Study of Supercritical Carbon Dioxide Power Cycle for Low Grade Heat Conversion

by Rachana Vidhi1, D. Yogi Goswami1, Huijuan Chen1, Elias Stefanakos1, Sarada Kuravi1, & Adrian S. Sabau2
1University of South Florida, Clean Energy Research Center
2Oak Ridge National Laboratory, Materials Science and Technology Division

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Research on supercritical carbon dioxide power cycles has been mainly focused on high temperature applications, such as Brayton cycle in a nuclear power plant. This paper conducts a comprehensive study on the feasibility of a CO2-based supercritical power cycle for low-grade heat conversion. Energy and exergy analyses of the cycle were conducted to discuss the obstacles as well as the potentials of using supercritical carbon dioxide as the working fluid for supercritical Rankine cycle, Carbon dioxide has desirable qualities such as low critical temperature, stability, little environmental impact and low cost. However, the low critical temperature might be a disadvantage for the condensation process. Comparison between a carbon dioxide-based supercritical Rankine cycle and an organic fluid-based supercritical Rankine cycle showed that the former needs higher pressure to achieve the same efficiency and a heat recovery system is necessary to desuperheat the turbine exhaust and pre-heat the pressure charged liquid.