Energy crystals

Energy crystals are the backbone of many of the machines in the falling city. Discovered a few hundred years ago, it's only in recent times their full potential has been relized and usable. The crystal, when fed a charge, can hold it better than any other known material, far outclassing any batteries invented at the time. At first the biggest problem wasn't charging the crystals, but how you then get the charge back out. The only way they naturally let out a charge was when they reached capacity, and let it all out at once creating a small lightning strike. Not only is this very dangerous, its also unpractical since its hard to control something that comes in such force so suddenly. That's when "netting" was invented, making it so you could get a far more stable energy stream. Thanks to this invention people now had access to a battery that could hold a charge powerfulll enough to drive large electrical machines. The energy crystals were mined in large mines. It was never really known how the crystals formed, but a large deposit was found in a particularly stormy area near the mountains, so there were some theories stating that the lightning somehow helped with the forming of the crystals. They were always much closer to the surface than most other crystals too, which made the theory more plausable. When they were mined, the workers had to be careful to make sure the crystals weren't charged or accidentally being charged by the mining equipment. Therefore a net was usually installed at the same time the crystals were mined, powering some of the machines at the site. Usually it didn't give much power that had been naturally built up, but some accidents prove that it's still importnat to do in case.