Dynamo

I had a dynamo on my bike as a kid, just like the one in the picture below. These have a little electric motor, driven in reverse by the friction with the tyre in order to generate current.

The negatives were the incredible momentum-slowing friction and the wires all over the bike. Plus the feeble little light it helped generate was velocity dependent; if you stopped moving you stopped being visible.

Today’s dynamos are a tad more efficient, create less friction, and help pump out much more light thanks to high efficiency LEDs.

Some dynamo driven systems even include batteries or capacitors so that there is no velocity dependence.

The negatives?

They are hanging off, or around, or in hub of the wheels because this is the most useful rotating device for generating electricity. Hence wires are still present.

They tend to be bulky and heavy in one form or another. This worries some and not others that ride big ugly hybrids or that live in flat countries.

They usually cost a bomb and are eminently thievable, especially when built into a front wheel hub.

And they simply aren’t as bright as battery driven systems. Plenty of lux but bugger all lumens – that’s the give-away. They are useful for seeing but not for being seen.

All up, it’s a non-starter for me.