For discussion purposes, we can assume one of two Green methods are used to produce Hydrogen using Renewables produced electricity: 1.PEM Electrolysis; 2.Reversible Solid Oxide Fuel Cell (RSOFC)(High-Temperature Electrolysis (HTE) steam system).
1. Electrolysis is a well documented method using electricity to breakdown water into Hydrogen and oxygen. Proton Exchange Membrane (PEM) technology is a good choice for the electrolysis system. A typical PEM layout as shown with a photograph of Siemens Silyzer 300 unit for PEM electrolysis.
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Future large scale applications of the Siemens Silyzer 300 units are Module Arrays with 24 modules rated at 17.5 MW, system efficiency ~75%, producing 340 kg/hr of Hydrogen (0.02kg/kWh).
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A 10 MW ITM electrolyser facility was installed with 5 submodules rated at 2 MW each, stack efficiency 0.02kg/kWh.
2. RSOFC is an interesting method to use solid oxide fuel cells able to work in two directions: initially one direction to produce Hydrogen and subsequently the reverse direction to produce energy from the Hydrogen. The solid oxide fuel cells (SOFC) act as a High-Temperature Steam Electrolyser.
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