As electric powered unmanned aerial vehicles enter a new age of commercial viability, market opportunities in the small UAV sector are expanding. Extending UAV flight time through a combination of fuel cell and battery technologies enhance the scope of potential applications. A brief survey of UAV history provides context and examples of modern day UAVs powered by fuel cells are given. Conventional hybrid power system management employs DC-to-DC converters to control the power split between battery and fuel cell. In this study, a transistor replaces the DC-to-DC converter which lowers weight and cost. Simulation models of a lithium ion battery and a proton exchange membrane fuel cell are developed and integrated into a UAV power system model. Flight simulations demonstrate the operation of the transistor-based power management scheme and quantify the amount of hydrogen consumed by a 5.5 kg fixed wing UAV during a six hour flight. Battery power assists the fuel cell during high throttle periods but may also augment fuel cell power during cruise flight. Simulations demonstrate a 60 liter reduction in hydrogen consumption when battery power assists the fuel cell during cruise flight. Over the full duration of the flight, averaged efficiency of the power system exceeds 98%. For scenarios where inflight battery recharge is desirable, a constant current battery charger is integrated into the UAV power system. Simulation of inflight battery recharge is performed. Design of UAV hybrid power systems must consider power system weight against potential flight time. Data from the flight simulations are used to identify a simple formula that predicts flight time as a function of energy stored onboard the modeled UAV. A small selection of commercially available batteries, fuel cells, and compressed air storage tanks are listed to characterize the weight of possible systems. The formula is then used in conjunction with the weight data to generate a graph of power system weight versus potential flight times. Combinations of the listed batteries, fuel cells, and storage tanks are plotted on the graph to evaluate various hybrid power system configurations.

Determining the thermal conductivity of carbon gas diffusion layers used in hydrogen fuel cells is a very active topic of research. The primary driver behind this research is due to the need for development of proton exchange membrane fuels with longer usable life cycles before failure. As heat is a byproduct of the oxygen-hydrogen reaction an optimized pathway to remove the excess heat is needed to prevent thermal damage to the fuel cell as both mechanical and chemical degradation is accelerated under elevated temperatures. Commercial systems used for testing thermal conductivity are readily available, but are prohibitively expensive, ranging from just over $10,000 to $80,000 for high-end systems. As this cost can exclude some research labs from experimenting with thermal conductivity, a low cost alternative system is a desirable product. The development of a low cost system that maintained typical accuracy levels of commercials systems was carried out successfully at a significant cost reduction. The end product was capable of obtaining comparable accuracy to commercial systems at a cost reduction of more than 600% when compared to entry level commercial models. Combined with a system design that only required some basic fabrication equipment, this design will allow many research labs to expand their testing capabilities without straining departmental budgets. As expected with the development of low cost solutions, the reduction in cost came at the loss in other aspects of system performance, mainly run time. While the developed system requires a significate time investment to obtain useable results, the system can be improved by the used of RTDs in place of thermocouples or incorporation of an isothermal cold plate. These improvements would reduce the runtime to less than that of a standard work day while maintaining an approximate reduction in cost of 350%.

There was a growing trend in the automotive market on the adoption of Hybrid Electric Vehicles (HEVs) for consumers to purchase. This was partially due to external pressures such as the effects of global warming, cost of petroleum, governmental regulations, and popularity of the vehicle type. HEV technology relied on a variety of factors which included the powertrain (PT) of the system, external driving conditions, and the type of driving pattern being driven. The core foundation for HEVs depended heavily on the battery pack and chemistry being adopted for the vehicle performance and operations. This paper focused on the effects of hot and arid temperatures on the performance of LiFePO4 (LFP) battery packs and presented a possible modeling method for overall performance.

Lithium-ion battery (LIB) packs were subjected to room and high temperature settings while being cycled under a current profile created from a drive cycle. The Federal Urban Driving Schedule (FUDS) was selected and modified to simulate normal city driving situation using an electric only drive mode. Capacity and impedance fade of the LIB packs were monitored over the lifetime of the pack to determine the overall performance through the variables of energy and power fade. Regression analysis was done on the energy and power fade of the LIB pack to determine the duration life of LIB packs for HEV applications. This was done by comparing energy and power fade with the average lifetime mileage of a vehicle.

The collected capacity and impedance data was used to create an electrical equivalent model (EEM). The model was produced through the process of a modified Randles circuit and the creation of the inverse constant phase element (ICPE). Results indicated the model had a potential for high fidelity as long as a sufficient amount of data was gathered. X-ray powder diffraction (XRD) and a scanning electron microscope (SEM) was performed on a fresh and cycled LFP battery. SEM results suggested a dramatic growth on LFP crystals with a reduction in carbon coating after cycling. XRD effects showed a slight uniformed strain and decrease in size of LFP olivine crystals after cycling.

Hydrogen fuel cells have been previously investigated as a viable replacement to traditional gas turbine auxiliary power unit onboard fixed wing commercial jets. However, so far no study has attempted to extend their applicability to rotary wing aircrafts. To aid in the advancement of such innovative technologies, a holistic technical approach is required to ensure risk reduction and cost effectiveness throughout the product lifecycle. This paper will evaluate the feasibility of replacing a gas turbine auxiliary power unit on a helicopter with a direct hydrogen, air breathing, proton exchange membrane fuel cell, all while emphasizing a system engineering approach that utilize a specialized set of tools and artifacts.

Proton exchange membrane fuel cells have attracted immense research activities from the inception of the technology due to its high stability and performance capabilities. The major obstacle from commercialization is the cost of the catalyst material in manufacturing the fuel cell. In the present study, the major focus in PEMFCs has been in reduction of the cost of the catalyst material using graphene, thin film coated and Organometallic Molecular catalysts. The present research is focused on improving the durability and active surface area of the catalyst materials with low platinum loading using nanomaterials to reduce the effective cost of the fuel cells. Performance, Electrochemical impedance spectroscopy, oxygen reduction and surface morphology studies were performed on each manufactured material.

Alkaline fuel cells with anion exchange membrane get immense attention due to very attractive opportunity of using non-noble metal catalyst materials. In the present study, cathodes with various organometallic cathode materials were prepared and investigated for alkaline membrane fuel cells for oxygen reduction and performance studies. Co and Fe Phthalocyanine catalyst materials were deposited on multi-walled carbon nanotubes (MWCNTs) support materials. Membrane Electrode Assemblies (MEAs) were fabricated using Tokuyama Membrane (#A901) with cathodes containing Co and Fe Phthalocyanine/MWCNTs and Pt/C anodes. Fuel cell performance of the MEAs was examined.

Objective of the study is to get a clear idea on the cyclic performance of duty operation of Batteries. Batteries are an integral part of solar plants and wind energy farms due to the fact that energy storage is vital in these places. Various types of losses related to the performance are clearly analyzed and studied. Assessment of State Of Health and State Of Charge is critical in order to maximize the performance and lifetime of a battery. Batteries were subjected to temperature and charge/discharge rate variations and found that the state of health degradation was severe at high temperature along with faster rate of charging compared to other evaluation conditions. The entire research was conducted at the Alternative Energy Technology Laboratory located at Arizona State University, Mesa. It involved the use of various instruments namely the Programmable Voltage Regulator for charging, Computerized Battery Analyzer and Programmable Electric Load for discharging and also the PARSTAT potentiostat for measuring the impedance of various battery technologies under study. At first, the Batteries were discharged and based on the time taken, it was charged for the next cycle. Impedance measurement was done at regular cycle intervals in order to study the degradation of health. For every cycle, the battery capacity was also calculated and noted down. . The results obtained show that low and stable impedance over the given cycle life is an important consideration in the selection of batteries according to the applications.

Battery performance has been studied at different temperature, C rate. Different types of batteries have been used. Capacity and impedance are two factors, which are focused in the thesis. To evaluate battery performance and battery conditions, the SOC (state of charge) determination methods have been studied in the thesis. There are two types of batteries divided in three groups: group I. Ni-Cd battery (2V, 8Ah); group II. Lead-acid battery (2V, 8Ah); and group III. Lead-acid battery (2V, 25Ah). The impedance testing is using electrochemical impedance spectroscopy methods. AC impedance method has been used to test different state of charge (100%, 80%, 60%, 40%, 20%). For the corrosion part, the corrosion rate of metal material in the heat transfer fluids has been tested at different temperature. Hastelloys C-276 in eutectic molten salts a mixture of NaCl, KCl and ZnCl2 using potentiodynamic method (swap from ± 30 mV in 0.2 mV.s-1). The lowest corrosion rate of Hastelloy C-276 is 5.51 µm per year at 250 °C. Particularly, the corrosion rate of Hastelloy C-276 jumps up to 53.33 µm per year at 400 °C.

In this work, we focused on the stability and reducibility of quasi-periodic systems. We examined the quasi-periodic linear Mathieu equation of the form x ̈+(ä+ϵ[cost+cosùt])x=0 The stability of solutions of Mathieu's equation as a function of parameter values (ä,ϵ) had been analyzed in this work. We used the Floquet type theory to generate stability diagrams which were used to determine the bounded regions of stability in the ä-ù plane for fixed ϵ. In the case of reducibility, we first applied the Lyapunov- Floquet (LF) transformation and modal transformation, which converted the linear part of the system into the Jordan form. Very importantly, quasi-periodic near-identity transformation was applied to reduce the system equations to a constant coefficient system by solving homological equations via harmonic balance. In this process we obtained the reducibility/resonance conditions that needed to be satisfied to convert a quasi-periodic system to a constant one.