High flexibility in Francis turbine operation and design philosophy: A review

Abstract

This paper examines and discusses how various operation schemes and design philosophies can prolong the expected lifetime of a hydro turbine subjected to many start-stop cycles and high ramping rates. With the proliferation of renewable and non-dispatchable energy sources in Europe, a higher demand for flexible operation is put on the rest of the system. Given the short response time of hydro power, there is a huge potential for the Norwegian power sector to act as a stabiliser for the rest of mainland Europe. With a more flexible operation however, the turbines will experience a higher load variation which can lead to premature fatigue and failure of existing turbines. This research reviews the current startup and ramping schemes, as well as design aspects, which might affect and reduce the mechanical stresses experienced by the hydro turbine.