Second Law Analysis of Ammonia-Water Power Cycle for Direct-Fired Cogeneration Application

Exergy analysis is performed for four biomass-fueled power cycles presented in a previous study, (Dejfors et al. 1997). Ammonia-water power cycles are compared with Rankine steam cycles for both direct-fired cogeneration application and conventional condensing power application. For all applications studied, the ammonia-water cycle has less exergy losses in the condensers but higher exergy losses in the boiler and in the internal heat exchange system compared with the Rankine cycle. In the condensing case, the superior heat exchange in the condenser for the ammonia-water cycle counterbalances the inferior heat exchange in the internal heat exchangers and in the boiler. In the cogeneration case, the useful exergy out from the turbines and to the district heating network is higher for the Rankine cycle. This paper was presented at the ECOS’98 Conference in Nancy, June 8-10, 1998