Thermal, electric and durability characterization of supercaps for energy back-up of automotive ECU

A new generation of mechatronic devices, such as the E-latch for door closure, is introduced in the automotive field to replace mechanical systems with electro-actuated parts with embedded electronic control unit (ECU) connected to the main vehicle network. Due to severe automotive safety-critical requirements an energy back-up solution is proposed, based on supercaps and boost converter, to ensure E-latch operation even in case of main battery failure. An in-depth thermal, electrical and durability characterization of the supercaps proves the suitability of the energy back-up unit for automotive applications

Implementation and in-depth analyses of a battery-supercapacitor powered electric vehicle (E-Kancil)

This thesis contributes to the research issue pertaining to the management of multiple energy sources on-board a pure electric vehicle; particularly the energy dense traction battery and the power dense supercapacitor or ultracapacitor. This is achieved by analysing real world drive data on the interaction between lead acid battery pack and supercapacitor module connected in parallel while trying to fulfil the load demands of the vehicle. The initial findings and performance of a prototype electric vehicle conversion of a famous Malaysian city car; the perodual kancil, is presented in this thesis. The 660 cc compact city car engine was replaced with a brushless DC motor rated at 8KW continuous and 20KW peak. The battery pack consists of eight T105 Trojan 6V, 225 Ah deep cycle lead acid battery which builds up a voltage of 48V. In addition to this, a supercapacitor module (165F, 48V) is connected in parallel using high power contactors in order to investigate the increase in performance criteria such as acceleration, range, battery life etc. which have been proven in various literatures via simulation studies. A data acquisition system is setup in order to collect real world driving data from the electric vehicle on the fly along a fixed route. Analysis of collected driving data is done using MATLAB software and comparison of performance of the electric vehicle with and without supercapacitor module is made. Results show that with a parallel connection, battery life and health is enhanced by reduction in peak currents of up to 49%. Peak power capabilities of the entire hybrid source increased from 9.5KW to 12.5KW. A 41% increase in range per charge was recorded. The author of this work hopes that by capitalizing on the natural peak power buffering capabilities of the supercapacitor, a cost effective energy management system can be designed in order to utilize more than 23.6% of the supercapacitor energy

Implementation and in-depth analyses of a battery-supercapacitor powered electric vehicle (E-Kancil)

This thesis contributes to the research issue pertaining to the management of multiple energy sources on-board a pure electric vehicle; particularly the energy dense traction battery and the power dense supercapacitor or ultracapacitor. This is achieved by analysing real world drive data on the interaction between lead acid battery pack and supercapacitor module connected in parallel while trying to fulfil the load demands of the vehicle. The initial findings and performance of a prototype electric vehicle conversion of a famous Malaysian city car; the perodual kancil, is presented in this thesis. The 660 cc compact city car engine was replaced with a brushless DC motor rated at 8KW continuous and 20KW peak. The battery pack consists of eight T105 Trojan 6V, 225 Ah deep cycle lead acid battery which builds up a voltage of 48V. In addition to this, a supercapacitor module (165F, 48V) is connected in parallel using high power contactors in order to investigate the increase in performance criteria such as acceleration, range, battery life etc. which have been proven in various literatures via simulation studies. A data acquisition system is setup in order to collect real world driving data from the electric vehicle on the fly along a fixed route. Analysis of collected driving data is done using MATLAB software and comparison of performance of the electric vehicle with and without supercapacitor module is made. Results show that with a parallel connection, battery life and health is enhanced by reduction in peak currents of up to 49%. Peak power capabilities of the entire hybrid source increased from 9.5KW to 12.5KW. A 41% increase in range per charge was recorded. The author of this work hopes that by capitalizing on the natural peak power buffering capabilities of the supercapacitor, a cost effective energy management system can be designed in order to utilize more than 23.6% of the supercapacitor energy

Supercapacitor assisted bicycle for the future of efficient mobility

With the world becoming more aware about climate change and being climate conscious, the move away from conventional gasoline powered mobility is accelerated. The public, looking for alternate methods of transportation, are taking up bicycle riding for its low carbon impact and health aspects. As a result, electrically assisted bicycles powered by Li-ion batteries have risen in popularity for the added convenience they allow. This newfound interest allows for more development in the e- mobility sector. This is where a supercapacitor assisted bicycle (SCA-Bicycle) fits in. Compared to existing bicycles in the market a supercapacitor assisted bicycle, due to the nature of supercapacitors, allows the user to store a portion of the energy used while riding on level terrain and use it to assist the user when navigating positive gradient terrain. Supercapacitors can undergo limitless charge-discharge cycles and unlike Li-ion batteries do not need charging to be heavily regulated. This results in a fit and forget system with minimal maintenance required for the onboard electronics. Along with sustainable ingredients, the energy density of supercapacitors has reached closer to lead-acid batteries while newer development has achieved capacity of Li-ion batteries. This rapid pace of development along with the benefits they provide show that supercapacitors will be the future of energy storage. Another avenue supercapacitors allow, due to their low internal resistance, is brake energy recovery. When braking is applied, while traversing negative gradient slopes, energy is usually lost as heat. This is due to the use of conventional friction braking. A brake energy recovery system enables the storing of this lost energy for later use. This allows for efficient cycling of the energy available for the rider and results in a mode of transport with minimal energy waste

Low cost vertical axis wind energy harvesting system using supercapacitors for rural Malaysia

Numerous countries worldwide are conscious about the fact that the past and current trends of energy system are not sustainable and a solution needs to be drawn to protect the world energy from a drastic falling. One of the sources that can replace the current trend is surely wind energy that momentously depends on the availability of the wind resource. For a typical horizontal axis wind turbine to run and generate power, a wind speed of at least 5 m/s is required. Countries like Malaysia have less than 5m/s average wind speed. Another predicament is that these regions face unsteady multi-directional winds making HAWT totally incompatible in such areas. The vertical axis wind turbine on the other hand is appropriate for such regions due to its ability to capture wind energy at any direction. Also, the use of Neodymium magnets for suspension at the bottom surface assist attaining nearly zero friction (Maglev), could be of help improving the output efficiency. Conventional generators now-a-days have been replaced with Permanent Magnet Synchronous Generator (PMSG). Although a number of researches in the area of VAWT and PMSG are carried through separately, few attempts were taken to build a system that work efficiently at low wind speed. Moreover, there is another gap in research for an off-grid standalone energy harvesting device incorporated with low wind Maglev VAWT. This thesis provides a platform for a novel innovative approach towards an off-grid energy harvesting system (EHS) for Maglev VAWT. This EHS basically a Supercapacitor based hybrid battery charging energy harvesting device. Rural areas in countries like Malaysia where grid connection is not always available, this standalone system there can make a difference for small scale electronic devices. In this thesis, a complete simulation analysis is done for all 3 types of PMSG connected to VAWT and result was compared. This novel comparison showed that 5-phase is a better performer both in high and low speed comparing with 3-phase and dual stator. Moreover, although at high speed dual stator provides better power efficiency than 3-phase, at low wind, output power performance in 3-phase surpasses that of dual stator. At low wind, even though 5-phase PMSG shows better performance in low wind speed, 3-Phase PMSG was chosen for low maintenance cost, light weight and less complicated design. With the variation of design parameters under low wind speeds, two configurations were optimized for rural Malaysia in terms of low speed, high power and output torque. First configuration was a 1.5KW 220V 20 Pole AFPMSG adopted to a Maglev based VAWT having radius and height of 1m and 2.6m respectively. The other configuration presents a 200W 12V 16 Pole AFPMSG attached to Maglev VAWT of 14.5cm radius and 60cm of height. Later weight to Power Ratio is applied subsequently and the second configuration has been proved to be more cost-effective. The proposed system was also compared with existing models in rural Malaysia for cost-efficiency. A prototype version of the low cost optimized system is built up in lab for open circuit performance and with satisfactory findings, design is sent for fabrication. Upon arrival, the optimized system is implemented into the energy harvesting circuit and field testing is carried to observe the performance. The energy harvesting circuit shows better efficiency in charging battery in all aspects comparing to direct charging of battery regardless of with or without converter. Sufficient groundwork and results have been laid out in this thesis to deliver the necessary development and framework for further improvements. Based on analysis and results carried out in this thesis, all feasibility studies and information are provided for the next barrier

Multiobjective Optimization of the Power Flow Control of Hybrid Electric Power Train Systems within Simulation and Experimental Emulation Applications

In this thesis, the power flow control of hybrid electric power train systems is discussed using the focus of multiobjective optimization goals and related algorithms, based on different control optimization methods, are developed and applied within simulation and experimental environments. Based on the basic relations of hybrid power train systems, an improved technique for the experimental realization and evaluation of these systems is developed and the related Hardware-in-the-Loop (HiL) hybrid electric power train emulation system is demonstrated. Hereby, it is shown that this emulation system technique is suitable to be applied for a more generalized view of the power train structures (consideration of the components as power sources, sinks, transmission elements, storage elements etc.) and its power flow control. The principal applicability of the system is demonstrated using the example of a hybrid electric vehicle as well as other system technologies such as hybrid hydraulic power trains and wind energy conversion systems. The core of the thesis is the discussion, development, application, and evaluation of power flow control optimization algorithms. Hereby, the considered power flow control techniques of the power train are realized with respect to a multiobjective framework using the example of drivability, fuel economy, and component life time as system requirements to be optimized during the operation. From this requirements, a multiobjective control optimization problem results consisting of a suitable combination of the known control goals power management, energy management, and lifetime management is realized. After a discussion about the principal influences of the power flow control on the different performance properties, the application of different control optimization techniques is discussed. Hereby, the example of a fuel cell/supercapacitor-based hybrid electric power train system including braking energy recovery is used. As control optimization methods, parameter optimization techniques are applied at first. Hereby, an embedded-online optimization based on a Golden Section search and an offline optimization based on Global Optimation methods are discussed and applied. Furthermore, direct optimization techniques based on Dynamic Programming (DP) and Model Predictive Control (MPC) are realized. Subsequently, an Instantaneous Optimality (IO)-based technique, which consists of a lookup table-based Time-Invariant Feedback Controller technique, is developed. It becomes clear that all methods leads to suitable results and significant improvement of the control performance. A concluding overview of the methods and its strengths and weaknesses dependent on the application is provided.In dieser Arbeit wird die Leistungsflussregelung bei hybridelektrischen Antriebssystemen mit dem Schwerpunkt der Mehrkriterienoptimierung diskutiert. Hierbei werden geeignete Algorithmen, basierend auf verschiedenen Stellgrößenoptimierungsmethoden, entwickelt und in Simulationen sowie in experimentellem Umfeld angewendet. Aufbauend auf die Grundzusammenhänge hybrider Antriebssysteme wird eine weiterentwickelte experimentelle Umgebung zur Untersuchung und Bewertung vorgestellt und der entsprechende Hardware-in-the-Loop (HiL)-Versuchsstand zur Emulation entsprechender Systeme demonstriert. Diese Emulationstechnik erlaubt eine generalisierte Betrachtung von Antriebssystemstrukturen (Betrachtung der Komponenten als Quellen, Senken, Übertragungselemente, Speicher etc.) und der entsprechenden Leistungsflussregelung. Den Hauptteil dieser Arbeit bildet die Diskussion sowie die Entwicklung, Anwendung und Bewertung von Algorithmen zur Optimierung der Leistungsflussregelung hybridelektrischer Antriebssysteme. In diesem Zusammenhang erfolgt eine mehrkriterielle Betrachtung und Bewertung des Antriebssystems in Hinblick auf die Dynamik, die Kraftstoffökonomie und die Komponentenlebensdauer. Das hieraus resultierende mehrkriterielle Optimierungsproblem der Stellgrößenfolge kann hierbei als Überlagerung von Leistungs-, Energie- und Lebensdauermanagement aufgefasst werden. Basierend auf den Haupteinflüssen der Leistungsflussregelungen auf verschiedene Systemeigenschaften erfolgt die Entwicklung, Anwendung, Bewertung und Diskussion verschiedener Stellgrößenoptimierungsmethoden und -algorithmen. Diese werden am Beispiel eines Brennstoffzellen/Supercap-basierten hybridelektrischen Antriebssystems mit Bremsenergierekuperation demonstriert. Zur Optimierung der Leistungsflussregelung werden als erstes Parameteroptimierungstechniken vorgestellt, wobei eine Embedded-online-Optimierung basierend auf der Methode des Goldenen Schnitts sowie eine Offline-Optimierung unter Verwendung von globalen Optimierungsalgorithmen diskutiert und angewendet werden. Nachfolgend werden direkte Stellgrößenoptimierungstechniken vorgestellt, wobei die Verfahren der Dynamischen Programmierung und des Modelprädiktiven Reglers realisiert werden. Abschließend wird die Entwicklung und Anwendung eines Algorithmus basierend auf der momentanen Optimalität (Instantaneous Optimality) diskutiert, welcher aus einem kombinierten Geschwindigkeits-Prädiktionsalgorithmus und vordefinierten Kennfeldern für die Regelung besteht. Die verwendeten Methoden werden vergleichend gegenübergestellt und gemäß ihrer Stärken und Schwächen bewertet

Analysis on Supercapacitor Assisted Low Dropout (SCALDO) Regulators

State-of-the-art electronic systems employ three fundamental techniques for DC-DC converters: (a) switch-mode power supplies (SMPS); (b) linear power supplies; (c) switched capacitor (charge pump) converters. In practical systems, these three techniques are mixed to provide a complex, but elegant, overall solution, with energy efficiency, effective PCB footprint, noise and transient performance to suit different electronic circuit blocks. Switching regulators have relatively high end-to-end efficiency, in the range of 70 to 93%, but can have issues with output noise and EMI/RFI emissions. Switched capacitor converters use a set of capacitors for energy storage and conversion. In general, linear regulators have low efficiencies in the range 30 to 60%. However, they have outstanding output characteristics such as low noise, excellent transient response to load current fluctuations, design simplicity and low cost design which are far superior to SMPS. Given the complex situation in switch-mode converters, low dropout (LDO) regulators were introduced to address the equirements of noise-sensitive and fast transient loads in portable devices. A typical commercial off-the-shelf LDO has its input voltage slightly higher than the desired regulated output for optimal efficiency. The approximate efficiency of a linear regulator, if the power consumed by the control circuits is negligible, can be expressed by the ratio of Vo/Vin. A very low frequency supercapacitor circulation technique can be combined with commercial low dropout regulator ICs to significantly increase the end-to-end efficiency by a multiplication factor in the range of 1.33 to 3, compared to the efficiency of a linear regulator circuit with the same input-output voltages. In this patented supercapacitor-assisted low dropout (SCALDO) regulator technique developed by a research team at the University of Waikato, supercapacitors are used as lossless voltage droppers, and the energy reuse occurs at very low frequencies in the range of less than ten hertz, eliminating RFI/EMI concerns. This SCALDO technique opens up a new approach to design step-down, DC-DC converters suitable for processor power supplies with very high end-to-end efficiency which is closer to the efficiencies of practical switching regulators, while maintaining the superior output specifications of a linear design. Furthermore, it is important to emphasize that the SCALDO technique is not a variation of well-known switched capacitor DC-DC converters. In this thesis, the basic SCALDO concept is further developed to achieve generalised topologies, with the relevant theory that can be applied to a converter with any input-output step-down voltage combination. For these generalised topologies, some important design parameters, such as the number of supercapacitors, switching matrix details and efficiency improvement factors, are derived to form the basis of designing SCALDO regulators. With the availability of commercial LDO ICs with output current ratings up to 10 A, and thin-prole supercapacitors with DC voltage ratings from 2.3 to 5.5 V, several practically useful, medium-current SCALDO prototypes: 12V-to-5V, 5V-to-2V, 5.5V-to-3.3V have been developed. Experimental studies were carried out on these SCALDO prototypes to quantify performance in terms of line regulation, load regulation, efficiency and transient response. In order to accurately predict the performance and associated waveforms of the individual phases (charge, discharge and transition) of the SCALDO regulator, Laplace transform-based theory for supercapacitor circulation is developed, and analytical predictions are compared with experimental measurements for a 12V-to-5V prototype. The analytical results tallied well with the practical waveforms observed in a 12V-to-5V converter, indicating that the SCALDO technique can be generalized to other versatile configurations, and confirming that the simplified assumptions used to describe the circuit elements are reasonable and justifiable. After analysing the performance of several SCALDO prototypes, some practical issues in designing SCALDO regulators have been identified. These relate to power losses and implications for future development of the SCALDO design

Energy Neutral Design of Embedded Systems for Resource Constrained Monitoring Applications

Automatic monitoring of environments, resouces and human processes are crucial and foundamental tasks to improve people's quality of life and to safeguard the natural environment. Today, new technologies give us the possibility to shape a greener and safer future. The more specialized is the kind of monitoring we want to achieve, more tight are the constraints in terms of reliability, low energy and maintenance-free autonomy. The challenge in case of tight energy constraints is to find new techniques to save as much power as possible or to retrieve it from the very same environment where the system operates, towards the realization of energy neutral embedded monitoring systems. Energy efficiency and battery autonomy of such devices are still the major problem impacting reliability and penetration of such systems in risk-related activities of our daily life. Energy management must not be optimized to the detriment of the quality of monitoring and sensors can not be operated without supply. In this thesis, I present different embedded system designs to bridge this gap, both from the hardware and software sides, considering specific resource constrained scenarios as case studies that have been used to develop solutions with much broader validity. Results achieved demonstrate that energy neutrality in monitoring under resource constrained conditions can be obtained without compromising efficiency and reliability of the outcomes

The accelerated life cycle testing and modelling of Li-ion cells used in electric vehicle applications

Li-ion batteries have become one of the chosen energy storage devices that are used in applications such as power tools, cellular phones and electric vehicles (EV). With the demand for portable high energy density devices, the rechargeable Li-ion battery has become one of the more viable energy storage systems for large scale commercial EVs because of their higher energy density to weight or volume ratio when compared to other current commercial battery energy storage systems. Various safety procedures for the use of Li-ion batteries in both consumer and EV applications have been developed by the international associations. The test procedures studied in this dissertation demonstrated the importance of determining the true capacity of a cell at various discharge rates. For this, the well known Peukert test was demonstrated. The study also showed that cells with different battery geometries and chemistries would demonstrate different thermal heating during discharge and slightly different Ragone results if different test methods were used as reported in the literature. Accelerated ageing tests were done on different cells at different Depth-of-Discharge (DoD) regions. The different DoD regions were determined according to expected stresses the electrode material in a cell would experience when discharged to specific DoD that follows the discharge voltage profile. Electrochemical Impedance Spectroscopy (EIS) was used to measure various electrochemical changes within these cells. The EIS results showed that certain observed modelled parameters would change similarly to the ageing of the cell as it aged due to the accelerated testing. EIS was also done on cells at different State-of-Charge (SoC) and temperatures. The results showed that EIS can be used as an effective technique to observe changes within a Li-ion cell as the SoC or temperature changed. For automotive vehicles that are powered by a fuel cell or battery, a supercapacitor can be coupled to a battery in order to increase and optimize the energy and power densities of the drive systems. A test procedure in the literature that evaluated the use of capacitors with Pb-acid batteries was applied to Li-ion type cells in order to quantify the increased power due to the use of a supercapacitor with a Li-ion cell. Both a cylindrical LiCoO2 cell and a VRLA Pb-acid cell showed some additional charge acceptance and delivery when connected to the supercapacitors. A LiMn2O4 pouch cell showed significant charge acceptance and delivery when connected to supercapacitors. The amount of additional charge acceptance and delivery of the different combinations could be explained by EIS, in particular, the resistance and capacitance of the cell in comparison to the combination of the cell and supercapacitor. A large capacity LiCoO2 cell showed high charge acceptance and delivery without connection with a supercapacitor. The study proved that EIS can be used to model the changes within cells under the different conditions and using different test procedures