An Integrated Thermal-Electrical Model for Simulations of Battery Behavior in CubeSats

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A MODULAR ELECTRICAL POWER SYSTEM ARCHITECTURE FOR SMALL SPACECRAFT

Small satellites and CubeSats have established themselves within the aerospace community because of their low cost and high return on investment. Many CubeSats are developed in a short time frame and often leverage commercial off the shelf components for quick turnaround missions. With regard to the Electrical Power System, commercially available products typically use a centralized architecture. However, a centralized architecture is not reusable, since missions that require additional solar arrays or batteries would necessitate a redesign of the power system. With the range of CubeSat sizes and mission goals, it is obvious that a one-size-fits-all solution is not appropriate. This thesis details a reusable and scalable power system architecture applicable to a variety of missions. Reusability is achieved by using common building blocks or modules, where the same modules can be used between missions. Scalability is achieved by not limiting the number of modules that can be connected together—more modules can be added as needed. In this system, solar arrays and battery units connect directly to a common bus, supplying an unregulated voltage to each subsystem. These subsystems then regulate the bus voltage to their individual needs. The power system also features direct energy transfer and solar-only operation

Mission Aware Energy Saving Strategies For Army Ground Vehicles

Fuel energy is a basic necessity for this planet and the modern technology to perform many activities on earth. On the other hand, quadrupled automotive vehicle usage by the commercial industry and military has increased fuel consumption. Military readiness of Army ground vehicles is very important for a country to protect its people and resources. Fuel energy is a major requirement for Army ground vehicles. According to a report, a department of defense has spent nearly $13.6 billion on fuel and electricity to conduct ground missions. On the contrary, energy availability on this plant is slowly decreasing. Therefore, saving energy in Army ground vehicles is very important. Army ground vehicles are embedded with numerous electronic systems to conduct missions such as silent and normal stationary surveillance missions. Increasing electrical energy consumption of these systems is influencing higher fuel consumption of the vehicle. To save energy, the vehicles can use any of the existing techniques, but they require complex, expensive, and time consuming implementations. Therefore, cheaper and simpler approaches are required. In addition, the solutions have to save energy according to mission needs and also overcome size and weight constraints of the vehicle. Existing research in the current literature do not have any mission aware approaches to save energy. This dissertation research proposes mission aware online energy saving strategies for stationary Army ground vehicles to save energy as well as to meet the electrical needs of the vehicle during surveillance missions. The research also proposes theoretical models of surveillance missions, fuzzy logic models of engine and alternator efficiency data, and fuzzy logic algorithms. Based on these models, two energy saving strategies are proposed for silent and normal surveillance type of missions. During silent mission, the engine is on and batteries power the systems. During normal surveillance mission, the engine is on, gear is on neutral position, the vehicle is stationary, and the alternator powers the systems. The proposed energy saving strategy for silent surveillance mission minimizes unnecessary battery discharges by controlling the power states of systems according to the mission needs and available battery capacity. Initial experiments show that the proposed approach saves 3% energy when compared with the baseline strategy for one scenario and 1.8% for the second scenario. The proposed energy saving strategy for normal surveillance mission operates the engine at fuel-efficient speeds to meet vehicle demand and to save fuel. The experiment and simulation uses a computerized vehicle model and a test bench to validate the approach. In comparison to vehicles with fixed high-idle engine speed increments, experiments show that the proposed strategy saves fuel energy in the range of 0-4.9% for the tested power demand range of 44-69 kW. It is hoped to implement the proposed strategies on a real Army ground vehicle to start realizing the energy savings

Effective strategies to enhance electrochemical performance of carbon materials for non-aqueous potassium- and sodium-ion capacitors

Hybrid-Ionen-Kondensatoren werden seit Jahrzehnten als eine aufstrebende Klasse von Energiespeichersystemen betrachtet, die die Leistung kommerzieller elektrischer Doppelschichtkondensatoren mit hoher Leistung und konventioneller Sekundär-Ionen-Batterien mit ausgezeichnet energischem Output überbrücken können. In der letzten Zeit wurden Kalium- und Natrium-Ionen-Kondensatoren aufgrund der Abundanz und der Kosten-Günstigkeit des Kalium- und -Natriumressourcen als aussichtsreiche Energiespeicher für kommerzielle Anwendungen angesehen. Aber drei wesentliche Herausforderungen sollen zuerst diskutiert werden. Die limitierte Elektrodenkapazität aufgrund der Komplexität der hybriden Ionenspeicherung, die Diffusionskinematik der Ionen beschränkt durch den großen Radius der K- und Na-Ionen und die fehlende Elektrolytforschung. Um die obengenannten Herausforderungen zu bewältigen, werden drei neuartige und effektive Strategien entwickelt, sodass die drei wichtigen Komponenten bzw. die Kathode, der Elektrolyt und die Anode der Hybrid-Ionen-Kondensatoren optimiert werden können. Zuerst wird eine mit dem Sauerstoff funktionalisierter Kohlenstoff-Elektrode als höher Kapazität-Kathode der Kalium-Ionen-Kondensatoren hergestellt. Dabei wird die Rationalität der Auswahl der Kohlenstoff-Precursoren und die Sauerstofffunktionalisierungstechnik diskutiert. Demnächst wird eine systematische Korrelationsuntersuchung zwischen den Elektrolyten und der Dual-Ionenspeicherung der Sauerstoffkatode der Kalium-Ionen Kondensatoren durchgeführt. Die Interaktion zwischen Kationen und Anionen spielt eine wichtige Rolle bei der Dual-Ionen-Speicherung der Kohlenstoff-Kathode. Darüber hinaus wird gezeigt, dass der Ether-Elektrolyt bei der Kationen- und Anionen-Speicherung mit hohen Raten besser als der Ester-Elektrolyt wirkt. Drittens wird eine Kombination aus Adsorptions- und Co-Interkalationsmechanismus als neue Ionenspeicherungsmechanismus vorgeschlagen, um eine effiziente schnelle Na-Ionen-Speicherung auf der Kohlenstoff-Anode der Nalium-Ionen Kondensatoren zu realisieren. Alle drei Arbeiten werden sowohl in Halb- als auch in Vollzellen demonstriert, sodass eine verbesserte elektrochemische Leistung in Bezug auf große Kapazität, lange Lebensdauer und das High-Rate Vermögens erreichen werden kann. Die obengenannten effektiven Strategien haben ausführlich gezeigt, wie die Gestaltung der Materialsynthese, die Optimierung des Elektrolyten und die Modifizierung des Mechanismus für die leistungsstarken Hybrid-Ionen-Kondensatoren sind.Hybrid ion capacitors have attracted much attention for decades as an emerging class of energy storage system that may bridge the performance of commercial electric double-layer capacitors with high-power output and conventional secondary ion batteries with high-energy output. Recently, potassium- and sodium-ion capacitors have been considered as promising energy storage devices to realize commercial applications owing to the abundant and low-cost sodium and potassium resources. However, there are still three key challenges to promote their development. First, electrode capacity suffers from the complexity of hybrid ion storage. Second, ionic diffusion kinetics suffers from the large radius of Na and K ions. Third, the lack of electrolyte research. In order to tackle these challenges, three novel and effective strategies are developed to optimize three important components of hybrid ion capacitors: cathode, electrolyte, and anode. First, an oxygen-functionalized carbon electrode is fabricated as the high-capacity cathode for potassium-ion capacitor. The rationality of the carbon precursor selection and oxygen functionalization engineering are discussed. Second, a systematic investigation between the electrolytes and dual-ion storage is carried out. This work first reveals that the interaction of the cations and anions plays a key role in the dual-ion storage of the carbon cathode. It further demonstrates that the ether electrolyte outperforms the ester electrolytes in high-rate cation and anion storage. Third, a combination of adsorption mechanism and co-intercalation mechanism is proposed to realize fast Na-ion storage on the carbon anode. All three works are demonstrated in both half cells and full cells, they achieve improved electrochemical performance in terms of large capacity, long cycle life, and high rate capability. These effective strategies can provide valuable guidance regarding materials synthesis design, electrolyte optimization, and mechanism modification for approaching high-performance hybrid ion capacitors

Space Solar Power Satellite Systems, Modern Small Satellites, And Space Rectenna

Space solar power satellite (SSPS) systems is the concept of placing large satellite into geostationary Earth orbit (GEO) to harvest and convert massive amounts of solar energy into microwave energy, and to transmit the microwaves to a rectifying antenna (rectenna) array on Earth. The rectenna array captures and converts the microwave power into usable power that is injected into the terrestrial electric grid for use. This work approached the microwave power beam as an additional source of power (with solar) for lower orbiting satellites. Assuming the concept of retrodirectivity, a GEO-SSPS antenna array system tracks and delivers microwave power to lower orbiting satellites. The lower orbiting satellites are equipped with a stacked photovoltaic (PV)/rectenna array hybrid power generation unit (HPGU) in order to harvest solar and/or microwave energy for on-board use during orbit. The area, and mass of the PV array part of the HPGU was reduced at about 32% beginning-of-life power in order to achieve the spacecraft power requirements. The HPGU proved to offer a mass decrease in the PGU, and an increase in mission life due to longer living component life of the rectenna array. Moreover, greater mission flexibility is achieved through a track and power delivery concept. To validate the potential advantages offered by a HPGU, a mission concept was presented that utilizes modern small satellites as technology demonstrators. During launch, a smaller power receiving “daughter” satellite sits inside a larger power transmitting “mother” satellite. Once separated from the launch vehicle the daughter satellite is ejected away from the mother satellite, and each satellite deploys its respective power transmitting or power receiving hardware’s for experimentation. The concept of close proximity mission operations between the satellites is considered. To validate the technology of the space rectenna array part of the HPGU, six milestones were completed in the design. The first milestone considers thermal analysis for antennas, and the second milestone compares commercial off-the-shelve high frequency substrates for thermal, and outgassing characteristics. Since the design of the rectenna system is centralized around the diode component, a diode analysis was conducted for the third milestone. Next, to efficiently transfer power between the different parts of the rectenna system a coplanar stripline was consider for the fourth milestone. The fifth milestone is a balanced-to-unbalanced transition structure that is needed to properly feed and measure different systems of the rectenna. The last milestone proposes laboratory measurement setups. Each of these milestones is a separate research question that is answered in this dissertation. The results of these rectenna milestones can be integrated into a HPGU

Metal Hydrides as Enabling Technology for the use of Hydrogen-Based Energy Storage Systems on Telecommunication Satellites

Next generation telecommunication satellites will demand an increasing amount of power in the range of 30 kW or more within the next 10 years. Battery technology that can sustain 30 kW for an eclipse length of up to 72 minutes will represent a major impact on the total mass of the satellite, even with new Li-ion battery technologies. Regenerative fuel cell systems (RFCS) were identified years ago as a possible alternative to rechargeable batteries. Nevertheless, one major drawback was identified by several independent system studies, namely the need to dissipate large amounts of heat from the fuel cell (FC) during eclipse. This in turn requires massive thermal hardware (mainly large radiators) that can contribute up to 50% of the system mass. In order to overcome this issue, the use of metal hydrides (MH) as combined hydrogen and heat storage system was suggested as a starting point of the research presented in this thesis. During eclipse the FC must dissipate waste heat, and at the same time the MH tank must absorb heat in order to desorb hydrogen. Rather than dissipating the waste heat from the FC directly through a radiator, it can be stored solely, or partly, in the MH tank, to be dissipated during Equinox, with a 20 times slower rate, requiring a radiator with significantly less volume and mass. This thesis aims to present the potential of using such MH storage tanks to alternately store hydrogen and waste heat from the FC on-board a spacecraft, investigated by theoretical and experimental means. The model application for the MH tank technology considered in this thesis is a 39 kW telecommunication satellite. Nevertheless, the derived results are to be considered a generic outcome and can be translated or scaled to many other applications.:1 Introduction 2 The Metal Hydride Regenerative Fuel Cell System (MH-RFCS) 3 Metal Hydride Material Selection and Characterization 4 Design and Optimization of the Metal Hydride Tank System 5 Design and Manufacturing of a Technology Demonstrator 6 Simulation of the Metal Hydride Tank Performance 7 Experimental Results and Discussion 8 Outlook 9 BibliographyEs kann davon ausgegangen werden, dass der Trend hin zu Telekommunikationssatelliten mit immer höherer Leistung in den nächsten 10 Jahren zu Satelliten-Plattformen mit 30kW und mehr führen wird. Batterien, welche eine Leistung von 30kW für Eklipse-Längen von 72 Minuten zur Verfügung stellen müssen, werden daher einen immer größeren Einfluss auf die Gesamtmasse des Satelliten haben. Regenerative Brennstoffzellensysteme wurden daher schon vor Jahren als mögliche Alternative zu wieder aufladbaren Batterien untersucht. Mehrere unabhängige Studien sind zu dem Schluss gekommen, dass die größte Problematik in der Einführung von Brennstoffzellensystemen auf Satelliten darin besteht, die relativ großen Mengen an Abwärme effizient abzustrahlen. Die Radiatoren, die hierfür benötigt werden können 50% der Masse des Gesamtsystems ausmachen. Um dieses Problem zu überwinden wurde als Startpunkt der vorliegenden Arbeit die Nutzung von Metallhydriden als kombinierter Wasserstoff- und Wärmespeicher vorgeschlagen. Während sich der Satellit im Erdschatten befindet produziert die Brennstoffzelle Abwärme, während zur gleichen Zeit der Metallhydrid-Tank Wärme benötigt um Wasserstoff freizusetzen. Die Abwärme der Brennstoffzelle muss daher nicht direkt über Radiatoren abgestrahlt werden, sondern wird von Metallhydrid-Tank absorbiert um dann während dem restlichen Erdumlauf 20 mal langsamer mit einem deutlich kleinerem und leichteren Radiator abgegeben werden zu können. Diese Arbeit hat zum Ziel, das durch analytische und experimentelle Methoden untersuchte Potential der Anwendung einer solchen Technologie auf Satelliten zu präsentieren. Die Modellapplikation für diese Arbeit ist ein 39kW Telekommunikationssatellit. Die Ergebnisse lassen sich allerdings auch auf andere Anwendungen skalieren und übertragen.:1 Introduction 2 The Metal Hydride Regenerative Fuel Cell System (MH-RFCS) 3 Metal Hydride Material Selection and Characterization 4 Design and Optimization of the Metal Hydride Tank System 5 Design and Manufacturing of a Technology Demonstrator 6 Simulation of the Metal Hydride Tank Performance 7 Experimental Results and Discussion 8 Outlook 9 Bibliograph

Energy management and control strategies for the use of supercapacitors storage technologies in urban railway traction systems

In recent years the need to reduce global energy consumption and CO2 emissions in the environment, has been involved even in the railways sector, aimed at the highly competitive concept of new vehicles/transportation systems. The requirements hoped by the operating companies, particularly as concerns tramway and metro-train systems, are increasingly focused on products with so far advanced features in terms of energy and environmental impact. In order to accomplish this possible scenario, this could be put into effects in technological subsystems and critical components, which are able to fulfill not only functional and performance requirements, but also regarding the new canons of energy saving. On the other hand, the regional and national energetic political strategies impose a continuous effort in the eco-sustainability and energy saving direction both for the vehicles and for the infrastructure management. In this scenario, the thesis aims to fill the gap in the technical literature and deals with improving the energy efficiency of urban rail transport systems by proposing both design methodologies and effective control strategies for supercapacitor-based energy storage systems, to be installed on-board urban rail vehicles or along the rail track. Firstly, a deep, rigorous and comprehensive study on the factors which affect energy issues in a DC-electrified urban transit railway system is carried out. Then a widespread overview of the currently available strategies and technologies for recovery and management of braking energy in urban rail is presented, also by providing an assessment of their main advantages and disadvantages alongside a list of the most relevant scientific studies and well established commercial solutions. Afterwards, some effective control strategies for the optimal energy management of the supercapacitor-based energy storage system have been studied. Extensive simulations have been performed with the aim of validating the proposed techniques by employing a methodology which is based on tests carried out by means of scale models of the real systems. A wide range of experimental tests has been developed and carried out on a laboratory-scale simulator for a typical urban service railway vehicle, in order to fully confirm the theoretical performances, validity, and feasibility of the studied controls, and quantify the technical and economic advantages obtained in terms of global energy saving, voltage regulation, power compensation and infrastructure power loss reduction. The overall goal of this study is to gain an understanding of the methods and approaches for assessing the use of supercapacitor storage systems in urban rail transit oriented to the optimization of the energy saving and the reduction of the vehicle energy consumption, for whatever technological solutions are adopted