Currently, almost all coal-fired power plants are steam power generating units using the Rankine cycle. The maximum efficiency of a Rankine cycle is restricted by the second law of thermodynamics and is limited to below the Carnot efficiency. Over the past decades, extensive R&D and huge sums of money have been invested into the development of alternative systems, the so-called unconventional power generation concepts. A number of studies have been published on alternative power cycles and hybrid approaches to improve the overall efficiency of power generation by coal. Some of these studies focus on improving the basic power cycle, for example the integrated gasification fuel cell concepts, chemical looping concepts, and a renewed look at magnetohydrodynamic (MHD) and indirect coal combustion gas turbine power cycles. Other analyses seek to replace the working fluid with one that reduces parasitic losses intrinsic to the use of water as the working fluid. Systems based on a supercritical carbon dioxide Brayton cycle have been the subject of a number of studies and R&D. Bottoming and topping cycles are being studied as a means to extract additional energy from the process. This report reviews the R&D activities of and recent advances in these innovative power cycles alternative to the conventional steam Rankine cycle. Analyses and evaluations of these power systems are also discussed in the report.

Published Date: March 2015

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