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HELMETH project targeting >85% efficiencies for power-to-gas; high-temperature electrolysis

The HELMETH (“Integrated High-temperature ELectrolysis and METHanation for Effective Power to Gas Conversion”) project, coordinated by Karlsruhe Institue of Technology (KIT) is targeting power-to-gas (PtG) system efficiencies of more than 85% through better synergies with existing process steps. Power-to-gas (e.g., Audi e-Gas) uses renewable electricity for the production of hydrogen and then methane.

Renewable power is used for electrolysis to decompose water into oxygen and hydrogen. Then, hydrogen reacts with carbon dioxide or carbon monoxide to produce methane, which can be used seamlessly in the existing natural gas infrastructure facilities. Injection of hydrogen would possibly require an increased adaptation expenditure for transportation and application, as the energy density and chemical properties differ considerably.

Electrolysis and methanation are often analyzed and optimized separately, notes Dimosthenis Trimis, KIT. However, use of the process heat produced by methanation has a potential for use in electrolysis; high-temperature electrolysis at about 800°C is associated with thermodynamic advantages that increase efficiency.

The 3-year, €3.8-million (US$5.25) HELMETH project will start with a kickoff meeting of the project partners at the KIT this week. €2.5 million comes from the European Union’s Seventh Framework Programme (FP7/2007-2013) for the Fuel Cells and Hydrogen Joint Technology Initiative.

HELMETH is the acronym of KIT’s project partners are the University of Turin, the Technical University of Athens, the companies of Sunfire GmbH and Turbo Service Torino S.P.A, the European Research Institute of Catalysis ERIC, and the German Technical and Scientific Association for Gas and Water (DVGW).


Roger Pham

Hydrogen can be utilized at much higher efficiency than Methane by the end user. FCV is significantly more efficient than NG-ICEV. Home-based H2-FC with waste heat utilization will be more efficient than CCGT using Methane at the power plants.

If one talks about high-temperature electrolysis by using special ceramic electrodes, one can get efficiency to unity or almost 100%, if the entire unit is insulated and no heat is allowed to escape, since the heat produced from electrolysis from internal resistance is allowed to raise the temperature of the entire unit to 600 degrees C, and in so doing, will lower the voltage required to split water at higher temperatures.


Is this another early step towards future electro-fuels?


There is no 100% efficiency as even an insulated vessel will radiate energy in some form. You've heard of the Black-body problem? This is a thermionic issue that anticipates that a material will somehow absorb all ranges of radiation to perform useful work (like form chemical bonds, or produce free electrons that in turn will exert a Faraday force with super-utilizable efficiencies). And all that heat is hell on votaic cells.

What we have here is a hot battery that will probably best consist of molten sodium, which can be heated by nuclear fission. And no talk of nuclear in Germany these days.

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