A Controllable Membrane-Type Humidifier for Fuel Cell Applications - Part II: Controller Design, Analysis and Implementation (original) (raw)
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Control-oriented model of a membrane humidifier for fuel cell applications
Energy Conversion and Management, 2017
Improving the humidification of polymer electrolyte membrane fuel-cells (PEMFC) is essential to optimize its performance and stability. Therefore, this paper presents an experimentally validated model of a low temperature PEMFC cathode humidifier for control/observation design purposes. A multi-input/multi-output non-linear fourth order model is derived, based on the mass and heat dynamics of circulating air. In order to validate the proposed model and methodology, experimental results are provided. Finally, a non-linear control strategy based on second order sliding mode is designed and analysed in order to show suitability and usefulness of the approach.
International Journal of Hydrogen Energy, 2012
The proton exchange membrane fuel cell (PEMFC) system with a shell-and-tube gas-togas membrane humidifier is considered to be a promising PEMFC system because of its energyefficient operation. However, because the relative humidity of the dry air flowing into the stack depends on the stack exhaust air, this system can be unstable during transients. To investigate the dynamic behavior of the PEMFC system, a system model composed of a lumped dynamic model of an air blower, a two-dimensional dynamic model of a shelland-tube gas-togas membrane humidifier, and a one-dimensional dynamic model of a PEMFC system is developed. Because the water management during transient of the PEMFC system is one of the key challenges, the system model is simulated at the step change of current. The variations in the PEMFC system characteristics are captured. To confirm the superiority of the system model, it is compared with the PEMFC component model during transients.
International Journal of Hydrogen Energy, 2010
Water management is a crucial factor in determining the performance of proton exchange membrane fuel cell (PEMFC) for automotive application. The shell-and-tube water-togas membrane humidifier is useful for humidifying the PEMFC due to its good performance. Shell-and-tube water-togas membrane humidifiers have liquid water on one side of the tube wall and a dry gas on the other. In order to investigate humidifier performance, a twodimensional dynamic model of a shell-and-tube water-togas membrane humidifier is developed. The model is discretized into three control volumes-shell, tube and membrane-in the cross-sectional direction to resolve the temperature and species concentration of the humidifier. For validation, the dew point temperature of the simulation result is compared with that of experimental data and shows good agreement with only a slight difference. The distribution of humidification characteristics can be captured using the discretization along the air-flow direction. The humidification performance of two different flow configurations, counter and parallel, are compared under various operating conditions and geometric parameters. Finally, the dynamic response of the humidifier at the step-change of various air flow rates is investigated. These results suggest that the model can be used to optimize the inlet flow humidity of a PEMFC.
CONTROLLING PEM FUEL CELLS APPLYING A CONSTANT HUMIDITY TECHNIQUE
2008
Proton exchange membrane fuel cells (PEMFCs) have attracted great attention in recent years as a promising replacement for traditional stationary and mobile power sources, especially due to their high power density and low greenhouse gas emissions. However, a number of fundamental problems must be overcome to improve their performance and to reduce their cost. A control system is needed to ensure that the airflow rate and temperature are within prescribed limits during operation. The water content on the membrane influences the fuel cell (FC) performance, and this can be controlled by relative humidity. Therefore, in this research, a new control technique based on the regulation of relative humidity is introduced. The ideal operational condition is relative humidity in saturated conditions; the proposed control system adjusts the air-reaction volume to maintain this condition. From the mathematical model developed in Matlab , the evolutions of some variables that can be difficult to monitor in a real machine are observed. Also, prediction about the evolution of variables can be tested, optimizing time and resources. For experimental validation, tests in a fault tolerant fuel cell (FTFC) are conducted.
An analytic model of membrane humidifier for proton exchange membrane fuel cell
Environmental Engineering Science, 2014
An essential requirement for an operating PEM fuel cell is providing proper water content in the membrane. To avoid water flooding an appropriate water balance is required. Here, an analytic model of a planar membrane humidifier for PEM fuel cell is proposed where the effect of dimensional parameters includes membrane thickness, membrane area and channel hydraulic diameter are investigated. A Non-linear governing equations system is developed and solved. At each stage, the outlet temperatures, the water and heat transfer rates, relative humidity and the dew point at dry side outlet are presented and discussed. The humidifier is evaluated based on the decrease in difference between the dew point at wet side inlet and dry side outlet which leads to humidifier better performance. The results show that an increase in membrane thickness results in a decrease in dew point at dry side outlet which indicates a weak humidifier performance. Vaster membrane area can enhance humidifier performa...
Relative humidity control in polymer electrolyte membrane fuel cells without extra humidification
Journal of Power Sources, 2008
The performance of polymer electrolyte membrane fuel cells is highly influenced by the water content in the membrane. To prevent the membrane from drying, several researchers have proposed extra humidification on the input reactants. But in some applications, the extra size and weight of the humidifier should be avoided. In this research a control technique, which maintains the relative humidity on saturated conditions, is implemented by adjusting the air stoichiometry; the effects of drying of membrane and flooding of electrodes are considered, as well. For initial analysis, a mathematical model reveals the relationship among variables that can be difficult to monitor in a real machine. Also prediction can be tested optimizing time and resources. For instance, the effects of temperature and humidity can be analyzed separately. For experimental validation, tests in a fault tolerant fuel cell are conducted.
IFAC Proceedings Volumes, 2011
Hydrogen fed fuel cell systems are a promising technology for the energy supply of future aircraft applications. Currently, kerosene fed auxiliary power units (APU) supply an aircraft with electrical energy during ground operations while main engines are turned off. As environmental friendliness is more and more playing a crucial role for future aircraft generations, replacing the APU by an eco-friendly fuel cell technology becomes very attractive. On the other hand, fuel cell systems are a highly integrated technology and minimizing its complexity is highly favored. In contrast to liquid cooled fuel cell systems the evaporation cooled fuel cell system has a very low complexity. Nevertheless, fuel cell system controls is a central part of proper fuel cell operation to gain a maximum fuel cell lifetime. In this paper a dynamic simulation model of an evaporation cooled fuel cell stack is presented and validated against experimental data. The fuel cell system model will be central for a subsequent model based controller design.