Finite sum based thermoeconomic and sustainable analyses of the small scale LNG cold utilized power generation systems

Highlights: • An original finite sum approach is applied in three LNG importing countries. • Two different LNG cold utilized micro cogeneration systems are analyzed. • The morning session provides the best yearly performance results. • The combined system is more feasible and sustainable than the single system. Liquefied natural gas (LNG) cold utilized micro cogeneration systems are the feasible and sustainable solutions for the inland regions where the large scale LNG cold utilization or the conventional pipeline systems are not economically applicable. The present study investigates the single and combined systems in three LNG importing countries by using the finite sum modeling which is firstly performed for the LNG cold utilization systems with the sustainability index assessment. To generate electricity, the microturbine is integrated with an LNG vaporizer and an LNG pump in the single system while the combined system includes a Stirling engine and a thermal energy storage tank in addition to the microturbine and LNG cold utilization components. Thermodynamic, environmental, thermoeconomic and sustainable analyses are performed to obtain their yearly performance maps that are extremely difficult to obtain with the conventional dynamic modeling. The yearly performance trends of the net power generation rate, exergetic efficiency, and the levelized product cost are found similar to each other while they have contrary yearly trends with the overall energetic efficiency and the Stirling engine performance parameters. The net generated power rate, the Stirling engine performance parameters, the levelized product cost, the emission rate and the sustainability index have significant changes which must be considered for the real applications while the other factors are able to be neglected during the dynamic analysis since their fluctuations are small. The most convenient time are found at 08:00 am in all the case countries though the corresponding months change for each case country. The combined system is found more feasible than the single system from the thermodynamic, thermoeconomic, environmental and sustainable viewpoints.