I don’t know how much electricity they’d generate or how efficient they’d be viz a viz inputs versus outputs. But I’ve always thought it’d be cool if we had giant turbines powered simply by brawn, sort of like that mill-thingy that made Conan so strong in the first Conan movie. I’m not talking slave labor, but if we could work out the technological kinks we could hire people at minimum wage to push a giant wheel around and around generating electricity much the same way dams do. Teenagers who couldn’t find other work could do it. They’d get in shape, stay out of trouble, and earn a few bucks. Unemployed people would always have at least one fall back job available to them. It would help with health care costs as it would provide ample exercise. There would be no damage to the environment and pretty much the only foot print would be, well, footprints. People who worked nights or in bad weather would be paid a bit extra. PIRG hippy volunteers could do it too, in their spare time. Every human turbine spin is one less gallon of oil pumped from the ground.
Also, for criminals who commit petty crimes — particularly among the young and obese — this could be a community service option similar to picking up litter on the side of the roads. Lots of people would choose this kind of hard labor over, say, 30 days in jail.
I don’t think non-engineers can truly appreciate how much email I’m going to get from engineers about this idea.