This study is focused on the analysis of representative thermodynamic cycles for power generation at low-to-medium temperatures (with the highest cycle temperature from 450 to 700K). The natural working fluid of carbon dioxide is selected for the current tests and comparisons with suitable operation ranges. Energy balance and exergy loss models are established and applied to 10 selected representative thermodynamic cycles. One modified efficiency parameter is also defined for better comparison of performances, which has considered the effects of both specific thermodynamic process and cycle complexity. Based on the modified efficiency parameter, it is found that Rankine cycle yields the highest performance at 450-500K among the 10 representative cycles, while regenerative Brayton cycle shows better behavior for 550-700K. Detailed behaviors and optimal principals of regenerative Brayton cycles are also identified and compared in this study. Also, a new cycle is also proposed in this study, which combines the advantages of Rankine cycle and Brayton cycle. The new cycle is proved to have better work output potential but higher system complexity factor. In addition, based on the thermodynamic analysis, possible future directions of low-to-medium temperature power cycles are summarized. It is hoped that the results can be of help for related power generation system designs.
ASJC Scopus subject areas