Methane production through a solid oxide electrolyser with primary renewable source and carbon dioxide capture Renewable electric energy can be transformed into storable methane via electrolysis andsubsequent methanation. Power to Gas systems appear as a promising technology to ex-ploit the surplus energy from renewable power plants; different gases can be produced(e.g. methane or hydrogen).In this Master Thesis work, two different Power to Gas systems are modelled using Mat-lab Simulink: a Solid Oxide Electrolyser with aCO2-methanator and a Solid OxideCo-Electrolyser with aCO-methanator. This latter component can operate with an in-letH2/CO-ratio equale to 3 or larger. A ratio of 5 is also considered. TheCO2, comingfrom biogas produced in the Waste Water Treatment Plant ofEDAR Riu Secsituated inSabadell (Barcelona), is captured and processed in order to obtain methane. Additionally,according to the Master Thesis’ objectives, a photovoltaic power plant and aCO2stor-age are sized. An averaged power profile produced by a PV plant located in Barcelonais obtained with thePV*SOLprogramme. Therefore, the installation of a P2G systemallows to achieve two positive effects: firstly, theCO2is not released to the atmosphere.Secondly, theCO2is reused to produce methane without getting it, in a more pollutingway, from natural gas or coal.Nowadays not all the technologies analysed in this work are mature. Due to the com-plexity and partial lack of information simplified models and assumptions in operatingconditions have been employed.The main goal is to evaluate what is the most efficient Power to Gas choice in terms ofinstalled nominal power to exploit the entire amount of the carbon dioxide over one yearof operation. Furthemore the photovoltaic power plant is sized assuming operativity onlyduring the summer period; the differences with respect to yearly operation are illustratedin terms of required power and storage capacity.According to the results achieved in this work, the optimal Power to Gas system is theco-electrolyser coupled with aCO-methanator with aH2/CO-ratio equal to 3. Consid-ering the worst case of operation, thus during winter, a PV plant of 1.2 MW has to beinstalled to process the entire amount ofCO2available; regarding only summer opera-tion, a smaller plant of 0.8 MW plant is needed. The capacity of the storage, assumingonly summer operation, is also reduced of almost 30% with respect to winterly operation,where 995m3of storage are needed. The molar fractions of the outlet gas mixture, aftermethanation process, are around 30%CH4, 60%H2Oand 10%CO2.To obtain more precise results, improvements should be apported to the developed mod-els, enhancing the learning of the operating conditions
