Design of a Hydrogen Production System Considering Energy Consumption, Water Consumption, CO 2 Emissions and Cost

CO 2 emissions associated with hydrogen production can be reduced replacing steam methane reforming with electrolysis using renewable electricity with a trade-off of increasing energy consumption, water consumption and cost. In this research, a linear programming optimization model of a hydrogen production system that considers simultaneously energy consumption, water consumption, CO 2 emissions and cost on a cradle-to-gate basis was developed. The model was used to evaluate the impact of CO 2 intensity on the optimum design of a hydrogen production system for Japan considering different stakeholders’ priorities. Hydrogen is produced using steam methane reforming and electrolysis. Electricity sources include grid, wind, solar photovoltaic, geothermal and hydro. Independent of the stakeholders’ priorities, steam methane reforming dominates hydrogen production for cradle-to-gate CO 2 intensities larger than 9 kg CO 2 /kg H 2 , while electrolysis using renewable electricity dominates for lower cradle-to-gate CO 2 intensities. Reducing the cradle-to-gate CO 2 intensity increases energy consumption, water consumption and specific cost of hydrogen production. For a cradle-to-gate CO 2 intensity of 0 kg CO 2 /kg H 2 , the specific cost of hydrogen production varies between 8.81 and 13.6 USD/kg H 2 ; higher than the specific cost of hydrogen production targeted by the Japanese government in 2030 of 30 JPY/Nm 3 , 3.19 USD/kg H 2 .