Proposal a new hybrid system comprising of LNG regasification and geothermal sources: Exergy, exergo-economic, and optimization

In the current research, a novel hybrid cascade power generation system including an organic Rankine cycle (ORC), Kalina cycle (KC), and LNG regasification system assisted by geothermal energy is proposed and investigated. Geothermal fluid energy is used to drive the ORC and KC; at the same time, the waste heat of ORC and KC is utilized to power the LNG cycle. The main new aspect of the current work is the integration of cold energy of re-gasification with low-temperature geothermal source combined with a thermoelectric generator. The introduced system is investigated from the thermodynamic and exergo-economic points of view by considering net power generation, energy efficiency, exergy efficiency, and sustainability index as performance indicators. The study results show that energy and exergy efficiencies of the suggested system are approximately 24.33% and 51.6%, respectively, while sustainability index and total cost rate are 2.066, and 12.68 $/h, accordingly. In addition, different operating parameters (valve 2 outlet pressure, valve 2 inlet temperature and turbines inlet and outlet pressures) are varied to assess the system's performance comprehensively. The results of multi-criteria optimization for the suggested system represent that the output power can reach 32183.44 kW and SI = 2.062 with the total cost rate of 12.69 $/h.