A reader pointed us to this important article, written by Charlie Bayless for EEI (Edison Electric Institute). Mr. Bayless is a former provost at West Virginia University Institute of Technology and has served as CEO for several electric utilities and energy companies.
“The electric system is more than just the delivery of energy—it is the provision of reliability. First, the system must have capacity, that is the capability to furnish energy instantaneously when needed. The system also must have frequency control, retain stability, remain running under varied conditions, and have access to voltage control. Each of those essential services for reliability must come from a component on the system. Those components are not free, and they don’t just happen. They are the result of careful planning, engineering, good operating procedures, and infrastructure investment specifically targeting these items.”
Read the entire EEI article at this link.
Allegheny Treasures 
Charles Bayless’ article does a good job of summarizing key points about the electricity system, even providing a few paragraphs about the trade-offs between ramp rates/inertia rates. His points about natural gas storage limitations and cost problems vis a vis wind mirror those Jim Oswald made some years ago and, of course, are reflected today in the wind/gas contretemps in Texas. Bayless could have gone the extra mile to consider the thermal consequences of firming up wind, in terms of those ramp rates, if nothing else–and the financial implications for ratepayers.