Analysis of a gas turbine based hybrid system by utilizing energy, exergy and exergoeconomic methodologies for steam, power and hydrogen production

Energetic, exergetic and exergoeconomic assessments are performed for a novel cogeneration system of power, steam and hydrogen production, including a gas turbine (to produce power), a heat recovery steam generator (to produce steam) and an organic Rankine cycle equipped with a proton exchange membrane electrolyzer (to produce hydrogen). A comprehensive parametric study is reported and effects of such significant variables as air compressor pressure ratio, evaporator temperature, the pinch point temperature difference in the evaporator and degree of the superheat at the ORC turbine inlet on the exergy efficiency, rate of produced hydrogen and sustainability index of the proposed system investigated. Using direct search method by the EES software, the combined system is optimized to achieve the maximum exergy efficiency. It is observed that the rate of produced hydrogen decreases with an increase in superheating degree of ORC turbine and takes the maximum value with change in evaporator temperature. Under the base condition, the corresponding cost values for the power, steam and produced hydrogen are 4.811 cents/kWh, 20.56 $/ton, and 3.967 $/kg H2, respectively. Moreover, under the optimized condition, exergy efficiency, rate of the produced hydrogen and sustainability index of the proposed cogeneration system is 52.09%, 8.723 kg/hour and 2.162, respectively.