Review and future trends of supercritical CO2 Rankine cycle for low-grade heat conversion

Due to personal and environmental safeties along with various advantages, CO2 became a potential choice as working fluid for both heat engine and heat pump cycles. Because of better temperature glide matching between heat source and working fluid during heat addition leading to no pinch limitation, CO2 has been proposed recently as working fluid for supercritical Rankine cycle with low grade heat sources. Supercritical Rankine cycle and its various working fluids, heat sources, heat sinks and analysis approaches, and performance analyses and optimization of various supercritical CO2 Rankine cycle configurations along with comparison with other working fluids, prototype development, component design and challenges are well-grouped and discussed. Supercritical CO2 Rankine cycle is superior to both steam and organic Rankine cycles, whereas yields mix results compared to other fluids in supercritical Rankine cycle with system compactness and environmental benefit as unique advantages. Future research pathways regarding to system components, experimentation, operating parameter optimizations, control strategies, etc. are discussed as well. Although, there is no supercritical CO2 Rankine cycle in operation up to now, it is becoming a future pathway due to its promising research outcomes and this review will be useful for further progress.