Review—Engineering Challenges in Green Hydrogen Production Systems

Today, hydrogen (H 2 ) is overwhelmingly produced through steam methane reforming (SMR) of natural gas, which emits about 12 kg carbon dioxide (CO for 1 H (?12 kg-CO /kg-H ). Water electrolysis offers an alternative production, but today’s electrolyzers consume over 55 kWh electricity (>55 kWh/kg-H Electric grid-powered water would emit less CO than the SMR process when intensity grid power falls below 0.22 /kWh. Solar- and wind-powered electrolytic production promises 80% reduction process, large-scale (megawatt to gigawatt) direct solar- or has yet be demonstrated. In this paper, several approaches solar-powered are analyzed: (1) coupling a photovoltaic (PV) array with electrolyzer alternating current; (2) direct-current (DC) DC coupling; (3) DC-DC without converter. Co-locating solar wind farm provides lower loss upfront system cost long-distance transmission. A load-matching PV enables 10%–50% levelized other systems excellent scalability from few kilowatts gigawatt. The concept maximum current point tracking introduced in place maximize output by electrolysis.