Economic energy management strategy design and simulation for a dual-stack fuel cell electric vehicle

This paper presents the design and simulation validation of two energy management strategies for dual-stack fuel cell electric vehicles. With growing concerns about environmental issues and the fossil energy crisis, finding alternative methods for vehicle propulsion is necessary. Proton exchange membrane (PEM) fuel cell systems are now considered to be one of the most promising alternative energy sources. In this work, the challenge of further improving the fuel economy and extending the driving range of a fuel cell vehicle is addressed by a dual-stack fuel cell system with specific energy management strategies. An efficiency optimization strategy and an instantaneous optimization strategy are proposed. Simulation validation for each strategy is conducted based on a dual-stack fuel cell electric vehicle model which follows the new European driving cycle (NEDC). Simulation results show that a dual-stack fuel cell system with proposed energy management strategies can significantly improve the fuel economy of a fuel cell vehicle and thus lengthen the driving range while being able to keep the start-stop frequency of the fuel cell stack within a reasonable range.     

Analytical method to evaluate fuel consumption of hybrid electric vehicles at balanced energy content of the electric storage devices

Innovative analytically based method to calculate corrected fuel consumption of parallel and series hybrid electric vehicles (HEVs) at balanced energy content of the electric storage devices is proposed and validated in the paper. The proposed analytical method is generally applicable and features highly accurate corrected fuel consumption results. It enables calculation of the corrected fuel consumption out of a single fuel consumption test run in a single analytic post-processing step. An additional fuel consumption test run might be needed to obtain highly accurate results if ratio of the energy content deviation of the electric storage devices to the energy used for vehicle propulsion over the test cycle is high. Proposed method enables consideration of non-linear energy flow changes and non-linear HEV component efficiency changes caused by the energy management strategy or by the component characteristics. The method therefore features highly accurate results out of the minimum number of fuel consumption test runs and thus optimizes workload for development or optimization of HEVs. The input data of the method are characteristic energy flows and efficiencies that are derived from the energy flows on selected energy paths of HEVs.     

A comprehensive review of energy management optimization strategies for fuel cell passenger vehicle

With the gradual maturity of fuel cell vehicle technology, it gives a better opportunity for the application of passenger vehicles. In this paper, the energy management optimization strategies of fuel cell passenger vehicle (FCPV) are summarized for the first time. Initially, in this review, the topological configurations of FCPV are classified systematically. The optimization objectives, energy consumption and fuel cell life, are proposed for FCPV. Then the energy management strategies (EMSs) are illustrated and analysed based on the optimization objectives above. In terms of the complex and changeable characteristics of FCPV driving conditions, the latest FCPV EMSs which depend on driving information prediction technologies are discussed and summarized. The purpose of this paper is providing references for the development of new generation FCPV energy management optimization strategies.     

Potential for reducing GHG emissions and energy consumption from implementing the aluminum intensive vehicle fleet in China

The automobile industry in China has rapidly developed in recent years which resulted in an increase in gasoline usage and greenhouse gas (GHG) emissions. Focus on climate change has also accelerated to grow pressure on reducing vehicle weight and improving fuel efficiency. Aluminum (Al) as a light metal has demonstrated a great potential for weight savings in applications such as engine blocks, cylinder heads, wheels, hoods, tailgates etc. However, primary Al production requires intensive energy and the cost of Al is more than traditional steel, which may affect the total benefits realized from using Al in automobiles. Therefore, it is very essential to conduct a study to quantify the life cycle GHG emissions and energy consumption if the plan is to achieve fleet-wide Al intensive vehicles.     

The impact of fuel cell vehicle deployment on road transport greenhouse gas emissions: The China case

Considerable attention has been paid to energy security and climate problems caused by road vehicle fleets. Fuel cell vehicles provide a new solution for reducing energy consumption and greenhouse gas emissions, especially those from heavy-duty trucks. Although cost may become the key issue in fuel cell vehicle development, with technological improvements and cleaner pathways for hydrogen production, fuel cell vehicles will exhibit great potential of cost reduction. In accordance with the industrial plan in China, this study introduces five scenarios to evaluate the impact of fuel cell vehicles on the road vehicle fleet greenhouse gas emissions in China. Under the most optimistic scenario, greenhouse gas emissions generated by the whole fleet will decrease by 13.9% compared with the emissions in a scenario with no fuel cell vehicles, and heavy-duty truck greenhouse gas emissions will decrease by nearly one-fifth. Greenhouse gas emissions intensity of hydrogen production will play an essential role when fuel cell vehicles' fuel cycle greenhouse gas emissions are calculated; therefore, hydrogen production pathways will be critical in the future.     

Fuel conservation and GHG (Greenhouse gas) emissions mitigation scenarios for China’s passenger vehicle fleet

Passenger vehicles are the main consumers of gasoline in China. We established a bottom-up model which focuses on the simulation of energy consumptions and greenhouse gas (GHG) emissions growth by China’s passenger vehicle fleet. The fuel conservation and GHG emissions mitigation effects of five measures including constraining vehicle registration, reducing vehicle travel, strengthening fuel consumption rate (FCR) limits, vehicle downsizing and promoting electric vehicle (EV) penetration were evaluated. Based on the combination of these measures, the fuel conservation and GHG emissions mitigation scenarios for China’s passenger vehicle fleet were analyzed. Under reference scenario with no measures implemented, the fuel consumptions and life cycle GHG emissions will reach 520 million tons of oil equivalent (Mtoe) and 2.15 billion tons in 2050, about 8.1 times the level in 2010. However, substantial fuel conservation can be achieved by implementing the measures. By implementing all five measures together, the fuel consumption will reach 138 Mtoe in 2030 and decrease to 126 Mtoe in 2050, which is only 37.1% and 24.3% of the consumption under reference scenario. Similar potential lies in GHG mitigation. The results and scenarios provided references for the Chinese government’s policy-making.     

Energy distribution analyses of an additional traction battery on hydrogen fuel cell hybrid electric vehicle

Hydrogen is the most abundant element in the world and produces only water vapor as a result of chemical reaction that occurred in fuel cells. Therefore, fuel cell electric vehicles, which use hydrogen as fuel, continue its growing trend in the sector. In this study, an energy distribution comparison is carried out between fuel cell electric vehicle and fuel cell hybrid electric vehicle. Hybridization of fuel cell electric vehicle is designed by equipped a traction battery (15 kW). Modeled vehicles were prepared under AVL Cruise program with similar chassis and same fuel cell stacks for regular determining process. Numerical analyses were presented and graphed with instantaneous results in terms of sankey diagrams with a comparison task. WLTP driving cycle is selected for both vehicles and energy input/output values given with detailed analyses. The average consumption results of electric and hydrogen usage is found out as 4.07 kWh and 1.125 kg/100 km respectively for fuel cell electric vehicle. On the other hand, fuel cell hybrid electric vehicle’s average consumption results figured out as 3.701 kWh for electric and 0.701 kg/100 km for hydrogen consumption. As a result of this study, fuel cell hybrid electric vehicle was obtained better results rather than fuel cell electric vehicle according to energy and hydrogen consumption with 8% and 32%, respectively.     

Prediction-based optimal power management in a fuel cell/battery plug-in hybrid vehicle

A prediction-based power management strategy is proposed for fuel cell/battery plug-in hybrid vehicles with the goal of improving overall system operating efficiency. The main feature of the proposed strategy is that, if the total amount of energy required to complete a particular drive cycle can be reliably predicted, then the energy stored in the onboard electrical storage system can be depleted in an optimal manner that permits the fuel cell to operate in its most efficient regime. The strategy has been implemented in a vehicle power-train simulator called LFM which was developed in MATLAB/SIMULINK software and its effectiveness was evaluated by comparing it with a conventional control strategy. The proposed strategy is shown to provide significant improvement in average fuel cell system efficiency while reducing hydrogen consumption. It has been demonstrated with the LFM simulation that the prediction-based power management strategy can maintain a stable power request to the fuel cell thereby improving fuel cell durability, and that the battery is depleted to the desired state-of-charge at the end of the drive cycle. A sensitivity analysis has also been conducted to study the effects of inaccurate predictions of the remaining portion of the drive cycle on hydrogen consumption and the final battery state-of-charge. Finally, the advantages of the proposed control strategy over the conventional strategy have been validated through implementation in the University of Delaware's fuel cell hybrid bus with operational data acquired from onboard sensors.     

Model for optimizing energy efficiency through controlling speed and gear ratio

Specific fuel consumption of vehicles has been improved through technical changes in the last three decades. There has been little study of the impact of behavioral aspects on the specific fuel consumption of vehicles. Analytical tools developed recently have included options for quantifying the specific fuel consumption in certain predefined driving cycles. Empirical studies have shown that real driving cycles are different from predefined ones. It has also been observed that optimal coordination of both speed of vehicle and gear ratio are detrimental to the improved performance of a vehicle. Previous studies have only considered the vehicle speed as the explanatory parameter, and gear ratio has rarely been discussed. Therefore, an optimal model of vehicle fuel consumption has been developed on the basis of microeconomic theories. The application of this model helps to identify the optimal driving strategy of a vehicle in a certain real driving cycle. The model has then been applied to estimate the optimal fuel consumption of a vehicle in a given real case, and the results of model estimate have been compared with measured data. It has been found that the implementation of optimal driving strategy based on the model estimates may help to reduce specific fuel consumption by 3.2 l/100 km on average (37% of actual specific consumption). It is also observed that the potential for energy saving prevails when the traffic flow is dense and slow. Hence, the implementation of optimal driving strategy based on the coordination of speed and gear ratio would lead to the realization of energy saving potential that is considerable.

新能源汽车发展现状及应用前景

本文对新能源汽车包括清洁替代燃料汽车、混合动力汽车、纯电动汽车的定义、分类和特点进行了总结,综述了各类新能源汽车最新技术进展及其性能,通过分析新能源汽车应用现状,指出纯电动汽车和燃料电池汽车推广应用需解决的问题,对各类新能源汽车的发展前景进行了展望。     

Grid to wheel energy efficiency analysis of battery‐ and fuel cell–powered vehicles

Sustainable energy consumption is an important part of the renewable energy economy as renewable energy generation and storage. Almost one‐third of the global energy consumption can be credited to the transportation of goods and people around the globe. To move towards a renewable energy–based economy, we must adopt to a more sustainable energy consumption pattern worldwide especially in the transportation sector. In this article, a comparison is being made between the energy efficiency of a fuel cell vehicle and a battery electric vehicle. A very simple yet logical approach has been followed to determine the overall energy required by each vehicle. Other factors that hinder the progress of fuel cell vehicle in market are also discussed. Additionally, the prospects of a hydrogen economy are also discussed in detail. The arguments raised in this article are based on physics, economic analyses, and laws of thermodynamics. It clearly shows that an “electric economy” makes far greater sense than a “hydrogen economy.” The main objective of this analysis is to determine the energy efficacy of battery‐powered vehicles as compared to fuel cell–powered vehicles.     

Electric vehicle energy consumption modelling and estimation—A case study

Electric vehicles (EVs) have a limited driving range compared to conventional vehicles. Accurate estimation of EV's range is therefore a significant need to eliminate “range anxiety” that refers to drivers' fear of running out of energy while driving. However, the range estimators used in the currently available EVs are not sufficiently accurate. To overcome this issue, more accurate range estimation techniques are investigated. Nonetheless, an accurate power‐based EV energy consumption model is crucial to obtain a precise range estimation. This paper describes a study on EV energy consumption modelling. For this purpose, EV modelling is carried out using MATLAB/Simulink software based on a real EV in the market, the BMW i3. The EV model includes vehicle powertrain system and longitudinal vehicle dynamics. The powertrain is modelled using efficiency maps of the electric motor and the power electronics' data available for BMW i3. It also includes a transmission and a battery model (ie, Thevenin equivalent circuit model). A driver model is developed as well to control the vehicle's speed and to represent human driver's behaviour. In addition, a regenerative braking strategy, based on a series brake system, is developed to model the behaviour of a real braking controller. Auxiliary devices are also included in the EV model to improve energy consumption estimation accuracy as they can have a significant impact on that. The vehicle model is validated against published energy consumption values that demonstrates a satisfactory level of accuracy with 2% to 6% error between simulation and experimental results for Environmental Protection Agency and NEDC tests.     

Quantitative analysis of fuel-saving potential for waste heat recovery system integrated with hybrid electric vehicle

Hybrid electric vehicles (HEVs) with low fuel consumption, low emissions, and long driving range are the ideal transition models between conventional fuel vehicles and pure electric vehicles. The growing demand for increased vehicle efficiency has motivated the introduction of waste heat recovery (WHR) technology in the automotive industry, with the organic Rankine cycle (ORC) as the most promising measure for recycling waste energy. Currently, only a few studies have been conducted to couple HEV and WHR systems. These studies have mainly focused on the hybrid powertrain control strategy, but lack quantitative methods to comprehensively analyze the fuel-saving potential due to the WHR system. In this study, an HEV-WHR integrated system that includes a mechanism-based dynamic model of ORC and a hybrid diesel-electric truck model is established. Further, a quantitative evaluation method that simultaneously considers the negative integrated effects (increased vehicle weight and increased exhaust back pressure) and the positive impact values of the engine, motor, and WHR system on the fuel-saving potential is proposed. Finally, the influence of two environmental factors (wind speed and ambient temperature) on the fuel-saving performance is analyzed. The results reveal that under the standard highway driving cycle (HWY), the negative integrated effects reduce the ideal fuel-saving potential of the HEV-WHR system from 6.10% to 5.42%. However, the optimized performances of the engine, motor, and WHR system improve the fuel-saving rate by 0.39%, 1.81%, and 3.22%, respectively. The results also indicate that the fuel-saving potential increases from 1.62% to 8.60% with increasing wind speed and decreases from 6.70% to 4.25% with increasing ambient temperature.     

Comparison of well-to-wheels energy use and emissions of a hydrogen fuel cell electric vehicle relative to a conventional gasoline-powered internal combustion engine vehicle

The operation of hydrogen fuel cell electric vehicles (HFCEVs) is more efficient than that of gasoline conventional internal combustion engine vehicles (ICEVs), and produces zero tailpipe pollutant emissions. However, the production, transportation, and refueling of hydrogen are more energy- and emissions-intensive compared to gasoline. A well-to-wheels (WTW) energy use and emissions analysis was conducted to compare a HFCEV (Toyota Mirai) with a gasoline conventional ICEV (Mazda 3). Two sets of specific fuel consumption data were used for each vehicle: (1) fuel consumption derived from the U.S. Environmental Protection Agency's (EPA's) window-sticker fuel economy figure, and (2) weight-averaged fuel consumption based on physical vehicle testing with a chassis dynamometer on EPA's five standard driving cycles. The WTW results show that a HFCEV, even fueled by hydrogen from a fossil-based production pathway (via steam methane reforming of natural gas), uses 5%–33% less WTW fossil energy and has 15%–45% lower WTW greenhouse gas emissions compared to a gasoline conventional ICEV. The WTW results are sensitive to the source of electricity used for hydrogen compression or liquefaction.     

Energy management of a fuel cell hybrid ultra-energy efficient vehicle

This paper focuses on energy management in an ultra-energy efficient vehicle powered by a hydrogen fuel cell with rated power of 1 kW. The vehicle is especially developed for the student competition Shell Eco-marathon in the Urban Concept category. In order to minimize the driving energy consumption a simulation model of the vehicle and the electric propulsion is developed. The model is based on vehicle dynamics and real motor efficiency as constant DC/DC, motor controllers and transmission efficiency were considered. Based on that model five propulsion schemes and driving strategies were evaluated. The fuel cell output parameters were experimentally determined. Then, the driving energy demand and hydrogen consumption was estimated for each of the propulsion schemes. Finally, an experimental study on fuel cell output power and hydrogen consumption was conducted for two propulsion schemes in case of hybrid and non-hybrid power source. In the hybrid propulsion scheme, supercapacitors were used as energy storage as they were charged from the fuel cell with constant current of 10 A.     

Life cycle study of coal-based dimethyl ether as vehicle fuel for urban bus in China

With life cycle assessment (LCA) methodology, a life cycle model of coal-based dimethyl ether (CBDME) as a vehicle fuel is established for China. Its life cycle from well to wheel are divided into three phases. They are feedstock extraction, fuel production and fuel consumption in vehicle. The primary energy consumption (PEC) and global warming potential (GWP) of CBDME pathway are analyzed and compared with coal-based diesel (CBD) as a latent rival to replace conventional petroleum-based diesel (CPBD).     

Comparative life cycle assessment of hydrogen pathways from fossil sources in China

Emissions of multiple hydrogen production pathways from fossil sources were evaluated and compared with that of fossil fuel production pathways in China by using the life cycle assessment method. The considered hydrogen pathways are gasoline reforming, diesel reforming, natural gas reforming, soybean‐derived biodiesel (s‐biodiesel) reforming, and waste cooking oil‐derived biodiesel reforming. Moreover, emissions and energy consumption of fuel cell vehicles utilizing hydrogen from different fossil sources were presented and compared with those of the electric vehicle, the internal combustion engine vehicle, and the compression ignition engine vehicle. The results indicate both fuel cell vehicles and the electric vehicle have less greenhouse gas emissions and energy consumption compared with the traditional vehicle technologies in China. Based on an overall performance comparison of five different fuel cell vehicles and the electric vehicle in China, fuel cell vehicles operating on hydrogen produced from natural gas and waste cooking oil‐derived biodiesel show the best performance, whereas the electric vehicle has the worse performance than all the fuel cell vehicles because of very high share of coal in the electricity mix of China. The emissions of electric vehicle in China will be in the same level with that of natural gas fuel cell vehicle if the share of coal decreases to around 40% and the share of renewable energy increases to around 20% in the electricity mix of China. Copyright © 2016 John Wiley & Sons, Ltd.     

Fuel cell hybrid powertrains for use in Southern Italian railways

This paper analyses the use of a fuel cell hybrid powertrain for different uses on rail. Four vehicles are numerically tested on suitable tracks. The implemented model calculates the vehicle power demand, starting from track altitude, train speed and vehicle characteristics. For each track, a powertrain composed of a fuel cell system and an energy storage system, battery and/or supercapacitor, is used, suitable for the purpose. Each component is modelled separately and is validated. It should be underlined that the whole system is validated, by means of experimental data found in the literature. A comparison analysis between the simulation results is done: the H₂ consumption varies between 5 kg/cycle and 160 kg/cycle, according to the track energy consumption, while the fuel cell efficiency is between 50% and 47%, since the fuel cell works at different power rates.     

Diffusion of new automotive technologies for improving energy efficiency in Brazil’s light vehicle fleet

Historically, Brazil has promoted the development and sales of light duty vehicles running on ethanol (firstly, ethanol-dedicated cars, and recently flexfuel cars). In the 1990s, the country also favored the sales of compact cars to middle and low-income classes. However, in the last years, the profile of vehicles sold in Brazil has converged towards larger and less-efficient vehicles. In 2008, Brazil launched the vehicle labeling program. Based on the outcomes of the historical programs oriented towards the development of automotive innovations, and on a survey conducted with the country’s main auto makers, this article evaluates whether the vehicle labeling program will both improve the energy efficiency of light vehicles, and introduce new technologies. Our results indicate that, despite its virtuous intentions, the program will not control the tendency of rising fuel consumption of passenger cars sold in Brazil. Therefore, other policies are needed to boost innovations in Brazil’s automotive industry.     

Commercial vehicle auxiliary loads powered by PEM fuel cell

The commercial vehicles are in leadership in emission production for on-road vehicles. This high rate of emission is released in highly populated areas where diesel driven internal combustion engines are running in inefficient operating ranges. Except the propulsion, the internal combustion engine is powering the auxiliary devices such as refrigerator unit, etc. The auxiliary units are significant contributor to the overall pollutant production. In this paper the auxiliary load power supply for refrigerator unit is shifted from internal combustion engine to PEM fuel cell. The decrease in CO₂ accumulated emissions was estimated by simulation model containing vehicle model (tire, brake, differential, gearbox and driver model), diesel engine model and auxiliary power demand model. Four stroke diesel engine was modeled and investigated. For this investigation the fully filled truck was used for simulating 100% weight load. The gross weight is 7500 kg.The novelty of the approach is the simulation performed on realistic combination of city and urban road cycle. The focus was on modelling the realistic truck driving cycle in order to correctly predict emission and fuel consumption reduction. Since initial investigation are performed on constant load demand of fuel cell, simplified model of PEMFC was applied. PEM fuel cell stack was designed in order to meet the demands of auxiliary consumers. The H₂ consumption and size of hydrogen tank was estimated based on assumed 8-h daily drive. Finally, the migration of power supply for auxiliary units on commercial vehicle from internal combustion engine showed potential of fuel savings and CO₂ reduction of up to 9% for a given case on this specific test cycle.