A 75-kW methanol reforming fuel cell system

A 75-kW methanol reforming fuel cell system, which consists of a fuel cell system and a methanol auto-thermal reforming fuel processor has been developed at Dalian Institute of Chemical Physics, Chinese Academy of Sciences (CAS). The core of the fuel cell system is a group of CO tolerant PEMFC stacks with a double layer composite structured anode. The fuel cell stacks show good CO tolerance even though 140 ppm CO was present in the reformate stream during transients. The auto-thermal reforming (ATR) fuel cell processor could adiabatically produce a suitable reformate without external energy consumption. The output of hydrogen-rich reformate was approximately 120 N m³ h⁻¹ with a H₂ content near 53% and the CO concentrations generally were under 30 ppm. The fuel cell system was integrated with the methanol reforming fuel processor and the peak power output of the fuel cell system exceeded 75 kW in testing. The hydrogen utilization approached 70% in the fuel cell system.     

Compact gasoline fuel processor for passenger vehicle APU

Due to the increasing demand for electrical power in today's passenger vehicles, and with the requirements regarding fuel consumption and environmental sustainability tightening, a fuel cell-based auxiliary power unit (APU) becomes a promising alternative to the conventional generation of electrical energy via internal combustion engine, generator and battery. It is obvious that the on-board stored fuel has to be used for the fuel cell system, thus, gasoline or diesel has to be reformed on board. This makes the auxiliary power unit a complex integrated system of stack, air supply, fuel processor, electrics as well as heat and water management. Aside from proving the technical feasibility of such a system, the development has to address three major barriers:start-up time, costs, and size/weight of the systems. In this paper a packaging concept for an auxiliary power unit is presented. The main emphasis is placed on the fuel processor, as good packaging of this large subsystem has the strongest impact on overall size.The fuel processor system consists of an autothermal reformer in combination with water–gas shift and selective oxidation stages, based on adiabatic reactors with inter-cooling. The configuration was realized in a laboratory set-up and experimentally investigated. The results gained from this confirm a general suitability for mobile applications. A start-up time of 30 min was measured, while a potential reduction to 10 min seems feasible. An overall fuel processor efficiency of about 77% was measured. On the basis of the know-how gained by the experimental investigation of the laboratory set-up a packaging concept was developed. Using state-of-the-art catalyst and heat exchanger technology, the volumes of these components are fixed. However, the overall volume is higher mainly due to mixing zones and flow ducts, which do not contribute to the chemical or thermal function of the system. Thus, the concept developed mainly focuses on minimization of those component volumes. Therefore, the packaging utilizes rectangular catalyst bricks and integrates flow ducts into the heat exchangers. A concept is presented with a 25 l fuel processor volume including thermal isolation for a 3 kW_el auxiliary power unit. The overall size of the system, i.e. including stack, air supply and auxiliaries can be estimated to 44 l.     

Thermal integration of a cylindrically symmetric methanol fuel processor for portable fuel cell power

The realization of a proven approach combining small hydrogen fuel cells with reformed methanol has continued to be elusive. This is so because of the overwhelming challenge of thermally integrating a chemical process involving many steps, each at a unique temperature, within a confined volume. In addition, heat loss to the environment becomes correspondingly higher as overall size shrinks due to increasing surface-to-volume ratio, requiring an inordinate use of system volume on thermal insulation. To address these challenges, we present a study based on extrapolation of experiment which incorporates novel cylindrical symmetry of the methanol fuel processor based on microchemical system technology. Models for two different fuel processor-proton exchange fuel cell systems of 4-W and 20-W scale are presented. ASPEN process simulation was used to establish basic system operating parameters. Finite difference modeling of the axisymmetric configuration was used to establish the heat flows in the systems. The results indicate strong potential for the cylindrical arrangement to provide viable self-contained small form factor battery replacements.     

A complete miniaturized microstructured methanol fuel processor/fuel cell system for low power applications

A complete miniaturized methanol fuel processor/fuel cell system was developed and put into operation as compact hydrogen supplier for low power application. The whole system consisting of a micro-structured evaporator, a micro-structured reformer and two stages of preferential oxidation of CO (PROX) reactor, micro-structured catalytic burner, and fuel cell was operated to evaluate the performance of the whole production line from methanol to electricity. The performance of micro methanol steam reformer and PROX reactor was systematically investigated. The effect of reaction temperature, steam to carbon ratio, and contact time on the methanol steam reformer performance is presented in terms of catalytic activity, selectivity, and reformate yield. The performance of PROX reactor fed with the reformate produced by the reformer reactor was evaluated by the variation of reaction temperature and oxygen to CO ratio. The results demonstrate that micro-structured device may be an attractive power source candidate for low power application.     

Drive-train simulator for a fuel cell hybrid vehicle

The model formulation, development process, and experimental validation of a new vehicle powertrain simulator called LFM (Light, Fast, and Modifiable) are presented. The existing powertrain simulators were reviewed and it was concluded that there is a need for a new, easily modifiable simulation platform that will be flexible and sufficiently robust to address a variety of hybrid vehicle platforms. First, the structure and operating principle of the LFM simulator are presented, followed by a discussion of the subsystems and input/output parameters. Finally, a validation exercise is presented in which the simulator's inputs were specified to represent the University of Delaware's fuel cell hybrid transit vehicle and “driven” using an actual drive cycle acquired from it. Good agreement between the output of the simulator and the physical data acquired by the vehicle's on-board sensors indicates that the simulator constitutes a powerful and reliable design tool.     

Simulation of a hybrid vehicle powertrain having direct methanol fuel cell system through a semi-theoretical approach

Different operating scenarios can be used in a hybrid system based on a direct methanol fuel cell (DMFC) and a battery. In this paper, a DMFC system model is integrated into a model formed for a hybrid vehicular system that consists of a battery, a DMFC stack and its auxiliary equipments; and the model is simulated in Matlab/Simulink environment using a quasistatic approach. An algorithm for the energy management of the system is also developed considering the state of charge (SOC) of the battery. In the DMFC system model, the current and empirical data for the polarization curves as well as methanol crossover and water crossover rates are taken as the input parameters, whereas the stack voltage, the remaining methanol in the fuel tank, and the power demand of auxiliary equipments are taken as the output parameters. In this model, the methanol consumption, and the water and CO₂ production are found applying mass balances for each component of the system. The results of the simulations help to give more insights into the operation of a DMFC based hybrid system.     

A novel hybrid Nafion-PBI-ZP membrane for direct methanol fuel cells

Methanol crossover through proton conducting membranes represents one of the main drawbacks in DMFCs. This study presented a novel organic-inorganic hybrid membrane with several different compositions by casting mixtures of zirconium phosphate (ZP), polybenzimidazole (PBI) and Nafion dispersion in dimethylacetamide. The presence of PBI and ZP in the membranes was demonstrated with energy dispersive X-ray (EDX) analysis. From the scanning electron microscopy (SEM) analysis, it was observed that the hybrid Nafion-PBI-ZP membrane had the finest structure. This is because the synthesized films were homogeneous and therefore formed a dense membrane. The water content was higher in the hybrid membrane: 39.91% compared with 35.52% in Nafion117. The water content is important for the ion transportation in the membrane; therefore, a higher water uptake rate will contribute to a better fuel cell performance. It was determined that the proton conductivity of the hybrid membrane was 0.020 S cm⁻¹, which was comparable with Nafion117, which had a proton-conductivity of 0.022 S cm⁻¹. The methanol permeability of the hybrid membrane was 2.34 × 10⁻⁷ cm² s⁻¹, while the value for Nafion117 was 8.91 × 10⁻⁷ cm² s⁻¹. This showed that the methanol permeability of the hybrid membrane was almost 4 times lower than that of Nafion117. The selectivity factor for the Nafion-PBI 1%-ZP 1% membrane was 8.64 × 10⁴ Scm⁻³, while that of Nafion117 was 2.48 × 10⁴ S scm⁻³. From a thermogravimetry analysis (TGA), the addition of PBI and zirconium phosphate was shown to improve the thermal durability in the temperature range from room temperature to 450 °C over that of Nafion117. This study proofed that the Nafion-PBI 1%-ZP 1% performed better than commercial Nafion117 and other type of membranes. The membrane was tested on as single cell of DMFC. It gave the highest power density as compared to other type of membrane and proofed that it has potential to be used in DMFCs.     

PEM fuel-cell stack design for improved fuel utilization

We propose a new design for a polymer electrolyte membrane (PEM) fuel-cell stack that can achieve higher fuel utilization without using hydrogen recirculation devices such as hydrogen pumps or ejectors, which consume parasitic power and/or require additional control schemes. The basic concept of the proposed design is to divide the anodic cells of a stack into several blocks by inserting compartments between the cells, thereby constructing a multistage anode with a single-stage cathode in a single stack. In this design, a higher gaseous flow rate is maintained at the outlet of the anodic cells, even under dead-end conditions, and this results in a reduction of purge-gas emissions by hindering the accumulation of liquid water and nitrogen in the anodic cells. A 15 kW-class PEM fuel cell stack is designed, fabricated, and tested to investigate the effectiveness of the proposed design. The experimental results indicate that the amount of purge gas is significantly reduced, and consequently, a higher fuel utilization of more than 99.6% is achieved. Additionally, the output voltage of the stack fluctuates much less than that of conventional fuel cells owing to the multistage anode design.     

Online management of lithium-ion battery based on time-triggered controller area network for fuel-cell hybrid vehicle applications

This paper introduces a state of charge (SOC) estimation algorithm that was implemented for an automotive lithium-ion battery system used in fuel-cell hybrid vehicles (FCHVs). The proposed online control strategy for the lithium-ion battery, based on the Ah current integration method and time-triggered controller area network (TTCAN), incorporates a signal filter and adaptive modifying concepts to estimate the Li₂MnO₄ battery SOC in a timely manner. To verify the effectiveness of the proposed control algorithm, road test experimentation was conducted with an FCHV using the proposed SOC estimation algorithm. It was confirmed that the control technique can be used to effectively manage the lithium-ion battery and conveniently estimate the SOC.     

Conceptual design and selection of a biodiesel fuel processor for a vehicle fuel cell auxiliary power unit

Within the European project BIOFEAT (biodiesel fuel processor for a fuel cell auxiliary power unit for a vehicle), a complete modular 10 kW_e biodiesel fuel processor capable of feeding a PEMFC will be developed, built and tested to generate electricity for a vehicle auxiliary power unit (APU). Tail pipe emissions reduction, increased use of renewable fuels, increase of hydrogen-fuel economy and efficient supply of present and future APU for road vehicles are the main project goals. Biodiesel is the chosen feedstock because it is a completely natural and thus renewable fuel.Three fuel processing options were taken into account at a conceptual design level and compared for hydrogen production: (i) autothermal reformer (ATR) with high and low temperature shift (HTS/LTS) reactors; (ii) autothermal reformer (ATR) with a single medium temperature shift (MTS) reactor; (iii) thermal cracker (TC) with high and low temperature shift (HTS/LTS) reactors. Based on a number of simulations (with the AspenPlus^® software), the best operating conditions were determined (steam-to-carbon and O₂/C ratios, operating temperatures and pressures) for each process alternative. The selection of the preferential fuel processing option was consequently carried out, based on a number of criteria (efficiency, complexity, compactness, safety, controllability, emissions, etc.); the ATR with both HTS and LTS reactors shows the most promising results, with a net electrical efficiency of 29% (LHV).     

Metal hydride hydrogen storage tank for light fuel cell vehicle

We describe a metal hydride (MH) hydrogen storage tank for light fuel cell vehicle application developed at HySA Systems. A multi-component AB₂-type hydrogen storage alloy was produced by vacuum induction melting (10 kg per a load) at our industrial-scale facility. The MH alloy has acceptable H sorption performance, including reversible H storage capacity up to ∼170 NL/kg (1.5 wt% H). The cassette-type MH tank was made up of 2 cylindrical aluminium canisters with transversal internal copper fins and external aluminium fins for improving the heat exchange between the heating medium and the MH tank. Heat supply and removal was provided from the outside using air at T = 15–25 °C. The MH tank was tested at the conditions of natural or forced (velocity ∼2 m/s) air convection. The tests included H₂ charge of the tank at P = 15–40 bar and its discharge at P = 1 bar. The tank in the H₂ discharge mode was also tested together with open cathode low-temperature proton exchange membrane fuel cell (LT PEMFC).     

Sorbitol-plasticized chitosan/zeolite hybrid membrane for direct methanol fuel cell

Organic–inorganic hybrid membranes, as promising direct methanol fuel cell membranes, have become a research focus in recent years. Wherein interfacial morphology, greatly influenced by the polymer chain flexibility and interfacial stress generated during membrane formation, is a critical determinant of efficient suppression of methanol crossover. In this study, a novel and feasible approach for rational fabrication of organic/inorganic hybrid direct methanol fuel cell (DMFC) membrane is tentatively explored. By adding plasticizer in the membrane casting solution and/or elevating solvent evaporation temperature during membrane fabrication, the glass transition temperature (T_g) and crystallinity of the chitosan/zeolite hybrid membrane are both remarkably decreased. In particular, the interface voids are substantially eliminated, generating a more desirable interfacial morphology and consequently leading to an improved performance in suppressing methanol crossover. The chitosan/mordenite/sorbitol hybrid membrane prepared with 30 wt% of sorbitol and 15 wt% of mordenite exhibits a 44% reduction in methanol permeability compared with chitosan control membrane. The variation of methanol permeability with mordenite and sorbital content is tentatively elucidated by the change of free volume cavity size in the membrane determined by positron annihilation lifetime spectroscopy (PALS) measurements.     

Development of the integrated methanol fuel processor using micro-channel patterned devices and its performance for steam reforming of methanol

A plate-type integrated fuel processor consisting of three different micro-structured modules was developed for hydrogen production in a 150 W PEMFC system. This system includes a reformer with combustor, two heat exchangers, and an evaporator with a combustor. Methanol steam reforming was chosen as a means to produce hydrogen for the PEMFC system. This system could be operated without any external heat supply. Hydrogen was used as the initial combustion fuel during startup, while methanol was used later. Cu/Zn/Al₂O₃ and Pt/Al₂O₃ catalysts were chosen for the steam reforming of methanol and the combustion, respectively, and coated on microchannel-patterned stainless steel sheets.

The integrated system was operated consistently with 80% of methanol conversion at for 20 h without deactivation of the catalysts. The production rate on dry basis and the composition of hydrogen was and ca 70%, respectively. Overall the thermal efficiency of this fuel processor based on the LHV was 56.7%.     

Overview of hybrid membranes for direct-methanol fuel-cell applications

The direct-methanol fuel cell (DMFC), a type of polymer-electrolyte membrane fuel cell, has lately received much attention because of its potential applicability as a good alternative power source for the future. In order to achieve commercially viable performance goals for the DMFC, a membrane with several important selective behaviors will need to be developed. Over roughly the past four decades, researchers have used the commercial Nafion membrane by DuPont as a proton-conductive membrane in DMFCs due to its chemical stability and high proton conductivity, as well as high mechanical strength. However, Nafion membranes also have several weaknesses such as high methanol permeability and an operational temperature limited to ∼100 °C or lower, and Nafion is also a very expensive material. Besides Nafion, there have been several engineering thermoplastic polymers such as poly(etheretherketone) (PEEK), polysulfone (PSF) and polybenzimidazole (PBI) used as alternative membranes due to their lower cost and very high mechanical and thermal stability in high temperature operation. To date, there has been continuous extensive research on developing a membrane which can fulfill all of the essential characteristics to yield the desired performance in DMFCs. In the course of this research, hybrid membranes have been developed by modifying the original membranes to produce new membranes with variously enhanced properties. This review discusses recent advances in hybrid membranes of two main types: Nafion-based and non-Nafion-based membranes. Recent achievements and prospect of applications also been included in this paper.     

Potential air quality benefits of methanol as a vehicle fuel

Air pollution regulation in industrial cities limits economic growth. Cleaner vehicles can reduce this effect by reducing pollution. The air quality and consequent economic benefits of methanol are assessed. Air pollution is a pervasive by-product of industrial development. Substitution of cleaner fuels for the current generation of fossil fuels can reduce the need for and economic cost of traditional add-on pollution controls. I will assess the potential of methanol to reduce vehicle emissions, and consequently to reduce regulatory pressure on industry and economic growth. The impact of releasing capital investment from pollution control to other productive uses and preserving existing manufacturing jobs are two of the economic benefits addressed.     

Onboard fuel processor for PEM fuel cell vehicles

To lower vehicle greenhouse gas emissions, many automotive companies are exploring fuel cell technologies, which combine hydrogen and oxygen to produce electricity and water. While hydrogen storage and infrastructure remain issues, Renault and Nuvera Fuel Cells are developing an onboard fuel processor, which can convert a variety of fuels into hydrogen to power these fuel cell vehicles.The fuel processor is now small enough and powerful enough for use on a vehicle. The catalysts and heat exchangers occupy 80 l and can be packaged with balance of plant controls components in a 150-l volume designed to fit under the vehicle. Recent systems can operate on gasoline, ethanol, and methanol with fuel inputs up to 200 kWth and hydrogen efficiencies above 77%. The startup time is now less than 4 min to lower the CO in the hydrogen stream to the target value for the fuel cell.     

Analysis of a fuel cell hybrid commuter railway vehicle

This study presents paper presents an analysis of the potential CO₂ savings that could be gained through the introduction of hydrogen-powered fuel cells on a commuter-style railway route. Vehicle is modelled as a fuel cell series hybrid. The analysis consists of power/energy flow models of a fuel cell stack, battery pack and hybrid drive controller. The models are implemented in a custom C# application and are capable of providing key parametric information of the simulated journey and individual energy drive components. A typical commuter return journey between Stratford Upon Avon and Birmingham is investigated. The fuel cell stack and battery pack behaviour is assessed for different stack sizes, battery sizes and control strategies to evaluate the performance of the overall system with the aim of understanding the optimum component configuration. Finally, the fuel (H₂) requirements are compared with typical diesel and hybrid-diesel powered vehicles with the aim of understanding the potential energy savings gained from such a fuel cell hybrid vehicle.     

Biodiesel fuel processor for APU applications

Tail pipe emission reduction, increased use of renewable fuels and efficient supply of auxiliary power for road vehicles using fuel cells have been the main drivers of the European project BIOFEAT (biodiesel fuel processor for a fuel cell auxiliary power unit for a vehicle). Within the project a biodiesel fuelled heat integrated fuel processor for 10 kW_e capacity has been designed and constructed. Demonstration tests showed a high quality reformate with less than 10 ppm of CO and a gross efficiency of 87%.