Performance Evaluation of a Novel Multigeneration Plant of Cooling, Power, and Seawater Desalination Using Supercritical CO2 Partial Cooling, ME-TVC Desalination, and Absorption Refrigeration Cycles

Abstract

Multigeneration systems have gained popularity and approval from scientific minds due to the enhancements these systems bring to total energy utilization efficiency. The use of waste heat from different thermodynamic cycles ensures deceleration of environment pollution. In this paper, a newly conceptualized poly-generation system combining power, cooling and desalination is proposed. Despite the high efficiency generated by the next generation supercritical CO2 (sCO2) Brayton cycles, the pre-coolers (cooling components) of the power block experience a substantial amount of low-grade energy loss. Utilizing this energy loss to increase thermal efficiency further has been the driving force behind this research. The proposed system has three subsystems which are sCO2 Partial cooling cycle with reheat for power generation, followed by a ME-TVC (multi-effect desalination-thermal vapor compression) cycle for producing fresh water and finally an absorption refrigeration cycle (ARC) to provide refrigeration effect. The waste heat from precoolers of sCO2 partial cooling cycle are being utilized by the desalination plant and refrigeration cycle for enhanced system performance. A comprehensive mathematical model is developed and a parametric assessment is performed. The parametric investigation focuses on the primary performance parameters, namely net power output, freshwater yield, energy utilization efficiency, coefficient of performance, and gain output ratio, to assess the multi-generation system's performance across various operational scenarios. The variables that are optimized are turbine inlet temperature of the sCO2 cycle, temperature difference of the generator and the evaporating temperature of the absorption cycle, the number and temperature of the effects of the desalination system. The results show that the greatest energy efficiency of the developed system is up to 70%. The 1st law energy efficiency is termed as Energy Utilization Factor (EUF) in the present work. This term adheres to the logic of the first law of thermodynamics by relating the total energy outputs to the system (work plus refrigeration capacity and heat supplied to the desalination plant) to the total energy input. Using the default parameters, the COP of the ARC is 0.667 and the EUF of the combined system is 59%. Both of these values are higher when compared to previous combined cycles found in literature.