Supercritical Fossil Steam Plants: Operational Issues and Design Needs for Advanced Plants

As electricity markets become increasingly competitive, ultrasupercritical power plants must operate efficiently and flexibly. This necessitates attention to equipment design features and optimal material selection. Early studies by EPRI highlighted the need for boiler and steam turbine design improvements, as well as material advances, to enable the flexible operation of advanced supercritical units. Improvements such as turbine rotor cooling, cycling capability through improved control systems, enhanced blade tip sealing designs, turbine vibration control approaches, and erosion-resistant control stage designs were required. With ultrasupercritical plants moving towards even higher steam temperatures exceeding 700°C, these concerns need to be revisited from both metallurgical and design perspectives. Furthermore, features for efficiency improvements beyond advanced steam conditions should be considered, while minimizing environmental emissions like CO₂. This paper reviews the needs for future ultrasupercritical plants with steam temperatures approaching or exceeding 700°C.