Maintenance and operational patterns in thermal power generation

Abstract

With increasing shares of solar and wind generation in the power system, the understanding of power generation system as we know it today, needs to be reassessed. Wind and solar power, known as the non-dispatchable generation, are likely to impact the net load on the grid and dispatchable power production, typically thermal power plants, will face more frequent starts and stops and volatile operational patterns. This is expected to cause tougher conditions for the plant and result in more critical wear on the equipment, which must be considered and accounted for. This master’s thesis develops a method to evaluate maintenance costs depending on the operational pattern - in terms of the number and types of start-ups - of a steam cycle. The work focus on the steam turbine rotor but could be applied also to other critical components of the plant. The method includes a rotor model to perform transient simulations of the rotor temperature during start-ups. The rotor temperature was then related to thermal stresses and life expenditure of the rotor, which are typical input parameters to estimate maintenance costs from an LCC-perspective. The method may be applied to evaluate the influence of energy system scenarios, process designs, and maintenance policies. To exemplify, this work evaluates the maintenance cost of the rotor for six defined scenarios, four maintenance policies, i.e. failure-based, time-based, condition-based and opportunity-based maintenance, and three types of labour services, internal, external and contract service. The examples illustrate how the maintenance costs may be related to the number of starts and that the proposed method may be provide initial support to the initial discussions on the maintenance of thermal power plant components.