Scudrunners

I don't understand how driving a generator with a  turbine to
produce electricity to power electric motors to drive the propellers,
converting mechanical energy into electrical energy with the associated losses
then powering the electric motors, more losses, and finally turning the props,
plus the weight of the batteries and fuel for the turbine, can be better than
the direct route turbine-propeller

[quote author=Chuck Ellsworth link=topic=9635.msg27542#msg27542 date=1554320467]
[quote]  I don't know much but I tell you something I do know.
Dyson Dustbusters don't work at 10,000 feet.[/quote]

Use your hand.
[/quote]

Not with coffee in the other hand ! It all about safety

[quote author=vanNostrum link=topic=9635.msg27544#msg27544 date=1554349601]
I don't understand how driving a generator with a  turbine to
produce electricity to power electric motors to drive the propellers,
converting mechanical energy into electrical energy with the associated losses
then powering the electric motors, more losses, and finally turning the props,
plus the weight of the batteries and fuel for the turbine, can be better than
the direct route turbine-propeller
[/quote]

Electric motors are much more efficient at creating torque than an internal combustion engine, I'm not sure if a large electric fan jet can be as efficient or even create as much thrust as a fuel burning unit.

Electric powered R/C planes are amazing but also much lighter than a real plane and fly over the airport so they can typically glide back once the fan stops. The crash rate is pretty bad too.

The bigger problem currently is the time you can run off batteries, they don't have enough energy storage capacity for much range yet.

I believe a turbine powered generator is more efficient at creating electricity than thrust but as you point out there will be losses using that potential energy to create thrust.

Lack of range was why hybrid cars were more common than battery only units for a couple of years before the Tesla factory got going. I am not sure if there are more hybrids or pure battery fueled electric cars now. The people driving pure electrics are willing to live with a shorter range. Charging stations are not too difficult to find now in large cities, though sometimes they seem to be out of order. I think you can charge slower from the nearest regular recepticle but they don't need to make it to a particular charging place and can just pull over.

I was extremely excited by the development of both pure battery light singles and the Pipistrel Panthera hybrid planes. They are unfortunately a little way off yet. I think it is important to develope them. Not because it will fix the weather just because it leads to better things.

[quote author=vanNostrum link=topic=9635.msg27544#msg27544 date=1554349601]
I don't understand how driving a generator with a  turbine to
produce electricity to power electric motors to drive the propellers,
[/quote]
That probably won't be particularly efficient but in the case of a hybrid, you could have generators that are supplemented by batteries.  The idea is that the generators slow the depletion rate of the batteries on takeoff and climb, recharge as required in cruise, and shut off entirely when not needed.  In doing so, you should be able to get your very best specific fuel consumption out of the turbine by running it only on its design point.  I don't know if the other inefficiencies introduced by heat loss at various stages of the system would negate the advantages but it's a thought.

I'm all for risky innovation as long as I don't have to pay for it if I don't want to.

A gallon of jet fuel [6.8 lb] stores close to 40 KWH of energy
Energy density of Lithium batteries is about 14lb per KWH
Even with the turbine running at 35-40% efficiency ,around 250 lb of
batteries are needed to produce the same amount of energy
In an all electric airplane, how would the  pressurization system work?
Air conditioning, heat, deicing?

I think we have long ways to go before a practical electric airplane
is commercially viable

Resistive heat requires rather large amounts of energy. Much more than motors. I have wondered how that affects the range of Teslas.

The use of heat/ac in e-cars can reduce range by 40%
according to a study done by AAA
Cold temperatures are another factor to consider in an e-airplane
as anything bellow ideal temperature,around 18C drops the range
rapidly
An e-car  50%  at -20

I've always wondered how quickly batteries can be re charged.
In the case of a pure battery powered vehicle, that is used in a commercial situation time is money and waiting for the batteries to charge is $$.
Could batteries that are already charged be swapped out at airports instead of taking on fuel?
Also cold affects the life of and charge a battery holds, will it be efficient/ effective in the Canadian winter?

Currently batteries required are too huge for the perfect temperatures. Swapping out a giant battery is a bigger job than re-fueling. Compare this electric forklift with one that would typically run off a 30lb propane cylinder.



Even I wouldn't have made this next video claiming, "Electric planes are already in production and don't pollute." Then later admitting motors need to be more efficient and batteries lighter.

Where is the electricity coming from. In theory you can use solar and wind power but I am pretty sure they are just charging off the existing public generation system. It's better that thirty years ago but barely.

Nevada has clean electricity but there are a few places where running 100LL is probably a clean alternative to their electric grid.

Anyway, hope you are as amused as me by this.



I'm still optimistic one day it will eventually happen, but less optimistic I'll be getting type checked on one. Then flying it on any long trips.