Experimental and modelling investigation on H2 production through low temperature electrolysis

Nowadays, because of the increase in energy consumption and global warming and due to the policy of the European commission, there is a necessity to go towards new and clean energy production technologies like renewable energy sources (RES). Although RES are crucial elements in order to arrive at electrification and decarbonisation of processes, they are intermittent sources that need large scale electrical energy storage. In this sense, a technology able to overcome these issues is Power-to-Gas (PtG), in which the produced electricity from RES can be stored in the form of Hydrogen. H2 is a clean fuel that has a fundamental role in solving the main problems connected to fossil fuels. So, the RES can be coupled with an innovative technology like Polymer Exchange Membrane Water Electrolysis (PEMWE). PEMWE is a technology based on a structure consisting of different components such as: membrane electrode assembly (MEA), Gas Diffusion Layers (GDLs), Gaskets, Bipolar Plates (BP), current collectors and end plates. It is able to produce hydrogen at higher purity than other methods and it can reach up to 99.99%. In particular, the produced hydrogen acts as energy carrier for energy storage and can also guarantee the grid stabilization. The goal of this thesis is to perform an experimental investigation on the hydrogen production through tests conducted on an electrolytic cell installed in a test bench that is located at HYSISLAB, a laboratory used for hydrogen production technologies at the Environment Park in Turin. Initially, the assembling procedures has been carried out and consequently, the polarization measurements have been performed for defined time-steps. Experimental results have been used to characterize the MEA and, in particular, to understand how the system reacts by changing the main parameters: temperature, pressure and current. Moreover, the hydrogen production has been also investigated. A mathematical model has been elaborated on MATLAB® environment exploiting mass and energy balance equations, considering overall mass transport, thermal, electrical and electrochemical phenomena of PEMWE. More in detail, OCV, activation overpotential, ohmic overpotential and diffusion overpotential have been modelled. A validation procedure of the model has been carried out using the experimental results with the help of the Sum Squared Error (SSE). This permits the evaluation of some fitting parameters in order to understand how they influence the performance of the cell. In this context, using the model, the best fit for the polarization curve can be found. The validated model can be used as a tool to predict the performances of the PEM electrolyser. In conclusion, in this thesis several procedures have been conducted and polarization curves are extracted. It is a fundamental work since it represents the basis for further experimental procedures and measurements for PEMWE, for example degradation tests. Considering future works, there are different aspects that need to be improved, for example going towards to a more automated test bench with the installation of an automatic refilling system, the installation of an extra conductivity meter on the cathode inlet to catch the difference in conductivity between inlet and outlet and the installation of Mass Spectroscopy to understand the composition of produced gases.