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In this paper, performance analysis and optimization of a trigeneration system based on different thermodynamic criteria such as energy and exergy efficiency, power and dimensionless power have been investigated. The trigeneration system consists of three subsystems which including the solar subsystem, Kalina subsystem and lithium bromide-water absorption chiller subsystem. The proposed system uses solar energy generates power, cooling and domestic water heating. Power is introduced as a tool for understanding thermodynamic concepts of limited time. Dimensionless power is defined as the ratio of power to the product of total thermal conductivity and minimum temperature of the system. Dimensionless power can be used as a tool to understand the concepts of finite time thermodynamics. The exergy analysis has shown that the most exergy destruction is related to boiler. As a result, energy and exergy efficiencies, capital cost rates and dimensionless power are 17.77%, 18.82% and 9.63 dollars per hour, 0.01781 respectively. Sensitivity analysis has shown that increasing parameters such as ambient temperature, solar radiation, the dimensionless mass flow rate of the Kalina cycle, collector inlet temperature and pressure ratio of the Kalina cycle increase energy and exergy efficiencies. Also increasing pressure ratio the of Kalina Cycle, reducing the dimensionless mass flow rate of the Kalina cycle, the ambient temperature and collector inlet temperature has led to increased dimensional power. In addition, the optimization criteria such as energy efficiency, exergy efficiency, power and dimensional power have been compared. The results showed that power and dimensional power are the best thermodynamic optimization criteria.

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In recent years, the use of Gas Turbine-Modular Helium Reactor (GT-MHR) which operates in accordance with closed Brayton cycle with helium fluid as working fluid has attracted researchers’ attention because of its high efficiency, high reactor safety, being economical, and low maintenance costs. In the present study, a combined system, including GT-MHR cycle, Kalina cycle and Ammonia-water absorption cycle is investigated with respect to energy, exergy, and exergoeconomic. As the bottoming cycle, Kalina cycle and absorption cycle are used in order to avoid energy wasted by gas turbine cycle and to increase efficiency of energy conversion. The results of the simulated model show that, in the basic input mode, the overall work is 304462 kW, the overall exergy destruction is 289766kW and the overall exergy efficeincy of cogeneration cycle is 0.689kW. Also reactor, turbine and compressor in helium cycle are the component to which more attention should be paid with respect to exergoeconomic because the highest amount of cost rate is related to these components. At the end, parametric analysis is carried out in order to evaluate the effect of the changing pressure ratio of helium compressor, input temperature of helium compressor, input pressure and temperature of turbine and mass fraction of the base mode of the Kalina cycle on the output parameters.

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In the present study, a new combined cycle (including a two-step flash evaporation, the Kalina cycle, and a proton-exchange membrane) for simultaneous power and hydrogen generation from Sabalan geothermal wells has been proposed and analyzed from the viewpoints of energy and exergy. The effects of important parameters including separators pressure of flash evaporation, the minimum temperature difference in the pinch point, Kalian higher pressure, superheated geothermal fluid, the ratio of consumed power for hydrogen production and dead state temperature on the amount of produced hydrogen, the net generating power, thermal and exergy efficiencies of the proposed combined cycle have been studied. The results show that for the investigated case in the proposed combined cycle, the amount of the produced hydrogen, net generating power and energy, and exergy efficiency were 1536kg/hr, 12.83MV, 11.39% and 43.64%, respectively. Increasing the pressure of the separators was not effective in increasing hydrogen production, while with increasing the first separator pressure, as well as, the second separator pressure to the optimum pressure, the thermal and exergy efficiency increase. With increasing the temperature of the proton membrane electrolyzer, the produced hydrogen discharge increases and while maintaining cycle net output power, thermal and exergy efficiencies increase. Also, at the optimum point for high-pressure Kalina, the maximum amount of hydrogen production is obtained. The highest amount of exergy degradation was obtained for the protonated membrane electrolyzer, evaporator and condenser 2, respectively.