First, some background on CAISO (California Independent System Operator) and the Duck Curve. CAISO oversees the operation of California's bulk electric power system, transmission lines, and electricity market generated and transmitted by its member utilities.
Net load is the difference between forecasted load and expected electricity production from variable generation resources. In certain times of the year, these curves produce a “belly” appearance in the mid-afternoon that quickly ramps up to produce an “arch” similar to the neck of a duck—hence the industry moniker of “The Duck Chart”.
Decarbonizing the grid while keeping it running is so hard for many reasons, big and small. I'm in awe that it works at all, much less works so reliably that we take it for granted.