
Ask HN: If electricity was $1 per barrel could we see an electric jet engine? - mentos
Really curious to know if the economic incentive was there if the engineering could fill the demand for all commercial flights?
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petra
Not an expert, just the result of a Google search:Fuel has roughly 100x better
energy density than lithium-ion batteries(both in weight and in volume), and
batteries improve pretty slowly. Before take-off , the weight of fuel is
25-47% of the aircraft's weight.

And since the propulsive efficiency of a jet engine is relatively high(rough
search gives 45%-80%) an electric engine doesn't buy much here.

So this isn't really a question of money, but basic limits.

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flubert
You may also be interested in aluminum-air batteries, which have better than
10 times the specific energy density compared to lithium ion chemistries. The
downside is that they aren't rechargable, but that may not matter for flights
(they are recyclable though).

[https://en.wikipedia.org/wiki/Aluminium%E2%80%93air_battery](https://en.wikipedia.org/wiki/Aluminium%E2%80%93air_battery)

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staunch
> _" Given that practical lithium-ion batteries were capable of achieving
> energy-densities of 113Wh/kg in 1994, 202Wh/kg in 2004, and are now capable
> of approximately 300Wh/kg, it’s reasonable to assume that they will hit
> 400Wh/kg in the coming decade."_ -Elon Musk

[http://www.aviation.com/general-aviation/elon-musk-toying-
de...](http://www.aviation.com/general-aviation/elon-musk-toying-designs-
electric-jet/)

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sjs382
How much electricity is in a barrel?

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apryldelancey
That's exactly what I thought.

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claysmithr
1.21 gigawatts

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gusmd
Not sure If I understand your question, but my understanding is that we don't
yet have the means to store energy in such a dense manner as to able to power
a jet engine. Energy density of aircraft fuel is much higher than any battery
available.

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flubert
Here's a starting point for you in your investigations into electrical
propelled airplanes:

[https://www.nasa.gov/centers/armstrong/Features/leaptech.htm...](https://www.nasa.gov/centers/armstrong/Features/leaptech.html)

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ksherlock
With a piston-prop or turbo-prop airplane, the engine rotates the propeller so
it's easy enough to use an electric engine for that.

Jet engine thrust comes from the exhaust gas. How do you replace that with
electricity? compressing air (pulse jets)? generate plasma?

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chris_va
Not entirely. Modern jet turbines have ~12:1 bypass ratios, meaning the
exhaust is mostly just turning a fan, pushing 11 times the amount of air as
goes into combustion.

