Exergy and energy analysis of a novel power cycle utilizing the cold energy of liquefied natural gas

Abstract

The liquefied natural gas, LNG, possesses cold energy that can be put to use in the regasification process for various purposes. In this paper the proposed configuration consists of a Rankine cycle, an Organic Rankine cycle, and a Stirling cycle. The LNG cold energy and the enthalpy of the flue gas, which are the product of the combustion chamber, are used as the heat sink and the heat source of the mentioned cycles, respectively. Thermal and exergy analysis are conducted on the novel cycle. A parametric study is also carried out and finally the optimum working condition for the plant is obtained. The results indicate that in an optimum condition the thermal and exergy efficiencies can reach up to 53.51% and 47.43%, respectively. The parametric analysis shows that the pressure ratio of the Rankine cycle’s turbine and the Brayton cycle’s compressor can have a significant effect on the overall performance of the proposed plant. The overall result from the analysis suggests that implementing the three mentioned cycles (Organic Rankine Cycle, Stirling cycle and Rankine cycle) that employ the LNG cold energy, can lead to 43% increase in the output power in comparison with utilizing the Brayton cycle alone.