Techno-economic and 4E comparisons of various thermodynamic power cycles for low-medium grade heat recovery

Abstract

Various thermodynamic power cycles can be utilized to convert the low-to-medium temperature heat (available from many sources and has huge potential) to electricity and a detailed comparison between all of them is essential to identify the suitable one. Hence, to fulfill this research gap, six thermodynamic power cycles (Organic Rankine cycle with dry fluid, Organic Rankine cycle with wet fluid, Transcritical CO2 Rankine cycle, Kalina cycle, Organic flash cycle and Trilateral flash cycle) have been compared for various heat source and sink temperatures. Objective functions are power generation, efficiency, irreversibility, cost, profit, environmental benefit, techno-economic parameters, etc. Study shows that the trilateral flash cycle is best for medium heat source temperature and the CO2 cycle is best for low heat source temperature. The trilateral flash cycle shows an 11.5% higher exergy efficiency and 16.16% increment in annual profit at 160 °C heat source temperature as compared to the organic Rankine cycle with dry fluid. A decrease in condenser temperature is more advantageous than an increase. The study reveals that the CO2 Rankine cycle would be advantageous for low-grade heat sources while the trilateral flash cycle for medium-grade heat sources in terms of performance, cost, design, operation and environmental benefits.