Thermodynamic Study of the Supercritical, Transcritical Carbon Dioxide Power Cycles for Utilization of Low Grade Heat Sources Application

Low-grade heat (LGH) sources, here defined as those below 500 oC, are a group of abundant energy sources available as industrial waste heat, solar thermal, and geothermal which are not used to their full advantages. For example, they are not adequately for conversion to power because of low efficiency energy conversion. The utilization of LGH can become advantageous for achieving to the highest thermal efficiency. Technologies that allow the efficient conversion of low-grade heat into mechanical and electrical power need to be developed. Various studies have been carried out to appraise the potential of using supercritical carbon dioxide (S-CO2) in a closed Brayton cycle using LGH source for power generation. In this study, the objective of research is to perform a thermodynamic analysis on five different configurations of S-CO2 Brayton cycle. Different configurations are examined among which recompression and partial cooling have been found very promising. The main part of this study is focused on carbon dioxide Brayton cycle. CO2 Brayton cycle has wide range of applications such as heat and power generation and in automotive and aircraft industry. Proposed configurations of each carbon dioxide Brayton cycle performance simulation are conducted and subsequently compared with other power cycles utilizing LGH sources. The CO2 transcritical power cycle (CDTPC) utilizing LGH is also studied. The models are developed by using the Engineering Equation Solver (EES) for several different Brayton cycle configurations. The choice was made to pursue Brayton cycle with regeneration configuration for further, due to its simplicity and high efficiency. Keywords: Supercritical CO2 Brayton cycle, transcritical CO2 cycle, simulation, low-grade heat.