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The use of new energies, including geothermal energy, is rapidly devoloping in the world. In Iran, the Sabalan area has a great potential for generating energy from geothermal energy sources. In this paper, a new power generation combined cycle (flash combined cycle with supercritical carbon dioxide and organic Rankine cycle) is proposed with respect to two wells with different temperatures and pressures for Sabalan geothermal sources. For the organic Rankine cycle, four fluids are considered appropriately and then proposed combination cycle is investigated by energy and exergy analysis. In this study, a new method proposed for the determination of Pinch point for carbon dioxide heat exchangers. In the end the proposed cycle has been optimized relative to seprators pressure, the second evaporator temperature and the carbon dioxide cycle pressure ratio. The results show that the n-butane agent has been selected as the most suitable fluid for the Rankine cycle. For the optimal condition, the net power of the proposed cycle is 19934 kW, the cycle efficiency will be 17.05% and the exergy efficiency will be65.38 %.The results of exergy analysis show that the low pressure turbine in geothermal have the highest value of exergy destruction. The results show that net power output, energy and exergy efficiencies of the proposed cycle in this paper is 15.29 %, 17.06% and 18.35% higher than the corresponding values obtained for the previously proposed system.

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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.