Exergy assessment and energy integration of a novel solar-driven liquid carbon dioxide and liquefied natural gas cogeneration system using liquid air cold energy recovery

This study is focused on presenting a novel approach for the cogeneration of liquid carbon dioxide (LCO2) and liquefied natural gas (LNG). The main idea of this development is to use air for storing and producing energy, meanwhile, transferring cold energy for the liquefaction process of natural gas. Therefore, a mixed refrigeration cycle and liquid air cold energy recovery are considered to liquify natural gas. A carbon dioxide liquefaction cycle and a combined cooling and power cycle are also integrated to increase the output performance of the system by taking advantage of carbon dioxide liquefaction and power production. The power production sub-cycle is assisted with solar parabolic trough collectors, which are placed in the city of Bandar-Abbas, Iran. The obtained results demonstrate that the developed system supplies liquefied natural gas and liquid carbon dioxide at 3600.4 and 1188.2 kg h−1, respectively. The exergy calculation displays that the heat exchanges (45.14%), compressors (17.24%), and collectors (14.03%) have the most share of exergy destruction compared to other compounds. The exergy efficiency and irreversibility of the proposed integrated system achieve a 48.91% and 1175 kW, respectively. The sensitivity investigation indicates that the specific energy decreases to 813.6 kJ kg−1-LNG and exergy efficiency increases up to 48.91% when the pressure in liquid air increases from 20 to 60 bar. The specific energy and exergy efficiency decrease to 799.9 kJ kg−1-LNG and 47.76%, respectively with the increase in outlet temperature of the solar collector exchanger from 155 to 175 °C.