[manigandham]

Cars are not airplanes. Electric cars are much heavier but weight isn't a big problem on the road. That's why they work, and they're still catching up to traditional range expectations.

With airplanes, you have to lift that weight using the same energy stored within. In that case, energy density is the absolute issue. Nothing else matters.

There's no magical solution, a high-school physics class will teach you how to calculate the potential energy requirement to lift up a certain amount of weight, and dividing by energy density and volume of current battery tech does not lead to a working jet any time soon.

[mcsb4]

> the potential energy requirement to lift up a certain amount of weight, and dividing by energy density and volume of current battery tech does not lead to a working jet any time soon.

E=mgh

E=(1kg * 9.81m/s^2 * 10.000m) / 3600s = 27.25Wh.

Tesla currently is at around 260Wh/kg thus roughly ten times the amount of potential energy needed to get to 10.000m altitude.

I'd assume that till 2030 we get to ~500Wh/kg by improving current technology. And maybe some quantum leap to 1500-2000Wh/kg within 20 years.

An A320 or A380 will likely always need a fuel cell but a 15 seater with 1000km range is only a question of time.

[variaga]

>Tesla currently is at around 260Wh/kg thus roughly ten times the amount of potential energy needed to get to 10.000m altitude.

That's the energy - assuming 100% efficient conversion of battery power to altitude - to lift _only_ the battery to altitude (and then immediately fall back down).

Actual engines are nowhere near that efficient and you'll presumably want to lift the rest of the airplane too. Then you have to keep using power to keep the plane aloft and land it safely.

Your hypothetical 2000Wh/kg future batteries still have a specific energy less than 1/5 that of aviation fuel (Jet A = 11950Wh / kg). A 15-seater electric with 1000km range based on those magic (7.5x better than state-of-the-art) batteries would instantly upgrade to a 5000km range if you tore out the batteries and replaced them with a gas tank of equal weight.

Batteries need a ~40x improvement in their specific energy density to make sense as an energy source for aircraft that depend on thrust for lift.

Tragically, physics doesn't care that battery powered planes would be cool.

[Dylan16807]

> Batteries need a ~40x improvement in their specific energy density to make sense as an energy source for aircraft that depend on thrust for lift.

I don't know how I can say "no" strongly enough.

If you only need 500km of range, it does not matter a single bit that jet fuel would increase your range from 1000km to 5000km. (Or 100km/180km/5000km respectively, if you want to talk about more contemporary batteries.)

Two things matter. Is the range good enough? How much does it cost? Jet fuel should not even be considered when answering the first question.

[Gibbon1]

A good way to think of this is as a venn diagram. If an electric plane has 1000km of range then it overlaps with jet aircraft. And probably also cars, buses, and trains. I think of friends that live in the middle of Nebraska. If you want to take a plane first you drive three hours to Omaha. If electric aircraft were cheap enough perhaps they would come out ahead flying to Denver instead.

[leoedin]

Potential energy is only one component of the power required by aircraft. If you want to actually go somewhere, you need speed, which means drag.

Drag increases the square of the velocity. That means going at 500knots (as an airliner does) uses a lot more power than going at the 150knots this seaplane might fly at.

You can calculate an approximate power requirement for the aircraft based on its glide ratio [1] or look at the power based on engine thrust [2]. In all cases you get figures in the 14-80MW range (engines don't tend to be full throttle during cruise)

That means your 260Wh/kg battery would need to weigh somewhere between 54 and 308 tonnes to sustain an hour of flight. That doesn't include takeoff, which is only a few minutes but might reach towards 200MW.

For reference, the 737 (low end power calculation) max takeoff weight is 62 tons and the 747-400 max takeoff weight is 397 tons. So in both cases you're looking at basically 30 minutes of useful cruise with current battery tech.

The range loss is additionally confounded by the fact that current aircraft lose fuel, so lose weight, during the flight. This accounts for a not-insignificant portion of the range.

[1]: http://large.stanford.edu/courses/2013/ph240/eller1/ [2]: https://aviation.stackexchange.com/questions/19569/how-many-...

So basically for electric passenger aircraft with even remotely comparable performance, we need a battery revolution. It definitely won't be by 2030.