Gas turbine cycles for intermediate load power generation
The objective of this thesis is to determine if an advanced gas turbine cycle exists, which can compete with the simple and the combined cycles in the intermediate load electricity generation market; defined as the market with annual utilisation between 3,000 to 6,000 operating hours. Several thermodynamic cycles in the 100MW and 200MW power output range are investigated and compared to base reference simple and combined cycles that have been defined by a survey of existing models in the market. For the investigation of these cycles, gt-ETA (gas turbine - Economic and Technical Analysis) has been developed; a software for the design and off-design thermodynamic performance and the economic evaluation of gas turbine cycles. A new method is proposed for calculating the total capital investment of a advanced cycle engine project. This is based on deriving empirical relations linking the purchased equipment cost to power output and thermal efficiency, based on published data for simple cycle engines. Standardised values are used for the specific costs of different performance improvement' packages. A optimisation process is developed for the determination of the optimum split between the capital investment of a baseline' simple cycle engine and a 'performance improvement package. For accurate performance calculations a cooling air model has been created based on either the direct definition of cooling air amounts or the required hot gas path component metal temperatures. The model is able to select the optimum cooling configuration considering the temperature and pressure of mixing streams. The advanced cycles are competitive against base reference cycles only in the power range of l00MW. From the configurations considered, the recuperated cycle with spray intercooling seems to be the most promising option with a wide range of competitiveness at both design and off-design operating conditions and along the sensitivity range of changing fuel prices.