Originally Posted by
ecto1
Because in cars, the penalty for overweight is zero at constant speed, and very little at variable speed if you compare with a solution without generative braking*.
Drag (the main reason you need energy to commute) is proportional to frontal area, which is not affected by how many kgs of "energy storage" you move about (in cars). Weight is cancelled "for free" by the wheels.
But in planes, weight is balanced with lift, and lift needs wings, and wings produce drag (proportionally). So every new kg of weight need either more wings or more AOA, both producing drag proportionally. In addition, more wings are also more kgs, in a non-linear way (think of the base of the eiffel tower), which contributes to the problem.
*Model S has 540 kgs of batteries, more or less equivalent to 1.35 kgs of fuel, 1.83L of diesel and a range of 400km. You can have a x3 because batteries are very good expensive Li-IO, x2 of electric vs thermal motor at ideal conditions and then an additional x2 due to generative braking (plus you get a bonus of almost ridiculous acceleration if you install the motors and electronics you need for powerful regenerative braking). So, in ideal conditions, it carries the equivalent of 22L of diesel fuel. My car (same size and weight) uses 6.0 l of diesel each 100 km, pure thermal, so there you have it: 400km. In ideal conditions. But there are reports of much much shorter trips depleting the batteries, as it is no surprise for me.
I'm afraid neither of these arguments convinces me (yet). But I am willing to learn!
I think for the compassion to work you need to compare
- the weight of the fuel tank (and bits and pieces like fuel lines, exhaust system, etc) vs weight of the batteries
- the weight of the petrol or diesel vs the "weight" of a charged battery vs depleted battery
I appreciate that in a plane you need the engines to produce enough power to generate lift, which is not needed in a car. But I think that 400x figure is substantially too high.
Three years ago,
Forbes reported a study by scientists that Teslas (and EVs in general) produce substantially less pollution than ICE cars when all factors are taken into account.
(Incidentally, I photographed a
small electric plane at Farnborough Air Show a few years back.