New lifing criterion for land-based gas turbines in flexible operation mode

Abstract

Under the ongoing global energy transition, gas turbines are increasingly experiencing new modes of operation. In the recent years, primarily in Europe and similarly in various parts of the world, renewable energies are gaining momentum to support more environmentally friendly energy policies. Renewable Energy Sources (RES), such as wind and solar are intermittent by nature and a rise in their contribution is associated with grid instabilities. As a result, reliable energy sources such as fossil fuel-based plants are required to fill flexible back-up or reserve power, capable to rapidly response in case of RES downtime. This introduces new operating conditions, characterized by very high start/stop cycles (almost daily) and load cycling operations, beyond those foreseen under the classic base-load or cyclic operations.The present criteria used for establishing the inspection intervals and components’ lives, are put in place based on the assumptions that the gas turbine will operate at base load for the most part, with some exposure to cyclic operations. This paper identifies the most critical gaps in the present criteria, particularly due to increased thermal instability or sustained transient under the flexible operation requirements.

Keywords

• Creep-fatigue interaction
• Flexible operation
• Lifing criterion
• Peaking machine
• Thermal stability