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In the development of a range-extended electric vehicle, it is necessary to determine the control strategy of the range extender (REX) and evaluate the influence of its performance and operating conditions. In this paper, we propose a range-extender in-the-loop (REIL) method that is used to predict the vehicle fuel consumption more accurately. To develop the REIL method and perform experimental verification, the vehicle plant model, electric-drive control strategy, and REX control strategy are integrated into a vehicle control unit (VCU) for REX control, bench data acquisition, and bench monitoring. The VCU controls the REX to meet the power requirements of the simulated vehicle operations under a given driving cycle. The fuel consumed by the engine and power generated by the integrated starter-and-generator are measured during the tests, which are used in the vehicle fuel consumption calculation. We first describe the methodology and implementation of the REIL, and subsequently discuss the predicted results of a range-extended electric vehicle equipped with a 30 kW REX under the WLTC driving cycle. Comparing the predicted results of the REIL and software simulation methods, it is demonstrated that the REIL method improves the prediction accuracy of vehicle fuel consumption.

In this article, the development challenges of a fuel cell system are explained using the example of the BREEZE! fuel cell range extender (FC-REX) applied in an FEV Liiona. The FEV Liiona is a battery electric vehicle based on a Fiat 500 developed by FEV. The BREEZE! system is the first applied 30 kW low temperature polymer electrolyte membrane (LT PEM) fuel cell system in the subcompact vehicle class. Due to the highly integrated system approach and dry cathode operation, a compact design of the range extender module with a system power density of 0.45 kW/l can be achieved so that the vehicle interior including trunk remains completely usable. System development for fuel cells significantly influences performance, efficiency, package, durability, and required maintenance effort of a fuel cell electric powertrain. In order to ensure safe and reliable operation, the fuel cell system has to be supplied with sufficient amounts of air, hydrogen, and coolant flows. At the same time, the requirements for the auxiliary components necessary for fluid supply differ considerably compared to combustion engines. With respect to the FC-REX application, the pros and cons of selected balance of plant components are explained and evaluated. The BREEZE! FC-REX achieves load-dependent system efficiencies between 40% and 50%. Without limiting the usability of the vehicle interior, an additional range of 140 km can be provided by the FC-REX.

Emissions from the transportation sector are significant contributors to climate change and health problems because of the common use of gasoline vehicles. Countries in the world are attempting to transition away from gasoline vehicles and to electric vehicles (EVs), in order to reduce emissions. However, there are several practical limitations with EVs, one of which is the “range anxiety” issue, due to the lack of charging infrastructure, the high cost of long-ranged EVs, and the limited range of affordable EVs. One potential solution to the range anxiety problem is the use of range extenders, to extend the driving range of EVs while optimizing the costs and performance of the vehicles. This paper provides a comprehensive review of different types of EV range extending technologies, including internal combustion engines, free-piston linear generators, fuel cells, micro gas turbines, and zinc-air batteries, outlining their definitions, working mechanisms, and some recent developments of each range extending technology. A comparison between the different technologies, highlighting the advantages and disadvantages of each, is also presented to help address future research needs. Since EVs will be a significant part of the automotive industry future, range extenders will be an important concept to be explored to provide a cost-effective, reliable, efficient, and dynamic solution to combat the range anxiety issue that consumers currently have.

A very promising concept for small range extenders (peak power less than 40 kW) is represented by the 2-stroke, direct injection spark ignition engine, with scavenging and exhaust ports controlled by the piston, and an external pump. The most important issue to be addressed on this type of engines is the compliance with stringent rules on pollutant emissions, which depends on combustion patterns and the quality of the scavenging process. The latter is generally hindered by the symmetry of ports timings, but this handicap can be canceled by adopting a patented rotary valve, controlling the flow through a set of auxiliary transfer ports, and using a piston pump for delivering air to the power cylinder and enhancing the balance of the crankshaft. The paper reviews the design of a virtual engine, rated at 35 kW at 5600 rpm, and developed according to the above mentioned concepts. Design has been driven by CFD simulation, using, whenever possible, experimentally calibrated numerical models, or experimental information derived from similar projects. Particular care has been devoted to characterize the scavenging process and the flow patterns within the cylinder and through the ports, analyzing the influence of the rotary induction valve. Engine performance parameters have been predicted by using a well-established commercial software (GT-Power, by Gamma Technologies), while CFD-3D analyses have been carried out by means of a customized version of the KIVA-3V code. The whole study is conceived as the basis for the construction of a physical prototype. The power target has been virtually achieved with a very light and compact engine (estimated weight without the close-coupled electric motor: 35 kg). A three-way catalyst allows the engine to comply with the most stringent emission regulations, without relevant penalizations on fuel efficiency. Furthermore, the engine can work with lean mixtures, achieving a minimum specific fuel consumption comparable to a current automotive Diesel engine (223 g/kWh). This excellent result is due to the low friction and pumping losses of the 2-Stroke engine, as well as to the compactness of the combustion chamber and the capability to stratify the charge.

Metal–air batteries represent a category of energy storage system that leverages the reaction between metal and oxygen from the atmosphere to produce electricity. These batteries, known for their high energy density, have attracted considerable attention as potential solutions for extending the range of electric vehicles. Understanding the capabilities and limitations of metal-air batteries as range extenders is crucial for advancing electric vehicle technology, as these batteries could offer the additional energy needed to overcome current range limitations. This review paper provides a detailed overview of various metal-air battery technologies, delving into their design, functionality, and inherent challenges. By analyzing key theoretical and practical parameters, the study highlights how these factors influence overall battery performance. Additionally, the review addresses critical cost considerations, particularly the relationship between vehicle cost and driving range, uncovering the significant trade-offs involved in adopting metal-air batteries. Through an examination of nearly all the existing metal-air batteries, this paper sheds light on their potential to serve as effective range extenders, thereby facilitating the transition to a cleaner, more sustainable transportation landscape.

The adoption of autonomous-driving rovers represents a feasible solution to improve the sustainability of the agricultural sector, as they are smaller and more efficient compared to traditional machinery. However, endurance and productivity can be critical factors for the adoption of such vehicles. In addition, the autonomous-driving algorithm should guarantee that the rover is able to accomplish tasks without supervision. In this paper, a numerical analysis of an autonomous-driving rover with a hybrid fuel-cell powertrain, specifically designed for orchards and vineyards, is presented. The proposed powertrain presents a first innovative integration of a metal-hydride hydrogen-storage system into an orchard mobile machine. A Li-ion battery pack is the main energy source, while the fuel-cell system operates in a range-extender configuration. A co-simulation model was developed comprising the autonomous-driving algorithm, a multibody model, and a powertrain model. Experimental tests were carried out to characterize the fuel-cell system and the metal-hydride tank, and the obtained data were used to develop and tune their numerical models. A virtual test scenario consisting of a typical rover maneuver, namely a 180-degree turn, performed in different soil and payload conditions, was defined, and simulations were carried out evaluating the rover’s performance. The simulation results showed that the rover completed the mission in loam and hard soil conditions, and with up to 200 kg of payload. Moreover, the fuel-cell range extender significantly enhanced the rover’s endurance, with up to +60% of increase when employing a tank swap technique to replace the metal-hydride tank upon hydrogen depletion. On the contrary, in the case of critical terrain conditions, such as muddy and sandy soils, the rover was not capable of completing the task due to tire slipping.

Range extender hybrid vehicles have the advantages of better dynamics and longer driving range while reducing pollution and fuel consumption. This work focuses on the control strategy of an Auxiliary Power Unit (APU) operating in power generation mode for a range-extender mixer truck. When an operating point is switched, the engine speed and generator torque of the APU will switch accordingly. In order to ensure APU fast and stable adjustment to meet the power demand of the vehicle as well as operate at the lowest fuel consumption, a fuzzy adaptive PID coordination control strategy based on particle swarm optimization (PSO) is proposed to control the APU. The optimal operating curve of APU is calculated by coupling the engine and generator first. Then, the adaptive PID algorithm is used to control the speed and torque of the APU in a dual closed loop. The PSO is used to optimize the PID control parameter. Through hardware-in-the-loop tests under different working conditions, the control strategy is verified to be effective and real-time. The results show that the proposed control strategy can coordinate the operating of engine and generator and control the APU to track target power stably and quickly under minimum fuel consumption. Compared with traditional PID control strategy, the overshoot, regulation time and steady-state error are reduced by 55.1%, 11.1% and 77.3%, respectively.

In this work, the energy management strategy problem for extended-range electric vehicles is tackled by considering all the factors affecting the system costs and performance, ranging from traditional fuel consumption to noise emissions up to battery aging and engine start-up costs. To solve the resulting economic optimization problem, a control-oriented model of the powertrain is first derived focusing on power generation, thermal dynamics and noise emissions. Then, the energy management strategy problem is formally stated as a mixed-integer convex program involving all the costs of interest and solved with state-of-the-art optimization tools. The optimal strategy can be used as a benchmark for real-time controls, to understand whether to purchase a range extender is economically effective, or to assess the cost of operating the vehicle. An electric bus case-study is illustrated in detail to show the potential of the proposed approach.

The popularity of using phase change materials (PCMs) for heat storage and recovery of metal hydrides’ reaction has grown tremendously. However, a fundamental study of the coupling of such a system with a low-temperature PEM (polymer electrolyte membrane) fuel cell is still lacking. This work presents a numerical investigation of the dehydrogenation performance of a metal hydride reactor (MHR)-PCM system coupled with a fuel cell. It is shown that to supply the fuel cell with a constant H2 flow rate, the PCM properties need to be in an optimized range. The effects of some design parameters (PCM freezing point, the initial desorption temperature, the nature and the size of the PCM) on the dehydrogenation performance of MHR-PCM system are discussed in detail. The results showed that the MHR-PCM could supply hydrogen at 12 NL/min only for 20 min maximum due to the significant endothermic effect occurring in the MHR. However, reducing the requested H2 flowrate to 5.5 NL/min, the hydrogen desorption to a fuel cell is prolonged to 79 min. Moreover, this system can accommodate different PCMs such as paraffin and salt hydrates for comparable performance. This study demonstrates the ability of MHR-PCM systems to be used as range extenders in light-duty fuel cell vehicles.

Medium and heavy-duty battery electric trucks (BETs) may play a key role in mitigating greenhouse gas (GHG) emissions from road freight transport. However, technological challenges such as limited range and cargo carrying capacity as well as the required charging time need to be efficiently addressed before the large-scale adoption of BETs. In this study, we apply a geospatial data analysis approach by using a battery electric vehicle potential (BEVPO) model with the datasets of road freight transport surveys for analyzing the potential of large-scale BET adoption in Finland and Switzerland for trucks with gross vehicle weight (GVW) of over 3.5 t. Our results show that trucks with payload capacities up to 30 t have the most potential for electrification by relying on the currently available battery and plug-in charging technology, with 93% (55% tkm) and 89% (84% tkm) trip coverage in Finland and Switzerland, respectively. Electric road systems (ERSs) would be essential for covering 51% trips (41% tkm) of heavy-duty trucks heavier than 30 t in Finland. Furthermore, range-extender technology could improve the trip electrification potential by 3–10 percentage points (4–12 percentage points of tkm).