Comment by jacquesm
8 hours ago
You can't convert between kWh and kW. 100 kWh = 6 MW for one minute... so there is plenty of power if the flight is short enough. They said the plane has 4 Tesla's worth of battery power, let's assume they are 80KWh packs then that's 320kWh that they could use for a short flight. That's a fair amount of juice, they definitely won't be flying long in a 25 ton aircraft without starting up the auxiliary motor but I have no doubt it will be able to get off the ground on $5 worth of electricity.
To be fair though it is more likely to be 50 kWh just for the take-off, so that's probably where their $5 figure came from (at $0.10 / kWh). For comparison: a single gallon of Jet-A = ~150MJ. 320 kWh = 320,000 W for one hour so 3600 * 320,000 = 1150MJ, or about 40 gallons and I suspect that these electric motors are quite efficient.
So it does pencil out, I think. Or maybe my pencil is broken and no doubt HN will correct my math.
The specific claim from the company is that the entire 27 min flight was done with $5 worth of power using an all electric power system with a power output exceeding one megawatt.
https://www.heartaerospace.com/newsroom/heart-aerospace-comp...
I still think it is an amazing achievement. I just don’t see how they were able to get it done on $5 worth of power, or they just quoted the wrong price.
I still don’t see what the problem is. The entire flight was likely just a few patterns and your earlier figure of 100 kWh (let’s assume they get their electricity for cheap) is already a serious amount of energy. It takes 100 kWh of energy to lift a 10.4ton object by about 3.2 km, so we’re obviously in the same ballpark for the maiden flight, and the rest is just drag. For drag, I’ll approximate the plane fuselage as two EVs that I drive. A 737 has a lower drag coefficient than my car, but a plane also has wings, so let’s say that evens out. Out of that 100 kWh, we probably only needed like a half for pure altitude, so we have 50 kWh for drag. An EV can sustain 200 km/h with about 60 kW of power, so let’s say 120 kW for the plane, and the flight was less than half an hour. Also, the plane got to convert all the potential energy back to kinetic energy on descent, so that was “free”.
Again, I believe that the napkin math checks out.