Thermoeconomic assessment of a micro cogeneration system with LNG cold utilization

Abstract

Few studies have been reported for the small scale LNG regasification units in power generation systems although many applied LNG cold utilization systems exist for the large scale regasification plants. Impact of the LNG cold utilization system is investigated for the micro cogeneration systems thermoeconomically. An exergy-cost matrix is generated for the systems, which then compared to the conventional micro cogeneration systems. Ambient air temperature and compressor pressure ratio are analyzed. The required work for the LNG pump is found to be neglected in overall cycle analyses. In the cogeneration case, the exergetic and energetic efficiencies are roundly two and three times higher than the single power generation case. The exergoeconomic factor is roundly 26.8% less in the LNG cold utilized system while the relative cost is 75% higher in the conventional case. The LNG cold utilization increases the levelized product costs about 1.7 times at the pressure ratio of 3.64. A graphic-based single objective optimization is conducted by determining unit product cost and exergetic efficiency as the objectives. The maximum relative unit product cost difference is found at 308.15 K while the minimum relative exergetic efficiency difference is at 288.15 K. We suggest system improvements through the thermoeconomic evaluation.