Thermally integrated energy storage system for hybrid fuel cell electric bike: An experimental study

The hybrid fuel cell/battery technology is an attractive option for a sustainable mobility with zero emissions. In fact, this solution owns system scalability features and high efficiency and, compared to battery electric solutions, it offers advantages in terms of flexibility of use and fast charging times. However, the thermal management for the battery in this type of powertrain is a crucial issue, since operating temperatures can significantly affect safety and performance. In this study, an innovative system aimed at providing high storage energy density and improving the battery pack performance of hybrid fuel cell/battery vehicles is investigated for use on-board of a plug-in fuel cell electric bike. The proposed system, developed by the authors in previous studies, integrates the battery pack with a hydrogen storage based on metal hydrides. The idea behind this solution is to exploit the endothermic desorption processes of hydrogen in metal hydrides to cool down the battery pack during operation. An experimental analysis is conducted to assess the thermal management capabilities of this system: by considering a typical duty cycle designed on the base of road test measurements, battery pack temperature profiles are evaluated and compared against those from a control experiment where no battery thermal management is enabled (i.e. no hydrogen desorption from the metal hydride tank). The results show that, beside enhancing the on-board stored energy capacity, the proposed system represents an effective solution to provide an efficient thermal management for the battery pack, with significant advantages in terms of attainable riding range.     

Dynamic behaviour of Li batteries in hydrogen fuel cell power trains

A Li ion polymer battery pack for road vehicles (48 V, 20 Ah) was tested by charging/discharging tests at different current values, in order to evaluate its performance in comparison with a conventional Pb acid battery pack. The comparative analysis was also performed integrating the two storage systems in a hydrogen fuel cell power train for moped applications. The propulsion system comprised a fuel cell generator based on a 2.5 kW polymeric electrolyte membrane (PEM) stack, fuelled with compressed hydrogen, an electric drive of 1.8 kW as nominal power, of the same typology of that installed on commercial electric scooters (brushless electric machine and controlled bidirectional inverter). The power train was characterized making use of a test bench able to simulate the vehicle behaviour and road characteristics on driving cycles with different acceleration/deceleration rates and lengths. The power flows between fuel cell system, electric energy storage system and electric drive during the different cycles were analyzed, evidencing the effect of high battery currents on the vehicle driving range. The use of Li batteries in the fuel cell power train, adopting a range extender configuration, determined a hydrogen consumption lower than the correspondent Pb battery/fuel cell hybrid vehicle, with a major flexibility in the power management.     

Test of hybrid power system for electrical vehicles using a lithium-ion battery pack and a reformed methanol fuel cell range extender

This work presents the proof-of-concept of an electric traction power system with a high temperature polymer electrolyte membrane fuel cell range extender, usable for automotive class electrical vehicles. The hybrid system concept examined, consists of a power system where the primary power is delivered by a lithium ion battery pack. In order to increase the run time of the application connected to this battery pack, a high temperature PEM (HTPEM) fuel cell stack acts as an on-board charger able to charge a vehicle during operation as a series hybrid. Because of the high tolerance to carbon monoxide, the HTPEM fuel cell system can efficiently use a liquid methanol/water mixture of 60%/40% by volume, as fuel instead of compressed hydrogen, enabling potentially a higher volumetric energy density.     

Use of lithium-ion batteries in electric vehicles

An account is given of the lithium-ion (Li-ion) battery pack used in the Northern Territory University's solar car, Fuji Xerox Desert Rose, which competed in the 1999 World Solar Challenge (WSC). The reasons for the choice of Li-ion batteries over silver–zinc batteries are outlined, and the construction techniques used, the management of the batteries, and the battery protection boards are described. Data from both pre-race trialling and race telemetry, and an analysis of both the coulombic and the energy efficiencies of the battery are presented. It is concluded that Li-ion batteries show a real advantage over other commercially available batteries for traction applications of this kind.     

Development,analysis and assessment of fuel cell and photovoltaic powered vehicles

This paper deals with a new hybridly powered photovoltaic- PEM fuel cell – Li-ion battery and ammonia electrolyte cell integrated system (system 2) for vehicle application and is compared to another system (system 1) that is consisting of a PEM fuel cell, photovoltaic and Li-ion battery. The paper aims to investigate the effect of adding photovoltaic to both systems and the amount of hydrogen consumption/production that could be saved/generated if it is implemented in both systems. These two systems are analyzed and assessed both energetically and exergetically. Utilizing photovoltaic arrays in system 1 is able to recover 177.78 g of hydrogen through 1 h of continuous driving at vehicle output power of 98.32 kW, which is approximately 3.55% of the hydrogen storage tank used in the proposed systems. While, using the same photovoltaics arrays, system 2 succeeds to produce 313.86 g of hydrogen utilizing the ammonia electrolyzer system 2 appeared to be more promising as it works even if the car is not in operation mode. Moreover, the hydrogen produced from the ammonia electrolyzer can be stored onboard, and the liquefied ammonia can be used as a potential source for feeding PEM fuel cell with hydrogen. Furthermore, the effects of changing various system parameters on energy and exergy efficiencies of the overall system are investigated.     

The study on the power management system in a fuel cell hybrid vehicle

This paper presents a model of a hybrid electric vehicle, based on a primary proton exchange membrane fuel cell (PEMFC) and an auxiliary Li-ion battery, and its dynamics and overall performance. The power voltage from the fuel cell is regulated by a DC/DC converter before integrating with the Li-ion battery, which provides energy to the drive motor. The driving force for propelling the wheels comes from a permanent magnet synchronous motor (PMSM); where the power passes through the transmission, shaft, and the differential.     

车用锂电池充电技术综述

本文简单阐述了车用锂离子动力电池充放电的基本原理。在单体电池充电理论的基础上,对单体电池的充电方法进行了介绍和比较。根据国内外学者对电池组均衡充电的研究进展,总结了动力电池组均衡充电的各种技术,并对其性能进行分析,为动力电池充电技术的研究与发展提供参考。     

Experimental investigation on the dynamic performance of a hybrid PEM fuel cell/battery system for lightweight electric vehicle application

A hybrid system combining a 2 kW air-blowing proton exchange membrane fuel cell (PEMFC) stack and a lead–acid battery pack is developed for a lightweight cruising vehicle. The dynamic performances of this PEMFC system with and without the assistance of the batteries are systematically investigated in a series of laboratory and road tests. The stack current and voltage have timely dynamic responses to the load variations. Particularly, the current overshoot and voltage undershoot both happen during the step-up load tests. These phenomena are closely related to the charge double-layer effect and the mass transfer mechanisms such as the water and gas transport and distribution in the fuel cell. When the external load is beyond the range of the fuel cell system, the battery immediately participates in power output with a higher transient discharging current especially in the accelerating and climbing processes. The DC–DC converter exhibits a satisfying performance in adaptive modulation. It helps rectify the voltage output in a rigid manner and prevent the fuel cell system from being overloaded. The dynamic responses of other operating parameters such as the anodic operating pressure and the inlet and outlet temperatures are also investigated. The results show that such a hybrid system is able to dynamically satisfy the vehicular power demand.     

Development of an optimal charging algorithm of a Ni-MH battery for stationary fuel cell/battery hybrid system application

When installed in stationary fuel cell/battery hybrid systems, sealed nickel-metal hydride (Ni-MH) battery packs have low rates of charging behavior at high temperatures. They can also be charged with surplus power from fuel cell system when they are part of a small-capacity fuel cell/battery hybrid system. Test results indicate that when subjected to high temperatures and low rates of charging current, a Ni-MH battery experiences a sharp reduction in discharge capacity but does not experience an increase in voltage. To solve these problems, we have applied a new charging algorithm based on this pulse charging method to a Ni-MH battery. The pulse charging method reduces the charging time by 2 hrs and has a charging efficiency of over 97%. The charging current factor (β) in this pulse charging method should influenced the controlling the charging rate to the battery with applied voltages. The results show a 27% increase in efficiency with the new charging method compared to the system efficiency of the conventional constant-voltage charging method. Such a pulse charging method is expected to increase the lifespan of a Ni-MH battery by inhibiting gas generation.     

Design and experimental tests of control strategies for active hybrid fuel cell/battery power sources

Twenty-first century handheld electronic devices and new generations of electric vehicles or electric airplanes have fueled a need for new high-energy, high-power, small-volume, and lightweight power sources. Current battery technology by itself is insufficient to provide the mandatory long-term power these systems require. Fuel cells are also unable to provide the essentially high peak power demanded by these systems. Hybrid systems composed of fuel cells and secondary batteries could combine the high power density of clean fuel cells and the high energy density of convenient batteries. This paper presents an experimental study on control strategies for active power sharing in such a hybrid fuel cell/battery power source. These control strategies limited the fuel cell current to safe values while also regulating the charging current or voltage of the battery. The several tested control strategies were implemented in MATLAB/Simulink and then tested under the pulsed-current load condition through experiments. Experimental tests were conducted with three control objectives: maximum fuel cell power, maximum fuel cell efficiency, and adaptive.     

Performance and cost of fuel cells for urban air mobility

Several companies are developing enabling elements of urban air mobility (UAM) for air taxis, including prototypes of electric vertical take-off and landing (eVTOL) vehicles. These prototypes incorporate electric and hybrid powertrains for multi-rotor and tilt-rotor crafts. Many eVTOLS are using batteries for propulsion and charging them rapidly between the flights or swapping them for slow charging overnight. Rapid charging degrades the battery cycle life while swapping requires multiple batteries and charging stations. This study has conducted a technoeconomic evaluation of the eVTOL air taxis with alternate powertrains using hydrogen fuel cell systems being developed for light-duty and heavy-duty vehicles. We consider performance metrics such as fuel cell engine power, weight, and durability; hydrogen consumption and weight of storage system; and maximum take-off weight. The metrics for economic evaluation are capital cost, operating and maintenance cost, fuel cost, and the total cost of ownership (TCO). We compare the performance and TCO of battery, fuel cell and fuel cell – battery hybrid powertrains for multi-rotor and tilt-rotor crafts. We show that fuel cells are the only viable concept for powering multi-rotor eVTOLs on an urban scenario that requires 60-mile range, and hybrid fuel cells are superior to batteries as powertrains for tiltrotor eVTOLs.     

Heat transfer modeling of a novel battery thermal management system

A battery cooling system is proposed for future carbon-free ammonia-based hybrid electric vehicles. In the proposed design, aluminum cold plates with tubes that are filled with liquid ammonia are placed between the batteries in the battery pack. The ammonia evaporates while cooling the plate, which then cools the batteries in the pack. The generated ammonia vapor passes to the vehicle electrical generator where it is used to produce electrical energy for driving the vehicle or charging the batteries. The proposed system was able to perform better than mini-channel liquid cooling systems, air cooling systems, and direct contact boiling systems.     

Comparison of daily operation strategies for a fuel cell/battery tram

This paper focuses on describing the daily operation strategy of a tram powered by a hybrid system based on fuel cell stack and a battery pack. The daily operation strategy focusses on the hydrogen refueling and battery recharging timing in one-day operation of 18 h, combined with serval driving cycles and three operation modes. The battery state of charge balanced (SOC-) strategy and the dynamic programming (DP-) strategy are two proposed power allocation methods. For one-cycle operation, the latter save 6.6% hydrogen consumption than the former. As for one-day operation, a simplified DP-strategy is deduced to replace the DP-strategy and accelerate the calculation. It shares equivalent hydrogen consumption with the SOC-strategy but guarantees the durability of the fuel cell and prolongs the driving mileage.     

Measuring individual cell voltages in fuel cell stacks

The requirements for stack monitoring devices are becoming more strict as the fuel cell and battery technologies reach an advanced stage of development and move towards commercialisation. Different applications put restraints on such devices when it comes to cost, weight and size. No commercial products can meet the requirements with respect to both cost and performance. Individual cell voltage measurements are crucial to protect the fuel cell stack and ensure maximum stack lifetime. Different concepts for measuring individual cell voltages in large fuel cell stacks or battery stacks and their potential accuracy are discussed. A novel low cost, lightweight and compact multiplexer circuit was implemented based on a resistor–diode circuit. Based on this circuit a prototype 80-channel multiplexer device was built and tested on a fuel cell stack with satisfactory speed and accuracy.     

A robust cell voltage monitoring system for analysis and diagnosis of fuel cell or battery systems

Cell voltage monitoring (CVM) systems are essential for the operation of fuel cell stacks and some battery systems, in the field as well as in the laboratory, because they allow the diagnosis and correction of problems that would otherwise go unnoticed and cause impaired performance or even permanent damage. A robust, safe, and low-cost design for a CVM unit is presented, using electromechanical relays as multiplexing switches. Some examples from the application of the unit on the University of Delaware's fuel cell battery hybrid buses are presented, including its use in automatically correcting anode flooding and diagnosing air channel blockage.     

Illustration of experimental,machine learning,and characterization methods for study of performance of Li-ion batteries

The development of fault diagnosis of Li-ion batteries used in electric vehicles is vital. In this perspective, the present work conducted a comprehensive study for the evaluation of coupled and interactive influence of charging ratio, number of cycles, and voltage on the discharge capacity of Li-ion batteries to predict the life of battery. The charging-discharging experimental tests on Li-ion batteries have been performed. The data such as charging ratio, number of cycles, voltage, and discharge capacity of Li-ion batteries are measured. Machine learning approach of neural networks is then applied on the obtained data to compute the effects, normal distribution, parametric analysis, and sensitivity analysis of the input parameters on the capacity of battery. It can be noticed that discharge capacity increased with an increase in full voltage. Further, it has been observed from the sensitivity analysis that the full voltage is most relevant parameters to the capacity of the battery. Additionally, scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) of the electrodes before and after experiments have been performed, to investigate the elemental dissolution due to the charging/discharging cycles. The findings and analysis from the proposed study shall facilitate experts in making decisions on the remaining life and charging capacity of the battery.     

A study of solid oxide fuel cell stack failure by inducing abnormal behavior in a single cell test

It is well known that cell imbalance can lead to failure of batteries. Prior theoretical modeling has shown that similar failure can occur in solid oxide fuel cell (SOFC) stacks due to cell imbalance. Central to failure model for SOFC stacks is the abnormal operation of a cell with cell voltage becoming negative. For investigation of SOFC stack failure by simulating abnormal behavior in a single cell test, thin yttria-stabilized zirconia (YSZ) electrolyte, anode-supported cells were tested at 800 °C with hydrogen as fuel and air as oxidant with and without an applied DC bias. When under a DC bias with cell operating under a negative voltage, rapid degradation occurred characterized by increased cell resistance. Visual and microscopic examination revealed that delamination occurred along the electrolyte/anode interface. The present results show that anode-supported SOFC stacks with YSZ electrolyte are prone to catastrophic failure due to internal pressure buildup, provided cell imbalance occurs. The present results also suggest that the greater the number of cells in an SOFC stack, the greater is the propensity to catastrophic failure.     

Research and development of on-board hydrogen-producing fuel cell vehicles

Combining with the characteristics of different types of electric vehicles, the on-board hydrogen-producing fuel cell vehicle design is adopted, which eliminates the problems about the high-pressure hydrogen storage and the hydrogenation process. The fuel cell is used as the main power source to drive the motor, and the lithium battery is used as the auxiliary power source to accelerate and recycle energy in order to meet the special requirements, like energy recovery, power and dynamic characteristics, of fuel cell vehicles. On the ADVISOR simulation platform based on MATLAB/Simulink environment, a hybrid drive model and a pure fuel cell drive model are built, and simulation and comparative analysis are performed. In the hybrid drive model, fuel cells and lithium batteries work in the highly efficient and safe operating areas respectively, and the output power of fuel cell has small fluctuations, improving energy utilization efficiency and extending the service life of the fuel cell. At the same time, the charge and discharge of the lithium battery can be effectively managed to ensure the safety of charging and prolong the service life of the lithium battery.     

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.