I considered once, that when you place magnets with same poles close to each other, in unconfortable positions, you are storing energy. 

The idea is to pick up many tiny magnets, and place them in these positions in a container. Then you drip glue to them, holding them in place. This arranging and gluing is meant to be done by a machine.

Now the real issue, that I haven't worked completely, is releasing this energy in a controlled form. I though that you could melt the glue in a flame. You keep feeding the flame with this magnet bar, moving forward. The magnets would be set free, violently, and would collide with a rotating wheel, that would capture their motion.

There is a great change the overall efficiency would be really low.