Performance analysis of a combined power and refrigeration cycle

Abstract

In this paper a novel combined power and refrigeration cycle is proposed based on the ocean thermal energy conversion (OTEC) system, i.e. the Kalina cycle. In this combined cycle, solar energy is employed to raise the heat source temperature. Cooling capacity is generated concurrently by the ejector refrigeration cycle (ERC) which works on the exhaust heat extracted from the turbine in the Kalina cycle. Ammonia-water and isobutane are selected as the working fluid of Kalina cycle and ERC respectively. To evaluate the performance of the proposed cycle, the process is simulated in the commercial package ASPEN PLUS. It is found that, compared with the Kalina cycle, the proposed cycle has a higher primary energy ratio (PER) of 29.2% though it has a lower power output. Besides, the exergy efficiency and the primary energy saving ratio (PESR) in the proposed cycle reach as high as 41.88% and 8.3% respectively. It is also demonstrated that when the inlet pressure of the turbine exceeds 2.9 MPa and the outlet pressure of the turbine is between 1.3 and 1.6 MPa in the test range, the proposed cycle is better than the stand-alone systems from the energy saving perspective. Furthermore, parametric analysis shows that the inlet and outlet pressure of the turbine, the inlet temperature of the turbine, the basic concentration of ammonia-water, the generation pressure, ejector entrainment ratio and the outlet temperature of the condenser II have significant effects on the output of the turbine, refrigeration output, exergy efficiency, COP, PER as well as PESR.