

How many gallons of gasoline would it take to charge an iPhone? - srveit
http://www.exxonmobilperspectives.com/2011/12/14/how-many-gallons-of-gasoline-would-it-take-to-charge-an-iphone/

======
jbooth
"I bet they're going to talk about the total amount of energy in a gallon of
gas, without mentioning anything about how that's translated to electrity, and
how much of the energy is lost in the process"

 _click_

"Yup."

~~~
Tichy
Well how much energy is lost? 50%? 80%? Assuming it is 50%, then the answer
would be you could charge the iPhone for 10 years instead of 20 years. Still
interesting.

~~~
jbooth
Overwhelmingly most of it. Most generators run on diesel and not gasoline, and
I gave up trying to figure gallons per KwH after a few minutes of googling.
But you're talking about converting heat to mechanical energy with a ton of
lossage, and then mechanical to electricity with a ton more lossage.

The original article isn't interesting. You may as well say that your mouse
has enough energy to recharge your iphone for 10 years, provided we found a
way to convert the mass into energy.

~~~
Tichy
But the way to turn fuel into energy already exists, even if it is
inefficient. OK, you could also burn my mouse, but it would probably be even
less efficient...

I still think it makes a strong point for telecommuting.

------
martinkallstrom
Key takeaway: Vehicles powered by petroleum fuels are incredibly power
consuming. Driving a car a single hour on a highway consumes as much energy as
an iPhone does in about 46 years.

[http://www.wolframalpha.com/input/?i=1+hour+*+100km%2Fh+%2F+...](http://www.wolframalpha.com/input/?i=1+hour+*+100km%2Fh+%2F+27+mpg+*+20+years%2Fgallon)

~~~
jessriedel
_All_ vehicles are incredibly power consuming (compared to iPods) and there
are basic limits to improving this. If you want a vehicle that is large enough
to hold a human and can push air out of the way at 60 mph, it's going to take
a lot of energy. Driving habits, aerodynamics, and size can change this usage
by a factor of order unity, but they can't do it by orders of magnitude. Thus,
alternative energy sources _must_ approach the energy density of petroleum if
they are to be competitive.

~~~
Aqua_Geek
> If you want a vehicle that is large enough to hold a human and can push air
> out of the way at 60 mph

But do we really need to go 60 mph? Vehicles seem to be optimized for less-
common use cases (e.g. 5 people in the car traveling 60 mph) instead of their
more common uses (e.g. one person commuting at 30-40 mph). I, for one, would
like to see smaller vehicles - NOT SmartCars and the like but an actual
rethinking of the car that would be optimized for the single person commute.

~~~
guptaneil
I suppose this depends on where you live, but going above 60mph is normal
usage for me. In fact, a minimum speed limit of 45mph on freeways is fairly
common (unless you can't due to traffic, of course).

~~~
GFischer
On the other hand, I've never been able to drive above 45 mph on my normal
commute, I'm only able to do so when I go on holidays.

Some cities are just not planned for cars (European cities like Vienna for
example, where you cannot enter the downtown, or some South American cities
like Montevideo).

I used to have a Maruti car and it was plenty for 99% of the time, and I'd buy
a low-range electric/hydrogen/whatever car if it was cheap and offered me a
better mileage equivalent.

------
grecy
They neglected to mention that even modern internal combustion engines can
only capture about 18%-20% of that energy.[1]

[1][http://en.wikipedia.org/wiki/Internal_combustion_engine#Ener...](http://en.wikipedia.org/wiki/Internal_combustion_engine#Energy_efficiency)

~~~
teamonkey
Oil power stations are around 33% efficient[1]. Electric drives have up to 80%
efficiency[2].

Given those rough figures, even when powered by oil stations battery-powered
cars can theoretically be more efficient at using oil than a car with an ICE.

[1][http://en.wikipedia.org/wiki/Oil_power_plant#Heat_into_mecha...](http://en.wikipedia.org/wiki/Oil_power_plant#Heat_into_mechanical_energy)

[2] <http://en.wikipedia.org/wiki/Electric_car#Energy_efficiency>

~~~
gvb
You also need to account for the transmission line efficiency[1], the charger
efficiency (typically 90-95%), and battery efficiency[2] (80-90%).

If we assume the transmission lines are 98% efficient, the charger is 95%
efficient and the battery is 90% efficient, the motor controller is 95%
efficient, and the motor is 95% efficient (drive efficiency of 90% instead of
80% of the parent quote)...

0.33 * 0.98 * 0.95 * 0.90 * 0.95 * 0.95 = 25% efficient, with efficiency
numbers somewhere between "best case" and "optimistic". ICE in an _efficient
car_ is competitive with that. A hybrid will beat that.

[0] How Stuff Works estimate: [http://auto.howstuffworks.com/fuel-
efficiency/alternative-fu...](http://auto.howstuffworks.com/fuel-
efficiency/alternative-fuels/fuel-cell4.htm)

[1] Nobody knows for sure what the transmission line (including step-up and
step-down transformers) is in actual practice. Note the Wikipedia article says
"efficiency" several times, but never pins an estimate onto it:
<http://en.wikipedia.org/wiki/Electric_power_transmission>

[2] <http://en.wikipedia.org/wiki/Lithium-ion_battery>

------
bunderbunder
Well if we're going to consult the contrived statistics department, why not go
for broke?

If you want to get _really_ thorough about extracting _all_ of the energy in a
gallon of gasoline, you could power a US household for 7.5 million years.

------
notaddicted
Since they don't really follow through on the original question: the article
implies it will take ~137 micro gallons to charge an iphone. The size of the
fuel would be slightly inferior to an M&M [1].

[1]
[http://www.wolframalpha.com/input/?i=1+%2F+20+%2F+365+gallon...](http://www.wolframalpha.com/input/?i=1+%2F+20+%2F+365+gallons)

------
frankus
Petroleum is really frickin' energy-dense (leaving aside the fact that unless
you're heating something only a small fraction can be turned into useful
work).

A mid-range home EV charger peaks out at about 20kW.

By contrast, the energy flux of a gas pump is around 20MW.

~~~
bhousel
A mid-range home EV charger (like the GE WattStation), is spec'ed for 30A at
240V, which is 7.2kW, not 20kW.

You might be confused because a typical battery in an EV is around 20+kW _h_ ,
which is why it takes a few hours for the wall charger to charge it!

For comparison, a 20kW load would draw 83A at 240V. A smallish pole mounted
utility transformer may supply 20kW.

Of course, none of it detracts from your point that petroleum is very energy
dense :)

~~~
frankus
Good point. Most homes around here are wired with 200A, 240V power, so a 20kW
charger would eat up about half of that.

So a 7.2kW charger is about 2500 times slower than a fast gas pump.

Even slow gas pump (say 10MW), used with a conventional engine (say 20%
efficient), compared with a state-of-the-art fast charger (say 200kW) would
still be ten times as fast in a miles-per-hour contest.

EVs make up for this somewhat by being able to charge anywhere that has a
decent supply of electricity for hours at a time, but it still shows you what
they're up against.

------
rdtsc
> And energy density is one of the key factors behind the reliability

Density can actually be per-mass or per-volume. Per mass hydrogen is pretty
attractive.

<http://en.wikipedia.org/wiki/Energy_density>

Now we just need an efficient, safe and clean way to turn gasoline into
electricity and problem solved ;-) right ?

~~~
henrikschroder
> Per mass hydrogen is pretty attractive.

A bucket of gasoline contains more hydrogen than a bucket of liquid hydrogen,
and you can actually keep the gasoline in the bucket.

Hydrogen is awesome as an energy source if you look at the combustion formula
and the per-mass energy density. In all other aspects it's a horrible,
horrible, horrible fuel. :-)

~~~
rdtsc
I understand that. Not saying we should use it. Only highlighting that for
some domains a different type of energy density can be used.

------
wickedchicken
Gas has an incredible amount of energy density. You can do a fun calculation
as follows:

If you believe this calculator, it takes 2419kJ to go 20km while cycling.
(<http://www.tribology-abc.com/calculators/cycling.htm>)

A gallon of gas contains about 114,000BTU
(<http://en.wikipedia.org/wiki/Gasoline_gallon_equivalent>). Note that the
Exxon diagram is 'per fillup' not per gallon.

So...
[http://www.wolframalpha.com/input/?i=%281%2F%28%282419kJ%2F2...](http://www.wolframalpha.com/input/?i=%281%2F%28%282419kJ%2F20km%29%2F%28114000BTU+in+kJ%29%29%29)
yields 617MPG while biking.

It's approximate, but good to know that biking is roughly an order of
magnitude more efficient than cars.

~~~
iliis
Yes, bicycles are quite efficient. Not only compared to cars, but
interestingly also to animals. While a normal human is quite bad at converting
food into motion, the system bicycle+human is comparable to some of the most
efficient animals. Now, if they had bicycles as well...

[Source: Dad, hobby-bicyclist/mechanic]

------
waivej
Calculating the energy density of gasoline versus battery is misleading unless
you also include the engine, fuel system, radiator, battery, etc. Sure my
truck can hold 120pounds of gasoline but the energy density includes an 800 lb
"gasoline to transmission" adapter.

Once cars have "iPhone" batteries, gasoline cars will go away. A Nissan Leaf
is rated for 3x the energy efficiency of a comparable car. I doubt people will
mind giving up gasoline fumes and filling stations. (33khw in gallon of
gasoline versus 3.5khw/mile in a Leaf.)

I can pedal a bike at 200W for an hour. Isn't this enough to charge 80
iPhones? How is this a useful comparison?

------
drcube
Iphones run on oil too (and coal, gas, nuclear energy, and various renewable
fuels). It's just that giant synchronous generators are more efficient than a
million internal combustion engines, so they burn the oil at a central
location and pipe it to you over wires in the form of electricity.

It's like asking "how much gas does it take to run the LCD screen on my car
stereo?", comparing it to how much electricity a mansion uses and concluding
that gas is the old fuddy duddy stick in the mud holding back progress.

~~~
herge
How many times more efficient is a gas power plant than the average use of a
car?

~~~
drcube
Wikipedia says: "Even when aided with turbochargers and stock efficiency aids,
most engines retain an average efficiency of about 18%-20%."

<http://en.wikipedia.org/wiki/IC_engine>

Wikipedia again: "Typical thermal efficiency for electrical generators in the
industry is around 33% for coal and oil-fired plants, and up to 50% for
combined-cycle gas-fired plants."

<http://en.wikipedia.org/wiki/Fossil_fuel_power_plant>

~~~
drcube
That neglects to mention the inefficiency in distributing gasoline via gas-
powered vehicles to hundreds of millions of drivers.

------
baggachipz
That's odd, they neglect to mention the true cost of gasoline; both in
subsidies used to keep it cheap at the pump, as well as the environmental cost
associated with cleaning up their profit-generating mess.

ETA: Point out an oil company's dishonesty, get downvoted. Only on HN.

~~~
earnubs
US pump prices are low because you don't tax it like other countries, that's
not a subsidy.

Environmental cost? I'll grant you that accidents involving rigs and shipping
are spectacular and locally devastating when they happen, but what about the
pros of a cheap and relatively easy fuel, it has saved millions of lives.

To give some balance what about farming? Farming has devastated the
environment on a global scale. It's subsidised to the teeth too...

"Profit generating mess" is hyperbole, but you can have it since I went for
whataboutery.

~~~
baggachipz
It would be a fair trade, but your whataboutery didn't include the true
subsidies (<http://en.wikipedia.org/wiki/Energy_subsidies>) as well as the
much larger environmental cost: CO2 production from burning fossil fuels. It's
going to cost a lot to clean that up, and I sincerely doubt that ExxonMobil or
their brethren are going to foot that bill.

~~~
earnubs
I read the wikipedia link, it seemed inconclusive. Fossil fuel subsides are
less than that of renewables (unless I am reading the article wrong) and
that's a 1-1 comparison, fossil fuel must utterly dwarf renewable in terms of
revenue.

I'm not saying that big (or small) oil is innocent by any means, personally I
believe the problem lies with the political side of it, but certainly I don't
think the basics of oil extraction and delivery deserve the rep they currently
have.

And on farming, how much carbon do you think farmers released into the
atmosphere burning the trees and scrubs that stood in the way of the farmland?
Not to mention the damage done to the hydrosphere?

You might like this by the way, if you haven't already read it:
<http://harpers.org/archive/2004/02/0079915>

~~~
baggachipz
The fact that fossil fuels get _any_ subsidy is obnoxious. They're the
entrenched necessary evil that needs to be made obsolete. So of course
alternative fuels are subsidized, and should be until they displace fossil
fuels.

Farming is most certainly a problem, and I fully understand and agree with the
Harper's article -- but it is a straw man in this discussion. I merely pointed
out that an article authored by an oil company neglected to include the true
cost of their product vs. competitors. And, unless the true cost is realized
(most likely in the form of taxes on carbon emissions), fossil fuels will
remain the most viable source of energy. It doesn't mean I/we have to accept
it, there is a better way.

------
sgentle
My god, that website has the most amazingly civil and constructive comments
I've ever seen on a blog post. I wonder if they're moderated, or just getting
traffic from a very narrow section of people who write well.

------
barrkel
I guessed 5 ml; but I was off by an order of magnitude, it's more like 0.5 ml.

------
Adaptive
We don't mine batteries from the ground.

Misleading industry puff piece. The question isn't how much _would it_ take
but rather how much _does_ it take.

Petrochemical / coal, fossil fuels in general are _already_ generating our
power at increasing cost in terms of the raw materials, processing (more
difficult processing of oil sands, frakking, etc.)

Give me modern nuclear combined with alternatives like increasingly cheap
solar.

Of course, at this moment the US government is mulling tariffs on chinese
solar panels since they are too cheap. Evidently the free market is awesome
except when it results in cheap products that threaten an established
industry.

~~~
earnubs
"We don't mine batteries from the ground"

Er...

~~~
Adaptive
Maybe rephrase your question to be clearer, but I'm assuming you mean mining
the chemical components of batteries. Not what I was referring to.

I'm talking about the fundamental difference between a battery of any variety
(chemical, flywheel, etc.) and petrochemical energy _sources_.

The article compares energy density of gasoline and other energy sources with
"electric". It's a poor comparison. These are different categories. One is an
energy source which is also a storage medium (single use), the other is a pure
storage medium.

~~~
jules
Actually, lithium is a very depletable resource just like oil and coal are.
Not in the sense that we use it up for energy, but in the sense that if you
want to run all cars on lithium batteries there simply isn't enough easily
mine-able lithium in the world. In this sense it is valid to say that we mine
batteries. The same story goes for most solar panels.

Comparing the energy density of gasoline with the energy density of a charged
battery is obviously also valid.

------
billpatrianakos
Wow. Let's try to convince people why it's alright for us to use a fuel we
know to destroy the environment in countless ways and imply that it's someone
else's job to advance alternative, less harmful alternatives to gasoline.

I think using gasoline is fine for now. I'm not a hard line environmentalist
or anything. At the same time I don't get how these companies can justify this
kind of propaganda. Yes, it is their duty to their investors to make as much
money as possible but it's no secret that one day we won't have enough oil to
go around. I don't get it, logic dictates that you'd sell gasoline for the
time being but at the same time you'd be pumping huge amounts of money into
research and development of alternative technologies. The oil company that
brings the best alternative to market first has the most to gain in the long
term. Articles like this are so blatantly disingenuous and short sighted it
makes me want to puke.

------
recoiledsnake
Energy density of the batteries has been steadily increasing. There's no
reason to believe that it will hit a way, so this argument is misleading in
that it assumes the density will be constant.

------
revelation
This is a facepalm on so many levels:

\- oil company predicts oil will still be used in (a lot of) years

\- oil company realizes that a) there is an incredible amount of energy in oil
and b) the most efficient machines available use only small percentages of
that energy

Dumping the remaining energy as heat in a climate-change world. Great!

~~~
jessriedel
> Dumping the remaining energy as heat in a climate-change world. Great!

Obviously, the contribution to global temperature increases due to the literal
heat dissipation of engines is extremely, extremely negligible. Petroleum can
cause changes to global temperatures through the release of carbon, which
changes the Earth's insulation, but no through actual heat.

