Thermodynamic and multi-objective optimisation of solar-driven Organic Rankine Cycle using zeotropic mixtures

This paper communicates the performance of low-grade solar heat source powered Organic Rankine Cycle (ORC). To investigate the system performance, first law and exergetic efficiencies, power output are evaluated and compared for zeotropic mixtures of (iso)butane/(iso)pentane and cyclohexane/R123. The results indicate that there exists an optimal mass fraction for which energy and exergetic efficiencies, and power output are maximum corresponding to a given value of expander inlet temperature compared with pure fluids. However, the specific volume flow ratio of the expander is higher for zeotropic mixtures; which results in a lower economy of mixtures than pure fluids. The use of an internal heat exchanger in the system improves cycle performance. Moreover, the multi-objective genetic algorithm further improves the performance of ORC and exhibits better exergetic efficiency 51-57% and 0-14.09% reduction in lower expander-specific volume flow ratio (v(6)/v(5)) than thermodynamically optimised ORC.