---

In the present study, a novel integrated system containing biomass gasifier, sodium high-temperature heat pipes, and solid oxide fuel cells is introduced. The integrated system is taken into consideration due to its high efficiency and power in order to simultaneous producing electrical power and heat. The modeling of system is performed using equilibrium constants, mass and energy conservation law and the analysis of codes is done in EES software. The effect of gasifier STBR, current density, fuel utilization factor, and outlet fuel cell’s temperature as variable parameters is investigated on the power and total energy efficiency of integrated system using response surface method; after validation of modeling in comparison to the experimental results. The analysis of variance results indicate that fuel utilization factor (with 53% contribution) and current density (with 33% contribution) are the most effective parameter on the power and total efficiency, respectively. The power of integrated system is increased by increasing of temperature while power has an increasing behavior follows by decreasing behavior by increasing fuel utilization factor. The total efficiency is increased by increasing temperature and STBR while it is decreased by increasing current density and fuel utilization factor. The results revealed that the power and total efficiency is obtained at optimum states as high as 300 kW and 90%, respectively.

---

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.

---

In this article, a new power, cooling and heating cogeneration system consisting of a solid oxide fuel cell (SOFC) - gas turbine (GT), a heat recovery steam generator (HRSG), Generator-Absorber-heat eXchange (GAX) absorption refrigeration cycle and a heat exchanger for heat recovery (HR) has been studied from a thermodynamic and economic perspective. The modeling of this cycle was done by solving the electrochemical, thermodynamic and exergoeconomic equations for fuel cell and system components, simultaneously. The results showed that the exergy of our proposed combined cycle is 14.9% more and the irreversibility rate of this cycle is 10.6% less than that of the combined SOFC-GT-GAX systems in the same conditions. Also, the fuel cell and the afterburner have the highest rate of exergy destruction among other components due to irreversibility. Exergoeconomic analysis showed that the sum of uint cost of products (SUCP), the exergoeconomic factor, the capital cost rate and the exergy destruction cost rate for the overall system is equal to 331.1 $/GJ, 29.3%, 10.47 $/h and 25.32 $/h, respectively. Parametric studies showed that increasing the current density will increase the net electrical power, heating capacity of HRSG and HR heat exchanger, cooling capacity and total irreversibility. Also, with increasing of the current density, both the exergy efficiency and SUCP decrease.

---

---

---

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.