Britannica Sources used in this answer

Why does using both gas and steam turbines improve coal power plant efficiency?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

coal utilization Cross-regenerative coke oven. (A) Cross section, showing the alternating arrangement of flue walls and ovens; (B) longitudinal section, showing (left) a series of combustion flues in a single flue wall and (right) part of a long, slotlike oven.

Using both gas and steam turbines in a process known as the Integrated Gasification Combined Cycle (IGCC) improves coal power plant efficiency by capturing and utilizing energy that would otherwise be wasted.

In this system, coal is first gasified and burned to produce high-temperature combustion gases, which drive a gas turbine. The exhaust gases from this turbine remain very hot and are subsequently directed into a steam generator. This heat is then used to produce steam to power a conventional steam turbine. By effectively "stacking" these two cycles—using the high-temperature exhaust from the gas turbine to generate steam for the second turbine—the plant achieves a more thorough energy conversion process.

This combined-cycle operation allows the plant to reach an overall thermal efficiency of approximately 42 percent, which is significantly higher than the 36 to 38 percent efficiency typical of conventional coal-fired power plants. Similar combined-cycle configurations using other fuels can even reach efficiencies of nearly 50 percent.12