Well the nut cases are out in full force I thought when I read someone on an online think tank state that we should put stationary bicycles in space craft and use the energy to charge the batteries or at least keep them topped off?

Whoooaa, I thought now we have plans to build our own human powered spacecraft? Yet as I got to think about it and followed the thread it actually makes sense in a way. There are numerous examples of human powered contraptions, from the Gossamer Albatross aircraft on down. There are LED circuit boards, lights and all sorts of low wattage devices available. Running on .5 watts and 4 watts.

Additionally astronauts must exercise anyway to stay in shape and prevent deterioration of their bodies, why waste that energy? So even if lets say an astronaut workout put out only 90 watts of power. If many of your subsystems only need 4 watts, that is worthy of mention and may as well not waste it. Never waste energy. Anyone can waste energy, efficiency is the key.

Regarding submarines, small future subs with small crews (1-3 man) cannot have nuclear power and the smaller the motor the better. Keeping batteries topped off is smart. I have a small tiny inverter for my car, which is 250 watts and it can run lots of things and small devices. You have to exercise anyway. Well I guess it really does make sense to use human energy even if only a little bit to add to the batteries of our spacecraft? Silly me, why didnt I think of that?