NOVELTY - The method comprises burning synthesis gas in a power plant to generate electrical energy in a power supplying phase or first operating phase, converting the gas into methane by adding hydrogen in a storage phase and second operating phase, introducing the methane into a natural gas network, and storing the methane in the natural gas network. The methane is obtained from synthesis gas by electrolysis of water. The synthesis gas is continuously produced by a power supplying phase and/or the storage phase. The hydrogen is separated to produce methane from a portion of the synthesis gas.    USE - The method is useful for generating and storing electrical energy in a power plant (claimed).    ADVANTAGE - The method enables for generation and storage of the electrical energy in the power plant in an economical and an environmentally friendly manner.    DETAILED DESCRIPTION - The method comprises burning synthesis gas in a power plant to generate electrical energy in a power supplying phase or first operating phase, converting the synthesis gas into methane by adding hydrogen in a storage phase and second operating phase, introducing the methane into a natural gas network, and storing the methane in the natural gas network. The methane is obtained from synthesis gas by electrolysis of water. The synthesis gas is continuously produced by the power supplying phase and/or the storage phase. The hydrogen is separated to produce methane from a portion of the synthesis gas, and the separated hydrogen is reacted to the rest of the reacted synthesis gas. The hydrogen-depleted portion of the synthesis gas is burned to generate electrical energy in the power plant. The methane or equivalent natural gas is drawn again from the natural gas network in the power supplying phase, and is converted back into electrical energy in power plant. The synthesis gas is produced by gasifying coal or coke and gasifying biomass and produced from mixtures of fossil carbon and biomass, and is converted in the storage phase into organic carbon biomethane. An amount of organic carbon in the methane produced in the storage phase and/or the carbon dioxide produced in the electricity generation phase is determined by the radiocarbon method. The water vapor as feed water for the electrolysis of water is separated by condensation from the flue gases in the combustion of methane or synthesis gas. The carbon dioxide is separated from the synthesis gas or methane. An INDEPENDENT CLAIM is included for a storage power plant.