THERMODYNAMIC PERFORMANCE AND DESIGN OF SMALL-SCALE H2O-LiBr VAPOR ABSORPTION SYSTEM FOR ROOM AIR COOLING

Abstract

The present study addresses the research gap in small-scale distributed trigeneration systems by investigating two novel configurations: (1) a solar power tower (SPT) driven helium Brayton cycle (HBC) integrated with a heat recovery steam generator (HRSG) and a vapor absorption cooling system (VACS), and (2) a solid oxide fuel cell-gas turbine (SOFC-GT) hybrid system coupled with a vapor absorption refrigeration system (VARS). The primary objectives of this thesis are: (i) to develop and simulate a novel SPT-HBC-HRSG-VACS trigeneration system for combined power, heating, and cooling; (ii) to perform comprehensive energy and exergy analysis of the proposed trigeneration system; (iii) to develop a SOFC-GT-VARS cogeneration system for small-scale room air conditioning; and (iv) to investigate the energy, exergy, economic, and environmental (4E) performance of the SOFC-GT-VARS system. The SPT-HBC-HRSG-VACS system exploits waste heat from a basic HBC driven by an SPT. The two subsystems, HRSG and VACS, recover waste heat for steam generation and air conditioning cooling, respectively. A comprehensive exergy and energy analysis of this proposed trigeneration system was carried out with parametric analysis using Engineering Equation Solver (EES) software. It was concluded that energy and exergy efficiency and net work output of the proposed trigeneration system were observed as 44.96%, 34.15%, and 14,562 kW respectively. The heating production through the HRSG was obtained as 8,510 kW while the cooling production by VACS was 115.10 kW. Moreover, the coefficient of performance (COP) of the VACS subsystem was observed as 0.8015. Energy and exergy efficiency of the SPT-operated basic HBC using the subsystems were improved by 58.98% and 12.92%, respectively. Parametric analysis revealed that the helium turbine inlet temperature and solar heliostat field efficiency significantly affect the trigeneration system performance. vi For the second configuration, a novel SOFC-GT-VARS system for combined cooling and power generation is developed. Thermodynamic, economic, and environmental analyses were performed on the proposed system using computational techniques. The proposed plant obtained power output, exergy efficiency, and energy efficiency of 551.29 kW, 48.03%, and 50.18%, respectively, at given operating conditions. The cooling effect of 5.275 kW (1.5 TR) was obtained from the VARS with a COP of 0.752. The total cost rate of the proposed plant was observed as 33.57 $/h, while the CO₂ emission per MWh of energy output was obtained as 394.70 kg/MWh. The research successfully fills the identified gaps in small-scale distributed trigeneration systems and provides a comprehensive framework for evaluating such systems under Indian climatic and economic conditions.