Assessment and optimization of a novel solar driven natural gas liquefaction based on cascade ORC integrated with linear Fresnel collectors

A novel cascade organic Rankine cycle (ORC) configuration involving ejector refrigeration loops is introduced to produce liquefied natural gas (LNG) and power. Linear Fresnel solar collectors are utilized to supply the required energy of the system. Exergy, exergoeconomic and exergoenvironmental concepts are undertaken upon the concerned system during a year. A multi-objective optimization procedure based on a fast and elitist non-dominated sorting genetic algorithm (NSGA-II) is conducted and three decision makers, i.e. Shannon Entropy, LINMAP and TOPSIS methods are employed to find the ultimate optimum thermodynamic, economic and environmental impact performances from Pareto frontier obtained by NSGA-II with corresponding design variables of the system. As a result, the solar radiation increment affects the efficiencies negatively and the lowest total product cost and EI rates are obtained within 78.588 $/h in May and 77.544 Pts/h in December, respectively. The optimum energy and exergy efficiencies are achieved respectively by about 7.3% and 12.6% in relation to the base point using Shannon Entropy decision maker. Moreover, the economic and EI performances of the system are improved respectively within 1.2% and 1.1% through the LINMAP method so that the highest reduction may be obtained for the cost and EI per unit exergies of LNG within 0.4200 $/GJ and 7.36 Pts/GJ, respectively.