Thermo-economic Comparison of Advanced Organic Rankine Cycles

Abstract

To improve the performances of the Organic Rankine cycle, several advanced cycle designs are proposed. Because different studies use varying boundary conditions, an assessment of the benefit of the cycle designs is complicated. Furthermore, the inclusion of economic parameters is valuable for a sound comparison. In this work, the subcritical cycle, the trilateral cycle and the transcritical cycle are compared on a thermodynamic and economic basis. The investigated cycles are optimized for three waste heat recovery cases within a temperature range of 100°C to 300°C. From a pure thermodynamic analysis only a marginal performance benefit is achieved for high temperature cases with the working fluids under consideration. Therefore, a thermo-economic analysis is provided for the low-temperature case. A multi-objective optimization is at the basis of the thermo-economic analysis and comparison. The thermodynamic performance of the cycles is compared with equal boundary conditions and actual cases are used. The results of such investigation are particularly interesting for manufacturers of ORCs.