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    A borohydride/peroxide fuel cell-Li-ion battery hybrid system controlled with a maximum peak power tracking algorithm
    (Pergamon-Elsevier Science Ltd, 2015) Yilmaz, Eyup; Canan, Belkis; Sanli, Ayse Elif; Mat, Mahmut D.; Gunlu, Goksel
    The present study was carried out to develop a direct borohydride/peroxide fuel cell (DBPFC)/Li-ion battery hybrid system. In the system, the battery was charged with DBPFC. The output power of the DBPFC was controlled by a MPPT algorithm. It consists of two main parts: a DC/DC converter and a DSP controller. TMS320F28027 DSP was used to manage the entire MPPT circuit. The DC/DC controller was placed between the fuel cell and the battery. The performance test results indicated that the output power remained constant at 1.3 W during the test. Moreover, the voltage ripples that are generally observed in the fuel cells were prevented. The fuel cell provided the power at the maximum peak power for approximately 211 min. It was obvious that the Li-Ion battery was charged with a stable DBPFC power. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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    Comparison of Power and Energy Density after Full Shunting-Balancing in Serial Connected Lithium-ion Batteries and Serial-Connected Supercapacitors
    (Ieee, 2015) Sertkaya, Melek Gulatik; Yilmaz, Eyup; Sanli, Ayse Elif; Gunlu, Goksel
    In this study, advantages and disadvantages of supercapacitors and batteries which are energy storing sources were examined and furthermore, energy density, voltage and current behaviors of 6 serial connected supercapacitors and 6 serial connected battery sequences were compared. While establishing these circuits, full shunting balancing methods were used. When 4 units of 6 serial connected batteries/supercapacitors reached to the 100% charged level, system passed to discharging mode from charging mode and total charge ratios of the systems were calculated.
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    Development of a power management unit for small portable direct borohydride fuel cell-NiMH battery hybrid system
    (Pergamon-Elsevier Science Ltd, 2012) Sanli, Ayse Elif; Gunlu, Goksel; Aytac, Aylin; Mat, Mahmut
    In this study, a small portable fuel cell/battery hybrid system has been developed. The system consists of a single portable direct borohydride/peroxide fuel cell (DBPFC), NiMH battery and power management unit (PMU). The battery has been used as a primary power source and has been discharged at constant load. When its state of charge is reduced, the DBPFC charges the battery and powers the load simultaneously. A DC-DC Boost converter has been used as a PMU. The DBPFC has provided the total power of 0.21 Wh into the system during the charge. During this experimental study fuel (NaBH4) efficiency of 37% has been achieved in the hybrid system, while the system efficiency has been calculated as 34.5%. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.
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    Effects of power control techniques on hydrogen and oxygen evolution in direct borohydride peroxide fuel cells
    (Pergamon-Elsevier Science Ltd, 2017) Yilmaz, Eyup Semsi; Canan, Belkis; Gunlu, Goksel; Sanli, Ayse Elif
    Direct borohydride/peroxide fuel cells (DBPFCs) have some attractive features, such as high energy density, high theoretical cell power and low operational temperature. The drawbacks that cause performance loss include low efficiency and security challenges. Hydrogen and oxygen evolutions are major issues that should be considered when stacking a DBPFC. These gas evolutions significantly affect the DBPFC performance, efficiency and security. However, the gases were also produced in the case of an open circuit potential and depend on the applied voltage and current. Therefore, in the present study, the effects of cell loading on gas evolution were investigated. The DBPFC was operated under a constant voltage of 1.2 V and controlled using the maximum peak power tracking (MPPT) method. The MPPT control provided higher power generation and higher hydrogen evolution than observed using the constant voltage mode. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    Embedded Face Detection and Recognition
    (Sage Publications Inc, 2012) Gunlu, Goksel
    The need to increase security in open or public spaces has in turn given rise to the requirement to monitor these spaces and analyse those images on-site and on-time. At this point, the use of smart cameras - of which the popularity has been increasing - is one step ahead. With sensors and Digital Signal Processors (DSPs), smart cameras generate ad hoc results by analysing the numeric images transmitted from the sensor by means of a variety of image-processing algorithms. Since the images are not transmitted to a distance processing unit but rather are processed inside the camera, it does not necessitate high-bandwidth networks or high processor powered systems; it can instantaneously decide on the required access. Nonetheless, on account of restricted memory, processing power and overall power, image processing algorithms need to be developed and optimized for embedded processors. Among these algorithms, one of the most important is for face detection and recognition. A number of face detection and recognition methods have been proposed recently and many of these methods have been tested on general-purpose processors. In smart cameras which are real-life applications of such methods - the widest use is on DSPs. In the present study, the Viola-Jones face detection method - which was reported to run faster on PCs - was optimized for DSPs; the face recognition method was combined with the developed sub-region and mask-based DCT (Discrete Cosine Transform). As the employed DSP is a fixed-point processor, the processes were performed with integers insofar as it was possible. To enable face recognition, the image was divided into sub-regions and from each sub-region the robust coefficients against disruptive elements - like face expression, illumination, etc. - were selected as the features. The discrimination of the selected features was enhanced via LDA (Linear Discriminant Analysis) and then employed for recognition. Thanks to its operational convenience, codes that were optimized for a DSP received a functional test after the computer simulation. In these functional tests, the face recognition system attained a 97.4% success rate on the most popular face database: the FRGC.
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    Fuel Cell Powered Hybrid System Controlled by the Maximum Peak Power Tracking Technique
    (Ieee, 2015) Gordesel, Merve; Canan, Belkis; Gunlu, Goksel; Sanli, Ayse Elif
    In the present study a borohydride/peroxide fuel cell/Li-ion battery hybrid system was developed. Output power of DBPFC was controlled and kept constant by MPPT algorithm. The voltage ripples of the fuel cell were prevented. Moreover, Li-ion battery was charged with a stable power of direct borohydride/peroxide fuel cell.
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    Investigation of Hybrid Fuel Cell-Battery Systems
    (Electrochemical Soc Inc, 2015) Gunlu, Goksel; Aktepe, Alper; Canan, Belkis; Sanli, Ayse Elif
    Hybrid electric vehicles (HEV) are considered as the alternative propulsion systems. In the hybrid systems electrical storage component is the key element. Because size and weight of the battery defines the cost and performance of the overall system. Another major component of a hybrid system is the fuel cell system consisted of a fuel cell stack, a membrane humidifier and hydrogen storage canisters. The power management system (PMS) is a critical component of hybrid electric vehicles. The purpose of the PMS is to maintain the safety and reliability of the battery, state monitoring and evaluation, charge control, and cell balancing. Three light electric vehicles (LEV) equipped a fuel cell-battery hybrid power system have reviewed in the present work. The hybrid power systems reviewed have consisted of a proton exchange membrane (PEM) fuel cell, a lithium battery and a power management unit. They are Buddy El-Jet Hybrid Vehicle from Toyota, Hydrogen-Electric Hybrid Microcab H2EV Vehicle tested at CABLED project in England and Norwegian Buddy El-Jet Hybrid System.
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    Performance improvement in direct borohydride/peroxide fuel cells
    (Pergamon-Elsevier Science Ltd, 2017) Sanli, Ayse Elif; Gordesel, Merve; Yilmaz, Eyup Semsi; Ozden, Suleyman Kursat; Gunlu, Goksel; Uysal, Bekir Zuhtu
    Direct borohydride/peroxide fuel cells (DBPFCs) show progressively deteriorating performance during operation for various reasons such as decreasing reactant concentrations, gas evolution and uneven distribution of liquids. The present study aims to emphasize the importance of certain design parameters, such as bipolar plate materials, flow fields and manifold design, in determining the DBPFC performance. Bipolar materials and flow channel design have been investigated. A power density of 67 mW cm(-2) has been obtained with composite graphite and parallel flow channel bipolar plates. It has increased to 87 mW cm(-2) using sintered graphite and then to 93.3 mW cm(-2) using sintered graphite with serpentine flow fields. The stacking of DBPFCs results in a loss of performance and unstable output. The performance has remained nearly unchanged as the cell number was increased by applying an independent cell liquid distribution network (ICLDN). Using an ICLDN, power densities of 98.3, 83.3 and 82 mW cm(-2) have been obtained for single-cell, 3-cell and 6-cell stacks, respectively. Finally, a controlled oxidant feeding system (COFS) has been developed to provide stable output power, and it has demonstrated a stable output power of 6 W for 2.5 h. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    The Multi-Windings Forward Structure Battery Balancing
    (Ieee, 2014) Gerislioglu, Burak; Ozturk, Furkan; Sanli, Ayse Elif; Gunlu, Goksel
    A structure for active battery balancing with using Multi-Windings Transformer is presented. Most of applications in electrical vehicles need smart voltage control and high effective battery systems. In generally, the battery stack systems consist of these three parts: management, safety and balancing. In these parts, balancing is the most significant part since the management demands to improve the cycle life, battery storage packs, and power capacity. This paper presents the real-time Multi-Windings Transformer balancing topology forward structure model, simulation, and real circuit implementation with using Texas Instruments Stellaris (R) Launchpad Evaluation Kit (EK-LM4F120XL) with Energia based coding. Also, this paper indicates the emphasis of using forward structure model of Multi-Windings Transformer balancing topology since we use forward structure converter for dimishing the extra energy loses and decrease cost of the system.