Polymer electrolyte membrane fuel cell fault diagnosis and sensor abnormality identification using sensor selection method

In this paper a control-oriented PEM fuel cell system model and a repetitive controller design strategy for PEM fuel cell systems is discussed. A mathematical model of a Polymer Electrolyte Membrane (PEM) Fuel Cell system is presented and then used to design the controller intended to improve system performance. The PEM Fuel cell is tested on an available test station (PEM-FCT) and the data used for the modelling and subsequent controller development study. For model validation a comparison is made between the results from a MATLAB/Simulink model and the test data from the PEM-FCT. The model is then used for repetitive controller design for the fuel cell system. Simulation results show that the repetitive controller tracks the reference signal very closely, with little deviation from the desired value.

Fuel cell technology is seen as a promising option for decarbonizing global mobility. The costs of fuel cell systems are currently too high for increasing market penetration. The Chair of Production Engineering of E-Mobility Components at RWTH Aachen University has developed a cost calculation model for Polymer Electrolyte Membrane (PEM) fuel cell systems based on the method of Process Based Cost Modeling (PBCM) and is investigating possibilities for reducing manufacturing costs through economies of scale in production. The aim of this publication is therefore to present the results of cost modeling of PEM fuel cell systems and to derive design areas for technical innovations in terms of cost reduction through economies of scale in production. To this end, technical production parameters with the greatest influence on the cost structure of PEM fuel cell systems are identified and ranked by applying a sensitivity analysis. Finally, this work provides a recommendation for strategic investments and formulates the need for further research to reduce PEM fuel cell system costs by economies of scale.

The transient behaviour of a polymer electrolyte membrane fuel cell (PEMFC) system following abrupt changes in the stack current is analysed using a non-linear dynamic, control-oriented computer model. Such changes in the stack current are associated with the abrupt changes in power demanded by a vehicle powered by the fuel cell system. The PEMFC system analysed consists of air and fuel supply subsystems, a perfect air/fuel humidifier, and a fuel cell stack, and is assumed to operate under a constant fuel cell temperature. The model is next used to develop a feedback control scheme to regulate the transient behaviour of the PEMFC system with respect to maintaining the necessary level of the oxygen partial pressure in the cathode following abrupt changes in the stack current demanded by the user. Maintaining the level of oxygen in the cathode is critical to prevent short circuit and membrane damage. The results obtained indicate that the oxygen level in the cathode can be successfully maintained using a feedback control of the air-compressor-motor voltage. However, the net power provided by the fuel cell system is compromised during the transients following abrupt changes in the stack current, suggesting a need for power management via a secondary power source, such as an electric battery.

Despite the wide range of applications for the polymer electrolyte membrane fuel cell (PEMFC), its reliability and durability are still major barriers for further commercialization. As a possible solution, PEMFC fault diagnosis has received much more attention in the last few decades. Due to the difficulty of developing an accurate PEMFC model incorporating various failure mode effects, data-driven approaches are widely used for diagnosis purposes. These methods depend largely on the quality of sensor measurements from the PEMFC. Therefore, it is necessary to investigate sensor reliability when performing PEMFC fault diagnosis.In this study, sensor reliability is investigated by proposing an identification technique to detect abnormal sensors during PEMFC operation. The identified abnormal sensors will be removed from the analysis in order to guarantee reliable diagnostic performance. Moreover, the effectiveness of the proposed technique is investigated using test data from a PEMFC system, where fuel cell flooding is observed. During the test, due to accumulation of liquid water inside the PEMFC, the humidity sensors will give misleading readings, and flooding cannot be identified correctly with inclusion of these humidity sensors in the analysis. With the proposed technique, the abnormal humidity measurements can be detected at an early stage. Results demonstrate that by removing the abnormal sensors, flooding can be identified with the remaining sensors, thus reliable health monitoring can be guaranteed during the PEMFC operation.

This paper presents a comparative study on the performance of different sizes of sensor sets on polymer electrolyte membrane (PEM) fuel cell fault diagnosis. The effectiveness of three sizes of sensor sets, including fuel cell voltage only, all the available sensors, and selected optimal sensors in detecting and isolating fuel cell faults (e.g., cell flooding and membrane dehydration) are investigated using the test data from a PEM fuel cell system. Wavelet packet transform and kernel principal component analysis are employed to reduce the dimensions of the dataset and extract features for state classification. Results demonstrate that the selected optimal sensors can provide the best diagnostic performance, where different fuel cell faults can be detected and isolated with good quality.

Fuzzy Logic based Control Strategies for Proton Exchange Membrane Fuel Cell System

A proper water management is important for an efficient operation of a polymer electrolyte membrane (PEM) fuel cell system. The humidity distribution in the anode gas channels is highly dependent on the cathode humidity and the resulting transmembrane water transport. Therefore, it can be assumed that the cell humidification is optimal when the relative anode humidity is nearly 100% and homogeneously distributed.In contrast to state‐of‐the‐art approaches, this study focuses on the humidity distribution on anode side in consideration of the anode recirculation loop.Therefore, a macroscopic 1D+1D simulation model was developed, which simulates humidity profiles along the gas channels with consideration of the transmembrane water transport and the anode gas recirculation.This study shows the impact of relevant input parameters, such as pressure, stoichiometry and cathode inlet humidity.Furthermore, the results show that it is possible to reach a nearly homogeneous humidity distribution along the anode gas channels for automotive fuel cell systems. This can be achieved through appropriate operation conditions, e.g., suitable combination of pressure and stoichiometry, and supportive flow directions of the gases and the coolant. The analysis was made for fuel cells operating at full load at system relevant conditions with and without external humidification.

A Deep Sea Cruising AUV “URASHIMA” has been developed by JAMSTEC since 1998. The dimensions and weight are 10m (L), 1.3m (W), 1.5m (H), and about 7.5 tons in air. A main power source device system of AUV “URASHIMA” is a large capacity of lithium-ion (Li-ion) rechargeable battery system or Solid Polymer Electrolyte Fuel Cell (PEFC) system. AUV “URASHIMA” will be able to cruise for about 100km with Li-ion battery system and it will cruise for about 300km with fuel cell system. The cruising trial used by the fuel cell system will start at the end of 2002. The instruments for science researches are an automatic multi-water-sampling system, a CTDO, a side-scan sonar, a digital still camera with a thermoelectrically cooled CCD image sensor, a TV camera, and so on. Three operation modes, which are UROV mode, acoustic remote control mode and autonomous mode, are available. Those three kinds of modes are used acceding to each development stage and ocean researches. UROV mode is to monitor the state of the vehicle with fiber optics. At the first development stage of AUV “URASHIMA”, we carried out long cruising trial for about 100km and maximum operational depth trial at 3,500m used by Li-ion rechargeable battery system. URASHIMA was succeeded to reach at 3,518m depth of the seafloor at the sea trial of August 2001. We also carried out long cruising trial that was controlled by autonomous mode. Then, URASHIMA was cruised 70km distance at the sea trial of December 2001. We will have a next sea trail on May 2002 for 100km long cruising test. At the next development stage, we will carried out long cruising trial for 300km used by the fuel cell system.

Detection, isolation and identification of multiple actuator and sensor faults in nonlinear dynamic systems: Application to a waste water treatment process

Fuel cell and hydrogen (FCH) technologies are expected to add to decarbonisation of energy and transport sector. One thing that prevents FCH commercialization is lack of recycling and dismantling strategies, due to not available lists of critical materials. One of the considered FCH technologies within the EU funded HyTechCycling project is polymer electrolyte membrane fuel cell (PEMFC), which is the focus of this paper. One of the goals of EU project HyTechCycling is to carry out a Life Cycle Assessment (LCA) of PEMFC technology. Main focus of this paper is to gather and properly set all the data needed for LCA study of the PEMFC system. First the PEMFC was broken down to core components to identify all materials constituting the PEMFC components. For PEMFC the LCA numerical model was done in GaBi Thinkstep software. In first part of the paper the list of common PEMFC materials were identified. Furthermore with this list of materials a LCA study for 1kW PEMFC system was done. The scope of the study was “cradle to gate” with four different scenarios of hydrogen production and 20,000 h of operation. For environmental impact assessment the CML2001 life cycle impact assessment (LCIA) methodology was used. LCA results of 1kW PEMFC system shows that in manufacturing phase the stack contributes 60-90% in total environmental impacts and the BoP components are in range of 10-20%. In operation phase the hydrogen production with electrolysis using hydroelectricity and natural gas reforming are scenarios with lowest environmental impacts. The platinum group metals (PGM's), among which Pt is standing out the most, are the biggest contributors in the total environmental impact in the manufacturing phase of 1 kW PEMFC system. Therefore, on average 61% reduction in environmental impacts can be achieved with an assumption of 95% recycling of Pt.

Summary: Branched/crosslinked sulfonated polyimide membranes incorporating superior mechanical properties, high proton conductivity, and excellent fuel cell performance were successfully developed. The resulting polymer electrolytes displayed conductivity values of about 0.2 S · cm−1 at 120 °C and 100% relative humidity. In a single H2/O2 fuel cell system at 90 °C, they exhibited reasonably high fuel cell performances comparable to that of Nafion 112.The structure of the branched/crosslinked sulfonated polyimide membranes studied here.imageThe structure of the branched/crosslinked sulfonated polyimide membranes studied here.

Fuel cells are in risk of starvation due to a possible drop of the oxygen partial pressure during a dynamic operation. Therefore, feedback control of the cathode pressure plays an important role towards an efficient operation of a polymer electrolyte membrane (PEM) fuel cell system. In this paper, hence, a model-based nonlinear pressure control approach using a variable turbine geometry (VTG) is presented. The system model is derived from physical considerations in symbolic form, and parametrized by a least-squares parameter identification. As the derived dynamic model of the cathode subsystem is highly nonlinear, appropriate techniques using differential flatness are applied. Moreover, a sigma-point Kalman filter (SPKF) provides accurate estimates for the state variables and a lumped disturbance. Simulation results show the effectiveness and illustrate the achieved control performance.

Lunar development efforts continue to gain momentum, several programs are underway to achieve sustainable activities on the Moon. Therefore, there is a need for a sustainable energy supply system utilizing sunlight, which is available on the Moon. Currently, Regenerative Fuel Cell system (RFC system) are expected to develop as one of the energy supply systems. The RFC system electrolyzes the water utilizing solar power to produce hydrogen and oxygen. These generated gases are supplied to the FC system to generate electricity. The byproduct water generated during power generation is re-electrolyzed to store energy. This cycle allows the RFC system to continuously generate electricity without additional water supply. Honda has developed a high-differential-pressure water electrolysis system in parallel with the development of fuel cells system since the 1990s. In this system, protons generated by water electrolysis are transferred to the cathode side to generate high-pressure hydrogen. This creates a differential pressure across the Proton Exchange Membrane (PEM), and Honda has achieved a maximum pressure increase of 70 MPa by using its own structure. Moreover, this principle can be applied not only to the generation and pressurization of hydrogen, but also to that of oxygen. And, Honda has integrated the high-differential-pressure water electrolysis system and the fuel cell systems to develop Honda's own RFC system. Honda calls the system Circulative Renewable Energy System (CRE system). The CRE system consists of the high-differential-pressure water electrolysis system, an Electrochemical Hydrogen Compressor system (EHC system), and a fuel cell system. In the CRE system, water is first supplied to the high-differential-pressure water electrolysis system, which electrolyzes water to produce hydrogen and high-pressure oxygen. Hydrogen generated by water electrolysis is supplied to the EHC system and electrochemically pressurized. These high-pressure gases are stored in their own tanks and supplied to the fuel cell system when electricity is required. Byproduct water generated during power generation is supplied again to the water electrolysis system to enable continuous power generation. A feature of the CRE system is the pressurization of each gas, which allows them to store more gas in a smaller volume. The future gravimetric energy density of CRE systems is greater than that of a future Li-ion battery, which is thought to be advantageous in terms of helping reduce transport cost. When the CRE system is used on the Moon, fuel cells generate electricity at night when solar power is unavailable. During the daytime, hydrogen and oxygen are generated and stored by water electrolysis utilizing solar power. On the Moon, the nighttime is continuous for up to 14 days. One lunar project requires a three-year power supply, during which there will be a total of 39 lunar nights. Last year, Honda created a breadboard model for the project, and conducted 39 cycles operation test. The purpose of this cycle test was to confirm that the water could circulate and continue to generate power for 39 cycles. Several initiatives were implemented in order to complete this cycle test. For example, since the EHC system pressurize hydrogen to 70 MPa, water in the high-pressure hydrogen permeates the PEM due to differential pressure and stays in the membrane reaction part. This water causes a voltage increase. Therefore, water discharge was enhanced by optimizing the flow path structure. Another issue was the pressure increase in components that are not expected to increase internal pressure due to the movement of supply and generated gases. Therefore, we worked to build a system control that circulates the gases without external venting. As a result of this series of initiatives, it was confirmed that electricity could be generated through 39 cycles without terminating the test, and proof of principle was completed. Going forward, it will be necessary to cope with space-specific events such as vibration during launch, radiation, and low gravity. CRE system is being developed for use in lunar missions after 2030. Figure 1

In grinding process, sensor fusion methods for inferring the surface roughness from online sensing information have received much attention, because it is quite time consuming to measure manually the surface roughness during process. In addition, recently, it is necessary to select the sensing information for adapting to various situation flexibly. This paper proposes a sensor fusion system with sensor selection method for a grinding system. The sensor selection method is based on the production rules, considering the reliability calculated by the possibility measure which is a type of fuzzy measure. Then, the sensor fusion system fuses the sensor information selected by the sensor selection method using a recurrent neural network.

This paper describes a proton exchange membrane (PEM) fuel cell system model for automotive applications that includes an air compressor, cooling system, and other auxiliaries. The fuel cell system model has been integrated into a vehicle performance simulator that determines fuel economy and allows consideration of control strategies. Significant fuel cell system efficiency improvements may be possible through control of the air compressor and other auxiliaries. Fuel cell system efficiency results are presented for two limiting air compressor cases: ideal control and no control. Extension of the present analysis to hybrid configurations consisting of a fuel cell system and battery is currently under study.