A power cycle generates electricity from the heat of combustion of fossil fuels. Its efficiency is governed by the cycle configuration, the operating parameters, and the working fluid. Typical designs use pure water as the fluid. In the last two decades, hybrid cycles based on ammonia water, and carbondioxide mixtures as the working fluid have been proposed. These cycles may improve the power generation efficiency of Rankine cycles by 15%. Improved efficiency is important for two reasons: it lowers the cost of electricity being produced, and by reducing the consumption of fossil fuels per unit power, it reduces the generation of environmental pollutants. The goal of this project is to develop a computational optimizationbased method for the design and analysis of hybrid bottoming power cycles to minimize the usage of fossil fuels. The development of this methodology has been achieved by formulating this task as that of selecting the least cost power cycle design from all possible configurations. We employ a detailed thermodynamic property prediction package we have developed under a DOEFETC grant to model working fluid mixtures. Preliminary results from this work suggest that a pure NH3 cycle outperforms steam or the expensive Kalina cycle. The lack of a unified framework to systematically develop cycle design alternatives results in missed opportunities. Hence, for process representation, we propose a new graph theoretic approach to power cycle design. The key feature of this representation is that it reformulates the nonconvex problems (with multiple minima) that result from an optimization based for mulation of the power cycle synthesis task as a linear program which can be solved globally. We have applied this method to save energy costs in other chemical process design problems, such as in liquidliquid extraction, and in air separation. This work in progress provides the basis for a general method to evaluate and design Vision 21 plant configurations. Though bottoming cycles are only a component of the energy plex, our design methodology can be modified to design the entire complex with watergas shift reactions, fuel cells, and gas turbine cycles. The proposed innovative concept work will develop this capability for this component of the Vision 21 plant: the bottoming cycle to recover heat from the stack gases. a 10% improvement in fossil fuel power plant efficiency may lead to a
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Title Design of Hybrid Power Generation Cycles Employ