Identification of PEM fuel cells based on support vector regression and orthonormal bases

© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Polymer Electrolyte Membrane Fuel Cells (PEMFC) are efficient devices that convert the chemical energy of the reactants in electricity. In this type of fuel cells, the performance of the air supply system is fundamental to improve their efficiency. An accurate mathematical model representing the air filling dynamics for a wide range of operating points is then necessary for control design and analysis. In this paper, a new Wiener model identification method based on Support Vector (SV) Regression and orthonormal bases is introduced and used to estimate a nonlinear dynamical model for the air supply system of a laboratory PEMFC from experimental data. The method is experimentally validated using a PEMFC system based on a ZB 8-cell stack with Nafion 115 membrane electrode assembliesPeer ReviewedPostprint (author's final draft

Water transport study in high temperature proton exchange membrane fuel cell stack

A study of water transport in a high temperature phosphoric acid doped polybenzimidazole (PBI) membrane fuel cell stack is reported. Tests with different stoichiometries of dry cathode and different humidity levels of anode are performed. It is found that water transport across the membrane electrode assembly (MEA) is noteworthy and that water vapor partial pressure on the anode outlet is almost always higher than on the cathode outlet, even when using dry hydrogen. The water transport is a strong function of current density but it also depends on stoichiometry and humidity level. In a series of tests with dry nitrogen on one side and humid nitrogen on the other side, the membrane's water permeability coefficient is determined to be 2.4 × 10-13 mol s-1 cm-1 Pa-1 at 160 °C which is more than an order of magnitude higher than the values previously reported in the literature. Also, the results indicate that the permeability coefficient might be relative humidity dependent and could even be somewhat higher than the value reported here, but further investigation is needed. The experimental findings are reproduced and explained with a 2D steady state computational fluid dynamics (CFD) model. Internal water transport profiles across the membrane and along the gas flow channels are presented and discussed.Peer ReviewedPostprint (author’s final draft

Adaptive nonlinear parameter estimation for a proton exchange membrane fuel cell

© 2022 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting /republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksParameter estimation is vital for modeling and control of fuel cell systems. However, the nonlinear parameterization is an intrinsic characteristic in the fuel cell models such that classical parameter estimation schemes developed for linearly parameterized systems cannot be applied. In this paper, an alternative framework of adaptive parameter estimation is designed to address the real-time parameter estimation for fuel cell systems. The parameter estimation can be divided into two cascaded components. First, the dynamics with the unknown parameters are estimated by a new unknown system dynamics estimator (USDE). Inspired by an invariant manifold, this USDE is designed by applying simple filter operations such that the information of the state derivative is not required. Secondly, an adaptive law driven by the function approximation error is proposed for recovering unknown model parameters. Exponential convergence of the estimated parameters to the true values can be proved under the monotonicity condition. Finally, experimental results on a practical proton exchange membrane fuel cell system are given to verify the effectiveness of the proposed schemes.Peer ReviewedPostprint (author's final draft

Experimental decoupling of single cell polarization losses

The decoupling of the current sweep with the Ohmic resistance is a very powerful tool to determine the magnitude of the voltage losses inside of a fuel cell. In a time frame of seconds, the fuel cell can be diagnosed and critical information on the state of the membrane, catalyst and diffusion layer can be assessed. The losses determined by this technique are the Ohmic, mass transport and activation. With this technique flooding and dry can be isolated and degradation studies can be made. Finally, this technique can be applied to a real system were this data can be used to improve control strategies for performance and durability when integrated in to a model based controller.Peer ReviewedPostprint (author's final draft

Modelling of solid oxide electrolizer and hydrogen leak estimation

Solid Oxide Elecyrolizers (SOEC) are electrochemical devises that produce hydrogen from water using the energy of an electric power source. SOEC operate at high temperatures (around 800ºC) and have efficiencies around 53% [1]. One of the most interesting scenarios of SOEC use is the storage of energy in hydrogen form when renewable power sources do not match the load. Because of this, it is important to study the dynamic behavior of SOEC systems in order to know their ability to adapt to changing power profiles. Different works describe SOEC models in the literature, as reviewed in [2], but time dependent models are scarse [3] and very few of the models are experimentally validated. This work presents a dy-namic model of a SOEC implemented in MATLAB Simulink and its match with experimental data. One important issue in SOEC stacks is hydrogen leak, which aggravates with ageing and is mostly caused by the high operating temperatures. The analysis of the experimental data of this work suggested hydrogen leak. Based on the SOEC thermal model, a methodology to quantify the flow of hydrogen that is leaked out is proposed and applied to the experimental system.Postprint (published version

Effect of metal hydride properties in hydrogen absorption through 2D-axisymmetric modeling and experimental testing in storage canisters

A two-dimensional axisymmetric model is developed to study the hydrogen absorption reaction and resultant mass and heat transport phenomena inside a metal hydride canister. The model is compared against published literature and experimental data. Experimental tests are performed on an in-house fabricated setup using different cooling scenarios. An extensive study on the effects of the metal properties on charging performance is carried out through non-destructive testing (NDT). Results show that the properties that most influence the charging performance are: absorption rate constant (Ca), activation energy (Ea) and thermal conductivity (km). A Higher porosity (e) reduces charging time and amount of hydrogen stored while a higher cooling level produces a faster charging process. These results can be used to select metal hydride materials but also to estimate the metal hydride internal state and the process can be used for future evaluation of metal hydride degradation.Postprint (author's final draft

Mathematical modeling, numerical simulation and experimental comparison of the desorption process in a metal hydride hydrogen storage system

Peer ReviewedPostprint (author's final draft

Combined production of electricity and hydrogen from solar energy and its use in the wine sector

© . This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/In the present research, the energy demanded by the wastewater treatment plant of a winery and the pumping station of the irrigation system of a vineyard is supplied by a stand-alone renewable energy system formed by three photovoltaic arrays connected to a microgrid. A relatively small battery maintains the stability and quality of the energy supply acting as a short-term energy storage. Hydrogen is generated in a production and refueling plant specifically designed for this project, and it is eventually used in a plug-in BEV properly modified as a hybrid vehicle by adding a PEM fuel cell. On the one hand, the technical and economic feasibility of the on-site electricity production for the winery and vineyard, compared to the commercial electricity from the grid and diesel gensets, is demonstrated. On the other hand, the diesel savings by the hydrogen generated on site are assessed. The electricity (72 MWh) and hydrogen (1,214 m3) produced in the first year have saved the emission of around 27 tons of equivalent CO2.Peer ReviewedPostprint (author's final draft

Experimental decoupling of single cell polarization losses

The decoupling of the current sweep with the Ohmic resistance is a very powerful tool to determine the magnitude of the voltage losses inside of a fuel cell. In a time frame of seconds, the fuel cell can be diagnosed and critical information on the state of the membrane, catalyst and diffusion layer can be assessed. The losses determined by this technique are the Ohmic, mass transport and activation. With this technique flooding and dry can be isolated and degradation studies can be made. Finally, this technique can be applied to a real system were this data can be used to improve control strategies for performance and durability when integrated in to a model based controller.Peer Reviewe

Identification of PEM fuel cells based on support vector regression and orthonormal bases

© 20xx IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Polymer Electrolyte Membrane Fuel Cells (PEMFC) are efficient devices that convert the chemical energy of the reactants in electricity. In this type of fuel cells, the performance of the air supply system is fundamental to improve their efficiency. An accurate mathematical model representing the air filling dynamics for a wide range of operating points is then necessary for control design and analysis. In this paper, a new Wiener model identification method based on Support Vector (SV) Regression and orthonormal bases is introduced and used to estimate a nonlinear dynamical model for the air supply system of a laboratory PEMFC from experimental data. The method is experimentally validated using a PEMFC system based on a ZB 8-cell stack with Nafion 115 membrane electrode assembliesPeer Reviewe