# 100 KW alternator with drone

Did you phynk that this generator can function with 4 drones without camera?

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davenn

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russ_watters
Mentor
Did you phynk that this generator can function with 4 drones without camera?
Welcome to PF.

You're trying to use the propellers on the drone to spin the generator? No, it won't and it should be pretty clear why. So why don't you tell me your understanding of the energy transfer going on here.

Note, if you mean to try this for real, the drone's controller would not allow it because it won't like being rolled.

and without controller...

Borek
Mentor
and without controller...
Which part of

No, it won't
you didn't understand?

then maybe it will work with jet engines

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russ_watters
Mentor
then maybe it will work with jet engines
Sure, it will work if the jet engines have enough thrust. But it's a pretty roundabout way to generate power, since you could just attach the generator to the jet engine shaft....which is, in fact, how a large fraction of our electricity is generated.

Astronuc, jim mcnamara and Vanadium 50
fueling rotating jet motor

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russ_watters
Mentor
fueling rotating jet motor
It looks to me like you're trying to advance a design (albeit crudely) without first evaluating if the basic idea would be better or worse in efficiency/power production than existing designs. The practical issues of running a jet engine on a rotating structure aren't trivial, but if the setup won't improve efficiency/power production, why even bother looking at them?

The opening post implied that you could have a fundamental misunderstanding of conservation of energy as pertains to power production and I don't see any indication that you have even attempted to fix that.

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Astronuc, davenn and Averagesupernova
The illustration in post #1 says 100KW, and in post #5 the label says 1MW and the caption says 1GW. Here's an image of a 25MW turbine -- it's 11m long:

From https://www.siemens-energy.com/global/en/offerings/power-generation/gas-turbines/sgt-100.html:

A basic principle is that you can't get as much usable energy in wattage out of a generator or alternator as you have to input in kinetic energy to drive it. 1KW is about 1.3hp, but the generator isn't 100% efficient − it loses some of the energy to heat.

For example, a Kodiak SGB4000HX generator uses a Honda 8hp gasoline engine, and produces up to about 3600W.

A 100KW generator typically has a massive diesel engine − this one is rated at 125KW:

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berkeman
Here's a selection from the page that you referenced:

and from another page at the same same domain ##-## https://www.alibaba.com/product-detail/1500RPM-3-phase-Electric-Generator-Dynamo_60764682931.html

For further perspective, from another page there:

and here's a chart from further down that page, that lists the KTAA19-G6A at 560KW, 3.9m in length, and 4600kg:

I think that the 1MW header listing on the page that you referenced is an error ##-## a chart from further down on that page list models in the GSG2 series as ranging from 10KW to 200KW . . .

I've presented the foregoing illustrations for the sake of perspective regarding magnitudes ##=## the principle that a device that converts mechanical energy to electrical energy electrical requires input of more mechancanical energy than it produces as electrical energy output is true for all such devices ##-## that pesky Second Law of Thermodynamics again . . .

davenn
That's a nice little engine, and at about 396W each, you would need at least 4 of them to drive a 1KW alternator.

davenn
russ_watters
Mentor
@disclosurex you are being non-responsive. You are going to need to start making this thread more productive or it will be locked.

@russ_watters I think that it's apropos to let our friend the late member Jim Hardy have the last word on this (from Jim's post in a 2012 thread):

Rest assured the electrical power output from the alternator remains less than the mechanical power input to it.​
##-## Old Jim ##-##​

sophiecentaur, anorlunda, russ_watters and 3 others
Erratum: in post #9 (now too many hours old for me to edit), I inadvertently said "Here's an image of a 25MW turbine -- it's 11m long:" ##-## the "25MW" should have been "5.4MW to 5.7MW (depending on the application)".

sophiecentaur
Gold Member
Energy is like money. If you only earn 200 pounds a week then you cannot buy yourself a Ferrari. A drone engine can develop a very few  `watts of power. No one can expect it even to overcome the friction to turn a massive generator, let alone make it generate any measurable power.

sysprog
@disclosurex but can you tell us what is the point in trying to turn a generator in the first place?

an electrical generator is used to generate electricity from mechanical power , like rotating bodies like steam turbines , gas turbines , jet engines (just another gas turbine type) etc.
a drone motor is already using electricity to turn something so what's the point of using electricity to then turn a generator to get back electricity?

sysprog