The limited availability of fossil fuels, the technical challenges associated with existing vehicles, and their emissions, have made the study of efficient energy converters and clean fuels a top priority for research centers and automobile companies worldwide. Using a hybrid or non-hybrid FC system conventional vehicles can address some of their existing problems. Therefore, this study investigates a Polymer Electrolyte Membrane FC (PEMFC) system for vehicle applications. Modeling is performed using MATLAB software. According to the specifications of real-world samples, system components including stack, hydrogen and air humidifier, air compressor, humidifier pump, and cooling pump are modeled. The results indicate that 14% of the power generated by the FC stack is consumed by the peripheral components. In the basic state at a current density of j=0.7 A/cm2, the total efficiency of the system is 48.15%, while the net efficiency is 34.3%. By fully condensing the water vapor exiting the stack and using it to humidify the reactors, the need for an additional water tank is eliminated. For j<0.047 A/cm2, the stack cannot provide sufficient power for the system components, necessitating an auxiliary energy source, such as a battery, to start operation.

Improving the subsea endurance and the power system efficiency of unmanned underwater vehicles (UUVs) has become more important in recent years as their growing demands in different applications. Integrated electric power systems are commonly applied in UUVs with different types of batteries as power sources. Utilizing fuel cells hybridized with batteries is one of the most efficient ways to increase the UUV's range and overall system efficiency. In this paper, a conceptual design is presented for fuel cell/battery hybrid UUV. To elaborate on the design process, the UUV fuel cell stacks, the commercial fuel cell UUVs, the technologies of the fuel and oxidant storage, and the electrical energy storage subsystems are reviewed. Also, analytical investigations have been presented on the degree of hybridization (DOH) between fuel cells and batteries. The fuel cell/battery hybrid system for UUV is designed and the technologies of its main components are proposed as the final step of the conceptual design process.

Environmental pollution and reduction of fossil fuel resources can be considered as the most important challenges for human society in the recent years. The results of previous studies show that the main consumer of fossil fuels and, consequently, most of the air pollutants, is related to the transportation industry and especially cars. The increasing growth of vehicles, the increase in traffic and the decrease in the average speed of inner-city vehicles have led to a sharp increase in fuel consumption. To address this problem, automakers have proposed the development and commercialization of hybrid vehicles as an alternative to internal combustion vehicles. In this paper, the design of an energy management system in a fuel-cell hybrid vehicle based on the look-ahead fuzzy control is considered. The preparation of fuzzy rules and the design of membership functions is based on the fuel efficiency curve of the fuel-cell. In look-ahead fuzzy control, the ahead conditions of the vehicle are the basis for decision in terms of slope and speed limit due to path curves as well as battery charge level. The fuzzy controller will determine the on or off status of the fuel-cell, as well as the power required. The motion of the fuel-cell hybrid vehicle on a real road is simulated and the performance of the proposed look-ahead controller is compared with the base controller (thermostatic method). The simulation results show that using the proposed approach can reduce the fuel consumption of the fuel-cell hybrid vehicle as well as travel time.

In recent years, using the renewable energy resources has attracted the attention of researchers and automobile companies, because of limited fossil fuel resources, low efficiency of internal combustion engines and their contribution to environmental pollution. By using the fuel cell systems instead of internal combustion engines overcome these problems can be partially overcome. In this regard, the present article examines a PEM fuel cell system for use in an urban vehicle. In the first part of this article, by using the real component of system, the fuel cell system components including stack, membrane humidity of air and hydrogen, air compressor, water pump and pump cooler stack have been modeled in MATLAB Simulink environment. The mentioned model can evaluate the power consumption of system and its auxiliary components and also the required water, hydrogen and air for system. At the base case and the current density of 0.7A / cm2, 14% of power productions of stack are consumed by auxiliaries units. At this current density, the overall and net system efficiencies are 48.15% and 34.3%. Also, by increasing the air stoichiometric coefficient due to increased compressor power consumption, there is not a significant increase in output voltage. In the second part of this article, the system from the point of view of the first law of thermodynamics has been optimized with objective functions of maximum output power and maximum efficiency. The results indicate that first, the model search method is the best method for optimization, second, the optimization with the aim of maximum power, pure power and system efficiency are increased by 11.9% and 4% respectively and the power consumption by auxiliary unit is reduced about 42%.

The design of energy management strategy is one of the main challenges in the development of fuel cell electric vehicles. The proposed strategy should be well responsive to provide the demanded power of fuel cell vehicle for motion, acceleration, and different driving conditions resulting in reduced fuel consumption, the increased lifetime of power sources and overall fuel efficiency. The purpose of this paper is to identify precisely the different driving conditions, to separate the battery state of charge regions based on combined efficiency and its mathematical calculations, to determine the fuel value of each gram of hydrogen in generating electric power, to classify the fuel cell output power, to extract the required information quickly, and to distribute power optimally regarding efficiency and lifetime. This paper presents a new multi-level online energy management strategy that is based on operational mode control aiming to operate at minimum equivalent consumption. Battery charging is also done at the optimum point of the fuel cell so that along increasing total efficiency, subsequent maximum instantaneous power is also satisfied. The simulation results of the proposed strategy indicate a reduction in fuel consumption and an increment in energy consumption efficiency compared to other energy management methods.

The world's most economically developed countries are facing an energy crisis caused by geopolitical instability, rising energy costs, global stock disruptions, and a shift towards low-carbon energy sources that has yet to be fully realized. Electrification of the transportation industry offers the advantages of increased energy efficiency and reduced local pollutants. Electric Vehicles (EVs) are environmentally friendly because they reduce fossil fuels usage even zero consumption, need fewer maintenance requirements, and lower operating costs than the vehicles powered by gasoline or diesel. However, this study focuses on comparing various energy management strategies (EMS) for a backup energy supply system for EVs. The hybrid power system (HPS) considered in this study includes DC-DC and DC-AC synchronous converters, as well as supercapacitors, batteries, and fuel cells. The EMS analyzed includes state machine control, classical proportional-integral control, equivalent consumption minimization, frequency decoupling, rule-based fuzzy logic, and fuzzy logic control. The HPS's efficiency, hydrogen fuel, supercapacitor or battery state of charge levels, and overall performance are evaluated as primary efficiency criteria. Additionally, the HPS not only increases system energy but also reduces the number of pack batteries required. This study designs and constructs the combined power systems to enhance EV power schemes with rechargeable battery power supplies. The results show that a 6-kW fuel cell hybrid increases the power system capacity to 408 kWh. Moreover, a novel method based on wavelet transforms of the instantaneous power of each energy source is used to quantify the stressors on each energy source that impact its life cycle. To validate all analyses and performance, a simulation model and an experimental test bench are created. Finally, simulation results demonstrate a synchronous converter with a 6-kW output power and 96% efficiency, validating the optimization results.

Polymer electrolyte membrane fuel cells (PEMFCs) produce high power density efficiently and in a pollution-free way. Therefore, it is employed in UAVs. Flow fields play key role in the performance of PEMFC-powered UAVs. In this study, a novel flow field named modified combined was introduced and investigated by a three-dimensional and two-phase PEMFC model. In the flow field main channels are tapered aiming to reinforce the performance. The study consists of two steps. In the first stage, modified combined was compared with parallel, serpentine, interdigitated, and combined. The results showed that in the modified combined compared with simple combined, pressure drop decreased 22.6%. Modified combined demonstrated suitable oxygen distribution and appropriate management and the specific power of modified combined is the highest value among all flow fields. Finally, the effect of atmospheric conditions on the performance of the PEMFC with modified combined flow field was studied and two equations were presented to predict the performance at 0.4V and 0.7V at the different altitudes of flight. The findings unveiled the point that in the cruise phase of the flight, low voltage is more suitable for PEMFC-driven UAV with modified combined flow field. All in all, modified combined flow field and low voltage are recommended to be utilized in PEMFCs as propulsion system of UAVs.