Anyone tried using a motor-generator set eg for mppt ?
Obviously it was an old technology, which was not as efficient and
had moving parts etc. But modern motors and generators are much better now.
CSIRO put forward a "Aurora" motor, mainly forgotten, which was very efficient.

The idea is to use a DC motor driving a generator at roughly constant speed. The field
windings can be electronically controlled such that the panel output is loaded and
used at the useful point.

Probably not cost effective, easier just to use some excess panel capacity.  

In some DC3 aircraft the DC HT supply for all the valve equipment was a type of M-G set that would be better described as a motor-transformer.
It had a single armature with two sets of windings on the armature and a commutator at each end. 28V in one end and 300V out the other.

The main reason for it was lighter weight but it was also more efficient than separate motor and generator.

Are you thinking using a DC motor to drive a generator, which then powers the motor?

If so, then stop right now, it cant work, and any youtube video showing it working is faked. It falls into the category perpetual motion, or over unity, and has wasted more hour is peoples sheds than anything else.

Simple rule, you need to put energy in to get energy out, and its always less.

  Gizmo said  

Are you thinking using a DC motor to drive a generator, which then powers the motor?

I hate to put words in somebody else's mouth but to save time....

Maximum Power Point Tracking (MPPT) is an innovative solar charging technique that helps maximize the efficiency of portable solar panels.

He is talking about using a mostly mechanical method to accomplish this instead of doing it entirely with electronics.   He isn't talking about getting more power than he puts in.
Edited 2025-06-03 14:25 by EDNEDN

Definitely NOT about perpetual motion.

A motor/generator set was a method of transforming voltage/current supplies without a traditional transformer and AC. Eg 110v 20 amp motor would drive a 220v generator giving theoretically 10 amp but in reality somewhat less owing to losses.

The motor and generator typically used electromagnets to create the required magnetic fields. By varying the magnet current the voltage/current/speed characteristics of the motor or generator can be varied. So it should be possible to match the electrical load set by the motor to match the output of the solar panel. Then the generator could be tweaked so the mechanical load was suitable to maintain the speed.

The losses through inefficiency would probably outweigh any advantage. But it could be  very robust.

[Remember it was the pre-electronics era...efficiency wasn't a concern. A Melbourne tram was controlled by passing the current through a huge carbon block aka variable resistor, varied by the driver altering the physical pressure on the block. And they say it wasn't sophisticated     ]

I think you answered your own question Zeitfest, just not cost effective.

Having a motor generator pair you've increased the amount of copper in the system compared to a single inductor in a buck converter. You'll introduce a lot of weight from the shaft and motors that would be expensive to ship as well.

It still needs electronic control of the field coils for MPPT so still requires a software solution. Downside now you've got bearings that would wear out as well.

A modern high quality electronic solution is going to be cheaper to implement and lower maintenace due to lack of wear parts.