A Promethean Thought Experiment

[IggyZ]

Thank you Tarsier_79 the video was helpful.

[IggyZ]

Due to cash flow problems the Prometheus Generator web site is gone, but it is archived at
https://web.archive.org/web/20201101032855/http://www.prometheusturbine.info/prometheus_eccentric_direct_drive_or_geared_generator.html

I wonder if it would more efficient to build the Prometheus Generator without an axis (please see attached picture).
Virtual all the weight would be situated at the edge, so spinning it should be easier.
It seems to work for this revolving platform ->https://www.youtube.com/watch?v=1RXrlbHe66Q

I also wonder if it is possible to use carbon fibre for the rotor instead of steel. Carbon fibre is 5 times lighter than steel, so less energy is needed to spin the rotor. Is it possible?

[IggyZ]

I guess it is no surprise for you guys but I still find a bit hard to understand how much of the energy consumed by e.g. a gas turbine is lost due to eddy currents.

Question: Suppose a gas turbine needs 30.000kW of fuel in order to spin the rotor of a generator at 3.600 rpm. The generator has an efficiency of 90%. Please see fig. 1

How fast will the generator's rotor spin when there is no stator and therefor there are no eddy currents? Please see fig. 2.

My guess: The energy input is the same (30.000 kW) and the generator's efficiency is 90%. So the rotor will spin at 3.600 rpm + 360 rpm = 3.960 rpm. Is this correct?