Portable PEM fuel cell‐ultracapacitor system: Model and experimental verification

This paper presents a comparative study between a model of portable direct hydrogen‐fed proton exchange membrane fuel cell‐ultracapacitor (PEMFC‐UC) power source and experimental results obtained from an actual PEMFC‐UC system in the authors' laboratory. In the proposed system the UC is directly connected to the PEMFC output terminals. The UC is used to supply the power mismatch during the sudden load variations when the load is higher than the PEMFC maximum capacity. The model is then used to estimate the output voltage and study the transient response of the PEMFC‐UC system when subjected to rapid changes in the load. To validate the model, laboratory experiments are carried out using a 100 W commercially available PEMFC and an UC. The model results are verified against the experimental data using three statistical indices to measure the variations, unbiasedness, and accuracy. The indices indicate a maximum difference of 1.06%, which shows a close agreement between the voltage and power responses of the proposed model and the actual PEMFC‐UC system. Copyright © 2009 John Wiley & Sons, Ltd.     

Portable direct hydrogen fed PEM fuel cell model and experimental verification

This paper focuses on the experimental verification of an electrochemical model of 100 W portable direct hydrogen fed proton exchange membrane (PEM) fuel cell (FC). The model is built based on the relationship between the FC terminal voltage and the partial pressures of hydrogen and oxygen. The model is then used to predict the output voltage and study the transient response of a PEMFC when subjected to rapid changes in the load. To validate the model, the measurements obtained from a commercially available 100 W FC are compared against the model results. Three different scenarios are considered for testing the model and the actual FC. In the first two scenarios, a step change in the load is used. In the third scenario, the load is replaced by a laptop computer. Results show a close agreement between the voltage and the power responses of the proposed model and the actual PEM FC. Copyright © 2009 John Wiley & Sons, Ltd.     

Thermal coupling of an open-cathode proton exchange membrane fuel cell with metal hydride canisters: An experimental study

In this paper, the impacts of utilising the heat generated by a 2.5-kW open-cathode proton exchange membrane fuel cell (PEMFC) on enhancing the hydrogen release rate of nine 800 NL AB₅ metal hydride (MH) canisters were experimentally investigated. Thermal coupling of MH canisters with PEMFC offers a potential to improve the hydrogen discharge rate of MH canisters by utilising its waste heat. However, the added complexity for implementing this idea remains to be a barrier. Open-cathode fuel cells with hot air exiting the cathode side offer an opportunity to simplify its thermal coupling arrangement with MH canisters. The set-up was designed with minimum added parts with just a ducting system to direct the hot exit air from the fuel cell passing over the MH canisters. The experimental results showed that the heat required by the MH canisters to supply enough hydrogen to the fuel cell at 500 W, 1000 W and 2000 W operating points accounts for around 40%, 36.5%, and 32% of the total heat removal from the stack, respectively. The arrangement proved to be feasible for serving its purpose and could eliminate the need for oversizing the MH hydrogen storage system that is normally practised to guarantee the right rate of hydrogen supply at higher power outputs.     

Adaptive estimation of PEMFC stack model parameters - An experimental verification

The growing popularity of using proton-exchange membrane fuel cells (PEMFCs) stacks in stationary, portable, and transportation applications is driving researchers to develop proper dynamic models for PEMFCs. These models are used to accurately capture the electrical characteristics and runtime performance. This work proposes a well-known equivalent circuit model of a battery, to be modified and used as a model for a PEMFC stacks voltage-current characteristics. This model is modified by finding suitable functions to model the open circuit voltage and the series resistance, required to model the electrical performance of a 200-W PEMFC stack. The paper also shows that the existing adaptive parameters estimation (APE) technique for Li-ion battery parameters estimation is also able to estimate parameters of the PEMFC stack's model. The model parameters are estimated using the APE technique that requires only five experiments. The model is validated experimentally under different load conditions for a 200-W PEMFC stack supplied from a hydrogen cylinder (voltage error ?0.2 V to 0.5 V), and a 30-W PEMFC stack supplied from a fuel stick (voltage error ?0.2 V–0.4 V). The results show that the parameters estimation methodology works well across PEMFC stacks of different sizes with different input fuel intake configurations, with a minimal terminal voltage estimation error in the order of millivolts. Open circuit voltage measurements (OCV) show that the OCV curve starts at a little lower than 31 V, declines slowly to around 30 V for a normalized hydrogen flow rate of 0.6, after which there is a sudden linear decline in OCV was observed. Most of the data has absolute estimation error less than 0.1 V. In fact, the terminal voltage estimation error across all tests, with different current discharge profiles, lies between ?0.2 and 0.2 V only. Also, 95.84% of the error samples lie between ±0.1% error.     

Performance prediction of PEM fuel cell with wavy serpentine flow channel by using artificial neural network

Effects of serpentine flow channel having sinusoidal wave at the rib surface on performance of PEMFC having 25 cm² active area are investigated at different flow rates, three different amplitudes changing from 0.25 mm to 0.75 mm and three different cell operation temperatures. A proton exchange membrane fuel cell (PEMFC) is modeled for the prediction of the output current by using artificial neural network (ANN) that is utilized the aforementioned experimental parameters. Effect of hydrogen and air flow rate, the fuel cell temperature, amplitude of channel is tested. The results indicated that model C1 having lowest amplitude is enhanced maximum power output up to 20.15% as compared to indicated conventional serpentine channel (model C4) for 0.7 SLPM H₂ and 1.5 SLPM air and also model C1 has better performance than C2, C3 and C4 models. The maximum power output is augmented with increasing the cell temperature due to raising the fuel and oxidant diffusion ratio. Cell temperature, amplitude, H₂ and air flow rate and input voltage is used as input variables in train and test of the developing ANN model. MAPE of training and testing is determined as 2.89 and 2.059, respectively. Prediction results of developed ANN model including two hidden layer shows similar trend with experimental results. Developed ANN model can be used to both decrease the number of required experiments and find the optimum operation condition within the range of input parameters.     

Hydrogen consumption minimization method based on the online identification for multi-stack PEMFCs system

The proton exchange membrane fuel cell (PEMFC) stacks are not widely used in the field of transportation industry, due to their limited power. Thus, the PEMFC stacks usually connected in parallel or series to meet the load demand power in high-power applications. The hydrogen consumption of multi-stack fuel cells (MFCs) system is related to the efficiency and output power. In addition, the efficiency of PEMFC depends on the applied voltage and other parameters. Consequently, the hydrogen consumption of system changes with varying load, because the system parameters are also varying. It makes reducing the fuel consumption of system a challenging assignment. In order to achieve the goal of minimizing fuel consumption of parallel-connected PEMFCs system, this paper proposes a novel power distribution strategy based on forgetting factor recursive least square (FFRLS) online identification. The FFRLS algorithm is based on data-driven and uses real-time data of the system to improve the estimation accuracy of PEMFC system parameters. On the test bench of parallel-connected PEMFCs system consists of two 300 W PEMFC stacks, PEMFC stack controller, DC/DC converters, and DSP controller etc., a multi-index performance test and comparative analysis are carried out. The results showed that, the performance of proposed power allocation strategy has been successfully validated. In addition, compared with the power average and daisy chain algorithms, the proposed online identification power distribution method can get more satisfactory results. Such as, reducing the hydrogen consumption and improving efficiency.     

Multivariable robust control of a proton exchange membrane fuel cell system

This paper applies multivariable robust control strategies to a proton exchange membrane fuel cell (PEMFC) system. From the system point of view, a PEMFC can be modeled as a two-input-two-output system, where the inputs are air and hydrogen flow rates and the outputs are cell voltage and current. By fixing the output resistance, we aimed to control the cell voltage output by regulating the air and hydrogen flow rates. Due to the nonlinear characteristics of this system, multivariable robust controllers were designed to provide robust performance and to reduce the hydrogen consumption of this system. The study was carried out in three parts. Firstly, the PEMFC system was modeled as multivariable transfer function matrices using identification techniques, with the un-modeled dynamics treated as system uncertainties and disturbances. Secondly, robust control algorithms were utilized to design multivariable H_∞ controllers to deal with system uncertainty and performance requirements. Finally, the designed robust controllers were implemented to control the air and hydrogen flow rates. From the experimental results, multivariable robust control is shown to provide steady output responses and significantly reduce hydrogen consumption.     

The optimal design for PEMFC modeling based on Taguchi method and genetic algorithm neural networks

This paper has presented a new approach to estimate the output voltage of proton exchange membrane fuel cell (PEMFC) accurately by combining the use of a genetic algorithm neural networks (GANN) model and the Taguchi method. Using the PEMFC experimental data measured from performance test equipment of PEMFC, the GANN model could be trained and constructed for obtaining the steady state output voltage of PEMFC. Furthermore, in order to determine the important parameters in GANN, the Taguchi method is used for parameter optimization, with the goal of reducing the estimation error. The test equipment of PEMFC is accurate enough for acquiring the output voltage of PEMFC, and is quite useful for teaching purpose. However, taking the high cost, complicated operation procedure and environment safety into consideration, it is necessary to develop a simulation model of PEMFC to benefit teaching and R&D. Therefore, this paper will present an approach for constructing a GANN model with precise accuracy for the output voltage of PEMFC. For achieving the GANN model with high precision, a troublesome work has to be taken care of, that is, to determine all the parameters required in GANN. We will introduce Taguchi method to solve this problem as well. Finally, to show the superiority of proposed model, this approach has compared the estimation values of output voltage for PEMFC from GANN and BPNN models without using Taguchi method. One can easily find that the error of the proposed method is much smaller than that of the GANN model without Taguchi method and of the BPNN model; that is, the proposed approach has better performance on estimation for PEMFC output voltages.     

PEM fuel cell performance with solar air preheating

Proton Exchange Membrane Fuel Cells (PEMFC) have proven to be a promising energy conversion technology in various power applications and since it was developed, it has been a potential alternative over fossil fuel-based engines and power plants, all of which produce harmful by-products. The inlet air coolant and reactants have an important effect on the performance degradation of the PEMFC and certain power outputs. In this work, a theoretical model of a PEM fuel cell with solar air heating system for the preheating hydrogen of PEM fuel cell to mitigate the performance degradation when the fuel cell operates in cold environment, is proposed and evaluated by using energy analysis. Considering these heating and energy losses of heat generation by hydrogen fuel cells, the idea of using transpired solar collectors (TSC) for air preheating to increase the inlet air temperature of the low-temperature fuel cell could be a potential development. The aim of the current article is applying solar air preheating for the hydrogen fuel cells system by applying TSC and analyzing system performance. Results aim to attention fellow scholars as well as industrial engineers in the deployment of solar air heating together with hydrogen fuel cell systems that could be useful for coping with fossil fuel-based power supply systems.     

Power assisted fuel cell

A hybrid fuel cell demonstrated pulse power capability at pulse power load simulations synonymous with electronics and communications equipment. The hybrid consisted of a 25.0 W Proton Exchange Membrane Fuel Cell (PEMFC) stack in parallel with a two-cell lead-acid battery. Performance of the hybrid PEMFC was superior to either the battery or fuel cell stack alone at the 18.0 W load. The hybrid delivered a flat discharge voltage profile of about 4.0 V over a 5 h radio continuous transmit mode of 18.0 W.     

Eco-green portable wireless power charger design with low-voltage,high-current fuel cell power source features

Since portable wireless power charger devices have grown rapidly in the market, this device has potential to become standard power charger for portable electronic devices. It offers enhanced consumer convenience and experience. This article presents an innovative portable wireless power charger that is more environmental-friendly because it uses a hydrogen gas fuel cell as the power source. Compared with fossil energy, the fuel cell is clean and renewable, which does not contribute a negative impact on the environment. A wireless power transmission (WPT) system was developed based on the electromagnetic induction technique in order to propagate electromagnetic energy from the transmitter to the receiver with operating frequency at 110 kHz. A four-cell proton exchange membrane fuel cell (PEMFC) planar module with open type at cathode side was applied to provide 4.11 W with its low-voltage and high-current features. A single-cell PEMFC produces output voltage ranging from 0.6 to 0.7 V and configures in serial to form a four-cell PEMFC planar module. Two DC-DC boost converter module in a parallel configuration was used to convert to a suitable voltage and current to the WPT module. The experimental validation shows that the developed system provides power around 1.6 W to the device battery under recharging with power efficiency delivery up to 70%. The charging experiment reveals the device battery capacity under recharging (cell phone) increases 1% in 3.3 minutes and it consumes the hydrogen at around 1.2 L.     

Investigating the transport characteristics and cell performance for a micro PEMFC through the micro sensors and CFD simulations

The local transport characteristics and the global polarization curve for a self-made micro proton exchange membrane fuel cell (PEMFC) have been experimentally and numerically investigated in this paper. The micro-sensors are developed to measure the local fluid temperature, cell voltage, and current density and the fuel cell test system is used to measure the polarization curve. A three-dimensional (3-D) non-isothermal compressible computational fluid dynamics (CFD) full-cell model is also adopted to simulate the test micro PEMFC. This CFD model has been validated with these global and local data. The ionic conductivity is increased as the water content in the membrane increases, enhancing the cell performance. This positive effect of inlet fuel humidity on the cell performance is also captured by the CFD simulation model.     

Characterization and experimental results in PEM fuel cell electrical behaviour

A control oriented electrochemical static model of a proton exchange membrane fuel cell (PEMFC) stack is developed in this paper. Even though its validation is performed on a specific 7-cell PEMFC stack fed by humidified air and pure hydrogen, the methodology and fit parameters can be applied to different fuel cell systems with minor changes. The fuel cell model was developed combining theoretical considerations and semi-empirical analysis based on the experimental data. The proposed model can be successfully included into a larger dynamic subsystem to complete the power generation system.     

Treatment of low concentration hydrogen by electrochemical pump or proton exchange membrane fuel cell

Proton exchange membrane fuel cell (PEMFC) can produce electricity through electrochemical reaction of hydrogen with oxygen with the use of a membrane and electrode assembly (MEA). In other words, the hydrogen pressure difference between the anode and cathode can produce electricity via an electrochemical process. Conversely, when we supply electricity to MEA from an external power source, we can pump up or separate hydrogen from the low-pressure anode to the high-pressure cathode, according to the principle of “concentration cell”. By the way, PEMFC cannot use the fuel completely, because a cell potential decreases and electrode material may corrode when most of the fuel is consumed. Therefore the fuel released from PEMFC should be treated safely. The depleted hydrogen from PEMFC can be recovered by the electrochemical hydrogen pump, or further can be used as a fuel for the power generation by PEMFC, even though the cell voltage might be low. In this study we preliminarily measured the voltage–current characteristics of hydrogen pump and PEMFC changing the hydrogen concentration from 99.99% to 1%, as another option to platinum catalytic combustion of low concentration hydrogen. Moreover we could successfully treat the low concentration hydrogen by electrochemical pump or PEMFC, for the widely changing hydrogen concentration and mixture flow rate. The gas chromatography confirmed the hydrogen concentration of the treated gas to be 1000 ppm at most.     

A hybrid neural network model for PEM fuel cells

The goal of this paper is to discuss a neural network modeling approach for developing a quantitatively good model for proton exchange membrane (PEM) fuel cells. Various ANN approaches have been tested; the back-propagation feed-forward networks and radial basis function networks show satisfactory performance with regard to cell voltage prediction. The effects of Pt loading on the performance of the PEM fuel cell have been specifically studied. The results show that the ANN model is capable of simulating these effects for which there are currently no valid fundamental models available from the open literature.

Two novel hybrid neural network models (multiplicative and additive), each consisting of an ANN component and a physical component, have been developed and compared with the full-blown ANN model. The results from the hybrid models demonstrate comparable performance (in terms of cell voltage predictions) compared to the ANN model. Additionally, the hybrid models show performance gains over the physical model alone. The additive hybrid model shows better accuracy than that of the multiplicative hybrid model in our tests.     

An overview: Current progress on hydrogen fuel cell vehicles

The harmful consequences of pollutants emitted by conventional fuel cars have prompted vehicle manufacturers to shift towards alternative energy sources. Currently, fuel cells (FCs) are commonly regarded as highly efficient and non-polluting power sources capable of delivering far greater energy densities and energy efficiency than conventional technologies. Proton exchange membrane fuel cells (PEMFC) are viewed as promising in transportation sectors because of their ability to start at cold temperatures and minimal emissions. PEMFC is an electrochemical device that converts hydrogen and oxidants into electricity, water, and heat at various temperatures. The pros and cons of the technology are discussed in this article. Various fuel cell types and their applications in the portable, automobile, and stationary sectors are discussed. Additionally, recent issues associated with existing fuel cell technology in the automobile sector are reviewed.     

Preliminary experimental study of the performances for a print circuit board based planar PEMFC stack

This paper presents a novel planar proton exchange membrane fuel cell (PEMFC) stack designed for portable electronic devices, consisting of twenty homemade membrane electrode assemblies (MEAs) arranged on a planar surface and three printed circuit boards (PCBs, including anode, interlayer and cathode PCBs) used to load these MEAs. The current collectors and electrical connectors are manufactured using printed circuit technology. The inlet holes of reaction gases are also machined on PCB substrates. The output performance tests are performed on the MEAs and the assembled planar PEMFC stack. The results show that the power densities of the MEAs and the planar PEMFC stack are 0.6 W/cm² and 0.361 W/cm² at rated voltage under ambient temperature and forced convection air conditions, respectively. The stability tests are also conducted on the planar PEMFC stack, and the results show no significant fluctuations in output current. The feasibility of the application of planar PEMFC stacks in portable electronic devices is preliminarily demonstrated, and the improvement directions for further improving the output performance are proposed accordingly.     

Development of optimisation model for direct methanol fuel cells via cell integrated network

A cell network consists of a combination of fuel cells to achieve the targeted power consumption for a specific application. The main objective of this study is to design and optimise direct methanol fuel cell (DMFC) via cell integrated network model targeted for small portable application, such as cell phones and tablets. The target current and voltage was 1400 mA and 3.7 V, respectively, for a 5.18 W of cell network power. The optimisation was performed using 16 cells that were arranged in series with a voltage output of 3.781 V and a current of 1400 mA. The overall active area for the cell network was 128 cm², and the cost of 1 set of cell networks is USD 1400.