I had an old Union sidewall tire driven generator on my errand bike. For a mile and a half to the grocery store, it was ok. But if using every night, I would look for something better. I have never seen a Velological, but they look interesting. Half the wattage of a dynohub, and expensive, but I suspect the drag is less than on a tire mounted sidewall. Someone told me that the Velological is noisy, but I have never seen one so I can't comment on that.
VELOGICAL RIM-DYNAMO - Standard Bicycle Dynamo - Smooth Running, Lightweight, Efficient

There are you tube videos that I never watched, but if I was thinking about buying it I would do a lot more research. Here I am only pointing out that they exist.