Method for the storage of energy in the form of electrical energy or heat, in an educt gas mixture, and a device for implementing the said method

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This patent describes a method and a device for storing surplus energy from renewable sources, such as wind or solar power, in methane-containing gas (such as natural gas or biogas) by partially converting methane to hydrogen, carbon dioxide, and carbon monoxide using an endothermic partial reforming process. Only a small fraction of methane is converted, so the resulting product gas can still be fed into existing natural gas infrastructure. The stored energy can later be retrieved by converting the hydrogen and carbon dioxide back into methane (methanation), generating heat or electricity as needed.

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• Storing excess renewable energy (wind or solar) by converting it into chemical energy within the natural gas grid.
• Energy buffering to balance supply and demand in power grids with large shares of renewable energy.
• Utilizing existing natural gas pipelines and storage facilities for chemical storage and transport of renewable energy.
• Industrial processes that require flexible, large-scale energy storage.
• Conversion of biogas into a form that can be integrated into national gas networks.

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• Uses existing natural gas infrastructure, reducing investment in new storage solutions.
• Minimizes energy losses compared to full methane reforming or conventional power-to-gas processes.
• Flexible: energy can be stored as heat or electricity, and retrieved on demand as gas, heat, or electricity.
• Improved efficiency and cost savings due to partial rather than complete methane conversion.
• Easy integration with renewable energy sources, supporting grid stability and decarbonization.
• Possibility to leverage both gas and electricity markets for stored energy.

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Patent Abstract

The method of storing energy (8) in the form of electric current or heat, in a reactant gas mixture containing methane by partial conversion of methane under addition of water vapor to hydrogen, carbon dioxide and carbon monoxide (CO) by an endothermic partial reforming process as a result of which a product gas mixture arises, is claimed, where the energy is stored into the reactant gas mixture. The reforming process is based on: a reaction temperature in accordance with a chemical equation, where the methane is reacted with water to give three moles of hydrogen and CO. The method of storing energy (8) in the form of electric current or heat, in a reactant gas mixture containing methane by partial conversion of methane under addition of water vapor to hydrogen, carbon dioxide and carbon monoxide (CO) by an endothermic partial reforming as a result of which a product gas mixture arises, is claimed, where the energy for the endothermic partial reforming process is stored into the reactant gas mixture. The endothermic reforming process is based on: a reaction temperature in accordance with a chemical equation, where the methane is reacted with water to give three moles of hydrogen and CO; a Sabatier-inverse reaction according to the reaction formula, where the methane is reacted with two moles of water to give four moles of hydrogen and CO; and/or a shift-reaction in accordance with the chemical equation, where the CO is reacted with the water to give one mole of hydrogen and carbon dioxide. The reactant gas mixture is natural gas and/or fermentation gas. A proportion of the hydrogen created by the endothermic partial reforming process is controlled by the reaction temperature of the partial reforming process and by a pressure at which the partial reforming process occurs. The reforming process is carried out by catalysts at the reaction temperature of 250-350[deg] C. The methane contained in the reactant gas mixture is converted by the partial reformation of 2-5%. The gas mixture resulting after the partial reformation corresponds to guidelines for natural gas quality in accordance with DVGW-guidelines (technical rule, worksheet G260, gas composition, May 2008). The stored energy originates from regenerative energy source that is a wind turbine. The heat is removed from the product gas to preheat the reactant gas mixture and to evaporate the added water. The hydrogen and carbon dioxide contained in the resultant product gas mixture are reacted before consumption of the product gas mixture by a partial exothermic methanation in methane and water vapor. A reactor vessel (2) is used for both the partial reformation process and methanation. An independent claim is included for a device for storing energy in the form of electric current or heat, in a reactant gas mixture containing methane by partial conversion of methane under addition of water vapor to hydrogen.