Replacing steam methane reforming with electrolysis using renewable electricity for hydrogen production can reduce CO2 emissions with a trade-off of larger energy use, water use and cost. A linear programming optimization model that accounts for energy use, water use, CO2 emissions and cost was developed to optimize the configuration of a hydrogen production system; considering Japan in 2030 as a case of study. Four scenarios were considered, prioritizing 1) cost, 2) energy use, 3) Water-Energy-Carbon nexus and 4) Water-Energy-Carbon nexus and cost; under maximum CO2 intensities for hydrogen production between 0 and 18 kg-CO2/kg-H2. Hydrogen production routes include steam methane reforming; and electrolysis using grid electricity, wind electricity, solar photovoltaic electricity, geothermal electricity and hydroelectricity. For CO2 intensities higher than 8 kg-CO2/kg-H2, steam methane reforming accounts for more than 50% of hydrogen production in all scenarios. For a CO2 intensity of 0 kg-CO2/kg-H2, hydroelectricity represents more than 76% of hydrogen production when energy use or cost are prioritized. Including water use in the priorities drives the share of wind electricity in hydrogen production to 37.6%. The remaining hydrogen is produced using solar electricity if cost is not prioritized; or 23.7% geothermal electricity and 38.7% hydroelectricity if cost is prioritized simultaneously.
Keywords Hydrogen Production, Water-Energy-Carbon Nexus, Hydrogen Economy, Low-Carbon Hydrogen Production, Linear Programming Optimization