Comparative study on the performance of cascade supercritical carbon dioxide power cycles for waste heat recovery.

For decades, in term of enhancement of overall power generation system efficiency, Waste Heat Recovery System (WHRS) is being spotlighted as eco-friendly technology. Steam Rankine Cycle has been used for usual bottoming cycle of WHRS until now. Recently, however, Supercritical Carbon Dioxide (S-CO₂) Power Cycle is being substituted for Steam Rankine Cycle, because of using supercritical fluid having the characteristics of both of liquid and gas, less compression and circulation work, and smaller size. In addition, for maximizing the overall net power of S-CO₂ Power Cycles in WHRS, Cascade cycle is being considered for advanced cycle modification of simple S-CO₂ Brayton Cycle. In this study, several combined cycles of WHRS such as Steam Rankine Cycle, Simple S-CO₂ Brayton Cycle and Cascade S-CO₂ Power Cycle was investigated by cycle analysis. For comparing the performance of each cycle under the identical situations, the thermodynamic analysis of each cycle which operated in the same heat sources and heat sinks was conducted.