High Performance Power Management Integrated Circuits for Portable Devices

abstract: Portable devices often require multiple power management IC (PMIC) to power different sub-modules, Li-ion batteries are well suited for portable devices because of its small size, high energy density and long life cycle. Since Li-ion battery is the major power source for portable device, fast and high-efficiency battery charging solution has become a major requirement in portable device application. In the first part of dissertation, a high performance Li-ion switching battery charger is proposed. Cascaded two loop (CTL) control architecture is used for seamless CC-CV transition, time based technique is utilized to minimize controller area and power consumption. Time domain controller is implemented by using voltage controlled oscillator (VCO) and voltage controlled delay line (VCDL). Several efficiency improvement techniques such as segmented power-FET, quasi-zero voltage switching (QZVS) and switching frequency reduction are proposed. The proposed switching battery charger is able to provide maximum 2 A charging current and has an peak efficiency of 93.3%. By configure the charger as boost converter, the charger is able to provide maximum 1.5 A charging current while achieving 96.3% peak efficiency. The second part of dissertation presents a digital low dropout regulator (DLDO) for system on a chip (SoC) in portable devices application. The proposed DLDO achieve fast transient settling time, lower undershoot/overshoot and higher PSR performance compared to state of the art. By having a good PSR performance, the proposed DLDO is able to power mixed signal load. To achieve a fast load transient response, a load transient detector (LTD) enables boost mode operation of the digital PI controller. The boost mode operation achieves sub microsecond settling time, and reduces the settling time by 50% to 250 ns, undershoot/overshoot by 35% to 250 mV and 17% to 125 mV without compromising the system stability.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

The Zinc/Bromine Flow Battery: Fundamentals and Novel Materials for Technology Advancement

Flow batteries are a promising solution for solving intermittency challenges and increasing uptake of renewable power sources such as wind and solar. In particular, zinc/bromine batteries are an attractive option for large-scale electrical energy storage due to their relatively low cost of primary electrolyte and high theoretical specific energy of 440 Wh kg-1. However, inefficient materials of construction hinder practical utilization of this capability and reduce power delivery. The work presented in this thesis aims to overcome these limitations by providing an understanding of the fundamental physical and electrochemical processes governing interactions within the bulk electrolyte and at the electrode–electrolyte interface. Suitable alternative materials to improve system performance are developed via electrochemical investigations, physical characterization and molecular modelling. It is shown that conventional chloride-based supporting electrolytes significantly influence the morphology of zinc electrodeposits generated. High chloride concentration causes removal of zinc from the bulk, causing coulombic losses in the system. It is shown that sulfates, phosphates or even a higher proportion of bromides, are potentially suitable alternatives. Single-halide type tetrahedral zinc complexes exist in conventional electrolytes, and a previously unreported Raman vibrational band at 220 cm-1 is assigned to the [ZnBr2Cl(H2O)]– complex. Ionic liquid additives are proven not to be merely spectators in the zinc half-cell, due to the effects of their chemical structures. Studies using hybrid ionic liquid mixtures indicate that each half-cell benefits from the use of different compounds. It is expected that the approaches and findings presented in this thesis contribute towards aiding and guiding the future search for novel materials to further improve Zn/Br battery technology

Power Converter of Electric Machines, Renewable Energy Systems, and Transportation

Power converters and electric machines represent essential components in all fields of electrical engineering. In fact, we are heading towards a future where energy will be more and more electrical: electrical vehicles, electrical motors, renewables, storage systems are now widespread. The ongoing energy transition poses new challenges for interfacing and integrating different power systems. The constraints of space, weight, reliability, performance, and autonomy for the electric system have increased the attention of scientific research in order to find more and more appropriate technological solutions. In this context, power converters and electric machines assume a key role in enabling higher performance of electrical power conversion. Consequently, the design and control of power converters and electric machines shall be developed accordingly to the requirements of the specific application, thus leading to more specialized solutions, with the aim of enhancing the reliability, fault tolerance, and flexibility of the next generation power systems

Exergy and exergoeconomic analyses and optimization of thermal management systems in electric and hybrid electric vehicles

With the recent improvements in battery technologies, in terms of energy density, cost and size, the electric (EV) and hybrid electric vehicle (HEV) technologies have shown that they can compete with conventional vehicles in many areas. Although EVs and HEVs offer potential solutions for many key issues related to conventional vehicles, they still face considerable challenges that prevent the widespread commercialization of these technologies, such as thermal management of batteries and electrification. In this PhD thesis, a liquid thermal management system (TMS) for hybrid electric vehicles is investigated and evaluated against alternative thermal management systems, and optimal parameters are selected to maximize the system efficiency. In order to achieve this goal, a model of the liquid thermal management system is established to determine the irreversibilities and second-law efficiencies associated with the overall system and its components. Furthermore, the effects of different configurations, refrigerants and operating conditions are analyzed with respect to conventional exergy analyses. In addition, advanced exergy analyses are also conducted in order to better identify critical relationships between the TMS components and determine where the system improvement efforts should be concentrated. Moreover, investment costs are calculated and cost formation of the system is developed in order to evaluate the TMS with respect to exergoeconomic principles and provide corresponding recommendations. Environmental impact correlations are developed, along with a cradle-to-grave life cycle assessment (LCA), to highlight components causing significant environmental impact, and to suggest trends and possibilities for improvement based on the exergoenvironmental variables. Finally, the TMS is optimized using multi-objective evolutionary algorithm which considers exergetic and exergoeconomic as well as exergetic and exergoenvironmental objectives simultaneously with respect to the decision variables and constraints. Based on the conducted research for the studied system under the baseline conditions, the exergy efficiency, total cost rate and environmental impact rate are determined to be 0.29, ??28/h and 77.3 mPts/h, respectively. The exergy destruction associated with each component is split into endogenous/exogenous and avoidable/unavoidable parts, where the exogenous exergy destruction is determined to be relatively small but significant portion of the total exergy destruction in each component (up to 40%), indicating a moderate level of interdependencies among the components of the TMS. Furthermore, it is determined that up to 70% of the exergy destruction calculated within the components could potentially be avoided. According to the analyses, electric battery is determined to have the highest exergoeconomic and exergoenvironmental importance in the system, with cost rate of ??3.5/h and environmental impact value of 37.72 mPts/h, due to the high production cost of lithium ion batteries and the use of copper and gold in the battery pack. From an exergoeconomic viewpoint, it is determined that the investment costs of the condenser and evaporator should be reduced to improve the costeffectiveness of the system. On the other hand, from an exergoenvironmental viewpoint, all the component efficiencies (except for the battery) should be improved in order to reduce the total environmental impact even if it increases the environmental impact during production of the components. In addition, it is determined that the coolant pump and the thermal expansion valve before the chiller are relatively insignificant from exergoeconomic and exergoenvironmental perspectives. Subsequently, objective functions are defined and decision variables are selected, along with their respective system constraints, in order to conduct single and multiple objective optimizations for the system. Based on the single objective optimizations, it is determined that the exergy efficiency could be increased by up to 27% using exergy-based optimization, the cost can be reduced by up to 10% using cost-based optimization and the environmental impact can be reduced by up to 19% using environmental impact-based optimization, at the expense of the nonoptimized objectives. Moreover, multi-objective optimizations are conducted in order to provide the respective Pareto optimal curve for the system and to identify the necessary trade-offs within the optimized objectives. Based on the exergoeconomic optimization, it is concluded that 14% higher exergy efficiency and 5% lower cost can be achieved, compared to baseline parameters at an expense of 14% increase in the environmental impact. Furthermore, based on the exergoenvironmental optimization, 13% higher exergy efficiency and 5% lower environmental impact can be achieved at the expense of 27% increase in the total cost

Exergy and exergoeconomic analyses and optimization of thermal management systems in electric and hybrid electric vehicles

With the recent improvements in battery technologies, in terms of energy density, cost and size, the electric (EV) and hybrid electric vehicle (HEV) technologies have shown that they can compete with conventional vehicles in many areas. Although EVs and HEVs offer potential solutions for many key issues related to conventional vehicles, they still face considerable challenges that prevent the widespread commercialization of these technologies, such as thermal management of batteries and electrification. In this PhD thesis, a liquid thermal management system (TMS) for hybrid electric vehicles is investigated and evaluated against alternative thermal management systems, and optimal parameters are selected to maximize the system efficiency. In order to achieve this goal, a model of the liquid thermal management system is established to determine the irreversibilities and second-law efficiencies associated with the overall system and its components. Furthermore, the effects of different configurations, refrigerants and operating conditions are analyzed with respect to conventional exergy analyses. In addition, advanced exergy analyses are also conducted in order to better identify critical relationships between the TMS components and determine where the system improvement efforts should be concentrated. Moreover, investment costs are calculated and cost formation of the system is developed in order to evaluate the TMS with respect to exergoeconomic principles and provide corresponding recommendations. Environmental impact correlations are developed, along with a cradle-to-grave life cycle assessment (LCA), to highlight components causing significant environmental impact, and to suggest trends and possibilities for improvement based on the exergoenvironmental variables. Finally, the TMS is optimized using multi-objective evolutionary algorithm which considers exergetic and exergoeconomic as well as exergetic and exergoenvironmental objectives simultaneously with respect to the decision variables and constraints. Based on the conducted research for the studied system under the baseline conditions, the exergy efficiency, total cost rate and environmental impact rate are determined to be 0.29, ??28/h and 77.3 mPts/h, respectively. The exergy destruction associated with each component is split into endogenous/exogenous and avoidable/unavoidable parts, where the exogenous exergy destruction is determined to be relatively small but significant portion of the total exergy destruction in each component (up to 40%), indicating a moderate level of interdependencies among the components of the TMS. Furthermore, it is determined that up to 70% of the exergy destruction calculated within the components could potentially be avoided. According to the analyses, electric battery is determined to have the highest exergoeconomic and exergoenvironmental importance in the system, with cost rate of ??3.5/h and environmental impact value of 37.72 mPts/h, due to the high production cost of lithium ion batteries and the use of copper and gold in the battery pack. From an exergoeconomic viewpoint, it is determined that the investment costs of the condenser and evaporator should be reduced to improve the costeffectiveness of the system. On the other hand, from an exergoenvironmental viewpoint, all the component efficiencies (except for the battery) should be improved in order to reduce the total environmental impact even if it increases the environmental impact during production of the components. In addition, it is determined that the coolant pump and the thermal expansion valve before the chiller are relatively insignificant from exergoeconomic and exergoenvironmental perspectives. Subsequently, objective functions are defined and decision variables are selected, along with their respective system constraints, in order to conduct single and multiple objective optimizations for the system. Based on the single objective optimizations, it is determined that the exergy efficiency could be increased by up to 27% using exergy-based optimization, the cost can be reduced by up to 10% using cost-based optimization and the environmental impact can be reduced by up to 19% using environmental impact-based optimization, at the expense of the nonoptimized objectives. Moreover, multi-objective optimizations are conducted in order to provide the respective Pareto optimal curve for the system and to identify the necessary trade-offs within the optimized objectives. Based on the exergoeconomic optimization, it is concluded that 14% higher exergy efficiency and 5% lower cost can be achieved, compared to baseline parameters at an expense of 14% increase in the environmental impact. Furthermore, based on the exergoenvironmental optimization, 13% higher exergy efficiency and 5% lower environmental impact can be achieved at the expense of 27% increase in the total cost

Smart Energy Management for Smart Grids

This book is a contribution from the authors, to share solutions for a better and sustainable power grid. Renewable energy, smart grid security and smart energy management are the main topics discussed in this book

Engineering Ionic Liquid EDLCs: Influence of Cation Type, Carbon Structure and Increased Operation Temperature

Development of safe, robust and reliable electrochemical energy conversion systems with high energy and power densities can be a response to the universal demand for a clean transport industry free from any fossil fuels derivatives. Electrochemical Double Layer Capacitors (EDLCs) are potential candidates that not only provide short pulses of energy at high powers but also deliver stable charge-discharge cycles in excess of 106 cycles. Correspondingly when used in conjugation with a battery stack in an electric vehicle can assist the battery when power boosts are required and therefore extending the battery lifetime. In literature studies these devices are commonly referred to as Electrochemical Capacitors (ECs) and supercapacitors. Commercially available EDLCs are based on aqueous or organic electrolytes that can safely operate in limited potentials. However the room temperature ionic liquids (RTILs) are promising alternatives to replace the current electrolytes as they demonstrate significantly higher and safer operating potentials, thus improving specific energy density. This study identified that the physiochemical properties, operating potential and the cation volume of the Ionic Liquids (ILs), as well as the pore size distribution of the carbon materials influencing the capacitance performance. Hence a systematic study of nine different ionic liquids with varying chain lengths and linkages from four classes of pyrrolidinium, sulfonium, ammonium and phosphonium RTILs was performed. The utilized IL cations in this study are the following: 1-methyl-1- propylpyrrolidinium [Pyr13], 1-butyl-1-methylpyrrolidinium [Pyr14], diethyl- methylsulfonium [S221], triethylsulfonium [S222], butyltrimethylammonium [N1114], butyltriethylammonium [N2224], N,N-diethyl-N-methyl-N-(2methoxy- ethyl)ammonium [N122(2O1)], pentyltriethylphosphonium [P2225] and (2methoxy- ethyl)triethylphosphonium [P222(2O1)] that are combined with a bis(trifluoro- methane)sulfonimide [NTf2] anion. The characterization of the utilized ILs was performed using Karl Fischer measurements, Differential Scanning Calorimetry, rheology, density and conductivity measurements and two/three electrode stability potential measurements. The effect of pore size distribution was also investigated by combining each liquid with four different activated carbons produced in-situ where the pore characteristics of the produced carbons was controlled with varying the precursors quantities. The temperature elevation approach was also used at 25°C, 40°C, 60°C and 80°C in order to study the effect of temperature on ILs physiochemical properties and capacitance response of the produced cells. The capacitance response was investigated with Galvanostatic cycling (GC) at a wide range of discharge densities. Electrochemical Impedance Spectroscopy (EIS) was also used to determine the capacitance performance at 0.01 Hz and monitor the solution, ionic and equivalent series resistances variation with pore size distribution and temperature

Engineering Ionic Liquid EDLCs: Influence of Cation Type, Carbon Structure and Increased Operation Temperature

Development of safe, robust and reliable electrochemical energy conversion systems with high energy and power densities can be a response to the universal demand for a clean transport industry free from any fossil fuels derivatives. Electrochemical Double Layer Capacitors (EDLCs) are potential candidates that not only provide short pulses of energy at high powers but also deliver stable charge-discharge cycles in excess of 106 cycles. Correspondingly when used in conjugation with a battery stack in an electric vehicle can assist the battery when power boosts are required and therefore extending the battery lifetime. In literature studies these devices are commonly referred to as Electrochemical Capacitors (ECs) and supercapacitors. Commercially available EDLCs are based on aqueous or organic electrolytes that can safely operate in limited potentials. However the room temperature ionic liquids (RTILs) are promising alternatives to replace the current electrolytes as they demonstrate significantly higher and safer operating potentials, thus improving specific energy density. This study identified that the physiochemical properties, operating potential and the cation volume of the Ionic Liquids (ILs), as well as the pore size distribution of the carbon materials influencing the capacitance performance. Hence a systematic study of nine different ionic liquids with varying chain lengths and linkages from four classes of pyrrolidinium, sulfonium, ammonium and phosphonium RTILs was performed. The utilized IL cations in this study are the following: 1-methyl-1- propylpyrrolidinium [Pyr13], 1-butyl-1-methylpyrrolidinium [Pyr14], diethyl- methylsulfonium [S221], triethylsulfonium [S222], butyltrimethylammonium [N1114], butyltriethylammonium [N2224], N,N-diethyl-N-methyl-N-(2methoxy- ethyl)ammonium [N122(2O1)], pentyltriethylphosphonium [P2225] and (2methoxy- ethyl)triethylphosphonium [P222(2O1)] that are combined with a bis(trifluoro- methane)sulfonimide [NTf2] anion. The characterization of the utilized ILs was performed using Karl Fischer measurements, Differential Scanning Calorimetry, rheology, density and conductivity measurements and two/three electrode stability potential measurements. The effect of pore size distribution was also investigated by combining each liquid with four different activated carbons produced in-situ where the pore characteristics of the produced carbons was controlled with varying the precursors quantities. The temperature elevation approach was also used at 25°C, 40°C, 60°C and 80°C in order to study the effect of temperature on ILs physiochemical properties and capacitance response of the produced cells. The capacitance response was investigated with Galvanostatic cycling (GC) at a wide range of discharge densities. Electrochemical Impedance Spectroscopy (EIS) was also used to determine the capacitance performance at 0.01 Hz and monitor the solution, ionic and equivalent series resistances variation with pore size distribution and temperature

Geothermal Energy Utilization and Technologies 2020

Rising pollution, climate change and the depletion of fossil fuels are leading many countries to focus on renewable-based energy conversion systems. In particular, recently introduced energy policies are giving high priority to increasing the use of renewable energy sources, the improvement of energy systems’ security, the minimization of greenhouse gas effect, and social and economic cohesion. Renewable energies’ availability varies during the day and the seasons and so their use must be accurately predicted in conjunction with the management strategies based on load shifting and energy storage. Thus, in order to reduce the criticalities of this uncertainty, the exploitation of more flexible and stable renewable energies, such as the geothermal one, is necessary. Geothermal energy is an abundant renewable source with significant potential in direct use applications, such as in district heating systems, in indirect use ones to produce electricity, and in cogeneration and polygeneration systems for the combined production of power, heating, and cooling energy. This Special Issue includes geothermal energy utilization and the technologies used for its exploitation considering both the direct and indirect use applications

Vehicle and Traffic Safety

The book is devoted to contemporary issues regarding the safety of motor vehicles and road traffic. It presents the achievements of scientists, specialists, and industry representatives in the following selected areas of road transport safety and automotive engineering: active and passive vehicle safety, vehicle dynamics and stability, testing of vehicles (and their assemblies), including electric cars as well as autonomous vehicles. Selected issues from the area of accident analysis and reconstruction are discussed. The impact on road safety of aspects such as traffic control systems, road infrastructure, and human factors is also considered