Thermodynamic study of the simultaneous production of electrical power and refrigeration capacity from regasification of liquefied natural gas

The simultaneous production of electrical power and refrigeration capacity from regasification of liquefied natural gas (LNG) is studied. Typical regasification systems, such as open rack vaporizers and submerged combustion vaporizers, do not envisage the possibility of recovering the LNG cryogenic energy to produce refrigeration or electrical power. This paper focuses on a regasification-cogeneration process, already reported in the literature, from the University of Palermo, Italy, that prioritizes the recovery of refrigeration heat transfer rate, with electrical power generation being regarded as a process by-product. A simple thermodynamic analysis compares the traditional and the cogeneration regasification processes by means of their energy utilization and exergy efficiency. An innovative approach is here employed where, in addition to the system thermal performance, refrigeration load demand is also taken into account as an independent variable. Fundamental principles of mass and energy conservation are applied to provide a description of the system thermal behavior, in terms of the independent electrical and cooling power demands. Model results show that significant improvement on system efficiency can be attained with the recovery of the cryogenic exergy of LNG, particularly when refrigeration and regasification thermal power load demands are of the same order of magnitude.