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Old 18th Oct 2018, 06:49
  #9 (permalink)  
msbbarratt
 
Join Date: Apr 2008
Location: UK
Posts: 340
Originally Posted by ion_berkley View Post
Serious back of the envelope calculation here with a little real world data thrown in:

Islander with 2x 300HP engines = approx 400kW peak power output

Lets assume that the whole 2 min sector is flown at full power to be nice and pessimistic...so 13.3kWh per sector.

Now the complete battery assembly for the Tesla Model3 is pretty representative of the bleeding edge of EV battery technology and it comes in at 168Wh/Kg.
The total mass of the ~75kWh battery pack in a Model3 is approx 470 Kg. Empirically I can tell you that my Model3 charges from say 20% to 80% in about 40 minutes from a DC fast charger.

That passes the smell test for me, it seems very practical for this particularly odd air route.
There are some downsides. The battery is heavier than the equivalent fuel tank. The power cables are heavier than the equivalent fuel lines. The motors are heavier than the equivalent gas turbines, and can't sustain max power for as long either (efficiency in a motor conflicts with cooling it with air). The batteries don't get lighter as they discharge. Charging times are longer than refueling times (but maybe irrelevant given other operational factors).

A lot of these downsides go away or become irrelevant if you consider the electricity to be free (solar, wind, etc). One way or another we seem to be heading kinda in that direction, but it's a long way from free still.
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