Too bad that 2018 NARUC paper is a pdf, but I’ll try my best to transcribe part of it. It talks about the difficulty of “cycling” a coal plant on/off or up/down as other sources of electricity come on line (solar and wind, highly variable).
“While they are currently being discussed, no specific market mechanisms exist to compensate fossil fuel power plants in the ERCOT and SPP markets...operators with the largest share of intermittent renewable energy resources...
More retirements of coal plants are likely, increasing the risk of potential power outages in states like Texas...
Thoughtful market mechanisms to compensate coal-fired units for providing balancing attributes, such as short-term generation flexibility...helping to ensure reliable operation of the nation’s electric power grid.”
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Comment: Keep in mind that coal is up against increased EPA restrictions, while solar and wind is getting tax cuts and incentives.
From that same paper, ERCOTT retired 5,000 MW of coal energy in just 2018 alone. SPP retired another 2,000 MW.
And add any carbon trading that might become the norm with any Green New Deal, and things snowball very quickly.