[dnel]

I wonder if anyone has tried feeding a skyscraper's lighting rod into a sand battery and let it charge up from lightning alone, so much potential for free energy there.

[withinboredom]

It would never strike the lightning rod. The entire reason lightning strikes is due to a circuit between the clouds and ground. If you were to put a "battery" like this somewhere, then the resistance would cause the lightning to go where you don't want it.

[dmitrygr]

I am aware of no energy storage system capable of absorbing 250000 Wh in under a second

[murderfs]

You just need to use a sufficiently large storage system. One of the proposals of Project Plowshare was to use underground detonation of thermonuclear weapons as a geothermal energy sources.