1 The Future of Gas Turbine Technology 8 th International Gas Turbine Conference 12-13 October 2016, Brussels, Belgium Paper ID Number (67-IGTC16) GAS TURBINE FLEXIBILITY AND LIFE ASSESSMENT METHOD David Bosak 1 , Siddig Dabbashi, Thank-God Isaiah, Pericles Pilidis, Giuseppina Di-Lorenzo Cranfield University, Cranfield, Bedfordshire, UK, MK43-0AL 1 david.bosak@gmail.com ABSTRACT In the current European energy market situation, gas power plants are required to operate in cyclical modes to fill the gaps in renewable energy supply. Renewable sources have priority in dispatching due to their relatively low variable operational costs. However, because of their high unpredictability, conventional power plants such as Simple Cycle Power Plants (SCPP) and Combined Cycle Power Plants (CCPP) suffer frequent load changes to fill the gaps in supply by participating in the balancing market. In this paper, the development work of two maps is presented. The first aims to provide a method to quickly assess life consumption in a critical gas path component. The second aims to provide a method to quickly assess gas turbine operational flexibility and performance trade-offs arising from various load change strategies. The results are speculated to support plant operators in load change decision making while exposing potential trade-offs in life consumption and flexible performance. Keywords: gas turbine, flexibility, performance, life consumption, trade-offs INTRODUCTION The realization of dramatic consequences from global warming lead to increasing mothballing of polluting power plants in attempt to reduce global production of green- house emissions. The resulting gap in capacity is filled with increasing mix of renewable/clean power generation. However, the irregular nature of renewable sources presents a challenge to dispatchers to fill comparatively much more stable electricity demand. The Combined Cycle Power Plants (CCPP) and Simple Cycle Power Plants (SCPP) provide a promising solution due to their much better load response characteristics than other conventional power plants such as coal or nuclear. Most of the existing CCPP and SCPP plants were built more than 20 years ago and were not designed to operate in cyclic modes, which now suffer frequent load changes as demanded by the competitive market. Because of more frequent operation at part-load, these power plants now suffer from higher variable operational costs due to lower thermal efficiencies and higher life consumption at part- load. The variable operating costs of power plants are a key factor in determining which units are dispatched first to meet the demand. Since renewable power plants have nearly negligible variable operating costs and are unpredictable, they have priority in dispatching and any gap in supply when renewable sources are unavailable needs to be filled quickly with other traditional power plants e.g. CCPP or SCPP. The extent to which renewable sources are unpredictable was experienced by Spain, where on the 17 September 2012 wind covered 1% of the instantaneous demand and one week later the production increased to 64% of the instantaneous demand (Alvarez, 2016). It is clear that conventional power plant operators need to look for solutions in order to remain competitive in the current market. Economic Pressure A load profile of a particular CCPP power plant in the UK on the 17 February 2016 is shown in Figure 1. The solid line represents the actual contracted load level, and the dotted line represents contracted load level in the balancing market. The balancing mechanism is used to continuously balance the grid to meet the demand by filling in the gaps generated by risky and unpredictable renewable electricity. When participating in the balancing market, the conventional power plant operator, such as the one operating in Figure 1, receives additional income stream by diverging from the original contracted load (solid line). Therefore, being able to provide much faster load response service, or in other words have higher plant flexibility, provides competitive advantage and higher revenue. However, this comes at a cost of increased life consumption of critical plant components and deterioration in thermal efficiency which leads to higher operational costs. Any short-notice load change induces additional thermal and mechanical stresses on the plant components, which effectively consume critical component life and