Thermodynamic feasibility evaluation of an innovative salinity gradient solar ponds-based ORC using a zeotropic mixture as working fluid and LNG cold energy

Abstract

Thermodynamic feasibility evaluation is investigated for a salinity gradient solar pond-based power generation system. A dual-pressure evaporation organic Rankine cycle using the zeotropic mixture as working fluid is employed for power generation. To increase power generation, liquefied natural gas cold energy is used as a heat sink. Furthermore, to reach reliable results, transient analysis is conducted on the overall system. Also, the solar pond walls shading effect as well as heat losses that could not be ignored (i.e., evaporation heat loss from pond surface) is considered in the simulation. The results show that for a system located in Urmia, Iran, the annual average solar pond energy efficiency for the first year is obtained 20%. Different zeotropic mixtures are examined to achieve the optimal thermal performance of the system. It is concluded that the system using R245ca/R236ea with a mass fraction of 0.6/0.4 has the optimal thermal performance among selected zeotropic mixtures. In this case, the values of the system generated power and exergy destruction are obtained 95.67 MJ year−1 m−2 and 133.7 MJ year−1 m−2, respectively, with an energy efficiency of 3.28%.