This is a very, involving idea.

Imagine that you have a long strip, made out of square blocks inside individual plastic pouchs. It looks rather like condom packaging, for lack of better object to compare. The blocks are of a magnetic material, but they are not magnetized yet.

Now do you remember those old cassette tapes? This invention is like a large cassette tape, but instead of the magnetic tape, we have the strip of magnets. In the middle of the tape there are two machines, the top one magnetizes a passing block. The bottom one heats it up beyond Curie temperature.

If you roll the reels to one direction, the blocks would become magnets, and the strip would be wound around the reel. It would become progressively hard to wound due to the magnets interaction. This would be storing energy.

If you let the reel loose, it should with some luck rotate the other side. As they are passing the magnets would be destroyed. You would get the energy from the motion of a shaft attached in either one of the reels.

Now, you can either use an ON/OFF switch to the heating element, and wait it to cool, or go even pro with Idea #011 and use a variable heat coefficient material.