The US grid is ready for 100% renewables, says DOE

The claim being made feels very much like click bait. It would be truly amazing if that were the case, but, think about it: a technical reason for maintaining a mix of energy sources, some from variable sources like wind and solar, others from stable sources, e.g. natural gas, hydro, coal, etc, is that you need to maintain both voltage and frequency. An example: push a 1000 amps of juice from a spinning windmill against a 100 amp generator - which, itself, determines voltage and frequency, and guess what happens.. If you install a field of variable energy sources, there's a limit to the capacity of that field when plugged into a stationary source. When I was involved in wind energy many years ago, that limit was something like 20%. I do not doubt that limit has risen over the years, but 100%? Sure, recent funding is allowing DOE to create a demonstration, one I expect will, in fact, establish new limits. I doubt we are ready for the claim made here.