Performance assessment of a dual loop organic rankine cycle powered by a parabolic trough collector for ammonia and hydrogen production purpose

Abstract

Energy systems used in the future will need to be cleaner and more sustainable. The use of liquid ammonia as a potential medium for hydrogen storage is an efficient solution from an economic, practical and environmental point of view. In this work, a new approach linked to the production of hydrogen and ammonia using a system combining an alkaline water electrolysis, an air separation unit and a Haber Bosch reactor is proposed. The electricity necessary to carry out this process is provided by a dual loop organic rankine cycle supplied by a parabolic trough collector and an auxiliary heater system. The survey was carried out by developing mathematical models on the different components of the combined system. The discrepancies between numerical and experimental results did no exceed 2% for the parabolic trough solar collector. Results demonstrated that hydrogen and ammonia flow rates increased as evaporation temperature of working fluid in the high –thermodynamics cycle increased. Results also showed that the thermal performance of the parabolic trough collector increased as inlet temperature and concentration factor increased. It was pointed out that the overall electrical efficiency of the combined system ranged from 15 to 20.28%. The specific energy consumption of the Back-up heater decreased as mass flow rate of Therminol® VP-1 decreased and its values ranged from 0 to 35 kWh.kg-1 of ammonia. Ammonia production efficiency and electricity consumption ratio varied between 59 to 63% and 8.25 to 8.67 kWh.kg-1of ammonia, respectively. Overall results showed that Cyclohexane, Octane, Toluene and Benzene can be used effectively as working fluid for the high temperature loop organic rankine cycle supplied by parabolic trough collectors for hydrogen and ammonia production purpose.