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The difficulties of providing 110-volt power to your airline seat

theatlantic.com

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Re: The difficulties of providing 110-volt power to your airline seat

#21

Post by riobard »

gvb wrote: post #17
riobard wrote: post #15

If 110V is not feasible, can we try lower voltage? 36V DC is sufficient for laptops with correct adapters. Also I don't really want to work on laptops in tight space anyway. A 5V USB port is sufficient. All Air Canada flights have this. (Due to RIM I guess?)

There is nothing wrong with the voltage (110vAC), the issue is power... and to achieve a given power amount (70W typically for laptops), lower voltage requires higher current. See my comment under the 12vDC lighter plug suggestion http://news.ycombinator.com/item?id=1828197 . 36vDC would have similar weight problems and, in addition, would require everybody to buy and haul around Yet Another Power Brick since it is o…

Ah, thanks for clearing it up! Another question: I saw many international flights feature a VOD system with a LCD screen that is playing some movies on the back of every seat. Does the power to drive the system enough to charge a laptop then?

Re: The difficulties of providing 110-volt power to your airline seat

#22

Post by vitaminj »

ars wrote: post #18

They already have 400hz power (not sure of the voltage) from the engines. Why not just use a switching power supply to change that to 60hz 110v? Why this whole business with inverters?

Switch-mode power supplies are essentially DC rectifiers, which will never ever give you 110V, 60Hz (an AC voltage).

One way to change the frequency of a power source is through a double-conversion type AC/AC converter, i.e. 1st stage is a rectifier which outputs a DC voltage - this is an arbitrary DC voltage, but it needs to be within the voltage tolerances of the 2nd stage - an inverter, which reconstructs an AC voltage from the DC link to whatever frequency you like.

This setup is also the basis of most UPS systems btw, with a battery connected in the DC link.

Re: The difficulties of providing 110-volt power to your airline seat

#23

Post by riobard »

merraksh wrote: post #5

Given that, in most overseas flights, sufficient voltage is available at every seat to power in-flight entertainment, I wonder if it's an easier engineering problem to have a 15-20 volt outlet instead (though I'm not sure if there's enough juice for the extra 2-3A). True, not laptops have the same AC plug, so an adapter would be necessary.

Not necessarily. Some sockets can cope with the majority of the AC plugs in Europe and America.

http://img.hisupplier.com/var/userImages/old/selong/selong$7...

Re: The difficulties of providing 110-volt power to your airline seat

#24

Post by gvb »

riobard wrote: post #21
gvb wrote: post #17

Earlier quoted context omitted.

There is nothing wrong with the voltage (110vAC), the issue is power... and to achieve a given power amount (70W typically for laptops), lower voltage requires higher current. See my comment under the 12vDC lighter plug suggestion http://news.ycombinator.com/item?id=1828197 . 36vDC would have similar weight problems and, in addition, would require everybody to buy and haul around Yet Another Power Brick since it is o…

Ah, thanks for clearing it up! Another question: I saw many international flights feature a VOD system with a LCD screen that is playing some movies on the back of every seat. Does the power to drive the system enough to charge a laptop then?

I am not familiar with the VOD systems, but I really doubt it. A typical laptop brick is rated at 70W and it probably pulls close to that with a discharged battery.

I would expect the VOD display system to be running around 10W. My guess is 1W lost in a 90% efficiency power supply, 5W for the display, 1W for an ARM processor, the rest for the video decoder chip and miscellaneous support chips.

Re: The difficulties of providing 110-volt power to your airline seat

#25

Post by nostromo »

stcredzero wrote: post #11

Here's my personal solution. It works for all airlines. It can also power my Cradlepoint 4G hotspot and recharge my iPad, iPhone, and any device using USB power. http://www.tekkeon.com/products-mypowerall.html I bought a male Adaptaplug and a Magsafe cord from eBay, and after 5 minutes with a soldering iron, it works for my 13" unibody MacBook as well. I plan on upgrading to a 13" MacBook Air soon. I should be able t…

I've considered these, but I've been afraid of taking it through security without causing any headaches. Have you had any problems?

Re: The difficulties of providing 110-volt power to your airline seat

#26

Post by evgen »

vilhelm_s wrote: post #19

"I wondered whether, as a technical matter, an airliner could actually produce enough power to keep a planeful of laptop users plugged in through a whole flight. [...] Short answer: No, you probably couldn't make this work." Given that the power output of the engines of a Boeing 747 is 140MW [1], enough to power 15 copies of the Empire State Building at peak business hours[2], I find this impossibility a bit depressi…

It is all about costs. Those engines are producing energy to keep the plane flying at 500mph. If you pull some power to spin an alternator then you need to run the engines faster and burn more fuel (which means you need even more fuel on board at takeoff to lug all of this extra fuel to the destination.) Add in the weight of the various inverters and equipment necessary to make this system safe on an airplane and I am surprised they even bother trying to run provide power to the seat at all.

Re: The difficulties of providing 110-volt power to your airline seat

#27

Post by Groxx »

a-priori wrote: post #20
ars wrote: post #18

They already have 400hz power (not sure of the voltage) from the engines. Why not just use a switching power supply to change that to 60hz 110v? Why this whole business with inverters?

There may also be concerns about insulating the flight electrical system from the cabin electrical system. What if there's a surge or huge load in the cabin? You need to be sure that that sort of thing can't affect the engine operation. The easiest way to be sure is to put an air gap between them.

They already tell you to turn off your Gameboy. I doubt they'd let passengers get anywhere near plugging directly into the power from the engines.

Re: The difficulties of providing 110-volt power to your airline seat

#28

Post by stcredzero »

nostromo wrote: post #25
stcredzero wrote: post #11

Here's my personal solution. It works for all airlines. It can also power my Cradlepoint 4G hotspot and recharge my iPad, iPhone, and any device using USB power. http://www.tekkeon.com/products-mypowerall.html I bought a male Adaptaplug and a Magsafe cord from eBay, and after 5 minutes with a soldering iron, it works for my 13" unibody MacBook as well. I plan on upgrading to a 13" MacBook Air soon. I should be able t…

I've considered these, but I've been afraid of taking it through security without causing any headaches. Have you had any problems?

I've only had a problem with the Cradlepoint because I had it on and it was warm. The battery? I just put it in my carryon, and it's never been a problem. I spent almost $7000 in cheap airfares in the last year, so this has definitely been tested!

Re: The difficulties of providing 110-volt power to your airline seat

#29

Post by stcredzero »

a-priori wrote: post #20
ars wrote: post #18

They already have 400hz power (not sure of the voltage) from the engines. Why not just use a switching power supply to change that to 60hz 110v? Why this whole business with inverters?

There may also be concerns about insulating the flight electrical system from the cabin electrical system. What if there's a surge or huge load in the cabin? You need to be sure that that sort of thing can't affect the engine operation. The easiest way to be sure is to put an air gap between them.

They could run a generator off a turbine in the airstream. A lot of EW pods were powered this way. This would cost a bit of fuel, but there would be no direct connection between the cabin electrical system and the engines.

Re: The difficulties of providing 110-volt power to your airline seat

#30

Post by nostrademons »

evgen wrote: post #26
vilhelm_s wrote: post #19

"I wondered whether, as a technical matter, an airliner could actually produce enough power to keep a planeful of laptop users plugged in through a whole flight. [...] Short answer: No, you probably couldn't make this work." Given that the power output of the engines of a Boeing 747 is 140MW [1], enough to power 15 copies of the Empire State Building at peak business hours[2], I find this impossibility a bit depressi…

It is all about costs. Those engines are producing energy to keep the plane flying at 500mph. If you pull some power to spin an alternator then you need to run the engines faster and burn more fuel (which means you need even more fuel on board at takeoff to lug all of this extra fuel to the destination.) Add in the weight of the various inverters and equipment necessary to make this system safe on an airplane and I a…

Some math: 120V * 2A = 240W * 300 passengers = 72 kW. That's 1/50th of a percent of the existing power output of a 747. If you figure a $600 plane ticket, I'd gladly pay 1/50th of a percent ($0.30) of that for electrical power on the flight.

The numbers get a bit more complicated when you figure in the weight for transformers, alternators, inverters, etc. But fuel is not a major component of this. The math really doesn't support the assertion that it's not cost-effective.

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