The efficiency of coal-fired combined-cycle powerplants

Conventional coal-based power generation has improved significantly in recent years. Efficiencies of around 45%, and even higher at particularly favourable locations, are nowadays achievable. Future developments will be aiming at 55%. New technologies make even greater increases possible. Concepts involving combined gas-turbine/steam-turbine power-generating plants, in which the fuel gas for the gas turbine is produced via the gasification of coal, are now extremely advanced. This technology already permits efficiencies of around 50%, a figure which will almost certainly reach 55% by the end of the decade. Current development targets view 65% as achievable. In conventional technology, efficiencies are tied to conditions, such as air and cooling-water temperatures, at the particular location. In combined-cycle powerplants, the properties of the fuel coal also play an important part. There are, in fact, coals which can be more advantageously used in a combined-cycle powerplant than in a conventional one. These differences, combined with advantageous concepts for coal-fired combined-cycle power-generating plants, are presented and analyzed. Particular attention is devoted to individual losses occurring at coal conversion, thermodynamic cycles, integration of processes and internal consumptions. Copyright (C) 1996 Published by Elsevier Science Ltd.