Optimization of powerplant component size on board a fuel cell/battery hybrid bus for fuel economy and system durability

The size of the individual powerplant components on board a fuel cell/battery hybrid vehicle affects the power management strategy which determines both the fuel economy and the durability of the fuel cell and the battery, and thus the average lifetime cost of the vehicle. Cost is one of the major barriers to the commercialization of fuel cell vehicles, therefore it is important to study how the sizing configuration affects overall vehicle cost. In this paper, degradation models for the fuel cell and the battery on board a fuel cell/battery hybrid bus are incorporated into the power management system to extend their lifetimes. Different sizing configurations were studied and the results reveal that the optimal size with highest lifetime and lowest average cost is highly dependent on the drive cycle. The vehicle equipped with a small fuel cell stack serving as a range extender will fail earlier and consume more fuel under drive cycles with high average power demand resulting in higher overall cost. However, the same configuration gives optimal results under a standard bus cycle with lower average power demand. At the other end of the spectrum, a fuel cell-dominant bus does not guarantee longer lifetime since the fuel cell operates mostly under low-load conditions which correspond to higher potentials reducing lifetime. Such a configuration also incurs a higher initial capital cost of the fuel cell stack resulting in a high average cost. The best configuration is a battery-dominated system with moderately-sized fuel cell stack which achieves the longest lifetime combined with the lowest average running cost throughout the lifetime of the vehicle.     

Impact of real world driving pattern and all-electric range on battery sizing and cost of plug-in hybrid electric two-wheeler

This study addresses the impact of an actual drive pattern on the sizing and cost of a battery pack for a plug-in hybrid electric two-wheeler. To estimate the daily average travel distance in fixing the all-electric range of two wheelers, a study conducted in Coimbatore city is presented. A MATLAB simulation model developed for estimating the energy and power requirements in an all-electric strategy using an Indian driving cycle (IDC) and a real-world driving pattern are discussed. The simulation results reveal the impact of the real-world driving pattern on energy consumption and also the influence of all-electric range in sizing the battery pack. To validate the results, a plug-in hybrid electric two-wheeler developed by modifying a standard two-wheeler has been tested on the road with the help of the IDC simulator kit. An annual battery cost comparison shows that nickel-metal-hydride batteries are more economical and suitable for in plug-in hybrid electric two-wheelers.     

A comparison of high-speed flywheels, batteries, and ultracapacitors on the bases of cost and fuel economy as the energy storage system in a fuel cell based hybrid electric vehicle

Fuel cells aboard hybrid electric vehicles (HEVs) are often hybridized with an energy storage system (ESS). Batteries and ultracapacitors are the most common technologies used in ESSs aboard HEVs. High-speed flywheels are an emerging technology with traits that have the potential to make them competitive with more established battery and ultracapacitor technologies in certain vehicular applications. This study compares high-speed flywheels, ultracapacitors, and batteries functioning as the ESS in a fuel cell based HEV on the bases of cost and fuel economy. In this study, computer models were built to simulate the powertrain of a fuel cell based HEV where high-speed flywheels, batteries, and ultracapacitors of a range of sizes were used as the ESS. A simulated vehicle with a powertrain using each of these technologies was run over two different drive cycles in order to see how the different ESSs performed under different driving patterns. The results showed that when cost and fuel economy were both considered, high-speed flywheels were competitive with batteries and ultracapacitors.     

On the sizing and energy management of an hybrid multistack fuel cell – Battery system for automotive applications

This study aims at highlighting the impact of the sizing of a hybrid multi-stack fuel cell – battery system on its behavior. Using a rule based energy management strategy, the influence of the hybridization rating is studied. The system's fuel consumption, operation duration, start/stop cycles, ampere-hour throughput and state of charge deviation are evaluated using an Energetic Macroscopic Representation (EMR) based dynamic model. The simulation results predict and expected superiority in both fuel economy and system degradation for systems with a high hybridization ratings whereas the use of systems with low hybridization ratings results in a reduced battery depth of discharge.     

Optimal sizing of a fuel processor for auxiliary power applications of a fuel cell-powered passenger car

The present study considers the optimal sizing of a three-way hybrid powertrain consisting of a compact reformer, a compact battery and a low temperature PEM fuel cell stack serving as the main power unit. A simulation model consisting of the relevant characteristic parameters of the three power sources has been developed and has been used to study the fuel utilization features of the hybrid powertrain while going through the NEDC driving cycle with a given auxiliary power requirement. The optimality is based on minimizing fuel cost while having an assured range of 500 km under practical driving conditions and a further 100 km under reduced auxiliary power usage. It is shown that for performance characteristics of Toyota Mirai and for average auxiliary power consumption of 5 kW, a smaller NiMH battery size of 1.3 kWh together with a fuel processor of 5.6 kW constant output would be optimal with a further requirement of 25% more hydrogen and 33 kg of ethanol to be carried on-board. Substantial reductions in vehicle mass and fuel load can be achieved for more modest performance characteristics and auxiliary power consumption.     

Efficiencies of hydrogen storage systems onboard fuel cell vehicles

Energy efficiency, vehicle weight, driving range, and fuel economy are compared among fuel cell vehicles (FCV) with different types of fuel storage and battery-powered electric vehicles. Three options for onboard fuel storage are examined and compared in order to evaluate the most energy efficient option of storing fuel in fuel cell vehicles: compressed hydrogen gas storage, metal hydride storage, and onboard reformer of methanol. Solar energy is considered the primary source for fair comparison of efficiencies for true zero emission vehicles. Component efficiencies are from the literature. The battery powered electric vehicle has the highest efficiency of conversion from solar energy for a driving range of 300 miles. Among the fuel cell vehicles, the most efficient is the vehicle with onboard compressed hydrogen storage. The compressed gas FCV is also the leader in four other categories: vehicle weight for a given range, driving range for a given weight, efficiency starting with fossil fuels, and miles per gallon equivalent (about equal to a hybrid electric) on urban and highway driving cycles.     

An innovative optimal power allocation strategy for fuel cell, battery and supercapacitor hybrid electric vehicle

An optimal design of a three-component hybrid fuel cell electric vehicle comprised of fuel cells, battery, and supercapacitors is presented. First, the benefits of using this hybrid combination are analyzed, and then the article describes an active power-flow control strategy from each energy source based on optimal control theory to meet the demand of different vehicle loads while optimizing total energy cost, battery life and other possible objectives at the same time. A cost function that minimizes the square error between the desired variable settings and the current sensed values is developed. A gain sequence developed compels the choice of power drawn from all devices to follow an optimal path, which makes trade-offs among different targets and minimizes the total energy spent. A new method is introduced to make the global optimization into a real-time based control. A model is also presented to simulate the individual energy storage systems and compare this invention to existing control strategies, the simulation results show that the total energy spent is well saved over the long driving cycles, also the fuel cell and batteries are kept operating in a healthy way.     

Fuzzy control based engine sizing optimization for a fuel cell/battery hybrid mini-bus

The fuel cell/battery hybrid vehicle has been focused for the alternative engine of the existing internal-combustion engine due to the following advantages of the fuel cell and the battery. Firstly, the fuel cell is highly efficient and eco-friendly. Secondly, the battery has the fast response for the changeable power demand. However, the competitive efficiency of the hybrid fuel cell vehicle is necessary to successfully alternate the conventional vehicles with the fuel cell hybrid vehicle. The most relevant factor which affects the overall efficiency of the hybrid fuel cell vehicle is the relative engine sizing between the fuel cell and the battery. Therefore the design method to optimize the engine sizing of the fuel cell hybrid vehicle has been proposed. The target system is the fuel cell/battery hybrid mini-bus and its power distribution is controlled based on the fuzzy logic. The optimal engine sizes are determined based on the simulator developed in this paper. The simulator includes the several models for the fuel cell, the battery, and the major balance of plants. After the engine sizing, the system efficiency and the stability of the power distribution are verified based on the well-known driving schedule. Consequently, the optimally designed mini-bus shows good performance.     

Experimental investigation of supercapacitor based regenerative energy storage for a fuel cell vehicle equipped with an alternator

Recently, researchers have devoted more attention to supercapacitors (SCs) to integrate with batteries in energy storage systems (ESSs) for vehicle applications. In this study, we attempted to characterize the use of SCs in the ESS for a PEM fuel cell vehicle equipped with an alternator to maximize the performance of regenerative braking. We applied lithium-ion batteries (LIBs) and SCs as energy storage devices to examine their effect on ESS. Then we used a hysteresis brake to apply controllable braking force on the flywheel to form hybrid braking (HB) and made efforts to study its behavior to suggest a braking control strategy. We also ran the whole system over the rotational speed to cover the range of driving speed. At last, we sized the SCs for the most commonly used fuel cell electric vehicle (FCEV) in Korea, i.e., Hyundai NEXO, based on the results obtained from the above study by alternator efficiencies.     

Implementation of self-adaptive Harris Hawks Optimization-based energy management scheme of fuel cell-based electric power system

This paper presents a hybrid Fuel Cell-based Power System (FCPS) consisting of fuel cell and hybrid Energy Storage Systems (ESSs), including a battery with high energy density and supercapacitor with high power density to overcome the sudden load demand change and improving the reliability of the delivered power. Any hybrid power system needs Energy Management Strategies (EMS) to balance the power between the different energy sources. In this paper, a comparative analysis of three energy management strategies, including the state machine control method, the classical PI control method and equivalent consumption minimization strategy (ECMS) is performed. The paper's main objective is enhancing the DC-bus voltage profile of a hybrid fuel cell/battery/supercapacitor power system equipped with the developed under-mentioned EMS by using a hybrid modified optimization technique that combines Harris Hawks optimization (HHO) and Sine Cosine Algorithm (SCA). The new hybrid HHO-SCA is employed to determine the optimal control parameters of the DC-bus voltage controller, which significantly assists in enhancing the DC-bus voltage profile as well as the performance of the applicable ESS in terms of improving efficiency and SoC. The effectiveness of the suggested control schemes is simulated using MATLAB/SIMULINK software. The simulation results confirmed that the proposed HHO-SCA is superior and efficient in improving the DC-bus voltage.     

Cost-optimal design and energy management of fuel cell electric trucks

Road freight transport on hilly routes represents a significant challenge for the advancement of fuel cell electric trucks because of the high-performance requirements for fuel consumption, vehicle lifetime, and battery charge control. Therefore, it is essential to optimize the vehicle design and energy management, which greatly influence the driving performance and total cost of ownership. This paper focuses on the cost-optimal design and energy management of fuel cell electric trucks, considering five key influencing factors: powertrain component sizing, driving cycle, vehicle weight, component degradation, and market prices. The cost optimization relies on a novel predictive energy management scheme based on dynamic programming and the systematic calibration of control parameters. The paper analyzes the simulation results to highlight three main findings for fuel cell electric trucks: 1) cost-optimal energy management is essential to define the best trade-off between fuel consumption and component degradation; 2) the total cost of ownership is significantly influenced by component sizing, driving cycles, vehicle weight, and market prices; 3) predictive energy management is highly beneficial in challenging road topographies for substantial cost-saving and lower component size requirements.     

Development of an optimization model for the feasibility analysis of hydrogen application as energy storage system in microgrids

Hydrogen can be used as an Energy Storage System (ESS) in a microgrid allowing to store surplus generation of variable renewable sources for later use. Research in the area mainly refers to the sizing of the components, however few studies evaluate the optimal technology selection and operation of microgrids using hydrogen as ESS. In this work, a model to determines optimal selection and to dispatch of Distributed Energy Resources (DER) allowing to evaluate the viability of hydrogen application as ESS in a microgrid is developed. The model is implemented in GAMS, using mixed integer linear programming, and applied in a hypothetical microgrid using as input data load profiles and commercial data available in literature. The results indicate the economical and environmental benefits of DER adoption, but the currently high investment costs make it infeasible to adopt hydrogen into a microgrid. However, when considering environmental costs and market prospects, the adoption of this technology became a good alternative, improving the energy management and reducing the total annual cost of the microgrid by 14.1%.     

A new application of the UltraBattery to hybrid fuel cell vehicles

This study involves investigation of fuel cell hybrid vehicles. The main power source in the dynamic configuration is a proton exchange membrane fuel cell. An energy performance comparison is conducted between the use of a lithium‐ion battery (Automotive Energy Supply Corporation, Japan) and the UltraBattery (Furukawa Battery Company, Japan) as auxiliary power sources. The MATLAB/Simulink for simulation is used to observe dynamic behavior and overall performance. This study describes the simulation frameworks of the proton exchange membrane fuel cell, ultracapacitor, lead–acid battery, and UltraBattery. Then, the Economic Commission for Europe 40 driving cycle is used to test and investigate the performance of the fuel cell hybrid vehicle. Four energy output models are adopted to simulate the energy demand and the energy motor output of the dual power source, namely the high‐load demand, general demand, low‐load demand, and charge models. The simulation results indicate that the lithium battery recycles 0.1% more work compared with the UltraBattery. Regarding fuel economy, the UltraBattery is only 0.1% inferior to the lithium battery. The expected cost of an UltraBattery with the same specifications is 35% less than that of a lithium battery. Considering fuel economy and cost simultaneously, the UltraBattery can compete with the lithium battery. Copyright © 2015 John Wiley & Sons, Ltd.     

Optimal integration strategies for a syngas fuelled SOFC and gas turbine hybrid

This article aims to develop a thermodynamic modelling and optimization framework for a thorough understanding of the optimal integration of fuel cell, gas turbine and other components in an ambient pressure SOFC-GT hybrid power plant. This method is based on the coupling of a syngas-fed SOFC model and an associated irreversible GT model, with an optimization algorithm developed using MATLAB to efficiently explore the range of possible operating conditions. Energy and entropy balance analysis has been carried out for the entire system to observe the irreversibility distribution within the plant and the contribution of different components. Based on the methodology developed, a comprehensive parametric analysis has been performed to explore the optimum system behavior, and predict the sensitivity of system performance to the variations in major design and operating parameters. The current density, operating temperature, fuel utilization and temperature gradient of the fuel cell, as well as the isentropic efficiencies and temperature ratio of the gas turbine cycle, together with three parameters related to the heat transfer between subsystems are all set to be controllable variables. Other factors affecting the hybrid efficiency have been further simulated and analysed. The model developed is able to predict the performance characteristics of a wide range of hybrid systems potentially sizing from 2000 to 2500 W m⁻² with efficiencies varying between 50% and 60%. The analysis enables us to identify the system design tradeoffs, and therefore to determine better integration strategies for advanced SOFC-GT systems.     

Optimal energy management strategy of fuel-cell battery hybrid electric mining truck to achieve minimum lifecycle operation costs

Proton exchange membrane fuel cell (PEMFC) electric vehicle is an effective solution for improving fuel efficiency and onboard emissions, taking advantage of the high energy density and short refuelling time. However, the higher cost and short life of the PEMFC system and battery in an electric vehicle prohibit the fuel cell electric vehicle (FCEV) from becoming the mainstream transportation solution. The fuel efficiency-oriented energy management strategy (EMS) cannot guarantee the improvement of total operating costs. This paper proposes an EMS to minimize the overall operation costs of FCEVs, including the cost of hydrogen fuel, as well as the cost associated with the degradations of the PEMFC system and battery energy storage system (ESS). Based on the PEMFC and battery performance degradation models, their remaining useful life (RUL) models are introduced. The control parameters of the EMS are then optimized using a meta-model based global optimization algorithm. This study presents a new optimal control method for a large mining truck operating on a real closed-road operation cycle, using the combined energy efficiency and performance degradation cost measures of the PEMFC system and lithium-ion battery ESS. Simulation results showed that the proposed EMS could improve the total operating costs and the life of the FCEV.     

Techno-economic study of off-grid hybrid photovoltaic/battery and photovoltaic/battery/fuel cell power systems in Kunming,China

The objective of this study is to evaluate the technical and economic feasibility of stand-alone hybrid photovoltaic (PV)/battery and PV/battery/fuel cell (FC) power systems for a community center comprising 100 households in Kunming by using the Hybrid Optimization Model for Electric Renewable (HOMER) software. HOMER is used to define the optimum sizing and techno-economic feasibility of the system equipment based on the geographical and meteorological data of the study region. In this study, different hybrid power systems are analyzed to select the optimum energy system while considering total net present cost (NPC) and levelized cost of energy (COE). The results showed that the optimal hybrid PV/battery system comprised 500 kW PV modules, 1200 7.6-kWh battery units, and 500 kW power converters. The proposed system has an initial cost of $6,670,000, an annual operating cost of $82,763/yr, a total NPC of $7,727,992, and a levelized COE of $1.536/kWh. While the PV/battery/FC power system is possible, the cost increases were due to the investment cost of the FC system. The optimal PV/battery/FC system has an initial cost of $6,763,000, an annual operating cost of $82,312/yr, a total NPC of $7,815,223, and a levelized COE of $1.553/kWh.     

Effects of drivetrain hybridization on fuel economy,performance and costs of a fuel cell hybrid electric vehicle

Fuel cell hybrid electric vehicles (FCHEVs) are considered to be the most attractive long-term option for passenger cars. Several barriers, such as cost, durability and hydrogen refueling infrastructure, must be overcome for a wider use of FCHEVs. In this paper, a mid-sized FCHEV is modeled and simulated in ADVISOR to analyze the influence of hybridization factor on vehicle performance and costs. The results are compared with those of the Toyota Mirai in order to find the optimum size of the fuel cell stack and the number of battery modules that meet various driving requirements, minimize hydrogen consumption and vehicle cost. The best results are obtained by reducing the fuel cell stack power by 58%. A 7.7% increase in equivalent fuel economy (71.6 MPGe) and a reduction of 25% in the vehicle cost is achieved.     

Lifespan-consciousness and minimum-consumption coupled energy management strategy for fuel cell hybrid vehicles via deep reinforcement learning

Energy management strategy (EMS) based on optimized deep reinforcement learning plays a critical role in minimizing fuel consumption and prolonging the fuel cell stack lifespan for fuel cell hybrid vehicles. The deep Q-learning (DQL) and deep deterministic policy gradient (DDPG) algorithms with priority experience replay are proposed in this research. The factors of fuel economy and power fluctuation are incorporated into the multi-objective reward functions to decline the fuel consumption and extend the lifetime of fuel cell stack. In addition, the degradation rate is introduced to reflect the lifetime of fuel cell stack. Furthermore, compared to the referenced optimally energy management strategy (dynamic planning), the DQL-based and DDPG-based EMS with prioritized experience replay (DQL-PER, DDPG-PER) are evaluated in hydrogen consumption and cumulative degradation of fuel cell stack under four driving cycles, FTP75, US06-2, NEDC and LA92-2, respectively. The training results reveal that the DQL-PER-based EMS performances better under FTP75 and US06-2 driving cycles, whereas DDPG-PER-based EMS has better performance under NEDC driving cycle, which provide a potential for applying the proposed algorithm into multi-cycles.     

A wavelet-fuzzy logic based energy management strategy for a fuel cell/battery/ultra-capacitor hybrid vehicular power system

Due to increasing concerns on environmental pollution and depleting fossil fuels, fuel cell (FC) vehicle technology has received considerable attention as an alternative to the conventional vehicular systems. However, a FC system combined with an energy storage system (ESS) can display a preferable performance for vehicle propulsion. As the additional ESS can fulfill the transient power demand fluctuations, the fuel cell can be downsized to fit the average power demand without facing peak loads. Besides, braking energy can be recovered by the ESS. This study focuses on a vehicular system powered by a fuel cell and equipped with two secondary energy storage devices: battery and ultra-capacitor (UC). However, an advanced energy management strategy is quite necessary to split the power demand of a vehicle in a suitable way for the on-board power sources in order to maximize the performance while promoting the fuel economy and endurance of hybrid system components. In this study, a wavelet and fuzzy logic based energy management strategy is proposed for the developed hybrid vehicular system. Wavelet transform has great capability for analyzing signals consisting of instantaneous changes like a hybrid electric vehicle (HEV) power demand. Besides, fuzzy logic has a quite suitable structure for the control of hybrid systems. The mathematical and electrical models of the hybrid vehicular system are developed in detail and simulated using MATLAB^®, Simulink^® and SimPowerSystems^® environments.     

Sizing of a fuel cell electric vehicle: A pinch analysis-based approach

Polymer electrolyte fuel cells are considered as a promising alternative to mitigate the CO₂ emission in the transport sector. To achieve an efficient and cost-effective system, hybridisation of the energy storage system with a fuel cell is important. Efficient management of energy is the key in order to achieve an efficient and cost-effective configuration for fuel cell electric vehicle. Optimum sizing of the power source and energy storage system, which is capable of meeting the load requirement of the driving cycle is the key challenge for achieving efficient and cost-effective system. In this work, an alternative methodology based on the principles of pinch analysis is proposed, for sizing the energy storage system and the fuel cell for fuel cell-based electric vehicle, and validated for the Worldwide Harmonized Light Vehicle Test Cycle (WLTC) class-3 driving cycle.