Design and Optimization of Fuel Cells: A Case Study on Polymer Electrolyte Membrane Fuel Cell Power Systems for Portable Applications (original) (raw)
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Renewable and Sustainable Energy Reviews, 2019
Polymeric Electrolyte Membrane Fuel Cell (PEMFC) modeling considering thermal and electrical behavior in a coupled manner is a key aspect when evaluating new designs, materials, physical phenomena or control strategies. Depending on the behavior to be emulated, it is important to choose the modeling technique that best suits the needs required. In this sense, this paper describes the most commonly used PEMFC modeling techniques in the context of analytical-mechanistic approach, semi-empirical approach based on theoretical formulation and empirical correlations, as well as empirical approach based on experimentation with a real system. In addition, an in-depth analysis of PEMFC models at the cell and stack level that emulate the thermal and electrical behavior of these systems in a coupled manner is carried out. A chronological classification of the most relevant models has been made based on the modeling technique used, purpose of the model, state and dimension of the model, and the real system, other developed models or experimental results that have been used to validate the proposed new model. Additionally, guidelines to improve the energy efficiency of PEMFC systems through the development of new models are given.
Thermodynamic Study of Operation Properties Effect on Polymer Electrolyte Membrane Fuel Cells (PEM)
2021
The thermodynamic analysis of PEM fuel cell energy production depends on the entropy and enthalpy of reaction with the changing of the operating temperatures that ranges between 50 and 100ºC, the electrical work done will be equal to the Gibbs free energy released. This paper presents a mathematical model of PEM fuel cells, based on physical-chemical procedures of the phenomena occurring inside the fuel cell, and it was theoretically studied the performance at different operation variables and conditions. The C++ program is designed to calculate all thermo-chemical parameters, i.e. enthalpy of formation, Gibbs free energy, work and efficiency for any type of fuel cells. The results are plotted as a function of fuel cell operating temperature. The results shows that the highest value of Gibbs energy is at the lowest operating temperature, and decreases gradually with increasing the temperature, the output voltage is determined by cell’s reversible voltage that arises from potential d...
The main objective of this work is to give information on the behavior of three small PEMFC (Polymer Electrolyte Membrane Fuel Cell/Proton Exchange Membrane Fuel Cell) prototypes under static and dynamic load conditions. This is a fuel cell that holds promise in the use for energy in automotive and household applications. A computational model was developed to simulate the static and dynamic performance of this particular type of fuel cell. This model is based on electrochemical equations and takes into consideration the advantages and disadvantages of the device in order to generate power. The model takes into consideration the operating and design parameters of the materials, with the results being compared with practical experiments. This research gives the possibility to infer, from steady state and dynamic studies, on the design of PEMFC's of different sizes and also to develop a further research on the need for control such as of hydrogen and oxygen pressure and flow. The study of sizing of the fuel cell is also an invaluable asset due to the low cost of the simulation.
Detailed thermodynamic analysis of polymer electrolyte membrane fuel cell efficiency
International Journal of Hydrogen Energy, 2013
It is common knowledge that efficiency of fuel cells is highest when no electric current is produced while when the fuel cell is really working, the efficiency is reduced by dissipation. In this paper the relation between efficiency and dissipation inside the fuel cell is formulated within the framework of classical irreversible thermodynamics of mixtures. It is shown that not only dissipation influences the efficiency but that there are also some other terms which become important if there are steep temperature gradients inside the fuel cell. Indeed, we show that the new terms are negligible in polymer-electrolyte membrane fuel cells while they become important in solid oxide fuel cells. In summary, this paper presents a formulation of non-equilibrium thermodynamics of fuel cells and provides analysis of efficiency in terms of processes inside the fuel cells, revealing some new terms affecting the efficiency.
A Computational Analysis on the Operational Behaviour of Open-Cathode Polymer Electrolyte Fuel Cells
ECS Meeting Abstracts, 2019
Polymer electrolyte membrane fuel cell (PEMFC) is a promising sustainable energy conversion technology to replace conventional fossil fuel based applications. The products of the fuel cell operation are electricity, water, and heat. A common strategy to achieve high power density is to operate at high current densities. However, the rate of heat generation is approximately proportional to the current density and waste heat removal is therefore a challenge for high power density systems. Overheating can cause drying of the conductive polymeric membrane inside the cell causing significant ohmic loss. It can also create local hot spots in the membrane electrode assembly (MEA) that are susceptible to degradation [1]. Hence, liquid coolant such as water or other thermal fluids is used in conventional PEMFCs by embedding separate cooling channels in the flow field plates. However, this type of cooling adds extra balance-of-plant (BOP) components into the system. This can be eliminated by ...
2010
Polymer Electrolyte Membrane (PEM) fuel cells are electrochemical power generators that converts the energy potential of a hydrogen-based fuel into electricity with water and heat as the major by-products. The sensitivity of the solid polymer membrane to temperature requires that thermal management of a PEM fuel cell stack operates efficiently to maintain the temperature at the optimal level. Air cooling is normally applied for industrial PEM fuel cells of up to 2 kW power output. A computational investigation on the effective micro cooling channel geometries was conducted in order to enhance the practical capability of air cooling for a 3 kW stack power output with a reduced conversion efficiency of 30%. Plate and stack assembly simulation cases of a single channel and 40 cooling channel configurations using Computational Fluid Dynamics (CFD) were conducted with constant heat generation. The cooling performance was evaluated based on the boundary heat transfer and shows 100% effect...
Asia-Pacific Journal of Chemical Engineering, 2009
Abstract The aim of this paper is to present a simple 3D computational model of a polymer electrolyte membrane fuel cell (PEMFC) that simulates over time the heat distribution, energy, and mass balance of the reactant gas flows in the fuel cell including pressure drop, humidity, and liquid water. Although this theoretical model can be adapted to any type of PEMFC, for verification of the model and to present different analysis it has been adapted to a single cell test fixture. The model parameters were adjusted through a series of ...
Effects of Flow Characteristics in Polymer Electrolyte Membrane Fuel Cell
An experimental and numerical study of polymer electrolyte membrane fuel cell (PEMFC) is presented and compared with the experimental data to investigate the effects of pressure gradient, flow rate, humidification and supplied oxidant type for the practical application. The membrane and electrolyte assembly (MEA) materials are implemented by double-tied catalyst layers. A single-phase two-dimensional steady-state model is is implemented for the numerical analysis. Testing condition is fixed at 60sccm and 70°C in anode and cathode, respectively. It is found that the performance of PEMFC depend highly on the conditions as gas pressure, temperature, thickness, supplied oxidant type (Oxygen/Air) as well as humidification. The results show that the humidification effect enhances the performance more than 20% and the pure oxygen gas as fuel improves current density more than 25% compared to ambient air suppliance as oxidant.
Journal of The Electrochemical Society, 2020
We show that the coupling effects in non-equilibrium thermodynamics for heat-, mass- and charge- transport in the polymer electrolyte membrane fuel cell (PEMFC) all give significant contributions to local heat effects. The set of equations was solved by modifying an open-source 1D fuel cell algorithm. The entropy balance was used to check for model consistency. The balance was obeyed within 10% error in all PEMFC layers, except for the cathode backing. The Dufour effect/thermal diffusion and the Peltier/Seebeck coefficient are commonly neglected. Here they are included systematically. The model was used to compute heat fluxes out of the cell. A temperature difference of 5 K between the left and right boundary of the system could change the heat fluxes up to 44%. The Dufour effect, for instance, increases the temperature of both anode and cathode, up to 9 K. The possibility to accurately predict local heat effects can be important for the design of fuel cell stacks, where intermediat...
The cooling system of a high-temperature PEM fuel cell with a nominal electric power of 1.5 kW for a combined heat and power unit (CHP) has been designed using a thermochemical model. The 1D model has been developed as a simple, predictive, and useful tool to evaluate, design, and optimize cooling systems of PEM fuel cells. As proved, it can also be used to analyze the influence of different operational and design parameters, such as the number and geometry of the channels, or the air flow rate, on the overall performance of the stack. To validate the model, predicted results have been compared with experimental measurements performed in a commercial 2 kW air-forced open-cathode stack. The model has then been applied to calculate the air flow required by the designed prototype stack as a function of the power output, as well as to analyze the influence of the cooling channels configuration (cross-section geometry and number) on the heat management. Results have been used to select the optimum air-fan cooling system, which is based on compact axial fans.