personal attachment to the 787 . I used to love showing our pilots the electric “packs”were flying. Reactions varied mostly depending on age, older guy’s were a little concerned since they have decades of experience with “bleed air” systems, younger guy’s not so much so.

    I have since moved onto a regional managers position in the South Pacific (Sydney) but miss my 787. Can’t wait to ride in one and tell the passenger next to me I knew it before it was born! Then show them pictures of what I did!

    The pack’s….. yes Chris. I wanted to get into the details of the ECS packs but may be it is an idea for another article about America’s—I mean the Worlds best Airplane!!


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    Apr 2nd, 2012 (12:50 pm)

    Boeing is light years behind Pipistrel, which has already produced a record prize winning all electric 4 seater air commuter with enough reasonable range and speed to be practical in general aviation. There’s also the Solar Impulse, an all-electric manned aircraft that has stayed aloft for more than 24 hours without the external refueling required by a gas hog aircraft, and the Zephyr, an all-electic drone that has stayed aloft for weeks (could be decades – depends on solar panel warranty and quality, I suppose). Not to mention all the various electric for launch and hybrid air gliders and trainers, more every year.

    Boeing’s baby steps are still good, though. Don’t let the perfect be the enemy of the good.

    Sure, there’s a whole lot of improvement that can happen, especially with intergrated sustems. As energy carriers, such as batteries, eventually improve in higher energy capacities and lower costs and weight, with sufficient investment, that’s a simple plug and play change over.

    With any amount of electric drive, you have a rotary rail gun under the hood. Who wouldn’t want that, even if just for runway taxiing?


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    Apr 2nd, 2012 (5:28 pm)

    Steve:
    Comparison to the Volt seems a bit of a stretch to me.This is just driving bigger starter/generators from the engine instead of bleeding compressor air.Starter/generators themselves aren’t even new to aircraft design.The propulsion is basically unchanged.This just changing how the accessories are driven.

    They no longer need to design the engine for the worst case bleed load at any thrust setting or environment. And the 787 has intelligent load management that will reduce electrical loading for many reasons, including limitations on engine horsepower extraction during some coffin-corner conditions.

    And yes, I’ll admit that the Volt is more of a radical departure from the traditional propulsion system than the 787, but for me (as an electrical power engineer) the 787 was a radical departure from the way *we* usually do things.