My layperson's understanding of the furnaces producing silicon ingots is that they can't power down in-process; best case, they take weeks to bring back into service, while the worst case is serious damage to the equipment as the silicon inside recrystallizes.

I wonder if it's even possible to ramp down this single process without a similar hit to productivity as an uncontrolled power loss, never mind the other stages in the fab process. If not, fabs can consume tens of megawatts, so what does it cost to build and maintain the necessary backup generation capacity to weather a 30-minute outage?

One interesting example: USD $1.5 million for 10MW of flywheel-based backup capacity (http://ir.p10industries.com/news-releases/news-release-detai...) - but these will last ~15 seconds under full load.