Along-the-channel modeling and analysis of PEFCs at low stoichiometry: Development of a 1+2D model

Water management remains a key challenge in polymer-electrolyte fuel cells. In this work, a pseudo 3-D (1+2D) model is developed to account better for changes of water management along the channel, as well as verify the possibilities of using differential cells for data capture and translation to integral cell performance. An accurate 2-D membrane-electrode-assembly model is developed for differential cell modeling, which is combined with an along-the-channel stepping algorithm to account for down the channel changes in pressure, temperature, reactant concentration, and relative humidity. Variations in cell performance along the channel due to changes in operating conditions are characterized quantitatively and optimized, where drier feed conditions demonstratively require such an approach. Overall, the study identifies gaps between differential and integral cells including those related to flow velocity and highlights the need for better models to understand and link integral cell performance and water management

Predictive-TOPSIS-based MPPT for PEMFC Featuring Switching Frequency Reduction

A maximum power point tracking (MPPT) for a proton exchange membrane fuel cell (PEMFC) using a combination of conventional finite control set model predictive control (FCS-MPC) and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) is proposed in this paper. The key idea is to maximize the power generation from a PEMFC while minimizing the switching frequency of the power converter. The FCS-MPC technique is formulated to track the maximum power of PEMFC highly affected by ever-changing internal parameters. Meanwhile, the TOPSIS algorithm is applied to overcome the potential weaknesses of insulated-gate bipolar transistor (IGBT), which can only withstand a lower switching frequency. In this project, all simulations were run using MATLAB software to display the output power of the PEMFC system. As a result, the proposed predictive-TOPSIS-based MPPT algorithm can track the MPP for various PEMFC parameters within 0.019 s with an excellent accuracy up to 99.11%. The proposed MPPT technique has fast-tracking of the MPP locus, excellent accuracy, and robustness to environmental changes

Synthesis of a 4-(Trifluoromethyl)-2-Diazonium Perfluoroalkyl Benzenesuflonylimide (PFSI) Zwitterionic Monomer for Proton Exchange Membrane Fuel Cell

In order to achieve a more stable and highly proton conducting membrane that is also cost effective, the perfluoroalkyl benzenesulfonylimides (PFSI) polymers are proposed as electrolyte for Proton Exchange Membrane Fuel Cells. 4-(trifluoromethyl)-2-diazonium perfluoro-3, 6-dioxa-4-methyl-7-octene benzenesulfonyl imide (I) is synthesized from Nafion monomer via a 5-step schematic reaction at optimal reaction conditions. This diazonium PFSI zwitterionic monomer can be further subjected to polymerization. The loss of the diazonium N2+ functional group in the monomer is believed to form the covalent bond between the PFSI polymer electrolyte and carbon electrodes support. All the intermediates and final products were characterized using 1H NMR, 19F NMR and IR spectrometry

Modeling and Control of a Proton Exchange Membrane Fuel Cell-Battery Power System

A general methodology of modeling, control and building a proton exchange membrane fuel cell-battery system is introduced in this thesis. A set of fuel cell-battery power system model has been developed and implemented into Simulink environment. The model is able to address the dynamic behaviours of PEM fuel cell stack, boost DC/DC converter and lithium-ion battery. In order to control the power system to achieve a proper performance, a set of system controller including a PEM fuel cell reactant supply control, a humidification controller, and a power management controller was developed based on the system model. A physical 100W PEM fuel cell-battery power system using microcontroller as embedded controller is built to validate the simulation results as well as demonstrate this new environment-friendly power source. Experimental results show that the 100W PEM fuel cell-battery power system can operates automatically with the varying load condition as a stable power supply. The experiment results follow the basic trend of the simulation results

Air-breathing polymer electrolyte fuel cells: A review

Air-breathing polymer electrolyte fuel cells have become a promising power source to provide uninterrupted power for small electronic devices. This review focuses primarily on describing how the air-breathing PEFC performance is improved through optimisation of some key parameters: the design and material of the current collector; the design and material of the cathode gas diffusion layer; the catalyst layer; and cell orientation. In addition, it reviews the impact of the ambient conditions on the fuel cell performance and describes the methods adopted to mitigate the effects of extreme conditions of ambient temperature and humidity. Hydrogen storage and delivery technologies used in air-breathing fuel cells are then summarised and their design aspects are discussed critically. Finally, the few reported air-breathing fuel cell stacks and systems are reviewed, highlighting the challenges to the widespread commercialisation of air-breathing fuel cell technology

Water management capabilities of bio-inspired flow field configurations for polymer electrolyte membrane fuel cells

Fuel cells have received an increasing amount of attention over the past decade for their power production capabilities. Polymer electrolyte membrane (PEM) fuel cells in particular are researched because of their high power density, large range of operating conditions, green products, and ease of scalability. PEM fuel cells do have a number of issues that reduce their overall performance. These issues include variations in reactant distribution, materials issues for the bipolar plate, and flooding caused by poor water management. Variations in the reactant distribution causes lower overall power output due to regions of low reactant density. This means that optimizing the flow field to increase reactant density increases performance. One optimization method is to mimic natural structures that have similar functions. Leaves, lungs, and vein structures all have similar purposes to those in PEM fuel cells. Imitating their structure has been shown to improve power. It is also important to determine their water management properties. The membrane in the fuel cell must be hydrated to operate at optimally; however excess water causes mass transport issues by either blocking the channels or filling pores in the gas diffusion layer (GDL). This means that the water content in a PEM fuel cell must be delicately balanced to ensure that the membrane stays hydrated without causing flooding issues. Therefore, it is important to determine the water management capabilities of various bipolar plate designs. Clear bipolar plates are used to directly observe the water management capabilities of different flow field designs, which will be verified by the finite element model. These tests have shown that bio-inspired designs perform well in comparison with their conventional counterparts --Abstract, page iii

Investigation of the Effects of Fuel Cells on V-Q & V-P Characteristics

In this paper, the use of a FC system connected to the network is proposed as a source of DG with high reliability, and for this purpose, the dynamic model of the fuel cell has been simulated. A hybrid system of fuel cell distributed generation (FCDG) is presented to provide electrical energy for a small isolated area. Boost converter (DC/DC), in order to increase the voltage level of the system and stabilize the DC link voltage has been used, which provides the possibility of connecting several different scattered production sources in parallel. Voltage stability is concerned with the ability of a power system to maintain acceptable bus voltages under normal conditions and after being subjected to a disturbance. The use of DG sources has many advantages, including meeting peak load needs, reducing network losses, providing reactive power locally, and regulating network voltage. Among all sources of distributed production, fuel cells are of special importance due to their high efficiency, high energy density, the ability to simultaneously produce heat and electric power, and low emission of pollutants. Using fuel cells (FCs) have several advantages and in this paper we investigate the effects of FCs on power systems via simulation a single machine (DG as small gas turbine coupled with a FC)   in the Dig Silent area for different PF of FC. Different PF for FC obtained with control the DC to AC inverter.  We found that by control the PF of FCs, we can increase the limitation of reactive generation of overall system and improve the V-P V-Q characteristics of overall system. With the grid-connected inverter's switching control, the active and reactive power injected into the grid is controlled independently