
The difficulties of providing 110-volt power to your airline seat - cwan
http://www.theatlantic.com/technology/archive/2010/10/nerds-only-about-ac-power-on-an-airplane/65033/
======
stcredzero
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 to get 14 hours working
time from this setup.

As a companion to my WiFi iPad, it's great. The Cradlepoint will run for 18
hours off of it. (I have the MP3450.) Not small enough for a pocket, but it
fits fine in most laptop bags.

EDIT: I bet there's a business renting these things out to people at airports!

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

~~~
stcredzero
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!

------
oiujmngbvfgh
Can't we just have exercise bikes linked to generators in economy class?

About time the lower orders did some work.

~~~
sliverstorm
Hey, if I could get something out of it (like fare), I'd gladly pedal away.

~~~
netcan
On a long enough flight, I'd probably pay to pedal.

Come to think of it. Maybe we should have excercise bikes in 1st powering
economy. On board gym?

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vilhelm_s
"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 depressing.

[1]
[http://en.wikipedia.org/wiki/Orders_of_magnitude_(power)#meg...](http://en.wikipedia.org/wiki/Orders_of_magnitude_\(power\)#megawatt_.28106_watts.29)
[2] <http://depletedcranium.com/what-is-a-megawatt/>

~~~
evgen
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.

~~~
nostrademons
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.

~~~
neutronicus
"fuel is not a major component of this ... The math really doesn't support the
assertion that it's not cost-effective."

How do you figure?

Say some extra weight delta_w in additional equipment is required, and say
that the fuel required to complete a given flight is a function f of the
plane's weight, and that the cost of the fuel is C. Further, let the lifetime
maintenance cost of the new equipment be E, and the lifetime maintenance of
the plane's structural components be g, also a function of its weight. As a
rough approximation, the additional cost should be

E + C df/dw|_W * delta_w + dg/dw|_W * delta_w

(Note that, really, f is a function of both passenger power consumption and of
weight, both of which we're varying here, but I'll buy your argument that
df/dp|_P * delta_p is neglible in comparison to f(P,W))

The article asserts that one or both of the derivates in this equation are
large enough that its product with delta_w is non-negligible (in fact,
prohibitive). I'm guessing that df/dp is not the problem, which is the only
term you really addressed.

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InclinedPlane
This is a pretty snarky and relatively uneducational article. A lot of
speculation, some ignorant rambling (nobody at The Atlantic seems to know
where electrical power on a plane actually comes from), and a lot of misplaced
vitriol. You'd think people would be grateful that airlines are offering
standard electric outlets on the plane at all.

[http://www.smbc-comics.com/index.php?db=comics&id=2035#c...](http://www.smbc-
comics.com/index.php?db=comics&id=2035#comic)

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jamesaguilar
Every pacific crossing I've been on in the last three years (all 747s) has had
AC to my seat. As far as I could tell all the seats had it. Large jets have
auxiliary engines that power the coffee makers, the ovens they use for cooking
in the plane, the lights, etc. You can normally see the exhaust for this
engine on the very tip of the tail.

Someone please correct me if I'm wrong, but I believe this article is defeated
by the actual fact of the matter that some planes do have AC to all the seats.

~~~
bonzoesc
The APU doesn't run in-flight (unless shit gets real and the engines are
disabled or need to be re-started). Everything electric pretty much runs off
the generators powered by the main engine (in-flight), or ground power (at the
gate).

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savrajsingh
Nobody needs 120v AC -- everyone on a plane is stepping it down and converting
it to dc! The solution here isn't 120vac to every seat -- it's coming up with
a new DC standard that plugs directly to our devices. The hard work of an
airplane based inverter is undone by our power bricks, and energy is lost to
heat in both. Lots of industry cooperation needed for this to happen, though.

~~~
samwillis
That industry standard DC supply is 5V from the USB port. Stick a USB port in
the arm of each seat and sell an adapter kit for common laptops and phones on-
board. Although i'm not sure a USB port will supply enough current for a
laptop.

~~~
w1nk
It won't. The solution is to force everyone to use the 'car' (or cigarette
lighter) variant of their chargers.

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varjag
Makes you wonder how they even manage to power those 500 Watt aircraft
headlight bulbs, tens of KW in avionics, coffee machines and kettles, ovens,
in-flight entertainment system per every seat etc etc

~~~
bradleyland
The reason none of those are a problem is pretty straight forward. Each of
those systems were designed to be powered by the aircraft's gen-sets, rather
than the other way around.

When designing an aircraft and its sub-systems, the engineer provides power
availability specifications. The people who make the headlights, avionics, and
coffee machines are all aware of the common power configurations and design
their equipment to work with that specification directly. I used to work on
light aircraft (private), which all used 24 VDC. Everything in the plane was
designed to run on 24 VDC. Commercial airliners likely have more than one
voltage specification available, but I'd imagine it's all DC.

Any time you have to convert voltage, you're going to lose some efficiency.
Inverters (DC to AC) have some particularly nasty characteristics that make
them undesirable on an aircraft. A DC voltage converter would work, but you
still introduce some degree of inefficiency. A good switching DC voltage
converter can exceed 90% efficiency, but so can an AC inverter. Neither
operates at that efficiency all the time though. I know that AC inverters
perform best when run at close to nominal load. At lower current levels,
efficiency drops. I don't know enough about DC converters to say.

Add to this the fact that inverters and converters are heavy, and you can
begin to understand why a power outlet at each seat is problematic.

~~~
sokoloff
I took 737 mini (two day) ground school about 10 years ago. I believe the
commercial jets' main electrical buses are 3-phase 110/200 volt 400Hz AC,
created by the starter-generators on the turbines. It's relatively
straightforward to tap across two of the terminals and get 110VAC, but it'll
be at 400Hz, meaning not everything designed for 110VAC/60Hz will be able to
handle it.

(Also, some older private aircraft, such as mine, use a 12VDC standard.)

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quellhorst
Since every laptop has a battery, you could do "rolling blackouts". The laptop
doesn't need power the whole flight. I know from going to conferences
sometimes just plugging in once in the middle of the day allowed me to make it
without being plugged in for the rest of the day.

~~~
orborde
You might have failed to consider conservation of energy here. The laptops use
a steady amount of energy whether plugged in or not (more or less), and if
they're unplugged for a while, then they'll draw more power during the time
they are plugged in as they recharge their batteries. In fact, if the
batteries are not perfectly efficient and thus don't provide the same energy
that was used to charge them, you're now using more energy per time by running
it through the batteries first.

Of course, doing the rolling blackouts might encourage less use of devices,
reducing power use.

~~~
quellhorst
Actually, in OS X my laptop will use less power when on battery power. The
clock speed goes down, the display dims, the hard drive goes to sleep faster,
the display adapter switches to the less powerful one.

~~~
orborde
That's a good point; it might well outweigh the battery inefficiency's
increase in power use.

------
twitter_v2
I think airlines could pre-wire all seats to be able to provide 110v supply if
purchased with your ticket or on-board as an add-on. Then have an intelligent
switcher, which only energizes the socket if they have been pre-purchased,
reducing the need to distribute live power around the plane.

Most people would really only want a few hours of charging. Then you could
have a capped number of active sockets per flight of say 50-100 seats.

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Yaggo
Interesting article, but a whopping quarter of kilowatt to every seat? Isn't
that a bit overkill? Assuming that typical laptop charger drinks 80 joules of
energy per second at most, and since laptops luckily have built-in energy
sources for couple of hours, the power output could be time-divided, eg. every
output is powered half of the time in 30 minute intervals. Assuming not
everyone needs power at all, two power outputs per three seats should be
enough. Suddenly we have reduced the needed peak power to 1/9th of the
original!

~~~
bonzoesc
The OEM DC adapters for Apple laptops prevent battery charging, because some
in-seat DC outlets don't provide that much power.

I've had trouble connecting a laptop that wants to charge to inverters before,
so this isn't without reason.

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joshwa
<http://www.seatguru.com/articles/in-seat_laptop_power.php>

For those advocating for a low-voltage DC power source, look at Empower--it's
installed on more than 40 airlines. 15V DC, 75W.

[http://en.wikipedia.org/wiki/EmPower_%28aircraft_power_adapt...](http://en.wikipedia.org/wiki/EmPower_%28aircraft_power_adapter%29)

------
Retric
For anyone who was wondering over a 12 hour flight the fuel cost would be
aproximatly:

(240 watt) * 12 hour * 500 people / 45 MJ (energy dencity per gallon) / .35
energy effecency = 330 gallons * 6.8 lb / gallion = ~2244 pounds. Granted this
is probably +/- 30% depending on the fuel, engine effecency, transmission
losses etc.

For comparison a 12 hour flight would burn ~ 43,000 gallons or 292,000 lb of
fuel.

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merraksh
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.

~~~
riobard
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...](http://img.hisupplier.com/var/userImages/old/selong/selong$71811154.jpg)

~~~
caf
That's similar to what Air Canada had on the seat back for the flight I took
SYD<->YVR (economy). My Australian laptop plug worked fine with it.

So it's definitely doable, and I'd be prepared to bet money that it runs off
the same APU that powers the entertainment system.

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hjalle
Even though the articles claims that its a worst case scenario, most people on
an airplane wouldn't use their 19", 8kg über-gaming laptop. Most people would
probably use more portable versions, ending up in a avarage effect that is
way, way below 220W.

------
riobard
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?)

~~~
gvb
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 oddball.

~~~
riobard
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?

~~~
gvb
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.

------
ars
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?

~~~
a-priori
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.

~~~
Groxx
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.

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fleitz
The difficulty is that everyone wants it yet no one wants to pay for it. (I'm
sure it works quite fine in first class)

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jbellis
So, why not cigarette adapter DC sockets?

~~~
oiujmngbvfgh
Because somebody would plug in something dangerous. Believe me there would be
some genius with a George Forman plugin grill or similar.

There are DC adapter plugins in aircraft - the idea is that they are only sold
for laptops and are expensive enough that few people use the.

~~~
fleitz
It would appear to me that most of the stupid stuff you could plug into a
cigarette lighter pales in comparison to the stupid stuff that you can plug
into a 120V AC. (eg. You're more likely to find a 120V AC plug on the
aforementioned George Foreman grill)

~~~
jewbacca
Perhaps this would be (or would be posed as) a security problem, too.

I am not familiar with any specific methods of causing a large explosion that
access to a 120V AC socket would allow, which not having access to one would
not, with what is currently allowed to passengers through airport security
[0]; But considering that producing a cigarette lighter or some nail polish
remover in the cabin are grounds to be tackled by an air marshal and
prosecuted, an electrical outlet is a hell of a lot of accessible power.

    
    
      [0] kindly disregard my past five minutes' search history, NSA sniffer

