I have found gas to be much more efficient than even thermonuclear cells up until getting water. The amount of heat to deal with doesn't seem to be worth it. I skipped nuclear altogether--I couldn't find a way to do it cheaper than gas.
For those of you like me who didn't understand the instructions given, click the how to play button in game, read through it, then just start filling in walls around circles, and it'll hit you.
The sad thing is, one of these anti-sweatshop movements got a sweatshop shutdown once. Those who didn't starve to death turned to crime. It's a difficult situation to deal with.
How about cartwheeling bears? Fish? Robots?