POWER-GEN Asia 2018

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Water-free Combined Cycle Distributed Power Generation (Room Garuda 12, 1st Floor)

Combined Cycle Gas Turbine (CCGT) power plant offer operators both environmental and economic benefits. The high efficiency achievable across a wide load range reduces fuel costs and CO2 emissions. However, the scale of the plant plays a major role in determining the cost and efficiency: a modern centralized CCGT of 600MW output will have full load efficiency over 61% and a very competitive installed cost on a $/kW basis. The smaller gas turbines required for distributed power applications are not optimized for combined cycle operation, with full load efficiencies ranging from 40% to 58% depending on the power output of the gas turbine, the exhaust gas conditions and the plant configuration, while the installed cost is double that of a large centralized CCGT on a $/kW basis. The drawback of a conventional combined cycle plant design is the need for water, which can be a scarce commodity. Air cooling of the CCGT can be used to reduce water consumption, but make-up water will still be required for the steam system. The lower exhaust gas temperature of smaller gas turbines impacts the combined cycle efficiencies achievable, but Organic Rankine Cycle (ORC) technology can be considered as an alternative combined cycle configuration. This paper compares both the capital and operating costs and performance of combined cycle power plants for distributed power applications in the 30MW to 250MW power range based on conventional steam and various different ORC configurations.