Coal Plant Operations

In 2023, coal generated 16% of U.S. electricity, down from 50% in 2005. Every remaining plant works the same way: pulverize coal to talcum-powder fineness, blow it into a furnace with air, boil water, spin a turbine. The Rankine cycle at industrial scale.

A coal plant pulverizes coal into particles smaller than 75 micrometers so it burns almost instantly when injected into the combustion chamber. The heat boils water into high-pressure steam (typically 540-600 degrees C at 150-250 bar), which expands through a multi-stage steam turbine to generate electricity. Exhaust steam is condensed back to water using a cooling tower or river water, and the cycle repeats. Subcritical plants operate below water's critical point and achieve 33-37% thermal efficiency. Supercritical and ultra-supercritical plants push above it, reaching 38-45%.

Trace the efficiency range. A subcritical plant burns 100 MW of coal and produces 33 MW of electricity. An ultra-supercritical plant: 45 MW from the same fuel input.

Connect efficiency to emissions. Coal emits about 820 gCO2/kWh at the global fleet average. At 33% efficiency: roughly 1,000 gCO2/kWh. At 45%: roughly 740 gCO2/kWh.

Can efficiency improvements alone bring coal's carbon intensity close to natural gas (~490 gCO2/kWh)?

Hit the floor. Even at a theoretical 100% efficiency, coal would emit about 330 gCO2/kWh due to its stoichiometry (high carbon, low hydrogen). No amount of efficiency improvement bridges the gap to natural gas. The carbon is in the fuel.

Coal plants are in structural decline across most OECD countries, displaced by cheaper gas and renewables, not by regulation alone.

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