Comparison of novel concepts of cogeneration systems used to regasify liquefied natural gas (LNG)

Abstract

Liquefied natural gas (LNG) will contribute in future significantly to the overall energy supply in the world. During the last two decades the effectiveness of the technologies associated with the chain “natural gas – LNG – natural gas” has increased. However, the regasification systems, which use approximately 1.5% of the LNG energy, have not been considerably improved. The objective of this paper is to demonstrate the potential for generating electricity while regasifying LNG, and to compare some novel concepts developed for this purpose. The concepts are based on combination of the open- and closed-cycle gas-turbine systems with combustion of natural gas as the heat source and regasification of LNG as the heat sink. The comparisons are conducted from the thermodynamic, economic and ecological points of view. The complications introduced to the Base Case in order to maximize the utilization of useful energy (transferred to the environment from the open-cycle gas-turbine system) have the following consequences: The overall energetic efficiency increases from 68% to 86%, the overall exergetic efficiency increases from 52.6% to 54.3% while the specific fixed capital investment is approximately 1.0 mil US$/MW for all schematics. The specific CO2 emissions (per unit of generated electricity) increase from 0.145 to 0.19 kg CO2/kWh while per kg of regasifyed LNG, the specific CO2 emissions decrease significantly from 0.09 to 0.067 kg CO2/kg LNG.