Energy, exergy, and exergoeconomic analysis and multi-objective optimization of a novel geothermal driven power generation system of combined transcritical CO2 and C5H12 ORCs coupled with LNG stream injection

Abstract

In many cases, inefficient economics and policies hinder renewable sources from being exploited. For the case of geothermal sources; however, using newer combined cycles has been proven to contribute to this issue. In this paper, ‏ a novel coupling of three geothermal cycles for power generation is studied and optimized for 8 parameters simultaneously. The optimization is interpreted through four scenarios to make the analysis a less complex task. CO2 and C5H12 are fed directly by the geothermal source, using LNG as the heat sink for power generation. The proposed cycle has a net output power of 1211 KW, an exergy destruction rate of 1593 KW, and fk of 16.2% that were later optimized to 271.6 KW, 1532 KW, 16.5%, respectively. The output pressure of the LNG is shown to equal that of city gas common pressure that is sold for 5 $/gallon in the US. The addition of the LNG stream to the system, added to the plant's investment costs; however, it needs to be taken into account that the configuration with the presence of the LNG showed greater energy efficiency and that the electricity generated can be sold or consumed by the system.