On Monday, February 17, 2020 at 8:48:19 PM UTC-8, Ralph Barone wrote:
On Mon, 17 Feb 2020 06:17:01 -0800 (PST), Tom Kunich
wrote:

I am quite aware that friction losses from a hub generator are minor but
that isn't so for a sidewall generator because it has to be pressed very
tightly against the sidewall to keep it was slipping. So it takes
probably two to three times the frictional losses as the light output.

Er... Tommy, frictional losses in mechanical devices is: " Friction
occurs when two bodies are in contact with each other and have
relative motion".

However you say " pressed very ti...

You seem to have a misunderstanding of frictional losses. The sidewall generator doesn't move relative to the tire but the tire and innertube are displaced because of the pressure of the generator to keep from slipping. There is relative motion but not any sort of slipping or rubbing.

You can also get frictional losses electro-magnetically such as in a hub generator where the magnetic field resists the coils moving through them and turning motion through the field into electrical power.