Thermodynamic investigation of a novel hydrogen liquefaction process using thermo-electrochemical water splitting cycle and solar collectors

Abstract

Hydrogen production and liquefaction using solar thermo-electrochemical water splitting systems can as an effective method for long-term renewable energy source storage are suggested. In this paper, a novel integrated configuration for the cogeneration of liquid hydrogen and oxygen by magnesium-chlorine thermo-electrochemical water splitting cycle, hydrogen liquefaction unit, and solar dish collectors is developed. The novel integrated structure produces 7116 kg/h liquid hydrogen and 57597 kg/h oxygen. Through the magnesium-chlorine cycle, pure hydrogen is produced and the required energy is supplied through solar renewable energy based on the climatic conditions of Isfahan city in Iran. Then the produced hydrogen enters the liquefaction process to generate liquid hydrogen. The heat and power consumption of the whole system for the cogeneration of liquid hydrogen and oxygen are 207.9 MW and 373.9 MW, respectively. The heat waste of the integrated structure is used to produce hot water as a by-product. The specific power consumption of the liquefaction cycle is 7.6 kWh/kg LH2 and also the total thermal efficiency of the whole integrated system is 71.4%. Through the pinch method, heat exchanger networks related to multi-stream heat exchangers of the present system are extracted. Sensitivity analysis is used to investigate the effects of changes in major parameters including operating conditions of the thermo-electrochemical cycle as well as changes in the solar dish collector main parameters and the results are reported.