Alternative electricity generation for aircraft

[renewable]

Hello,

so today i was thinking about alternative ways to provide electricity to a motor in a fixed wing aircraft.
Ideas:
1. Use thermoelectrics. They would generate the most voltage around the engine, so maybe they would only be placed here, or all over the aircraft. Advantage: unlike solar power, thermoelectics generate electrical energy from a temperature gradient. The outside of an airplane is often cold at high altitudes, and the motor is hot. They are not dependent on sunlight energy.
2. Motor-generator cycle. The back of the driver shaft from the propulsion motor would be connected to a generator, which would produce energy to charge capacitors that would then power the motor. I'm not sure that weight of this generator can be justified by it's energy production.
A demonstration of idea 2 can be found here

So what do you think? Are these ideas feasible?

Also 1st post on this forum :) hello everyone. not sure if this should be in electrical engineering.

 

[Simon Bridge]

Welcome to PF;
Is the idea that the engine itself should be electric rather than petroleum powered?
(That seems to be the case from the example video and the second option.)

If so then what you have proposed both have serious limitations due to the law of conservation of energy. There are a lot of hoax and devices on YouTube - do not believe everything you see.

 

[renewable]

Thanks for the reply Simon. I didnt make myself clear. Yes the engine would be electric. The objective of my OP was not to suggest a new type of electric motor, just new ways of powering one.

Wow I worded option 2 terribly! My intention isn't to use the motor-generator as the only source of electricity: that breaks the law of the coservation of energy. It would be used with other methods of producing electric energy such as option 1 or solar power.

 

[Simon Bridge]

Right - that's why I amended my point to "limitations".

In #2, the generator takes it's power from the engine and the engine takes it's power from the batteries (say) ... so all it does is move energy in a lossy way from the batteries to the capacitors ... i.e. it's just another drain on the batteries in addition to the engine.

In #1, the idea seems to be to recover waste heat - which is more feasable.
Clearly the engine will not generate enough heat to run itself this way, but you could eek out a little bit.
I think this is the one where the weight may be prohibitive.

The big problem with electric aircraft is the energy stored vs storage weight.

 

[renewable]

Okay, maybe #2 can't work. I do believe that thermoelectrics could help electric aircraft, especially if they could be used in the structure of the motor housing - not sure if this is possible though. Thanks Simon.

 

[Simon Bridge]

Yeah - if you imagine a motor in the nose turning a prop, you could plate the outside of the motor with TEGs then the skin of the aircraft goes on top of that. After that is is a matter of figuring the thermal gradient and TEG efficiency vs the extra weight.

For that matter you could increase the range by plating the outer hull with solar cells too couldn't you?
Maybe beam energy to aircraft (microwaves?)

The devil is in the details.

BTW: notice that if you take the example video at face value, all that's happened is that the capacitor bank has been charged from the battery bank via a lossy process.