Modelling, prototyping and economic analysis of a Membraneless Electrolyzer

Electrolysis has long been the preferred way to produce clean hydrogen. Until now, it is performed in electrolyzers that use diaphragms (alkaline) or membranes (PEM and SOEC) to keep separated the areas of hydrogen and oxygen reactions. However, recently a new variant of electrolysis has emerged, which does not involve the use of physical separators. These are membraneless electrolyzers, where the only thing that keep separated hydrogen from oxygen inside the cell is the fluid dynamic forces generated by the design and operation of the cell. This has direct repercussions on the investment cost since a membrane or a diaphragm is eliminated. Those ones are elements most susceptible to load changes and variations in operating temperature. This variant of electrolysers has been studied only for applications at low temperatures, in the range of alkaline and PEM electrolysers. Therefore, reducing the initial investment costs and increasing the versatility of the electrolyzer are two of the most important characteristics of this technology. Especially given that the initial investment costs of electrolyzers still remain one of the main issues to their large-scale use. In addition to the fact that the electrolysers would be coupled to intermittent renewable energy sources, such as solar and wind, so the versatility is fundamental. To study this technology, the first step was an analysis on the different types of membraneless electrolyzers present in the literature and then, a preliminary comparison was carried out based on the available data, to define which projects proved to be the most promising. Subsequently, a model was developed to obtain the flow rate and purity of the hydrogen produced, and the characterization of the cell with j-V curves. In this way it was possible to evaluate the efficiencies of the studied plants and compare them. After comparing the types of membraneless electrolyzers selected, the one that showed the most promising prospects was chosen. To validate the model data, a prototype was designed starting from the designs found in the literature and the versions used for the execution of the experimental tests were 3D printed. Tests of watertightness and operation of the circuits and subsequently, the electrochemical performance to obtain the polarization curves of the electrolyzer. Once the validation of the model data was performed, ways were also tried to evaluate the purity of hydrogen and the flow rates produced in the field. The economic analysis was performed on the chosen design. Different scenarios and possible cases have been developed, including technology level, power supply, taxation and four locations have been selected (China, USA, Hong Kong and EU-27), in which to carry out the economic analysis of plants capable of producing from 500 to 1000 tons of hydrogen per year. With this study very competitive prices were obtained, in a case the levelized cost of hydrogen evaluated was 1.95 USD/kg. Once the analyzes were carried out to determine the economic performance of a plant for the production of hydrogen by applying electrolysis without membranes, and compared the results, a sensitivity analysis was carried out. This analysis, applied to various parameters impacting on economic analysis, was used to determine the main intervention strategies to further reduce production costs and thus increase the marketability of hydrogen.