Natural gas was the big driver for retirement of coal plants before the greenie insanity arrived. Actually, the big increase in gas is what ignited and drove a lot of the greenie insanity.
The big advantage of gas is you can have combined cycle plants that combine the gas turbine making power (the Brayton Cycle) and a waste heat boiler running a steam turbine (the Rankine Cycle). You get a high peak cycle temperature in the gas turbine and a low exit temperature because of the heat recovery steam generator. Combined, they give you an overall efficiency of 60% to 65% which is way higher than the best coal plant (35%). The utility gas turbines were all derived from aircraft jet engines (”aeroderivative”), so they capitalized on that extensive R&D. The high efficiency keeps the fuel component of the total cost low. Plus, gas turbines can ramp up and down very quickly (more so for “simple cycle” gas turbines without a boiler at the back end). Also, the capital requirement for a a gas turbine is far below the capital required for a coal plant.
The industry has talked about a “gas bubble” for 35 to 40 years, but the supply just keeps growing — at least the supply that various states have not put off-limits with bans on fracking.
“The big advantage of gas is you can have combined cycle plants that combine the gas turbine”
I hadn’t thought of the fact that with natural gas you can drive a turbine directly from its combustion products but with coal you have to make steam to drive the turbine.