Performance analysis of a cascaded solar Organic Rankine Cycle with superheating

Abstract

A cascaded Organic Rankine Cycle (ORC) with scroll expanders is investigated in this paper, the system performances under various configurations are evaluated and the effect of superheating on the system efficiency is clarified. The efficiency of two-stage ORC system is 38.9% higher than that of single-stage system when R245fa is used as the working fluid, while the efficiency of two-stage ORC system is 10% lower than that of single stage when R134a is adopted. The specific work of single-stage ORC system with R245fa increases linearly with the degree of superheat. There is an optimal superheated degree for the system output power and efficiency, which is 35 K for the expansion ratio of 3.5 and 45 K for the expansion ratio of 5.