Just after having discussed on electric vehicles, cars mostly, I run into this news about NASA starting testing its X-57 electric airplane prototype. For the time being the testing is focussing on the software to control power to the engines (propellers, as seen in the photo) snd the vibrations. The power, at the moment, is taken from high voltage feeds provided by a nearby socket. Not exactly what you need for making her flying.
The battery pack for the X-57 is still under work. For an airplane weight is a crucial factor and batteries are heavy.
Sure we have drones powered with batteries but notice that:
- the autonomy of a drone is measured in minutes, not in hours
- the weigh of the battery pack increases rapidly, more than the volume of the airplane
The final plane is expected to have two bigger propellers (48.1 kW each) used for take off (and landing where required) plus 12 smaller propellers used for cruise, each requiring 14.4 kW. The big question is how can you power these engines for a significant amount of time keeping the battery weight within a reasonable range?
The first battery that will be used in the prototype will consist of two battery packs, each delivering some 23kWh and weighting 180Kg (400 pounds). That is fine for testing but you sure cannot fly very far with that (actually, current air regulation will not even let you take off with that since you are required to have sufficient fuel for diverting to an alternate airport and still having fuel to spare, which basically implies a minimum of 1 hour worth of fuel, which is what you get in this X 57 configuration at take off).
However technology is progressing. Bosh has set the goal to their researchers to create a battery pack that can deliver 50 kWh with a weight of 190 Kg (basically more than doubling the battery packs performance of the X 57 initial set). In present electric cars a 50 kWh battery pack would weight around 500 Kg.
I am not confident that I will ever be able to board a commercial electric plane: a 747-8 requires the equivalent of 183 MW power, that translate into 2 GWh for a flight from Frankfurt to New York. Using the kind of battery pack planned for the X-57 that would lead to a weight of 8 million tons! A 747-8 has a MTOW (Maximum Take Off Weight) of 447.7 tons. No way to power that bird with batteries, not for any foreseeable future.