[gvb]

Generators or alternators driven off the wheels are not free - the horse is now powering your lights as well as your wagon. The relatively high efficiency of LED lights helps a lot, but your horse still with thank you for using batteries.

The article discusses the higher efficiency of steel tires compared to rubber tires and the emphasis on light weight. Tens of Watts of generator load on the horse is probably more than the difference in steel vs. rubber tires.

[wiredfool]

If a guy that rides 1200km on a bike in 50 hours prefers a generator vs batteries based on drag vs weight I'd say that the generator + lights is pretty much solved technology.

[dripton]

They're not tens of watts. More like 3W. See http://www.nabendynamo.de/produkte/son_28_en.html

If it's not enough to bother a human cyclist, it's not enough to bother a horse.